The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform

Joseph H. Szurszewski - One of the best experts on this subject based on the ideXlab platform.

  • PACAP modulation of the colon–Inferior Mesenteric Ganglion reflex in the guinea pig
    The Journal of Physiology, 2004
    Co-Authors: Leonid G. Ermilov, P F Schmalz, Steven M. Miller, Joseph H. Szurszewski
    Abstract:

    We investigated the effect of pituitary adenylate cyclase activating peptide (PACAP) on the colon–Inferior Mesenteric Ganglion (IMG) reflex loop in vitro. PACAP27 and PACAP38 applied to the IMG caused a prolonged depolarization and intense generation of fast EPSPs and action potentials in IMG neurones. Activation of PACAP-preferring receptors (PAC1-Rs) with the selective agonist maxadilan or vasoactive intestinal peptide (VIP)/PACAP (VPAC) receptors with VIP produced similar effects whereas prior incubation of the IMG with selective PAC1-R antagonists PACAP6-38 and M65 inhibited the effects of PACAP. Colonic distension evoked a slow EPSP in IMG neurones that was reduced in amplitude by prolonged superfusion of the IMG with either PACAP27, maxidilan, PACAP6-38, M65 or VIP. Activation of IMG neurones by PACAP27 or maxadilan resulted in an inhibition of ongoing spontaneous colonic contractions. PACAP-LI was detected in nerve trunks attached to the IMG and in varicosities surrounding IMG neurones. Cell bodies with PACAP-LI were present in lumbar 2–3 dorsal root ganglia and in colonic myenteric ganglia. Colonic distension evoked release of PACAP peptides in the IMG as measured by radioimmunoassay. Volume reconstructed images showed that a majority of PACAP-LI, VIP-LI and VAChT-LI nerve endings making putative synaptic contact onto IMG neurones and a majority of putative receptor sites containing PAC1-R-LI and nAChR-LI on the neurones were distributed along secondary and tertiary dendrites. These results suggest involvement of a PACAP-ergic pathway, operated through PAC1-Rs, in controlling the colon–IMG reflex.

  • PACAP modulation of the colon-Inferior Mesenteric Ganglion reflex in the guinea pig.
    The Journal of physiology, 2004
    Co-Authors: Leonid G. Ermilov, Steven M. Miller, Philip F Schmalz, Joseph H. Szurszewski
    Abstract:

    We investigated the effect of pituitary adenylate cyclase activating peptide (PACAP) on the colon-Inferior Mesenteric Ganglion (IMG) reflex loop in vitro. PACAP27 and PACAP38 applied to the IMG caused a prolonged depolarization and intense generation of fast EPSPs and action potentials in IMG neurones. Activation of PACAP-preferring receptors (PAC1-Rs) with the selective agonist maxadilan or vasoactive intestinal peptide (VIP)/PACAP (VPAC) receptors with VIP produced similar effects whereas prior incubation of the IMG with selective PAC1-R antagonists PACAP6-38 and M65 inhibited the effects of PACAP. Colonic distension evoked a slow EPSP in IMG neurones that was reduced in amplitude by prolonged superfusion of the IMG with either PACAP27, maxidilan, PACAP6-38, M65 or VIP. Activation of IMG neurones by PACAP27 or maxadilan resulted in an inhibition of ongoing spontaneous colonic contractions. PACAP-LI was detected in nerve trunks attached to the IMG and in varicosities surrounding IMG neurones. Cell bodies with PACAP-LI were present in lumbar 2-3 dorsal root ganglia and in colonic myenteric ganglia. Colonic distension evoked release of PACAP peptides in the IMG as measured by radioimmunoassay. Volume reconstructed images showed that a majority of PACAP-LI, VIP-LI and VAChT-LI nerve endings making putative synaptic contact onto IMG neurones and a majority of putative receptor sites containing PAC1-R-LI and nAChR-LI on the neurones were distributed along secondary and tertiary dendrites. These results suggest involvement of a PACAP-ergic pathway, operated through PAC1-Rs, in controlling the colon-IMG reflex.

  • Modulation by opioid peptides of mechanosensory pathways supplying the guinea-pig Inferior Mesenteric Ganglion.
    The Journal of Physiology, 1996
    Co-Authors: R C, Joseph H. Szurszewski
    Abstract:

    1. Radioimmunological techniques were used in isolated guinea-pig Inferior Mesenteric Ganglion (IMG)-colon preparations to determine whether opioid peptides and neurotensin8-13 (NT8-13), the C-terminal region of NT1-13 recognized by neurotensin receptors, modulate distension-induced release of substance P (SP)- and vasoactive intestinal polypeptide (VIP)-like immunoreactive (LI) material. 2. Colonic distension significantly increased the amount of SP- and VIP-LI material released in the Ganglionic superfusate. A low-Ca2+ (0.1 mM), high-Mg2+ (15 mM) solution blocked their release. 3. In vivo capsaicin pretreatment abolished release of SP-LI material during colonic distension but had no significant effect on distension-induced release of VIP-LI material. 4. The addition of [Leu5]enkephalin, [Met5]enkephalin, PL017 (a mu-receptor agonist) and DPDPE (a delta-receptor agonist) to the Ganglion side of a two-compartment chamber blocked distension-induced release of SP-LI material. The addition of naloxone and ICI-174,864 (a delta-receptor antagonist) to the Ganglion compartment reversed the inhibitory effect of the mu- and delta-receptor agonists. 5. Addition of [Leu5]enkephalin and [Met5]enkephalin to the Ganglion compartment had no significant effect on release of VIP-LI material during colonic distension. 6. Addition of NT8-13 to the Ganglion compartment significantly increased in the amount of SP-LI material released during colonic distension but had no affect on distension-induced release of VIP-LI material. 7. The results suggest the hypothesis that under in vivo conditions, enkephalinergic nerves decrease and neurotensinergic nerves increase the release of SP from peripheral branches of primary afferent sensory nerves.

  • Enteric GABA‐containing nerves projecting to the guinea‐pig Inferior Mesenteric Ganglion modulate acetylcholine release.
    The Journal of physiology, 1993
    Co-Authors: H. P. Parkman, W. H. Stapelfeldt, Carol L. Williams, Vanda A. Lennon, Joseph H. Szurszewski
    Abstract:

    1. The effect of GABA and GABA receptor-modulating drugs on release of [3H]acetylcholine was studied in the guinea-pig Inferior Mesenteric Ganglion. 2. GABA caused a dose-dependent increase in [3H]acetylcholine release during stimulation of the lumbar colonic nerves. Muscimol (10 microM) and diazepam (5 microM) also increased [3H]acetylcholine release during stimulation of the lumbar colonic nerves whereas baclofen (10 microM) had no effect. 3. Bicuculline (20-100 microM) and picrotoxin (50 microM) alone reduced [3H]acetylcholine release during electrical stimulation of the lumbar colonic nerves whereas phaclofen (300 microM) had no effect. 4. Bicuculline (100 microM) significantly decreased whereas diazepam (5 microM) significantly increased distension-induced [3H]acetylcholine release. 5. Colonic distension significantly increased [3H]GABA release in the Inferior Mesenteric Ganglion compared to basal periods when the colon was not distended. Distension-induced release of [3H]GABA resulted from active neuronal transmission from the colon to the Inferior Mesenteric Ganglion, since perfusion of the Inferior Mesenteric Ganglion with tetrodotoxin (1 microM) reduced basal release of [3H]GABA and abolished distension-evoked increases in the release of [3H]GABA. 6. In contrast to its excitatory effects on peripheral colonic afferent cholinergic nerves, exogenous GABA caused a dose-dependent decrease in [3H]acetylcholine release during electrical stimulation of the central lumbar splanchnic nerves. Baclofen (10 microM) also inhibited [3H]acetylcholine release whereas muscimol (10 microM) or diazepam (5 microM) had no effect. Phaclofen (300 microM) antagonized the inhibitory effects of exogenous GABA (10 microM) and of baclofen (10 microM). Bicuculline (100 microM), picrotoxin (50 microM) and phaclofen (300 microM) alone had no effect on [3H]acetylcholine release during splanchnic nerve stimulation. 7. Phaclofen (300 microM) increased [3H]acetylcholine release during simultaneous electrical stimulation of the lumbar colonic nerves and splanchnic nerves and when GABAA receptors were blocked by bicuculline (20 microM). 8. The data suggest that GABAA receptors facilitate release of acetylcholine from peripheral cholinergic mechanosensory nerves projecting from the colon to the Inferior Mesenteric Ganglion and that GABAB receptors inhibit release of acetylcholine from central cholinergic nerves. Enteric GABA-containing nerves projecting to the Inferior Mesenteric Ganglion are mechanosensory. Endogenous release of GABA may act on GABAA receptors to facilitate peripheral cholinergic mechanosensory transmission and/or on GABAB receptors to inhibit central cholinergic transmission.

  • The electrophysiological effects of endogenous GABA in the guinea‐pig Inferior Mesenteric Ganglion.
    The Journal of physiology, 1993
    Co-Authors: W. H. Stapelfeldt, H. P. Parkman, Joseph H. Szurszewski
    Abstract:

    1. GABA receptor-modulating drugs and intracellular recording techniques were used to determine the functional significance of peripheral afferent GABA-containing nerves projecting from the distal colon to sympathetic neurones in the Inferior Mesenteric Ganglion of the guinea-pig. 2. GABAA receptor-modulating drugs added selectively to the Inferior Mesenteric Ganglion side of a two-compartment bath had pronounced effects on on-going colonic afferent cholinergic synaptic input. Bicuculline (20 microM) decreased the amplitude and frequency of fast excitatory postsynaptic potentials (EPSPs) by 40% whereas diazepam (5 microM) increased cholinergic input by 43%. Neither drug had any effect on the resting membrane potential or membrane input resistance of Ganglion cells. 3. Bicuculline (20 microM) significantly reduced, whereas diazepam (5 microM) significantly enhanced, distension-induced increases in nicotinic fast EPSPs and action potentials. 4. Slow EPSPs evoked by colonic distension were not affected by bicuculline or diazepam. 5. Manual voltage clamp of the postsynaptic depolarizing response to exogenous GABA revealed GABA-induced presynaptic facilitation of colonic afferent but not central preGanglionic efferent cholinergic synaptic input. 6. The data suggest that endogenously released GABA participates in on-going colo-colonic reflex activity by acting on presynaptic GABAA receptors to facilitate release of acetylcholine from colonic mechanosensory nerves.

V. I. Skok - One of the best experts on this subject based on the ideXlab platform.

  • The β-subunit composition of nicotinic acetylcholine receptors in the neurons of the guinea pig Inferior Mesenteric Ganglion
    Neuroscience letters, 2004
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, Elena Y Lykhmus, Victor I. Tsetlin, Maxim N. Zhmak, V. I. Skok
    Abstract:

    Abstract The antibodies against synthetic (183–192) fragments of β2- and β4-subunits of rat neuronal nicotinic acetylcholine receptor were used to study a β-subunit composition of nicotinic receptors in the Inferior Mesenteric Ganglion of the guinea pig by both immunocytochemical staining and blocking of excitatory postsynaptic potentials induced by electric stimulation of the pre-Ganglionic nerve (interMesenteric trunk). The β4-specific antibody stained 59.8±7.5% of neurons and inhibited the synaptic responses in all (n=10) neurons studied by 25.5±1.8%. The β2-specific antibody did not stain Ganglionic neurons and did not affect the synaptic transmission. Taking into account the previously obtained data on the α-subunits found in this Ganglion, it is concluded that the neurons of Inferior Mesenteric Ganglion contain nicotinic receptors of α3(α5)β4 subtypes involved in synaptic transmission through the interMesenteric tract.

  • β2- and β4-Subunit Composition of Nicotinic Acetylcholine Receptors in the Guinea Pig Inferior Mesenteric Ganglion: Immunohistochemical and Electrophysiological Studies
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, V. I. Skok
    Abstract:

    1 Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine. Correspondence should be addressed to L. P. Voitenko (e-mail: lvoit@serv.biph. kiev.ua). Affinity-purified rabbit antibodies (Ab) against extracellular fragments 193-204 of nicotinic acetylcholine receptor (nAChR) β2 and β4 subunits were used in the experiments with immunoperoxidase labeling of guinea pig Inferior Mesenteric Ganglion (IMG) neurons and intracellular recording of excitatory postsynaptic potentials (EPSP) from these units. Since the epitopes of these Ab are close to an acetylcholine-binding site located at the interface of α and β subunits, we expected that the Ab can block acetylcholine-mediated EPSP responses of IMG neurons, thus enabling us to determine the involvement of β2and β4-containing nAChR in synaptic transmission through interMesenteric pathways. Microscopic examination revealed the presence of two cell types in IMG preparations: principal Ganglionic neurons (PGN), 48-60 μm in diameter, and small cells of unknown origin, 6-18 μm in diameter. The β4-specifi c Ab labeled 59.8 ± 7.5% of PGN, while the β2-specifi c Ab labeled less than 1% of these cells, the β4-positive label being much more intensive than the β2-positive one. The β4-specifi c labeling was similar to that revealed with the α3-specifi c Ab. It should be noted that the percentage of α5-immunoreactive IMG neurons differed insignifi cantly from that of α3-labeled PGN. The somata of small cells were labeled with the β4-specifi c Ab too, and a group of β2-positive small cells was also found. Both β4and β2-positive neurons were localized near the origins of the main nerve trunks branching from the IMG (Mesenteric, colonic, and hypogastric nerves). In electrophysiological experiments, the β4-specific Ab decreased the EPSP amplitudes by 25.5 ± 1.8% in all 10 PGN tested. In contrast, the β2-specific Ab did not suppress the synaptic responses under study. Our findings showed that α3-, α5-, and β4-containing nAChR are present in the guinea pig IMG neurons and are involved in synaptic transmission through the interMesenteric pathways. Probably, the α3β4 nAChR subtype is more widespread that is consistent with the generally recognized nature of Ganglionic nAChR.

  • α-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Inferior Mesenteric Ganglion of the Guinea Pig: an Electrophysiological Study
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, Marina V. Skok, V. I. Skok
    Abstract:

    We studied the subunit composition of nicotinic cholinoreceptors (nChR) of neurons of the Inferior Mesenteric Ganglion (IMG) of the guinea pig using antibodies against the α_3, α_4, α_5, and α_7 nChR subunits and a standard technique of intracellular recording. Application of the α_3 subunit-specific antibodies resulted in a decrease in the EPSP amplitude by 29.7 ± 1.8%, on average, in 17 of 20 studied neurons. The α_4 subunit-specific antibodies evoked no changes in the amplitude of EPSP recorded from IMG neurons (n = 10). Effects of the α_5 subunit-specific antibodies were studied in 20 neurons, where the EPSP amplitude dropped after application of these antibodies by 40.0 ± 1.8%, on average. Superfusion of the neurons with a solution containing the α_3 and α_5 subunit-specific antibodies completely suppressed synaptic responses (n = 3). The α_7 subunit-specific antibodies provided an increase in the EPSP amplitude in 13 of 15 studied IMG neurons (by 37 ± 6%, on average); this fact allows us to suppose that α_7-containing nChR are present in the IMG neurons and are indirectly involved in the processes of synaptic transmission. Application of the antibodies evoked no significant shifts in the membrane potential in IMG neurons. Our findings demonstrate that synaptic transmission through the guinea pig IMG is realized mostly with the involvement of the α_3- and α_5-containing nChR; the α_4-containing receptors are not engaged in this process.

Olga M Koval - One of the best experts on this subject based on the ideXlab platform.

  • The β-subunit composition of nicotinic acetylcholine receptors in the neurons of the guinea pig Inferior Mesenteric Ganglion
    Neuroscience letters, 2004
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, Elena Y Lykhmus, Victor I. Tsetlin, Maxim N. Zhmak, V. I. Skok
    Abstract:

    Abstract The antibodies against synthetic (183–192) fragments of β2- and β4-subunits of rat neuronal nicotinic acetylcholine receptor were used to study a β-subunit composition of nicotinic receptors in the Inferior Mesenteric Ganglion of the guinea pig by both immunocytochemical staining and blocking of excitatory postsynaptic potentials induced by electric stimulation of the pre-Ganglionic nerve (interMesenteric trunk). The β4-specific antibody stained 59.8±7.5% of neurons and inhibited the synaptic responses in all (n=10) neurons studied by 25.5±1.8%. The β2-specific antibody did not stain Ganglionic neurons and did not affect the synaptic transmission. Taking into account the previously obtained data on the α-subunits found in this Ganglion, it is concluded that the neurons of Inferior Mesenteric Ganglion contain nicotinic receptors of α3(α5)β4 subtypes involved in synaptic transmission through the interMesenteric tract.

  • β2- and β4-Subunit Composition of Nicotinic Acetylcholine Receptors in the Guinea Pig Inferior Mesenteric Ganglion: Immunohistochemical and Electrophysiological Studies
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, V. I. Skok
    Abstract:

    1 Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine. Correspondence should be addressed to L. P. Voitenko (e-mail: lvoit@serv.biph. kiev.ua). Affinity-purified rabbit antibodies (Ab) against extracellular fragments 193-204 of nicotinic acetylcholine receptor (nAChR) β2 and β4 subunits were used in the experiments with immunoperoxidase labeling of guinea pig Inferior Mesenteric Ganglion (IMG) neurons and intracellular recording of excitatory postsynaptic potentials (EPSP) from these units. Since the epitopes of these Ab are close to an acetylcholine-binding site located at the interface of α and β subunits, we expected that the Ab can block acetylcholine-mediated EPSP responses of IMG neurons, thus enabling us to determine the involvement of β2and β4-containing nAChR in synaptic transmission through interMesenteric pathways. Microscopic examination revealed the presence of two cell types in IMG preparations: principal Ganglionic neurons (PGN), 48-60 μm in diameter, and small cells of unknown origin, 6-18 μm in diameter. The β4-specifi c Ab labeled 59.8 ± 7.5% of PGN, while the β2-specifi c Ab labeled less than 1% of these cells, the β4-positive label being much more intensive than the β2-positive one. The β4-specifi c labeling was similar to that revealed with the α3-specifi c Ab. It should be noted that the percentage of α5-immunoreactive IMG neurons differed insignifi cantly from that of α3-labeled PGN. The somata of small cells were labeled with the β4-specifi c Ab too, and a group of β2-positive small cells was also found. Both β4and β2-positive neurons were localized near the origins of the main nerve trunks branching from the IMG (Mesenteric, colonic, and hypogastric nerves). In electrophysiological experiments, the β4-specific Ab decreased the EPSP amplitudes by 25.5 ± 1.8% in all 10 PGN tested. In contrast, the β2-specific Ab did not suppress the synaptic responses under study. Our findings showed that α3-, α5-, and β4-containing nAChR are present in the guinea pig IMG neurons and are involved in synaptic transmission through the interMesenteric pathways. Probably, the α3β4 nAChR subtype is more widespread that is consistent with the generally recognized nature of Ganglionic nAChR.

  • α-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Guinea Pig Inferior Mesenteric Ganglion: an Immunohistochemical Study
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok
    Abstract:

    Using immunoperoxidase labeling, we studied the subunit composition of nicotinic acetylcholine receptors, nAChR, in preparations of the Inferior Mesenteric Ganglion, IMG, of the guinea pig. Antibodies against synthetic peptides corresponding to agonist-binding membrane components of the α_3, α_4, α_5, and α_7 nAChR subunits were used. The presence of α_3-specific antibodies was revealed on the membranes of about 58% of large neurons and of all small Ganglionic cells (means of the greater and smaller diameters of the somata 53.8 ± 1.8 vs 33.6 ± 1.4 μm, n = 20, and 14.1 ± 0.5 vs 7.5 ± 0.4 μm, n = 50, respectively). Labeled cells of the rostral node were distributed evenly, while those of the caudal node were localized mostly within the regions of branching of the lumbar, colonic, and both hypogastric tracts. Immune labels to the α_4 subunit were observed only on the membranes of small Ganglionic cells distributed mostly in the region of the internodal commissural tracts. α_5-Specific labeling was found on the membranes of about 63% large neurons, whose distribution was similar to that of the α_3-labeled units, and on all small cells. Immunoreactivity to the α_7 subunit was observed only on the membranes of small cells concentrated around unlabeled large neurons in the region of branching of the interMesenteric, colonic, and both hypogastric tracts. Thus, nAChR in the guinea pig IMG include α_3, α_4, α_5, and α_7 subunits. The nAChR with α_3 and α_5 subunits are localized on the membranes of large Ganglionic neurons, whose number and topographical distribution are very close to each other. Our data agree with our results of earlier electrophysiological experiments and are indicative of the crucial role of the α_3- and α_5-containing nAChR in synaptic transmission via the Ganglion under study. The presence of the α_4- and α_7-containing nAChR was found only on small Ganglionic cells (which are, probably, not the relay units) and their processes.

  • α-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Inferior Mesenteric Ganglion of the Guinea Pig: an Electrophysiological Study
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, Marina V. Skok, V. I. Skok
    Abstract:

    We studied the subunit composition of nicotinic cholinoreceptors (nChR) of neurons of the Inferior Mesenteric Ganglion (IMG) of the guinea pig using antibodies against the α_3, α_4, α_5, and α_7 nChR subunits and a standard technique of intracellular recording. Application of the α_3 subunit-specific antibodies resulted in a decrease in the EPSP amplitude by 29.7 ± 1.8%, on average, in 17 of 20 studied neurons. The α_4 subunit-specific antibodies evoked no changes in the amplitude of EPSP recorded from IMG neurons (n = 10). Effects of the α_5 subunit-specific antibodies were studied in 20 neurons, where the EPSP amplitude dropped after application of these antibodies by 40.0 ± 1.8%, on average. Superfusion of the neurons with a solution containing the α_3 and α_5 subunit-specific antibodies completely suppressed synaptic responses (n = 3). The α_7 subunit-specific antibodies provided an increase in the EPSP amplitude in 13 of 15 studied IMG neurons (by 37 ± 6%, on average); this fact allows us to suppose that α_7-containing nChR are present in the IMG neurons and are indirectly involved in the processes of synaptic transmission. Application of the antibodies evoked no significant shifts in the membrane potential in IMG neurons. Our findings demonstrate that synaptic transmission through the guinea pig IMG is realized mostly with the involvement of the α_3- and α_5-containing nChR; the α_4-containing receptors are not engaged in this process.

Marina V. Skok - One of the best experts on this subject based on the ideXlab platform.

  • The β-subunit composition of nicotinic acetylcholine receptors in the neurons of the guinea pig Inferior Mesenteric Ganglion
    Neuroscience letters, 2004
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, Elena Y Lykhmus, Victor I. Tsetlin, Maxim N. Zhmak, V. I. Skok
    Abstract:

    Abstract The antibodies against synthetic (183–192) fragments of β2- and β4-subunits of rat neuronal nicotinic acetylcholine receptor were used to study a β-subunit composition of nicotinic receptors in the Inferior Mesenteric Ganglion of the guinea pig by both immunocytochemical staining and blocking of excitatory postsynaptic potentials induced by electric stimulation of the pre-Ganglionic nerve (interMesenteric trunk). The β4-specific antibody stained 59.8±7.5% of neurons and inhibited the synaptic responses in all (n=10) neurons studied by 25.5±1.8%. The β2-specific antibody did not stain Ganglionic neurons and did not affect the synaptic transmission. Taking into account the previously obtained data on the α-subunits found in this Ganglion, it is concluded that the neurons of Inferior Mesenteric Ganglion contain nicotinic receptors of α3(α5)β4 subtypes involved in synaptic transmission through the interMesenteric tract.

  • β2- and β4-Subunit Composition of Nicotinic Acetylcholine Receptors in the Guinea Pig Inferior Mesenteric Ganglion: Immunohistochemical and Electrophysiological Studies
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, V. I. Skok
    Abstract:

    1 Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine. Correspondence should be addressed to L. P. Voitenko (e-mail: lvoit@serv.biph. kiev.ua). Affinity-purified rabbit antibodies (Ab) against extracellular fragments 193-204 of nicotinic acetylcholine receptor (nAChR) β2 and β4 subunits were used in the experiments with immunoperoxidase labeling of guinea pig Inferior Mesenteric Ganglion (IMG) neurons and intracellular recording of excitatory postsynaptic potentials (EPSP) from these units. Since the epitopes of these Ab are close to an acetylcholine-binding site located at the interface of α and β subunits, we expected that the Ab can block acetylcholine-mediated EPSP responses of IMG neurons, thus enabling us to determine the involvement of β2and β4-containing nAChR in synaptic transmission through interMesenteric pathways. Microscopic examination revealed the presence of two cell types in IMG preparations: principal Ganglionic neurons (PGN), 48-60 μm in diameter, and small cells of unknown origin, 6-18 μm in diameter. The β4-specifi c Ab labeled 59.8 ± 7.5% of PGN, while the β2-specifi c Ab labeled less than 1% of these cells, the β4-positive label being much more intensive than the β2-positive one. The β4-specifi c labeling was similar to that revealed with the α3-specifi c Ab. It should be noted that the percentage of α5-immunoreactive IMG neurons differed insignifi cantly from that of α3-labeled PGN. The somata of small cells were labeled with the β4-specifi c Ab too, and a group of β2-positive small cells was also found. Both β4and β2-positive neurons were localized near the origins of the main nerve trunks branching from the IMG (Mesenteric, colonic, and hypogastric nerves). In electrophysiological experiments, the β4-specific Ab decreased the EPSP amplitudes by 25.5 ± 1.8% in all 10 PGN tested. In contrast, the β2-specific Ab did not suppress the synaptic responses under study. Our findings showed that α3-, α5-, and β4-containing nAChR are present in the guinea pig IMG neurons and are involved in synaptic transmission through the interMesenteric pathways. Probably, the α3β4 nAChR subtype is more widespread that is consistent with the generally recognized nature of Ganglionic nAChR.

  • α-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Guinea Pig Inferior Mesenteric Ganglion: an Immunohistochemical Study
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok
    Abstract:

    Using immunoperoxidase labeling, we studied the subunit composition of nicotinic acetylcholine receptors, nAChR, in preparations of the Inferior Mesenteric Ganglion, IMG, of the guinea pig. Antibodies against synthetic peptides corresponding to agonist-binding membrane components of the α_3, α_4, α_5, and α_7 nAChR subunits were used. The presence of α_3-specific antibodies was revealed on the membranes of about 58% of large neurons and of all small Ganglionic cells (means of the greater and smaller diameters of the somata 53.8 ± 1.8 vs 33.6 ± 1.4 μm, n = 20, and 14.1 ± 0.5 vs 7.5 ± 0.4 μm, n = 50, respectively). Labeled cells of the rostral node were distributed evenly, while those of the caudal node were localized mostly within the regions of branching of the lumbar, colonic, and both hypogastric tracts. Immune labels to the α_4 subunit were observed only on the membranes of small Ganglionic cells distributed mostly in the region of the internodal commissural tracts. α_5-Specific labeling was found on the membranes of about 63% large neurons, whose distribution was similar to that of the α_3-labeled units, and on all small cells. Immunoreactivity to the α_7 subunit was observed only on the membranes of small cells concentrated around unlabeled large neurons in the region of branching of the interMesenteric, colonic, and both hypogastric tracts. Thus, nAChR in the guinea pig IMG include α_3, α_4, α_5, and α_7 subunits. The nAChR with α_3 and α_5 subunits are localized on the membranes of large Ganglionic neurons, whose number and topographical distribution are very close to each other. Our data agree with our results of earlier electrophysiological experiments and are indicative of the crucial role of the α_3- and α_5-containing nAChR in synaptic transmission via the Ganglion under study. The presence of the α_4- and α_7-containing nAChR was found only on small Ganglionic cells (which are, probably, not the relay units) and their processes.

  • α-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Inferior Mesenteric Ganglion of the Guinea Pig: an Electrophysiological Study
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, Marina V. Skok, V. I. Skok
    Abstract:

    We studied the subunit composition of nicotinic cholinoreceptors (nChR) of neurons of the Inferior Mesenteric Ganglion (IMG) of the guinea pig using antibodies against the α_3, α_4, α_5, and α_7 nChR subunits and a standard technique of intracellular recording. Application of the α_3 subunit-specific antibodies resulted in a decrease in the EPSP amplitude by 29.7 ± 1.8%, on average, in 17 of 20 studied neurons. The α_4 subunit-specific antibodies evoked no changes in the amplitude of EPSP recorded from IMG neurons (n = 10). Effects of the α_5 subunit-specific antibodies were studied in 20 neurons, where the EPSP amplitude dropped after application of these antibodies by 40.0 ± 1.8%, on average. Superfusion of the neurons with a solution containing the α_3 and α_5 subunit-specific antibodies completely suppressed synaptic responses (n = 3). The α_7 subunit-specific antibodies provided an increase in the EPSP amplitude in 13 of 15 studied IMG neurons (by 37 ± 6%, on average); this fact allows us to suppose that α_7-containing nChR are present in the IMG neurons and are indirectly involved in the processes of synaptic transmission. Application of the antibodies evoked no significant shifts in the membrane potential in IMG neurons. Our findings demonstrate that synaptic transmission through the guinea pig IMG is realized mostly with the involvement of the α_3- and α_5-containing nChR; the α_4-containing receptors are not engaged in this process.

L. P. Voitenko - One of the best experts on this subject based on the ideXlab platform.

  • The β-subunit composition of nicotinic acetylcholine receptors in the neurons of the guinea pig Inferior Mesenteric Ganglion
    Neuroscience letters, 2004
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, Elena Y Lykhmus, Victor I. Tsetlin, Maxim N. Zhmak, V. I. Skok
    Abstract:

    Abstract The antibodies against synthetic (183–192) fragments of β2- and β4-subunits of rat neuronal nicotinic acetylcholine receptor were used to study a β-subunit composition of nicotinic receptors in the Inferior Mesenteric Ganglion of the guinea pig by both immunocytochemical staining and blocking of excitatory postsynaptic potentials induced by electric stimulation of the pre-Ganglionic nerve (interMesenteric trunk). The β4-specific antibody stained 59.8±7.5% of neurons and inhibited the synaptic responses in all (n=10) neurons studied by 25.5±1.8%. The β2-specific antibody did not stain Ganglionic neurons and did not affect the synaptic transmission. Taking into account the previously obtained data on the α-subunits found in this Ganglion, it is concluded that the neurons of Inferior Mesenteric Ganglion contain nicotinic receptors of α3(α5)β4 subtypes involved in synaptic transmission through the interMesenteric tract.

  • β2- and β4-Subunit Composition of Nicotinic Acetylcholine Receptors in the Guinea Pig Inferior Mesenteric Ganglion: Immunohistochemical and Electrophysiological Studies
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok, V. I. Skok
    Abstract:

    1 Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine. Correspondence should be addressed to L. P. Voitenko (e-mail: lvoit@serv.biph. kiev.ua). Affinity-purified rabbit antibodies (Ab) against extracellular fragments 193-204 of nicotinic acetylcholine receptor (nAChR) β2 and β4 subunits were used in the experiments with immunoperoxidase labeling of guinea pig Inferior Mesenteric Ganglion (IMG) neurons and intracellular recording of excitatory postsynaptic potentials (EPSP) from these units. Since the epitopes of these Ab are close to an acetylcholine-binding site located at the interface of α and β subunits, we expected that the Ab can block acetylcholine-mediated EPSP responses of IMG neurons, thus enabling us to determine the involvement of β2and β4-containing nAChR in synaptic transmission through interMesenteric pathways. Microscopic examination revealed the presence of two cell types in IMG preparations: principal Ganglionic neurons (PGN), 48-60 μm in diameter, and small cells of unknown origin, 6-18 μm in diameter. The β4-specifi c Ab labeled 59.8 ± 7.5% of PGN, while the β2-specifi c Ab labeled less than 1% of these cells, the β4-positive label being much more intensive than the β2-positive one. The β4-specifi c labeling was similar to that revealed with the α3-specifi c Ab. It should be noted that the percentage of α5-immunoreactive IMG neurons differed insignifi cantly from that of α3-labeled PGN. The somata of small cells were labeled with the β4-specifi c Ab too, and a group of β2-positive small cells was also found. Both β4and β2-positive neurons were localized near the origins of the main nerve trunks branching from the IMG (Mesenteric, colonic, and hypogastric nerves). In electrophysiological experiments, the β4-specific Ab decreased the EPSP amplitudes by 25.5 ± 1.8% in all 10 PGN tested. In contrast, the β2-specific Ab did not suppress the synaptic responses under study. Our findings showed that α3-, α5-, and β4-containing nAChR are present in the guinea pig IMG neurons and are involved in synaptic transmission through the interMesenteric pathways. Probably, the α3β4 nAChR subtype is more widespread that is consistent with the generally recognized nature of Ganglionic nAChR.

  • α-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Guinea Pig Inferior Mesenteric Ganglion: an Immunohistochemical Study
    Neurophysiology, 2003
    Co-Authors: Olga M Koval, L. P. Voitenko, Marina V. Skok
    Abstract:

    Using immunoperoxidase labeling, we studied the subunit composition of nicotinic acetylcholine receptors, nAChR, in preparations of the Inferior Mesenteric Ganglion, IMG, of the guinea pig. Antibodies against synthetic peptides corresponding to agonist-binding membrane components of the α_3, α_4, α_5, and α_7 nAChR subunits were used. The presence of α_3-specific antibodies was revealed on the membranes of about 58% of large neurons and of all small Ganglionic cells (means of the greater and smaller diameters of the somata 53.8 ± 1.8 vs 33.6 ± 1.4 μm, n = 20, and 14.1 ± 0.5 vs 7.5 ± 0.4 μm, n = 50, respectively). Labeled cells of the rostral node were distributed evenly, while those of the caudal node were localized mostly within the regions of branching of the lumbar, colonic, and both hypogastric tracts. Immune labels to the α_4 subunit were observed only on the membranes of small Ganglionic cells distributed mostly in the region of the internodal commissural tracts. α_5-Specific labeling was found on the membranes of about 63% large neurons, whose distribution was similar to that of the α_3-labeled units, and on all small cells. Immunoreactivity to the α_7 subunit was observed only on the membranes of small cells concentrated around unlabeled large neurons in the region of branching of the interMesenteric, colonic, and both hypogastric tracts. Thus, nAChR in the guinea pig IMG include α_3, α_4, α_5, and α_7 subunits. The nAChR with α_3 and α_5 subunits are localized on the membranes of large Ganglionic neurons, whose number and topographical distribution are very close to each other. Our data agree with our results of earlier electrophysiological experiments and are indicative of the crucial role of the α_3- and α_5-containing nAChR in synaptic transmission via the Ganglion under study. The presence of the α_4- and α_7-containing nAChR was found only on small Ganglionic cells (which are, probably, not the relay units) and their processes.