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Patrice G Guyenet - One of the best experts on this subject based on the ideXlab platform.
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vesicular glutamate transporter 2 is required for the respiratory and parasympathetic activation produced by optogenetic stimulation of catecholaminergic neurons in the rostral ventrolateral medulla of mice in vivo
European Journal of Neuroscience, 2014Co-Authors: Stephen B G Abbott, Patrice G Guyenet, Benjamin B Holloway, Kenneth E ViarAbstract:Catecholaminergic neurons of the rostral ventrolateral medulla (RVLM-CA neurons; C1 neurons) contribute to the sympathetic, parasympathetic and neuroendocrine responses elicited by physical stressors such as hypotension, hypoxia, hypoglycemia, and infection. Most RVLM-CA neurons express vesicular glutamate transporter (VGLUT)2, and may use glutamate as a ionotropic transmitter, but the importance of this mode of transmission in vivo is uncertain. To address this question, we genetically deleted VGLUT2 from dopamine-β-hydroxylase-expressing neurons in mice [DβH(Cre/0) ;VGLUT2(flox/flox) mice (cKO mice)]. We compared the in vivo effects of selectively stimulating RVLM-CA neurons in cKO vs. control mice (DβH(Cre/0) ), using channelrhodopsin-2 (ChR2-mCherry) optogenetics. ChR2-mCherry was expressed by similar numbers of rostral ventrolateral medulla (RVLM) neurons in each strain (~400 neurons), with identical selectivity for catecholaminergic neurons (90-99% colocalisation with tyrosine hydroxylase). RVLM-CA neurons had similar morphology and axonal projections in DβH(Cre/0) and cKO mice. Under urethane anesthesia, Photostimulation produced a similar pattern of activation of presumptive ChR2-positive RVLM-CA neurons in DβH(Cre/0) and cKO mice. Photostimulation in conscious mice produced frequency-dependent respiratory activation in DβH(Cre/0) mice but no effect in cKO mice. Similarly, Photostimulation under urethane anesthesia strongly activated efferent vagal nerve activity in DβH(Cre/0) mice only. Vagal responses were unaffected by α1 -adrenoreceptor blockade. In conclusion, two responses evoked by RVLM-CA neuron stimulation in vivo require the expression of VGLUT2 by these neurons, suggesting that the acute autonomic responses driven by RVLM-CA neurons are mediated by glutamate.
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selective optogenetic activation of rostral ventrolateral medullary catecholaminergic neurons produces cardiorespiratory stimulation in conscious mice
The Journal of Neuroscience, 2013Co-Authors: Stephen B G Abbott, Ruth L. Stornetta, Seth D Depuy, Thanh Nguyen, Melissa B Coates, Patrice G GuyenetAbstract:Activation of rostral ventrolateral medullary catecholaminergic (RVLM-CA) neurons e.g., by hypoxia is thought to increase sympathetic outflow thereby raising blood pressure (BP). Here we test whether these neurons also regulate breathing and cardiovascular variables other than BP. Selective expression of ChR2-mCherry by RVLM-CA neurons was achieved by injecting Cre-dependent vector AAV2-EF1α-DIO-ChR2-mCherry unilaterally into the brainstem of dopamine-β-hydroxylaseCre/0 mice. Photostimulation of RVLM-CA neurons increased breathing in anesthetized and conscious mice. In conscious mice, Photostimulation primarily increased breathing frequency and this effect was fully occluded by hypoxia (10% O2). In contrast, the effects of Photostimulation were largely unaffected by hypercapnia (3 and 6% CO2). The associated cardiovascular effects were complex (slight bradycardia and hypotension) and, using selective autonomic blockers, could be explained by coactivation of the sympathetic and cardiovagal outflows. ChR2-positive RVLM-CA neurons expressed VGLUT2 and their projections were mapped. Their complex cardiorespiratory effects are presumably mediated by their extensive projections to supraspinal sites such as the ventrolateral medulla, the dorsal vagal complex, the dorsolateral pons, and selected hypothalamic nuclei (dorsomedial, lateral, and paraventricular nuclei). In sum, selective optogenetic activation of RVLM-CA neurons in conscious mice revealed two important novel functions of these neurons, namely breathing stimulation and cardiovagal outflow control, effects that are attenuated or absent under anesthesia and are presumably mediated by the numerous supraspinal projections of these neurons. The results also suggest that RVLM-CA neurons may underlie some of the acute respiratory response elicited by carotid body stimulation but contribute little to the central respiratory chemoreflex.
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Photostimulation of Phox2b Medullary Neurons Activates Cardiorespiratory Function in Conscious Rats
American journal of respiratory and critical care medicine, 2010Co-Authors: Roy Kanbar, Ruth L. Stornetta, Devin R. Cash, Stephen J. Lewis, Patrice G GuyenetAbstract:Rationale: Hypoventilation is typically treated with positive pressure ventilation or, in extreme cases, by phrenic nerve stimulation. This preclinical study explores whether direct stimulation of central chemoreceptors could be used as an alternative method to stimulate breathing. Objectives: To determine whether activation of the retrotrapezoid nucleus (RTN), which is located in the rostral ventrolateral medulla (RVLM), stimulates breathing with appropriate selectivity. Methods: A lentivirus was used to induce expression of the photoactivatable cationic channel channelrhodopsin-2 (ChR2) by RVLM Phox2b-containing neurons, a population that consists of central chemoreceptors (the ccRTN neurons) and blood pressure (BP)-regulating neurons (the C1 cells). The transfected neurons were activated with pulses of laser light. Respiratory effects were measured by plethysmography or diaphragmatic EMG recording and cardiovascular effects by monitoring BP, renal sympathetic nerve discharge, and the baroreflex. Measurements and Main Results: The RVLM contained 600 to 900 ChR2-transfected neurons (63% C1, 37% ccRTN). RVLM Photostimulation significantly increased breathing rate (+42%), tidal volume (21%), minute volume (68%), and peak expiratory flow (48%). Photostimulation increased diaphragm EMG amplitude (19%) and frequency (21%). Photostimulation increased BP (4 mmHg) and renal sympathetic nerve discharge (43%) while decreasing heart rate (15 bpm). Conclusions: Photostimulation of ChR2-transfected RVLM Phox2b neurons produces a vigorous stimulation of breathing accompanied by a small sympathetically mediated increase in BP. These results demonstrate that breathing can be relatively selectively activated in resting unanesthetized mammals via optogenetic manipulation of RVLM neurons presumed to be central chemoreceptors. This methodology could perhaps be used in the future to enhance respiration in humans.
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Photostimulation of channelrhodopsin 2 expressing ventrolateral medullary neurons increases sympathetic nerve activity and blood pressure in rats
The Journal of Physiology, 2009Co-Authors: Stephen B G Abbott, Ruth L. Stornetta, C Socolovsky, Gavin H West, Patrice G GuyenetAbstract:To explore the specific contribution of the C1 neurons to blood pressure (BP) control, we used an optogenetic approach to activate these cells in vivo. A lentivirus that expresses channelrhodopsin-2 (ChR2) under the control of the catecholaminergic neuron-preferring promoter PRSx8 was introduced into the rostral ventrolateral medulla (RVLM). After 2–3 weeks, ChR2 was largely confined to Phox2b-expressing neurons (89%). The ChR2-expressing neurons were non-GABAergic, non-glycinergic and predominantly catecholaminergic (∼54%). Photostimulation of ChR2-transfected RVLM neurons (473 nm, 20 Hz, 10 ms, ∼9 mW) increased BP (15 mmHg) and sympathetic nerve discharge (SND; 64%). Light pulses at 0.2–0.5 Hz evoked a large sympathetic nerve response (16 × baseline) followed by a silent period (1–2 s) during which another stimulus evoked a reduced response. Photostimulation activated most (75%) RVLM baroinhibited neurons sampled with 1/1 action potential entrainment to the light pulses and without accommodation during 20 Hz trains. RVLM neurons unaffected by either CO2 or BP were light-insensitive. Botzinger respiratory neurons were activated but their action potentials were not synchronized to the light pulses. Juxtacellular labelling of recorded neurons revealed that, of these three cell types, only the cardiovascular neurons expressed the transgene. In conclusion, ChR2 expression had no discernable effect on the putative vasomotor neurons at rest and was high enough to allow precise temporal control of their action potentials with light pulses. Photostimulation of RVLM neurons caused a sizable sympathoactivation and rise in blood pressure. These results provide the most direct evidence yet that the C1 neurons have a sympathoexcitatory function.
Shaul Druckmann - One of the best experts on this subject based on the ideXlab platform.
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targeted Photostimulation uncovers circuit motifs supporting short term memory
Nature Neuroscience, 2021Co-Authors: Kayvon Daie, Karel Svoboda, Shaul DruckmannAbstract:Short-term memory is associated with persistent neural activity that is maintained by positive feedback between neurons. To explore the neural circuit motifs that produce memory-related persistent activity, we measured coupling between functionally characterized motor cortex neurons in mice performing a memory-guided response task. Targeted two-photon Photostimulation of small (<10) groups of neurons produced sparse calcium responses in coupled neurons over approximately 100 μm. Neurons with similar task-related selectivity were preferentially coupled. Photostimulation of different groups of neurons modulated activity in different subpopulations of coupled neurons. Responses of stimulated and coupled neurons persisted for seconds, far outlasting the duration of the photostimuli. Photostimuli produced behavioral biases that were predictable based on the selectivity of the perturbed neuronal population, even though Photostimulation preceded the behavioral response by seconds. Our results suggest that memory-related neural circuits contain intercalated, recurrently connected modules, which can independently maintain selective persistent activity. Two-photon Photostimulation and imaging of a cortical short-term memory circuit reveal intercalated modules that can independently maintain memory. The modules are defined by connectivity between neurons with similar task-related tuning.
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targeted Photostimulation uncovers circuit motifs supporting short term memory
bioRxiv, 2019Co-Authors: Kayvon Daie, Karel Svoboda, Shaul DruckmannAbstract:Short-term memory is associated with persistent neural activity without sustained input, arising from the interactions between neurons with short time constants. A variety of neural circuit motifs could account for measured neural activity. A mechanistic understanding of the neural circuits supporting short-term memory requires probing network connectivity between functionally characterized neurons. We performed targeted Photostimulation of small (< 10) groups of neurons, while imaging the response of hundreds of other neurons, in anterior-lateral motor cortex (ALM) of mice performing a delayed response task. Mice were instructed with brief auditory stimuli to make directional movements (lick left or lick right), but only after a three second delay epoch. ALM contains neurons with delay epoch activity that is selective for left or right choices. Targeted Photostimulation of groups of neurons during the delay epoch allowed us to observe the functional organization of population activity and recurrent interactions underlying short-term memory. These experiments revealed strong coupling between neurons sharing similar selectivity. Brief Photostimulation of functionally related neurons produced changes in activity in sparse subpopulations of nearby neurons that persisted for several seconds following stimulus offset, far outlasting the duration of the perturbation. Photostimulation produced behavioral biases that were predictable based on the selectivity of the perturbed neuronal population. These results suggest that ALM contains multiple intercalated modules, consisting of recurrently coupled neurons, that can independently maintain persistent activity.
Karel Svoboda - One of the best experts on this subject based on the ideXlab platform.
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targeted Photostimulation uncovers circuit motifs supporting short term memory
Nature Neuroscience, 2021Co-Authors: Kayvon Daie, Karel Svoboda, Shaul DruckmannAbstract:Short-term memory is associated with persistent neural activity that is maintained by positive feedback between neurons. To explore the neural circuit motifs that produce memory-related persistent activity, we measured coupling between functionally characterized motor cortex neurons in mice performing a memory-guided response task. Targeted two-photon Photostimulation of small (<10) groups of neurons produced sparse calcium responses in coupled neurons over approximately 100 μm. Neurons with similar task-related selectivity were preferentially coupled. Photostimulation of different groups of neurons modulated activity in different subpopulations of coupled neurons. Responses of stimulated and coupled neurons persisted for seconds, far outlasting the duration of the photostimuli. Photostimuli produced behavioral biases that were predictable based on the selectivity of the perturbed neuronal population, even though Photostimulation preceded the behavioral response by seconds. Our results suggest that memory-related neural circuits contain intercalated, recurrently connected modules, which can independently maintain selective persistent activity. Two-photon Photostimulation and imaging of a cortical short-term memory circuit reveal intercalated modules that can independently maintain memory. The modules are defined by connectivity between neurons with similar task-related tuning.
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targeted Photostimulation uncovers circuit motifs supporting short term memory
bioRxiv, 2019Co-Authors: Kayvon Daie, Karel Svoboda, Shaul DruckmannAbstract:Short-term memory is associated with persistent neural activity without sustained input, arising from the interactions between neurons with short time constants. A variety of neural circuit motifs could account for measured neural activity. A mechanistic understanding of the neural circuits supporting short-term memory requires probing network connectivity between functionally characterized neurons. We performed targeted Photostimulation of small (< 10) groups of neurons, while imaging the response of hundreds of other neurons, in anterior-lateral motor cortex (ALM) of mice performing a delayed response task. Mice were instructed with brief auditory stimuli to make directional movements (lick left or lick right), but only after a three second delay epoch. ALM contains neurons with delay epoch activity that is selective for left or right choices. Targeted Photostimulation of groups of neurons during the delay epoch allowed us to observe the functional organization of population activity and recurrent interactions underlying short-term memory. These experiments revealed strong coupling between neurons sharing similar selectivity. Brief Photostimulation of functionally related neurons produced changes in activity in sparse subpopulations of nearby neurons that persisted for several seconds following stimulus offset, far outlasting the duration of the perturbation. Photostimulation produced behavioral biases that were predictable based on the selectivity of the perturbed neuronal population. These results suggest that ALM contains multiple intercalated modules, consisting of recurrently coupled neurons, that can independently maintain persistent activity.
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dual channel circuit mapping reveals sensorimotor convergence in the primary motor cortex
The Journal of Neuroscience, 2015Co-Authors: Caiying Guo, Ya M Hooks, Karel SvobodaAbstract:Cortical cells integrate synaptic input from multiple sources, but how these different inputs are distributed across individual neurons is largely unknown. Differences in input might account for diverse responses in neighboring neurons during behavior. We present a strategy for comparing the strengths of multiple types of input onto the same neuron. We developed methods for independent dual-channel Photostimulation of synaptic inputs using ChR2 together with ReaChR, a red-shifted channelrhodopsin. We used dual-channel Photostimulation to probe convergence of sensory information in the mouse primary motor cortex. Input from somatosensory cortex and thalamus converges in individual neurons. Similarly, inputs from distinct somatotopic regions of the somatosensory cortex are integrated at the level of single motor cortex neurons. We next developed a ReaChR transgenic mouse under the control of both Flp- and Cre-recombinases that is an effective tool for circuit mapping. Our approach to dual-channel Photostimulation enables quantitative comparison of the strengths of multiple pathways across all length scales of the brain.
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Laser Scanning Photostimulation Mapping of Thalamocortical Projections
2013Co-Authors: Ingrid Bureau, Francisca Von Saint Paul, Karel SvobodaAbstract:(A) Montage of a thalamocortical slice. (B) Layout of the experiment. Excitatory neurons were recorded in the barrel cortex while thalamic neurons were photostimulated by glutamate uncaging. The map pattern (red grid) was centered on the POm/VPM boundary. Dashed lines indicate a barrel-column. (C–E) Examples of synaptic input maps for individual L4 (C), L5B (D), and L5A (E) neurons. The pixel values encode the mean amplitudes of EPSCs measured within 100 ms after the stimulus (see [G]). The dashed lines indicate the borders between POm, VPM, and the ventral posterolateral nucleus (VPL) (see [B]). Letters mark a pair of pixels corresponding to the traces shown in (G). (F) Map of standard deviations across trials for an individual cell (same cell as in [E]). (G) Examples of individual EPSCs. The responses were evoked by Photostimulation at the sites indicated by letters in (C–E) (two sites per arrow). Arrowheads indicate the timing of the stimulus; dashed lines indicate the averaging window used for analysis. (H) Percentage of cortical cells with thalamic input. The percentage was computed for cells that were within a lateral distance of 300 μm of cells that showed thalamic input in the brain slice.
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Channelrhodopsin-2-assisted circuit mapping of long-range callosal projections
Nature Neuroscience, 2007Co-Authors: Leopoldo Petreanu, Aleksander Sobczyk, Daniel Huber, Karel SvobodaAbstract:The functions of cortical areas depend on their inputs and outputs, but the detailed circuits made by long-range projections are unknown. We show that the light-gated channel channelrhodopsin-2 (ChR2) is delivered to axons in pyramidal neurons in vivo. In brain slices from ChR2-expressing mice, Photostimulation of ChR2-positive axons can be transduced reliably into single action potentials. Combining Photostimulation with whole-cell recordings of synaptic currents makes it possible to map circuits between presynaptic neurons, defined by ChR2 expression, and postsynaptic neurons, defined by targeted patching. We applied this technique, ChR2-assisted circuit mapping (CRACM), to map long-range callosal projections from layer (L) 2/3 of the somatosensory cortex. L2/3 axons connect with neurons in L5, L2/3 and L6, but not L4, in both ipsilateral and contralateral cortex. In both hemispheres the L2/3-to-L5 projection is stronger than the L2/3-to-L2/3 projection. Our results suggest that laminar specificity may be identical for local and long-range cortical projections.
Stephen B G Abbott - One of the best experts on this subject based on the ideXlab platform.
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vesicular glutamate transporter 2 is required for the respiratory and parasympathetic activation produced by optogenetic stimulation of catecholaminergic neurons in the rostral ventrolateral medulla of mice in vivo
European Journal of Neuroscience, 2014Co-Authors: Stephen B G Abbott, Patrice G Guyenet, Benjamin B Holloway, Kenneth E ViarAbstract:Catecholaminergic neurons of the rostral ventrolateral medulla (RVLM-CA neurons; C1 neurons) contribute to the sympathetic, parasympathetic and neuroendocrine responses elicited by physical stressors such as hypotension, hypoxia, hypoglycemia, and infection. Most RVLM-CA neurons express vesicular glutamate transporter (VGLUT)2, and may use glutamate as a ionotropic transmitter, but the importance of this mode of transmission in vivo is uncertain. To address this question, we genetically deleted VGLUT2 from dopamine-β-hydroxylase-expressing neurons in mice [DβH(Cre/0) ;VGLUT2(flox/flox) mice (cKO mice)]. We compared the in vivo effects of selectively stimulating RVLM-CA neurons in cKO vs. control mice (DβH(Cre/0) ), using channelrhodopsin-2 (ChR2-mCherry) optogenetics. ChR2-mCherry was expressed by similar numbers of rostral ventrolateral medulla (RVLM) neurons in each strain (~400 neurons), with identical selectivity for catecholaminergic neurons (90-99% colocalisation with tyrosine hydroxylase). RVLM-CA neurons had similar morphology and axonal projections in DβH(Cre/0) and cKO mice. Under urethane anesthesia, Photostimulation produced a similar pattern of activation of presumptive ChR2-positive RVLM-CA neurons in DβH(Cre/0) and cKO mice. Photostimulation in conscious mice produced frequency-dependent respiratory activation in DβH(Cre/0) mice but no effect in cKO mice. Similarly, Photostimulation under urethane anesthesia strongly activated efferent vagal nerve activity in DβH(Cre/0) mice only. Vagal responses were unaffected by α1 -adrenoreceptor blockade. In conclusion, two responses evoked by RVLM-CA neuron stimulation in vivo require the expression of VGLUT2 by these neurons, suggesting that the acute autonomic responses driven by RVLM-CA neurons are mediated by glutamate.
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selective optogenetic activation of rostral ventrolateral medullary catecholaminergic neurons produces cardiorespiratory stimulation in conscious mice
The Journal of Neuroscience, 2013Co-Authors: Stephen B G Abbott, Ruth L. Stornetta, Seth D Depuy, Thanh Nguyen, Melissa B Coates, Patrice G GuyenetAbstract:Activation of rostral ventrolateral medullary catecholaminergic (RVLM-CA) neurons e.g., by hypoxia is thought to increase sympathetic outflow thereby raising blood pressure (BP). Here we test whether these neurons also regulate breathing and cardiovascular variables other than BP. Selective expression of ChR2-mCherry by RVLM-CA neurons was achieved by injecting Cre-dependent vector AAV2-EF1α-DIO-ChR2-mCherry unilaterally into the brainstem of dopamine-β-hydroxylaseCre/0 mice. Photostimulation of RVLM-CA neurons increased breathing in anesthetized and conscious mice. In conscious mice, Photostimulation primarily increased breathing frequency and this effect was fully occluded by hypoxia (10% O2). In contrast, the effects of Photostimulation were largely unaffected by hypercapnia (3 and 6% CO2). The associated cardiovascular effects were complex (slight bradycardia and hypotension) and, using selective autonomic blockers, could be explained by coactivation of the sympathetic and cardiovagal outflows. ChR2-positive RVLM-CA neurons expressed VGLUT2 and their projections were mapped. Their complex cardiorespiratory effects are presumably mediated by their extensive projections to supraspinal sites such as the ventrolateral medulla, the dorsal vagal complex, the dorsolateral pons, and selected hypothalamic nuclei (dorsomedial, lateral, and paraventricular nuclei). In sum, selective optogenetic activation of RVLM-CA neurons in conscious mice revealed two important novel functions of these neurons, namely breathing stimulation and cardiovagal outflow control, effects that are attenuated or absent under anesthesia and are presumably mediated by the numerous supraspinal projections of these neurons. The results also suggest that RVLM-CA neurons may underlie some of the acute respiratory response elicited by carotid body stimulation but contribute little to the central respiratory chemoreflex.
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Photostimulation of channelrhodopsin 2 expressing ventrolateral medullary neurons increases sympathetic nerve activity and blood pressure in rats
The Journal of Physiology, 2009Co-Authors: Stephen B G Abbott, Ruth L. Stornetta, C Socolovsky, Gavin H West, Patrice G GuyenetAbstract:To explore the specific contribution of the C1 neurons to blood pressure (BP) control, we used an optogenetic approach to activate these cells in vivo. A lentivirus that expresses channelrhodopsin-2 (ChR2) under the control of the catecholaminergic neuron-preferring promoter PRSx8 was introduced into the rostral ventrolateral medulla (RVLM). After 2–3 weeks, ChR2 was largely confined to Phox2b-expressing neurons (89%). The ChR2-expressing neurons were non-GABAergic, non-glycinergic and predominantly catecholaminergic (∼54%). Photostimulation of ChR2-transfected RVLM neurons (473 nm, 20 Hz, 10 ms, ∼9 mW) increased BP (15 mmHg) and sympathetic nerve discharge (SND; 64%). Light pulses at 0.2–0.5 Hz evoked a large sympathetic nerve response (16 × baseline) followed by a silent period (1–2 s) during which another stimulus evoked a reduced response. Photostimulation activated most (75%) RVLM baroinhibited neurons sampled with 1/1 action potential entrainment to the light pulses and without accommodation during 20 Hz trains. RVLM neurons unaffected by either CO2 or BP were light-insensitive. Botzinger respiratory neurons were activated but their action potentials were not synchronized to the light pulses. Juxtacellular labelling of recorded neurons revealed that, of these three cell types, only the cardiovascular neurons expressed the transgene. In conclusion, ChR2 expression had no discernable effect on the putative vasomotor neurons at rest and was high enough to allow precise temporal control of their action potentials with light pulses. Photostimulation of RVLM neurons caused a sizable sympathoactivation and rise in blood pressure. These results provide the most direct evidence yet that the C1 neurons have a sympathoexcitatory function.
Randy J. Nelson - One of the best experts on this subject based on the ideXlab platform.
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photoperiod induced testicular apoptosis in european starlings sturnus vulgaris
Biology of Reproduction, 2001Co-Authors: Kelly A Young, Gregory F Ball, Randy J. NelsonAbstract:To determine the extent to which testicular regression involves apoptotic cell death, photosensitive adult starlings were photostimulated for up to 9 wk by exposure to long-day (18 h of light) photoperiods. Apoptotic activity in recrudescing and regressing testes was assessed by in situ TUNEL labeling. Absolute testis mass in male starlings increased after 2 wk of Photostimulation and subsequently decreased with continued longday exposure. Seminiferous tubule diameter also increased after 1‐3 wk of Photostimulation, then decreased as photorefractoriness developed. Testosterone concentrations increased significantly by Week 2 of Photostimulation and declined with further light exposure. TUNEL labeling was significantly elevated in germ cells with 4 wk of Photostimulation. An approximate 7fold increase in the degree of apoptotic cell death was observed over the course of gonadal regression. Incidences of TUNEL labeling in somatic Sertoli cells also increased. Light and electron microscopy examination confirmed that these somatic cells displayed morphological characteristics of apoptotic death. In rodents, Sertoli cells have not been previously reported to die during gonadal regression. These results suggest that seasonal testicular regression in European starlings is mediated by apoptosis. apoptosis, seasonal reproduction, Sertoli cells, steroid hormones, testis
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photoperiod induced testicular apoptosis in european starlings sturnus vulgaris
Biology of Reproduction, 2001Co-Authors: Kelly A Young, Gregory F Ball, Randy J. NelsonAbstract:To determine the extent to which testicular regression involves apoptotic cell death, photosensitive adult starlings were photostimulated for up to 9 wk by exposure to long-day (18 h of light) photoperiods. Apoptotic activity in recrudescing and regressing testes was assessed by in situ TUNEL labeling. Absolute testis mass in male starlings increased after 2 wk of Photostimulation and subsequently decreased with continued long-day exposure. Seminiferous tubule diameter also increased after 1-3 wk of Photostimulation, then decreased as photorefractoriness developed. Testosterone concentrations increased significantly by Week 2 of Photostimulation and declined with further light exposure. TUNEL labeling was significantly elevated in germ cells with 4 wk of Photostimulation. An approximate 7-fold increase in the degree of apoptotic cell death was observed over the course of gonadal regression. Incidences of TUNEL labeling in somatic Sertoli cells also increased. Light and electron microscopy examination confirmed that these somatic cells displayed morphological characteristics of apoptotic death. In rodents, Sertoli cells have not been previously reported to die during gonadal regression. These results suggest that seasonal testicular regression in European starlings is mediated by apoptosis.