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Joan N Abbott - One of the best experts on this subject based on the ideXlab platform.

  • an electrophysiological method for measuring the Potassium Permeability of the nerve perineurium
    Brain Research, 1997
    Co-Authors: Joan N Abbott, Kevin J Ward, Faruhana Abdullah, Gillian Mitchell, Christopher I H Smith
    Abstract:

    Abstract An electrophysiological method is described for measuring the Potassium Permeability ( P K ) of the perineurium of the sciatic nerve of the frog. The method is based on the principle of grease-gap recording, in which an insulating compartment separates two surface recording electrodes. The sciatic nerves of frogs Rana temporaria and R. pipiens were isolated and mounted across a five compartment chamber, with Vaseline grease seals on the partitions between compartments. Compartments #1, #2 and #5 contained frog Ringer solution, #4 was filled with Vaseline and formed the grease gap, and #3 was the test compartment in which solutions could be changed. The nerve was stimulated via platinum electrodes in compartments #1 and #2, and DC potentials and compound action potentials (CAP) were recorded between Ag/AgCl electrodes connected through Ringer-agar bridges to compartments #3 and #5. In nerves with undamaged perineurium, changing from normal Ringer to high [K + ] Ringer (100 mM, KCl replacing NaCl) for 2 min caused negligible change in DC potential or CAP, indicating that raised [K + ] was not reaching the axon surface, and hence that the perineurium was exerting a diffusional restriction on K + entry. In nerves damaged by stretching or drying, K + pulses caused a depolarising change in DC potential (ΔDC), and corresponding decline in CAP amplitude, consistent with a leaky perineurium allowing K + entry and axonal depolarisation. Ringer made hypertonic by the addition of 2.5 M sucrose or 5 M NaCl caused increased perineurial Permeability to K + . The method was calibrated by measuring the ΔDC in response to raised [K + ] in the range 5–100 mM [K + ] in desheathed nerves; from this calibration curve relating ΔDC to endoneurial [K + ] it was possible to calculate the change in endoneurial [K + ] occurring in intact preparations. The calculations showed that the undamaged perineurium had a P K of −7 cm·s −1 , similar to the value calculated for in situ nerves using radioisotopic techniques, but less than the value reported for isolated perineurial cylinders. The method gives real-time information on the K + Permeability of the nerve perineurium and its modulation by experimental treatments.

  • effects of the bile salt sodium deoxycholate protamine and inflammatory mediators on the Potassium Permeability of the frog nerve perineurium
    Brain Research, 1997
    Co-Authors: B A Todd, E M Sedgwick, Joan N Abbott
    Abstract:

    Abstract An electrophysiological method was used to measure the Potassium Permeability ( P K ) of the perineurium of the sciatic nerve of frogs Rana temporaria and R. pipiens . Isolated but intact nerves were mounted in a grease-gap chamber, and compound action potential and DC potential monitored. Change in the DC potential (ΔDC) in response to challenge with 100 mM [K + ] Ringer was used to assess the K + Permeability of the perineurium, since change in DC potential under these conditions reflected changes in the axonal resting potential. The Permeability of the perineurium was calculated from the published calibration curve relating ΔDC to bathing [K + ] in desheathed nerves of Abbott et al. (1997). In the control condition, P K was −6 cm·s −1 . The bile salt sodium deoxycholate (DOC, 1–4 mM) caused a dose-dependent increase in P K , which reached a maximum of 1.7×10 −5 cm·s −1 after 2-min exposure to 4 mM DOC, but access of K + to the endoneurial compartment was more restricted after DOC than after desheathing. Protamine phosphate (1 mM) and protamine sulphate (0.1–5 mg/ml equals 0.125–6.25 mM) had no effect on P K . Neither histamine (0.4–40 mg/ml), bradykinin (0.1–5 mg/ml) nor serotonin (5-hydroxytryptamine, 0.1–5 mg/ml) affected P K . The frog nerve perineurium appears to be relatively insensitive to chemical agents and inflammatory mediators, in contrast to the endothelial cells forming the endoneurial blood–nerve barrier and the blood–brain barrier.

B A Todd - One of the best experts on this subject based on the ideXlab platform.

  • effects of the bile salt sodium deoxycholate protamine and inflammatory mediators on the Potassium Permeability of the frog nerve perineurium
    Brain Research, 1997
    Co-Authors: B A Todd, E M Sedgwick, Joan N Abbott
    Abstract:

    Abstract An electrophysiological method was used to measure the Potassium Permeability ( P K ) of the perineurium of the sciatic nerve of frogs Rana temporaria and R. pipiens . Isolated but intact nerves were mounted in a grease-gap chamber, and compound action potential and DC potential monitored. Change in the DC potential (ΔDC) in response to challenge with 100 mM [K + ] Ringer was used to assess the K + Permeability of the perineurium, since change in DC potential under these conditions reflected changes in the axonal resting potential. The Permeability of the perineurium was calculated from the published calibration curve relating ΔDC to bathing [K + ] in desheathed nerves of Abbott et al. (1997). In the control condition, P K was −6 cm·s −1 . The bile salt sodium deoxycholate (DOC, 1–4 mM) caused a dose-dependent increase in P K , which reached a maximum of 1.7×10 −5 cm·s −1 after 2-min exposure to 4 mM DOC, but access of K + to the endoneurial compartment was more restricted after DOC than after desheathing. Protamine phosphate (1 mM) and protamine sulphate (0.1–5 mg/ml equals 0.125–6.25 mM) had no effect on P K . Neither histamine (0.4–40 mg/ml), bradykinin (0.1–5 mg/ml) nor serotonin (5-hydroxytryptamine, 0.1–5 mg/ml) affected P K . The frog nerve perineurium appears to be relatively insensitive to chemical agents and inflammatory mediators, in contrast to the endothelial cells forming the endoneurial blood–nerve barrier and the blood–brain barrier.

  • Effects of the bile salt sodium deoxycholate, protamine, and inflammatory mediators on the Potassium Permeability of the frog nerve perineurium.
    Brain research, 1997
    Co-Authors: B A Todd, E M Sedgwick, N Joan Abbott
    Abstract:

    An electrophysiological method was used to measure the Potassium Permeability (PK) of the perineurium of the sciatic nerve of frogs Rana temporaria and R. pipiens. Isolated but intact nerves were mounted in a grease-gap chamber, and compound action potential and DC potential monitored. Change in the DC potential (delta DC) in response to challenge with 100 mM [K+] Ringer was used to assess the K+ Permeability of the perineurium, since change in DC potential under these conditions reflected changes in the axonal resting potential. The Permeability of the perineurium was calculated from the published calibration curve relating delta DC to bathing [K+] in desheathed nerves of Abbott et al. (1997). In the control condition, PK was < 1.1 x 10(-6) cm.s-1. The bile salt sodium deoxycholate (DOC, 1-4 mM) caused a dose-dependent increase in PK, which reached a maximum of 1.7 x 10(-5) cm.s-1 after 2-min exposure to 4 mM DOC, but access of K+ to the endoneurial compartment was more restricted after DOC than after desheathing. Protamine phosphate (1 mM) and protamine sulphate (0.1-5 mg/ml equals 0.125-6.25 mM) had no effect on PK. Neither histamine (0.4-40 mg/ml), bradykinin (0.1-5 mg/ml) nor serotonin (5-hydroxytryptamine, 0.1-5 mg/ml) affected PK. The frog nerve perineurium appears to be relatively insensitive to chemical agents and inflammatory mediators, in contrast to the endothelial cells forming the endoneurial blood-nerve barrier and the blood-brain barrier.

S M Wilson - One of the best experts on this subject based on the ideXlab platform.

H Y Elder - One of the best experts on this subject based on the ideXlab platform.

E M Sedgwick - One of the best experts on this subject based on the ideXlab platform.

  • effects of the bile salt sodium deoxycholate protamine and inflammatory mediators on the Potassium Permeability of the frog nerve perineurium
    Brain Research, 1997
    Co-Authors: B A Todd, E M Sedgwick, Joan N Abbott
    Abstract:

    Abstract An electrophysiological method was used to measure the Potassium Permeability ( P K ) of the perineurium of the sciatic nerve of frogs Rana temporaria and R. pipiens . Isolated but intact nerves were mounted in a grease-gap chamber, and compound action potential and DC potential monitored. Change in the DC potential (ΔDC) in response to challenge with 100 mM [K + ] Ringer was used to assess the K + Permeability of the perineurium, since change in DC potential under these conditions reflected changes in the axonal resting potential. The Permeability of the perineurium was calculated from the published calibration curve relating ΔDC to bathing [K + ] in desheathed nerves of Abbott et al. (1997). In the control condition, P K was −6 cm·s −1 . The bile salt sodium deoxycholate (DOC, 1–4 mM) caused a dose-dependent increase in P K , which reached a maximum of 1.7×10 −5 cm·s −1 after 2-min exposure to 4 mM DOC, but access of K + to the endoneurial compartment was more restricted after DOC than after desheathing. Protamine phosphate (1 mM) and protamine sulphate (0.1–5 mg/ml equals 0.125–6.25 mM) had no effect on P K . Neither histamine (0.4–40 mg/ml), bradykinin (0.1–5 mg/ml) nor serotonin (5-hydroxytryptamine, 0.1–5 mg/ml) affected P K . The frog nerve perineurium appears to be relatively insensitive to chemical agents and inflammatory mediators, in contrast to the endothelial cells forming the endoneurial blood–nerve barrier and the blood–brain barrier.

  • Effects of the bile salt sodium deoxycholate, protamine, and inflammatory mediators on the Potassium Permeability of the frog nerve perineurium.
    Brain research, 1997
    Co-Authors: B A Todd, E M Sedgwick, N Joan Abbott
    Abstract:

    An electrophysiological method was used to measure the Potassium Permeability (PK) of the perineurium of the sciatic nerve of frogs Rana temporaria and R. pipiens. Isolated but intact nerves were mounted in a grease-gap chamber, and compound action potential and DC potential monitored. Change in the DC potential (delta DC) in response to challenge with 100 mM [K+] Ringer was used to assess the K+ Permeability of the perineurium, since change in DC potential under these conditions reflected changes in the axonal resting potential. The Permeability of the perineurium was calculated from the published calibration curve relating delta DC to bathing [K+] in desheathed nerves of Abbott et al. (1997). In the control condition, PK was < 1.1 x 10(-6) cm.s-1. The bile salt sodium deoxycholate (DOC, 1-4 mM) caused a dose-dependent increase in PK, which reached a maximum of 1.7 x 10(-5) cm.s-1 after 2-min exposure to 4 mM DOC, but access of K+ to the endoneurial compartment was more restricted after DOC than after desheathing. Protamine phosphate (1 mM) and protamine sulphate (0.1-5 mg/ml equals 0.125-6.25 mM) had no effect on PK. Neither histamine (0.4-40 mg/ml), bradykinin (0.1-5 mg/ml) nor serotonin (5-hydroxytryptamine, 0.1-5 mg/ml) affected PK. The frog nerve perineurium appears to be relatively insensitive to chemical agents and inflammatory mediators, in contrast to the endothelial cells forming the endoneurial blood-nerve barrier and the blood-brain barrier.