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https://hdl.handle.net/2440/6007
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Type: | Journal article |
Title: | Tonic activation of presynaptic GABA (B) receptors in the opener neuromuscular junction of crayfish |
Author: | Parnas, I. Rashkovan, G. Ong, J. Kerr, D. |
Citation: | Journal of Neurophysiology, 1999; 81(3):1184-1191 |
Publisher: | American Physiological Society |
Issue Date: | 1999 |
ISSN: | 0022-3077 1522-1598 |
Statement of Responsibility: | Itzchak Parnas, Grigory Rashkovan, Jennifer Ong and David I. B. Kerr |
Abstract: | Release of excitatory transmitter from boutons on crayfish nerve terminals was inhibited by (R,S)-baclofen, an agonist at GABAB receptors. Baclofen had no postsynaptic actions as it reduced quantal content without affecting quantal amplitude. The effect of baclofen increased with concentration producing 18% inhibition at 10 microM; EC50, 50% inhibition at 30 microM; maximal inhibition, 85% at 100 microM and higher. There was no desensitization, even with 200 or 320 microM baclofen. Phaclofen, an antagonist at GABAB receptors, competitively antagonized the inhibitory action of baclofen (KD = 50 microM, equivalent to a pA2 = 4.3 +/- 0.1). Phaclofen on its own at concentrations below 200 microM had no effect on release, whereas at 200 microM phaclofen itself increased the control level of release by 60%, as did 2-hydroxy-saclofen (200 microM), another antagonist at GABAB receptors. This increase was evidently due to antagonism of a persistent level of GABA in the synaptic cleft, since the effect was abolished by destruction of the presynaptic inhibitory fiber, using intra-axonal pronase. We conclude that presynaptic GABAB receptors, with a pharmacological profile similar to that of mammalian GABAB receptors, are involved in the control of transmitter release at the crayfish neuromuscular junction. |
Keywords: | Axons Neuromuscular Junction Animals Astacoidea Baclofen Pronase Receptors, GABA-B Receptors, Presynaptic GABA Agonists GABA Antagonists Patch-Clamp Techniques Logistic Models Neural Inhibition Quantum Theory |
Rights: | © 1999 the American Physiological Society |
DOI: | 10.1152/jn.1999.81.3.1184 |
Published version: | http://jn.physiology.org.proxy.library.adelaide.edu.au/content/81/3/1184.full |
Appears in Collections: | Anaesthesia and Intensive Care publications Aurora harvest 5 |
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