A picrotoxin-resistant GABA-gated chloride channel receptor subtype in the cockroach central nervous system

✍ Scribed by Bernard Hue

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 144 KB
• Volume: 37
• Category: Article
• ISSN: 0739-4462
• DOI: 10.1002/(sici)1520-6327(1998)37:3<231::aid-arch6>3.0.co;2-v

✦ Synopsis

g-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the cockroach central nervous system (CNS). Electrophysiological assays performed at cercal-afferent giant-interneuron (GI) synapses demonstrated that a biphasic (transient and stable phases) increase in membrane conductance, in response to long-lasting (30-s) neuropilar pressure microapplication of GABA, could be explained by the presence of two GABA-operated chloride channel receptor subtypes in the postsynaptic membrane. The low stable membrane conductance increase, representing less than 30% of the maximum response, reached during the early transient phase, was not desensitized quickly. It was reproduced by neuropilar pressure microapplication of cis-4-aminocrotonic acid (CACA) and was not, as the fast phase, antagonized by bath application of 10mM picrotoxin (PTX). Imidazole-4-acetic acid (I-4AA) and Zn 2+ did not modulate GABA and CACA-induced responses. Furthermore, a presynaptic target site for CACA, that modulates ACh release, was identified. Arch. Insect