• DOI:10.1098/rspb.1988.0006
• Corpus ID: 40290279

GABA receptors on the cell-body membrane of an identified insect motor neuron

@article{Sattelle1988GABARO,
  title={GABA receptors on the cell-body membrane of an identified insect motor neuron},
  author={David B. Sattelle and Robert D. Pinnock and Keith A. Wafford and Jonathan A. David},
  journal={Proceedings of the Royal Society of London. Series B. Biological Sciences},
  year={1988},
  volume={232},
  pages={443 - 456}
}

• D. Sattelle, R. Pinnock, +1 author J. A. David
• Published 22 January 1988
• Biology
• Proceedings of the Royal Society of London. Series B. Biological Sciences

The pharmacology of a γ-aminobutyric acid (GABA) receptor on the cell body of an identified motor neuron of the cockroach (Periplaneta americana) was investigated by current-clamp and voltage-clamp methods. Iontophoretic application of GABA increased membrane conductance to chloride ions, and prolonged application resulted in desensitization. Hill coefficients, determined from dose–response data, indicated that binding of at least two GABA molecules was required to activate the chloride channel. Differences between vertebrate GABAA receptors and insect neuronal GABA receptors were detected. For the GABA receptor of motor neuron Df, the following rank order of potency was observed: isoguvacine > muscimol ≽ GABA > 3-aminopropanesulphonic acid. The GABAB receptor agonist baclofen was inactive. Of the potent vertebrate GABA receptor antagonists (bicuculline, pitrazepin, RU5135 and picrotoxin), only picrotoxin (10–7 M) produced a potent, reversible block of the response to GABA of motor neuron Df. Both picrotoxinin and picrotin also blocked GABA-induced currents. Bicuculline hydrochloride (10–4 M) and bicuculline methiodide (10–4 M) were both ineffective when applied at resting membrane potential (–65 mV), although at hyper-polarized levels partial block of GABA-induced current was sometimes observed. Pitrazepin (10–4 M) caused a partial, voltage-independent block of GABA-induced current. The steroid derivative RU5135 was inactive at 10–5 M. In contrast to the potent competitive blockade of vertebrate GABAA receptors by bicuculline, pitrazepin and RU5135, none of the weak antagonism caused by these drugs on the insect GABA receptor was competitive. Flunitrazepam (10–6 M) potentiated GABA responses, providing evidence for a benzodiazepine site on an insect GABA-receptor–chloride-channel complex.