Journal of Neuroscience, Vol 2, 966-971, Copyright © 1982 by Society for Neuroscience
A comparative study of avermectin B1a and other modulators of the gamma- aminobutyric acid receptor . chloride ion channel complex
SS Pong, R DeHaven and CC Wang
The interactions of the anthelmintic agent avermectin B1a, the
anticonvulsant pentobarbital, and the anxiolytic tracazolate with the
gamma-aminobutyric acid (GABA) receptor . chloride ion channel complex in
rat brain membrane were studied. The results indicated that they all
potentiated ligand binding to the GABA and benzodiazepine receptors. The
stimulatory effects of avermectin B1a and pentobarbital, but not
tracazolate, on GABA receptor binding were inhibited by picrotoxin. The
effect of avermectin B1a was not additive with those of tracazolate and
pentobarbital. On the other hand, the stimulatory effect of GABA on
benzodiazepine binding was additive with those of avermectin B1a and
pentobarbital, but tracazolate and pentobarbital inhibited the effect of
avermectin B1a. In the receptor heat inactivation experiments, avermectin
B1a and clonazepam protected GABA receptors, whereas avermectin B1a and
GABA protected benzodiazepine receptors. Tracazolate, pentobarbital, and
picrotoxin did not protect either receptor. These findings suggest that the
recognition sites for the benzodiazepines, avermectin B1a, pentobarbital,
and picrotoxin are coupled allosterically to the GABA receptor . chloride
ion channel complex in different ways. The binding sites for avermectin B1a
may be partially shared by picrotoxin, pentobarbital, and tracazolate.