GABA receptors in rats with spontaneous generalized nonconvulsive epilepsy.

We have used the technique of autoradiography to study the binding of [3H]-GABA to GABAA and GABAB receptors in brains taken from rats that are genetically predisposed to petit mal type seizures. A range of concentrations of [3H]-GABA were employed to test the hypothesis that this predisposition was due to regional changes in either the number of GABAA or GABAB receptors, or affinity of GABA for these receptors. We found no statistical difference in the levels of radioligand binding to GABAA and GABAB receptors in animals susceptible to seizures compared to control animals in any of the brain regions studied over the concentration range 25 nM to 400 nM. This indicated that there was no change in either the Kd (affinity) or Bmax (receptor number) in these animals and that the pharmacological basis for the efficacy of GABAB antagonists in this seizure condition probably lies elsewhere.