Area-dependent CNS membrane response of muscarinic receptor to convulsant 3-mercaptopropionic acid.

It has already been shown that the administration of convulsant 3-mercaptopropionic acid at 150 mg/kg enhances binding affinity of muscarinic antagonist [3H]quinuclidinyl benzilate ([3H]QNB) to certain rat CNS membranes without affecting site number. Herein we employed a 100 mg/kg dose and tested [3H]QNB binding to cerebellar, hippocampal, and striatal membranes obtained from rats killed at preseizure, seizure, and postseizure stages. In cerebellum, binding increased 24, 65, and 19% a1 preseizure, seizure, and postseizure stages, respectively; in hippocampus, values were 12 and 20% higher at pre- and seizure stages, but failed to differ from controls at postseizure; in striatum, increases of 10 and 18% were recorded at seizure and postseizure, with no changes at preseizure. Neither a subconvulsant dose (20 mg/kg) nor in vitro drug addition had any effect on binding. Results indicate a differential response to the convulsant, with reversible changes in cerebellum and hippocampus, and a delayed response in striatum, supporting the concept of area-dependent neuronal plasticity.