Cortical serotonin receptor subtypes after lesion of ascending cholinergic neurones in rat.

Serotonin (5-HT) S1 and S2 receptors were studied in rat cortex after lesion of the ascending cholinergic systems by injection of ibotenic acid into the nucleus basalis. The lesions produced a large (56%) decrease in choline acetyltransferase activity with no change in markers of gamma-aminobutyric acid, dopamine and 5-HT containing neurones. Lesions of the ascending cholinergic neurones were accompanied by a loss of 5-HT S1 receptor binding sites with no change in S2 receptors. These results suggest that a proportion of S1 receptors may be associated with cholinergic terminals.