The effect of kainic acid on cholinergic enzymes and receptors in the amygdala complex of the rat.

Kainic acid (KA) was injected into the amygdala (AM) complex of the rat and its effect on the cholinergic enzymes, choline acetyltransferase (CAT) and acetylcholinesterase (AChE), and the binding of the muscarinic ligand, [3H]quinuclidinyl-benzilate (QNB) and the nicotinic ligand [125I]alpha-bungarotoxin (aBuTX) was investigated. Ka produced a loss of approximately 35% of the CAT activity in the AM. However, no effect on AChE activity was observed. A 30--50% decrease in the number of muscarinic and nicotinic receptor sites was also found. CAT, AChE and QNB binding in the AM contralateral to the injection did not change. However, the binding of aBuTX was found to decrease by approximately 40%. The present results suggest that the loss of CAT activity in the AM after treatment with KA is due to the destruction of cholinergic neurons within the AM. The lack of effect on AChE suggests that the major cholinergic input to the AM is not affected by KA. In addition, the loss of nicotinic receptors in the contralateral AM may reflect anterograde degeneration of terminals that have nicotinic sites located on them, or may be secondary to the elicitation of intense seizure activity evoked by the KA.