Selective, unilateral cortical infarction increases striatal muscarinic receptor binding: potential evidence for cortical modulation of intrastriatal cholinergic transmission

The effects of unilateral cortical infarction on subcortical (striatal) muscarinic receptors in rat brain were studied by means of in vitro receptor autoradiography using 3H]quinuclidinyl benzylate (3H]QNB) and 3H]pirenzepine. The cortical lesions could be produced without compromising subcortical structures. A dramatic (20 to 59 per cent) increase in striatal 3H]QNB binding was observed ipsilateral to the damaged cortex. The increase in binding was greatest in the caudate-putamen, but was also noted in the nucleus accumbens. 3H]Pirenzepine binding (labeling M1 receptors) was also increased but to a lesser degree, as was 3H]QNB binding in the presence of 100 nM (unlabeled) pirenzepine (an indirect means of labeling M2 receptors). The results show that unilateral cortical infarction results in an upregulation of striatal muscarinic receptors, and suggest that both the M1 and M2 subtypes contribute to this effect. These findings provide evidence for cortical modulation of intrastriatal cholinergic transmission.