Muscarinic Binding Sites in Developing Normal and Mutant Mouse Cerebellum

The development of [ 3 H]quinuclidinylbenzilate ([ 3 H]QNB) binding to cerebellar homogenates of weaver (wv), reeler (rl), staggerer (sg) and jimpy (jp) mutants, in addition to their normal counterparts, was observed. The maximum increase in binding in normal mice occurred postnatally, during the period 5 to 15 days. [ 3 H]QNB binding was significantly reduced in wv, rl and sg mutants (40–50% of control) but was not so markedly affected in jp (80–100% control). Binding was saturable with an apparent K d of 0.15 nM and the affinity of [ 3 H]QNB for its receptor was not affected during the course of development or as a result of the mutation. The presence of significant numbers of binding sites in the agranular mutants suggests that QNB binding sites are localised on cells other than the granule neurons. The possibility of synaptic reorganisation is also discussed.