Effects of intrahippocampal injections with methylscopolamine and neostigmine upon exploratory behaviour in two inbred mouse strains

After stereotaxically injecting male mice of the inbred strains C57BL/6 and DBA/2 with two doses of methylscopolamine or with two doses of neostigmine into the left dorsal hippocampus, the frequencies of the exploratory acts rearing, leaning, and sniffing carried out in a novel environment were recorded. At the lower dose-level, the anticholinergic drug tended to augment exploration in strain DBA and to reduce it in strain C57BL; the two doses of anticholinesterase diminished the scores in both genotypes. From these data it is concluded that the hippocampus contains a cholinergic mechanism which regulates exploratory behaviour and which is genetically controlled.