Involvement of M1 and M2 muscarinic receptors of the basal forebrain in cholinergically mediated changes in the rat locomotion

1. Wistar rats were implanted with cannulae into the medial preoptic and anterior hypothalamic areas for intracerebral injections. 2. Unilateral intracerebral injections of carbachol (1 microgram) into a limited area of the basal forebrain decreased significantly both the distance travelled by the animals and time spent walking. 3. In addition to the decrease in locomotion, it was demonstrated for the first time that injections of carbachol also slow animal movement by significantly decreasing speed of forward progression. 4. All locomotor effects of carbachol were reversed by local pretreatment with atropine (1 microgram) but not by pirenzepine (2 micrograms) suggesting that these effects were mediated by M2 muscarinic receptors with minimal or no M1 receptor involvement.