Muscarinic m2 receptors in cerebellar granule cell cultures from rat: mechanism of short-term desensitization

Cerebellar granule cell cultures of rat express only muscarinic m2 and m3 receptor subtypes and exhibit the pharmacological profile of muscannic m2 receptors that couple to guanine nucleo-tide binding proteins to inhibit adenylyl cyclase. In vivo pretreat-ment with muscannic agonists desensitizes the muscarinic m2 receptor with 50 % complete desensitization within 15 to 20 mm. After a 1-hr pretreatment with a maximal concentration of car-bachol (short-term desensitization), m2 receptor responsiveness reappeared after a 1-hr treatment of cultures with atropmne. However, after a 6-hr pretreatment with carbachol (long-term desensitization), m2 receptor responsiveness did not reappear after 1-hr treatment with atropine. Short-term desensitization was homologous for the m2 receptor because treatment of cultures with carbachol did not alter y-aminobutyric acidB recep