The effects of mecholyl and atropine on the muscarinic receptors in rat small intestine after long-term atropine administration in vivo.
Rats were given atropine (AT) in 10 mg/kg doses daily during 14, 28 or 64 days. Another group of rats had AT withdrawn for 7 days after 64 days of its daily administration. Then the affinity of beta-methylacetylcholine (Mecholyl - MECH) and pA2AT for the muscarinic receptors was determined in the isolated small intestine by the method of Ariëns. No changes were observed in the pD2 value. The pA2 index increased in the rats receiving AT during 64 days and in those after AT withdrawal for 7 days. The results suggest a stronger effect of AT action after its long-term administration and withdrawal which may be due to its higher affinity to the receptors, as demonstrated, and also to an increase in the number of receptor sites, which is likely possibility.
D000818:Animals; D001285:Atropine / Q000008:administration & dosage* / Q000494:pharmacology; D005260:Female; D007421:Intestine, Small / Q000187:drug effects*; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000187:drug effects*; D013997:Time Factors
D008688:Methacholine Compounds; D011976:Receptors, Muscarinic; D016210:Methacholine Chloride; D001285:Atropine