MUSCARINIC RECEPTORS IN RAT UTERUS

The aim of this study was to characterise the muscarinic receptor pres ent in the uterus of the virgin rat. Homogenate binding studies were u ndertaken using [H-3]quinuclidinyl benzilate as the radioligand and at ropine (10 mu M) to determine non-specific binding. [H-3]Quinuclidinyl benzilate binding was saturable with a K-d of 63 pM and a B-max of 3 fmol/mg protein. The pK(i) values obtained using antagonists with high affinity for differing muscarinic receptor subtypes were pirenzepine, 6.2; hexahydrosiladifenidol, 6.9; AF-DX 116 ihydro-6H-pyrido[2,3-b][1 ,4]benzodiazepine-6-one), 7.0; and himbacine, 7.8. These findings sugg est that muscarinic M(2) receptors are present in rat uterus.