MUSCARINIC CHOLINERGIC RECEPTORS IN DORSAL-ROOT GANGLIA OF CHICK-EMBRYO - A RADIOLIGAND BINDING AND IMMUNOCYTOCHEMICAL STUDY

The presence and micro-anatomical localization of muscarinic cholinerg ic receptors were assessed in dorsal root ganglia of chick embryo duri ng development using radioligand binding and immunocytochemical techni ques, respectively. The non-selective muscarinic cholinergic receptor radioligand [H-3]quinuclidinyl benzilate was specifically bound to sec tions of chick dorsal root ganglia with a dissociation constant value (Kd) of 0.75+/-0.02 nM and a maximum density of binding sites (B-max) of 7.2+/-0.5 fmol/mg tissue. [H-3]Quinuclidinyl benzilate binding was partially sensitive to pirenzepine displacement. This suggests that mu scarinic cholinergic receptors expressed by dorsal root ganglia of chi ck embryo at least in part belong to the M(1) muscarinic receptor subt ype. Immunocytochemical analysis confirmed the presence of muscarinic receptors in the ganglia. These findings suggest that neurons of dorsa l root ganglia, which are known to express cholinergic markers such as choline acetyltransferase, acetylcholinesterase and high affinity cho line uptake, are also cholinoceptive.