Cholinergic nerves and receptors mediating contraction of the Graafian follicle.

Abstract

The theca externa of the bovine Craafian follicle contains numerous cholinergic nerves as demonstrated by cholinesterase histochemistry following specific inhibition of pseudochohinesterase. Nonadrenergic, probably cholinergic, axons were recognized in the electron microscope, where they could be distinguished from adrenergic nerves by incubation of the tissue with 5-hydroxydopamine, followed by fixation in potassium permanganate. Naked cholinergic terminals were located at a distance of 150 rim from smooth mucle-hike cells, i.e., a distance short enough to represent a functioning neuromuscular relationship. In addition, close contacts of 20-25 nm were sometimes seen between the two types of axon varicosities, indicating an axo-axonal interaction. The presence and characteristics of cholinergic receptors were studied in follicle strips on the basis of amine-induced contractile activity. Dose-response tests with acetyhchohine and carbamyichohine, alone or in the presence of atropine or hexamethonium, showed that the receptors were of the muscarinic type. The dissociation constants for the receptor-atropine complex (5.78 X 10� 0M in the case of acetylcholine and 7.75 X 10-10M for carbamylcholine) agreed with those reported for