alpha-Bungarotoxin binds to nicotinic cholinergic sites in the rat superior cervical ganglion. In physiological conditions the receptors are relatively independent upon preganglionic signals, as suggested by experiments of preganglionic denervation. In the present paper we show that the receptors are also uneffected by the afferent nerve fibres when preganglionic activation is induced by Reserpine administration or by cold exposure.