Cholinergic stimulation of phosphoinositide hydrolysis in the rat pineal gland.

Carbachol induced a dose-dependent accumulation of inositol monophosphates in the Wistar rat pineal gland. The relative potency of muscarinic antagonists (atropine greater than pirenzepine much greater than gallamine) in blocking this response suggests the involvement of muscarinic M1 receptors. Following bilateral superior cervical ganglionectomy, the carbachol-induced phosphoinositide response was similar to that seen in sham-operated controls, while adrenergic response was enhanced by 50%. The results indicate that the pineal has functional muscarinic receptors which are not affected by removal of the sympathetic innervation to the gland.