Pineal hyperactivity in spontaneously hypertensive rats: muscarinic regulation of indole metabolism.
 1.
 Choline acetyltransferase activity and [3H]quinuclidinyl benzylate-binding sites were detected in the pineal gland of normotensive Wistar-Kyoto rats and of spontaneously hypertensive rats.
 2.
 In vitro, muscarinic activation by pilocarpine increased the pineal metabolic production of hydroxyindole derivatives up to 5-hydroxytryptamine and produced a less marked stimulation of melatonin biosynthesis.
 3.
 Electrical field stimulation of pineal gland slices caused similar metabolic effects.
 4.
 Muscarinic blockade with atropine inhibited the effects on hydroxyindole metabolism.
 5.
 [3H]Quinuclidinyl benzylate-binding sites, indicative of muscarinic receptors, were more numerous, and basal 5-hydroxytryptamine and melatonin levels were higher, in the pineal gland of spontaneously hypertensive rats compared with Wistar-Kyoto rats.
 6.
 The atropine-sensitive metabolic effects of pilocarpine and electrical field stimulation on the pineal gland were increased in spontaneously hypertensive rats compared with Wistar-Kyoto rats.
