Neural control of the pineal gland.

The rhythm in melatonin production by the mammalian pineal gland is generated by the circadian timing system. The components of that system which mediate the function are: (1) visual projections through the retinohypothalamic tract to the circadian pacemaker, the suprachiasmatic nucleus (SCN) of the hypothalamus; (2) the SCN which generates a circadian signal transmitted by SCN projections to the parvocellular autonomic component of the paraventricular nucleus; (3) paraventricular nucleus projections to the upper thoracic intermediolateral cell column; (4) preganglionic sympathetic fibers to the superior cervical ganglion; (5) postganglionic sympathetic fibers from the superior cervical ganglion to the pineal.