Electrophysiological investigations on the central innervation of the rat and guinea-pig pineal gland.

The possible influence of central nervous structures on the electrical activity of single pineal cells was investigated in rat and guinea-pig. In the rat electrical stimulation of the hippocampal formation elicited both single cell responses with different latencies and mostly long-term excitations in single pineal cells, while stimulation of the habenular nuclei caused clear orthodromical responses with different latencies, alterations in the rate of spontaneous electrical activity and evoked discharges of "silent" units. In the guinea-pig electrical stimulation of the paraventricular nucleus influenced predominantly cells in the deeper layers of the posterior part of the pineal gland. Electrical stimulation of both the superior and inferior colliculi elicited field potentials with a constant latency, indicating a functional relationship between the corpora quadrigemina and the pineal organ.