Effects of central and peripheral inputs on single pineal cell activity in the rat

The influences exerted by central and peripheral afferents to the pineal gland have been studied in rats anesthetized with urethane (1.2 g/kg, i.p.). Spontaneous action potentials arising from the pinealocytes were recorded by means of glass micropipettes filled with 3 M NaCl containing a dye. The electrical stimulation of suprachiasmatic nucleus, superior cervical ganglia, sciatic nerve and retina evoked discharge changes in a significant number of pineal cells. However, a relatively higher proportion of pinealocytes failed to respond to these afferents. Three types of responses could be observed. Inhibitions were the predominant response patterns to suprachiasmatic nucleus, superior cervical ganglia and sciatic nerve, while excitations were mainly elicited following photic stimulation, whereas the remaining evoked activity was biphasic responses, which were observed in a small number of cells after stimulation of suprachiasmatic nucleus, superior cervical ganglia and retina. These data confirm some previous neural inputs to the pineal and demonstrate the existence of a modulatory effect of the suprachiasmatic nucleus on pinealocyte discharges as well as somatosensory afferents to the gland by way of the sciatic nerve.