Electrophysiological study of evoked electrical activity in the pineal gland

Experiments were carried out in rats, unanesthetized, paralyzed and artificially respirated. The electrical activity from the pineal gland was recorded with bipolar electrodes. Field potentials were evoked in the pineal after peripheral (photic and sciatic nerve) and central (septal area, habenular complex and optic tract) stimulations. In general these potentials were biphasic with the exception of that evoked by the sciatic nerve and optic tract, which exhibited a complex response and a triphasic field potential, respectively. Bilateral sympathectomy did not modify the pineal evoked responses, but when the pineal stalk was sectioned all the responses were immediately suppressed after the lesion. On the basis of the above experimental data one could conclude that the bulk of the inputs to the pineal gland come through its stalk. At the present, the physiological significance of these findings is not clear.