Persistence of Photic Evoked Responses in Pineal Gland After Its Pedunculotomy Superior Cervical Ganglionectomy

Abstract

The present study analyzes the participation of pineal stalk and superior cervical ganglia (SCG) in the conduction of photic evoked potentials (PEP) to the pineal body (PB) in unanesthetized freely moving rats implanted with semimicroelectrodes. The PEPs were recorded in PB, lateral hypothalamus (LH), and habenular complex (HC). In some rats the pineal stalk was lesioned either by electrolysis or by surgical means. Recordings were begun 3 days after electrode implantation; three recording sessions were performed before and after extirpation of SCG or lesion of pineal stalk. The PEPs recorded in LH and HC were characterized by 3 components (positive: PNP). The average latency of the first wave was 35.3 .+-. 1.7 and 38.8 .+-. 1.6 ms for LH and HC, respectively. The peaks of PEPs in PB showed different polarity (NPN), and the first component had a latency of 36.1 .+-. 1.2 ms. The PEPs persisted in all three structures after extirpation of SCG and after electrolytic lesion or transection of the pineal stalk. These results show that the PEPs recorded in PB are not generated in this structure, since they persist after interrupting its connections with the rest of the central nervous system; this suggests that PEPs could be the result of electrotonic transmission from neighboring structures.