6-OHDA BILATERAL LESIONS TO THE NUCLEUS SEPTI LATERALIS ATTENUATE VASOPRESSIN IMPROVEMENT OF RECALL IN RATS

Abstract

The investigation was aimed at investigating whether the dopaminergic projection arriving at the nucleus septi lateralis (NSL) is involved in the facilitatory effect of vasopressin (AVP) on memory retrieval. The bilateral 6-OHDA lesions to the NSL were made in 20 male Wistar rats before testing the intracerebroventricular (i.c.v.) AVP injection on recall in a passive avoidance situation. Eighteen additional rats served as sham-operated controls. Thirty minutes before surgery rats were pre-treated with an intraperitoneal injection of 25 mg kg−1of desmethylimipramine, an inhibitor of norepinephrine uptake. Sixteen lesioned and 16 sham-operated rats were included in the study. AVP (1 μg, i.c.v.) given 15 min before the retention testing significantly improved latencies both in lesioned and in sham-operated rats in comparison with the respective i.c.v. saline-injected animals. However, bilateral lesions to the NSL significantly diminished the facilitatory effect of AVP on recall. The insignificant decrease of spontaneous psychomotor activity in rats lesioned to the NSL was unlikely to interfere with the cognitive effect of AVP. These results suggest that dopaminergic projection to the NSL is involved in the facilitatory effect of AVP on the retrieval process in a passive avoidance situation.