BILATERAL TRANSECTIONS OF TEMPORO–ENTORHINAL CONNECTIONS ATTENUATE VASOPRESSIN IMPROVEMENT OF MEMORY IN RATS

Abstract

It has been found in our laboratory that the positive influence of vasopressin (AVP) on memory processes is mediated by excitatory amino acids, since it was abolished by NMDA receptor antagonists. The purpose of the present study was to investigate whether bilateral transections of glutamatergic temporo–entorhinal connections may have an influence on the facilitatory effect of AVP on retrieval process of a passive avoidance behaviour. The bilateral transections of temporo–entorhinal connections were made in male Wistar rats 10 days before testing of the influence of intracerebroventricular AVP (1 μg per rat) injection on memory, evaluated in a passive avoidance task. Although AVP significantly facilitated the retrieval process both in sham-operated and in lesioned groups of rats, bilateral disruption of temporo–entorhinal connections significantly attenuated the facilitatory effect of AVP on the retrieval process. Moreover, bilateral transections of temporo–entorhinal connections failed to affect motor activity, such as crossings of squares, without an influence on rearings and bar approaches evaluated in an open field test. These results may suggest that in the facilitatory effect of AVP on the retrieval process is involved a reciprocal glutamatergic connection between the lateral entorhinal cortex and the temporal cortex.