Effects of neuroactive peptides, vasopressin, vasopressin fragments, and its analog (NC-1900) on learning and memory

Here we describe effects of neuroactive peptides, vasopressin, vasopressin fragment, and its analog, NC-1900, on cognitive functions and CO2-induced amnesia. Vasopressin (AVP1-9) and its fragments are synthesized in the central nervous, and it is well known to regulate diuretic action. However, vasopressin receptors are distributed not only in the supraoptic nucleus and the paraventricular nucleus but also throughout the central nervous system. This fact shows that an action of AVP1-9 is not restricted to the antidiuretic action, and it is suggested that AVP1-9 and its metabolites regulate cognitive function such as learning and memory. In order to determine the mechanism of action of a new AVP4-9 analog, NC-1900, on memory process, we investigated the facilitative effect of NC-1900 on memory performance in eight-arm radial maze and in passive avoidance (PA) tasks in nonamnesic and amnesic mice. The improved effect of NC-1900 on the CO2-induced amnesia was caused by V1A receptor but not V2, and the effect of NC-1900 on memory retention test performance appeared to be due to activation of the protein kinase C (PKC) signaling pathway via V1A receptors.