Ameliorative effect of NC-1900, a new AVP4-9 analog, through vasopressin V1A receptor on scopolamine-induced impairments of spatial memory in the eight-arm radial maze
Mishima K, Tsukikawa H, Miura I, Inada K,
Abe K, Matsumoto Y, Egashira N, Iwasaki K, Fujiwara M.
Department of Neuropharmacology,
Faculty of Pharmaceutical Sciences,
Fukuoka University, Fukuoka 814-0180, Japan.
Neuropharmacology. 2003 Mar;44(4):541-52


IThe mechanism by which NC-1900, a new pGlu-Asn-Cys(Cys)-Pro-Arg-Gly-NH(2) (AVP(4-9)) analog, improves spatial memory in rats using an eight-arm radial maze was examined. Even at very low doses (0.2 ng/kg for s.c., 1 microg/kg for p.o., 1 fg for i.c.v.) NC-1900 improved scopolamine-induced impairment of spatial memory. NC-1900 (1 ng/kg, s.c.) also improved impairment of spatial memory induced by pirenzepine, a muscarinic(1) (M(1)) receptor antagonist, and by KN-62, a Ca2+/calmodulin (CaM)-dependent protein kinase II inhibitor. [Pmp(1), Tyr(Me)(2)]-Arg(8)-vasopressin, a vasopressin(1A) (V(1A)) receptor antagonist, and nicardipine, L-type Ca2+ blocker, but not OPC-31260, a V(2) antagonist, suppressed the effect of NC-1900 on scopolamine-induced impairment of spatial memory. A microdialysis study showed that NC-1900 did not affect acetylcholine release in the ventral hippocampus (VH) of intact rats or of scopolamine-treated rats. NC-1900 (1 microM) increased [Ca2+](i) in the VH than in the dorsal hippocampus (DH). Pretreatment with nicardipine (1 microM) and Ca2+ -free conditions inhibited the NC-1900-induced [Ca2+](i) response in the VH. Whereas co-administration of NC-1900 (1 microM) and carbachol (500 microM) increased [Ca2+](i) in the VH. Moreover, nicardipine concentration-dependently inhibited the increase in [Ca2+](i) induced by the co-administration of NC-1900 and carbachol in the VH. These results suggest that NC-1900 activates the V(1A) receptor at the postsynaptic cholinergic nerve, and causes a transient influx of intracellular Ca2+ through L-type Ca2+ channels, to interact with the M(1) receptor. The activation of these Ca2+ -dependent processes induced by NC-1900 may be involved in the positive effect of NC-1900 on scopolamine-induced impairment of spatial memory.

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