Neuropharmacological profile of V-9-M, a putative neuropeptide derived from procholecystokinin

(1) The present review suggests that V-9-M, a putative neuromodulator derived from pro-CCK, possesses apparent sedative actions and prevents experimental amnesia in both passive and active avoidance paradigms in rats. (2) These properties are similar to CCK-8, but some differences were noticed; (i) CCK-8 is a potent appetite inhibitor, while V-9-M does not affect food intake in fasted rats, and (ii) small doses of apomorphine cause hypomotility which is abolished by CCK-8, while V-9-M decreases the motility further. (3) More important is the fact that peripheral administration of CCK-8 produces central actions, but that of V-9-M is ineffective. (4) Although CCK-8 and V-9-M are derived from the same pro-CCK, their chemical structures are quite different, and the receptors for these two peptides are not the same. (5) CCK-8 has both central and peripheral receptors, but the presence of a peripheral receptor for V-9-M is questionable. (6) The different properties may be partially explained by this. (7) However, immunochemical studies indicated the coexistence of CCK and GABA in the cortical neurons. (8) This suggests that V-9-M may be present in the GABA neurons together with other CCK fragments. (9) There might be close interaction between V-9-M and the GABAergic system.