Are substance P neurons of the paraventricular nucleus related to the osmotic regulation in the Mongolian gerbil?

In recent years, the gerbil has been used as an experimental animal for stu dy osmotic regulation, because of its inherent high degree of water re-upta ke in kidney. Many evidences to explain this characteristic accumulated on the kidney level, it do not, however, manifest what concerns on hypothalmo- hypophyseal level. In this study, we have focused on the difference between the colchicine treated gerbil and rat in distributions of substance P (SP) , which is known to have antidiuretic property. Unlike rat, in which a few SP+ neuron is present, SP+ neurons were abundantly observed in the paravent ricular nucleus (PVN) of the gerbil. Furthermore SP+ cells in PVN were mani fested in dehydrated gerbils, in spite of non-colchicine treatment. Therefo re, we suggest that the abundant SP+ neurons in PVN may be a clue to addres s the neuroendocrinal mechanism concerning the high degree of osmotic regul ation in this animal. (C) 1999 Published by Elsevier Science B.V. All right s reserved.