EFFECTS OF DOPAMINERGIC DRUGS ON LOCOMOTOR-ACTIVITY IN TELEOST FISH OF THE GENUS OREOCHROMIS (CICHLIDAE) - INVOLVEMENT OF THE TELENCEPHALON

Single Oreochromis niloticus and O. mossambicus were placed in an unfa miliar white Sasin for 21 min, and their activity in this open-field s ituation was recorded from overhead on video. Apomorphine added to the water (2-8 mg/liter) caused a significant increase in locomotor activ ity, as assessed by the frequency that a fish swam over a rectilinear array of lines drawn on the base. This effect was attenuated by chlorp romazine (2 mg/liter) and abolished by the D-1, antagonist SCH-23390(1 mg/liter); the D-2 antagonist metoclopramide (8 mg/liter) had no effe ct. Removal of both hemispheres of the telencephalon abolished the res ponse to apomorphine, whereas removal of only one hemisphere or cauter ization of the nostrils had no effect. It is concluded that the role o f the dopaminergic system in the regulation of locomotor activity is r eminiscent of the mammalian mesolimbic, rather than the nigrostriatal, system but that further studies are required to determine the source of the dopaminergic innervation and its likely telencephalic targets. (C) 1998 Elsevier Science Inc.