Involvement of brain dopamine systems on neurotensin-induced protection against stress gastric lesions.

We have previously demonstrated that intracisternal (i.c.) administration of neurotensin (NT), a brain and gastrointestinal tridecapeptide, potently inhibits gastric ulcer formation induced by cold-restraint stress (CRS) in rats. This study evaluated the effect of i.c. NT (17.9 nmol) or vehicle (10 microliter of 0.9% NaCl) on the development of CRS-induced gastric ulcers and on dopamine (DA) concentrations and DA turnover (DOPAC/DA) in selected brain regions after 0, 1, 2 and 3 h of CRS. As anticipated, and in confirmation of previous findings, NT significantly reduced the incidence and severity of CRS gastric ulcers in a time-dependent manner. Neurotensin significantly decreased DA concentration and DA turnover in the striatum. In the nucleus accumbens, however, NT produced a decrease in DA concentration and a concomitant increase in DA turnover after 2 and 3 h of CRS. No significant effects of brain NT on DA concentration and DA turnover were observed in the hypothalamus or olfactory tubercles. These findings suggest that the anti-ulcer effect of brain NT may be mediated, at least in part, by a differential activation of the mesolimbic and nigrostriatal DA systems.