An investigation was undertaken to study the relationship between change in gastric lesion induced by cold-restraint stress and brain dopamine (DA) activity in male rat with chronic hyperprolactinemia. Male rats of Wistar strain were divided into two groups: one received extra two pieces of anterior pituitary (AP) from its littermates, the other grafted with several pieces of muscle served as control. Experiment I: From the 5th day to 40th day after transplantation, the levels of serum prolactin (PRL) in the AP-grafted group were higher than those of control (p < 0.05 or p < 0.01). Experiment II: On the 40th day after transplantation, AP-grafted and control rats were restrained and placed supine in a ventilated refrigerator with an ambient temperature of 5 degrees C for 3 hrs. Although gastric mucosal ulceration was observed in both groups, the ulcer index (including total number and length of gastric mucosal ulceration) was lower in AP-grafted group than that in control group (p < 0.05 or p < 0.01). Experiment III: On the 40th day after transplantation, all rats were divided into AP-grafted and muscle-grafted rats. Subsequently, they were allowed to expose to cold-plus-restraint stress and unstress (room temperature: 24 +/- 1 degrees C) respectively. After stress and unstress, all animals were immediately sacrificed by decapitation, the brains were dissected with Palkovits' micropunch technique. DA and its metabolites, DOPAC content in Nucleus accumbens (NAc) area of brain were assayed by HPLC with electrochemical detection. These results showed that concentrations of DA, DOPAC and their ratios (DOPAC/DA) in the NAc area of brain, were not statistically different under room temperature condition between muscle-grafted and AP-grafted rats. The DOPAC/DA ratio in both groups showed significant increase in the brain's NAc area under cold-restraint stress condition as compared with unstress condition. But AP-grafted rats exhibited significantly higher DOPAC content in the brain's NAc area when compared with muscle-grafted rats under cold-restraint stress condition (171.7 +/- 22.1 versus 101.5 +/- 14.2 ng/mg protein, p < 0.05). According to these findings, we suggest that reduced effect of chronic high serum PRL level from extra pituitary grafts on gastric mucosal ulceration produced by cold-restraint stress is probably mediated via Nucleus accumbens dopaminergic neuronal mechanism.