Involvement of dopamine receptors in experimental ulceration

The purpose of this study was to characterize dopamine binding sites in gastric (mucosa and muscle) tissue and to examine changes of gastric dopamine receptors in response to variable periods of cold-restraint stress (CRS). Scatchard analysis of binding data in tissues of non-stressed animals revealed a single, homogeneous class of saturable high-affinity dopamine binding sites in gastric mucosa (Bmax = 21.3 pmol/mg protein; KD = 4 X 10(-7) M) and in gastric muscle (Bmax = 34 pmol/mg protein; KD = 0.6 X 10(-7) M). After 1 h of CRS, a time at which a low (30%) incidence of gastric ulcers was observed, the binding in mucosa had increased by 53%. Scatchard analysis revealed a significant increase in dopamine receptor number (Bmax = 37.6 +/- 7.0 versus 21.3 +/- 2.0 pmol/mg protein) and no significant change in affinity (KD = 6.8 +/- 1.6 versus 4 +/- 0.7 X 10(-7) M). No change in 3H-dopamine binding to muscle tissue was observed. These results indicate that up-regulation of mucosal dopamine receptors may precede the development of gastric ulcers.