| Popis: |
Action of substance P on the contents of dopamine, dihydroxyphenylacetic acid and homovanillic acid in the nucleus accumbens of rats was investigated with microdialysis procedure. During 3 days, each animal daily received i.v. the saline (the 1st day), 0.1 mcg of substance P (the 2nd day), 1 mcg of substance P (the 3rd day). Elevation of accumbal dopamine was observed amounting up to 41% and 71% for 0.1 mcg and 1 mcg of substance P, resp. Rates and duration of these changes also depended on neuropeptide concentration. 1 mcg of substance P produced the dopamine elevation with a peak by the 50th min. Moreover, in 75 min. after infusion of the neuropeptide, the levels of dopamine still remained increased. Response of metabolites also proved to be dose-related. With 1 mcg of substance P, the contents of dihydroxyphenylacetic acid increased by 28%, while with 0.1 mcg of substance P, this parameter did not change. Contents of homovanillie acid was unaffected by central substance P at the above doses. The data obtained corroborate the assumption of influence of the substance P on the reward system arising from its dopaminergic properties and provide a possible explanation of the neuropeptide effects observed in the conditioned place preference paradigm. |
