Abstract
The effects of chlordiazepoxide (CDAP) on suppressed behavior of squirrel monkeys were determined alone and in combination with selected methylxanthines (caffeine, theophylline, 8-phenyltheophylline, theobromine, 3-isobutyl-1-methylxanthine) and analogs of adenosine (L-PIA, N6-cyclohexyladenosine, NECA). Monkeys responded under a fixed-interval schedule of food presentation in which responding was suppressed by a concurrent fixed-ratio schedule of response-produced electric shock. Dose-effect curves were determined by administering cumulative doses i.v. during timeout periods that preceded sequential components of the schedule. When administered alone, CDAP produced dose-related increases in the rate of suppressed responding at doses up to 17.8 mg/kg and decreased responding at a higher dose of 32.0 mg/kg. Under the same conditions, the methylxanthines usually had only small effects on responding over the range of doses studied, whereas L-PIA and NECA usually decreased responding in a dose-related manner. After presession treatment with intermediate doses of caffeine, 8-phenyltheophylline or 3-isobutyl-1-methylxanthine, the increases is suppressed responding produced by CDAP often were larger than those produced by CDAP alone. In contrast, after presession treatment with low doses of L-PIA, NECA or N6-cyclohexyladenosine the increases in suppressed responding normally produced by CDAP were either reduced or eliminated. Although L-PIA, NECA and N6-cyclohexyladenosine attenuated the rate-increasing effects of CDAP, there was no indication that they produced an overall rightward shift in the CDAP dose-effect curve, suggesting that the adenosine analogs did not act simply as competitive antagonists of CDAP.(ABSTRACT TRUNCATED AT 250 WORDS)