Interactions in the behavioral effects of methylxanthines and adenosine derivatives

J. J. Katims, Z. Annau, S. H. Snyder

Research output: Contribution to journalArticlepeer-review

Abstract

Te role of adenosine receptors in behavioral effects of alkylxanthines was evaluated in mice. The relative potencies of alkylxanthines in reversing locomotor activity depression elicited by L-phenylisopropyladenosine (L-PIA) were similar to relative potencies in competing for adenosine receptors labeled by [3H]cyclohexyladenosine. Whereas L-PIA at i.p. doses of 0.10 μmol/kg and higher depressed locomotor activity, lower doses (0.01 and 0.05 μmol/kg) augmented locomotor activity. At the doses evaluated, caffeine did not further augment the L-PIA (0.05 μmol/kg)-enhanced locomotor activity. Low doses of diazepam, like L-PIA, augmented locomotor activity. Combining locomotor depressant doses of diazepam and caffeine produced a paradoxical stimulation of activity, as observed also for L-PIA and caffeine. Low doses of diazepam but not L-PIA increased crossings between the light and dark sites in a shuttle box, indicating a difference in the behavioral profile of these two agents. At behaviorally effective doses, L-PIA did not alter blood pressure or heart rate, but elicited some premature ventricular contractions which, however, occurred to a similar extent at locomotor depressant and stimulant doses of L-PIA. Brain levels of L-PIA at the lowest behaviorally active doses were adequate to occupy more than 50% of adenosine receptors. Thus, the behavioral effects of L-PIA appeared to be mediated in the brain and were not secondary to the cardiovascular effects.

Original languageEnglish (US)
Pages (from-to)167-173
Number of pages7
JournalJournal of Pharmacology and Experimental Therapeutics
Volume227
Issue number1
StatePublished - 1983

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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