PT  - JOURNAL ARTICLE
AU  - J J Katims
AU  - Z Annau
AU  - S H Snyder
TI  - Interactions in the behavioral effects of methylxanthines and adenosine derivatives.
DP  - 1983 Oct 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 167--173
VI  - 227
IP  - 1
4099  - http://jpet.aspetjournals.org/content/227/1/167.short
4100  - http://jpet.aspetjournals.org/content/227/1/167.full
SO  - J Pharmacol Exp Ther1983 Oct 01; 227
AB  - The 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 mumol/kg and higher depressed locomotor activity, lower doses (0.01 and 0.05 mumol/kg) augmented locomotor activity. At the doses evaluated, caffeine did not further augment the L-PIA (0.05 mumol/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.