DISSOCIATION OF THE LOCOMOTOR AND HYPOTENSIVE EFFECTS OF ADENOSINE-ANALOGS IN THE RAT

Rats implanted with chronic indwelling cannulae were injected in the lateral cerebral ventricle with 2 adenosine analogs with the effects on spontaneous locomotor activity and blood pressure were recorded. Both analogs produced dose-related decreases in locomotor activity, with 5''-N-ethylcarboxamidoadenosine (NECA) exhibiting slightly more potent depressant activity than (-)-N-(1-methyl-2-phenylethyl)adenosine (L-phenylisopropyladenosine) (L-PIA). NECA and L-PIA also produced dose-related reductions in blood pressure, but the threshold dose for hypotensive activity was 10- to 100-fold higher than the dose required for depression of spontaneous locomotor activity. The depression of locomotor activity and the hypotensive effect of both analogs were antagonized by parenteral injections of caffeine. The hypoactive and hypotensive effects of adenosine analogs can be dissociated and methylxanthines probably exert an antagonism of central adenosine receptors in the rat.