EFFECT OF ADENOSINE ON CAROTID CHEMORECEPTOR ACTIVITY IN THE CAT

Abstract

The effects of intracarotid (i.e.) injections or infusions of adenosine on chemoreceptor activity recorded from the peripheral end of a sectioned carotid sinus nerve have been studied in cats anaesthetized with pentobarbitone Adenosine injections (0.1–100 μg) caused a rapid and marked increase of spontaneous chemoreceptor discharge, the intensity, duration and onset of which was dose‐dependent. Infusion of adenosine, 50 μg/min, also evoked an increase in discharge which persisted for the duration of the infusion Both theophylline (1 mg i.e.) and aminophylline (1 mg i.e.) caused short‐lasting decreases in spontaneous discharge but did not prevent the excitatory effect of adenosine. Theophylline increased the excitatory action of adenosine Naloxone (400 μg i.e.) antagonized the depressant effect of morphine on chemoreceptor discharge but not the excitatory action of adenosine It is concluded that exogenous adenosine can excite the cat carotid chemoreceptors, an effect which is not prevented by theophylline in the doses studied. The physiological significance of the findings is discussed. 1981 British Pharmacological Society