EXOGENOUS ADENOSINE POTENTIATES HYPNOSIS INDUCED BY INTRAVENOUS ANESTHETICS

We investigated the effect of adenosine on hypnosis induced by thiopen tone, propofol and midazolam in mice. The onset and duration of hypnos is were determined by the loss of righting reflex. Adenosine and 2-chl oroadenosine caused a significant shortening of onset of sleep-time an d prolongation of duration of sleep-time in all groups (p < 0.05). Dip yridamole administration before combined intravenous anaesthetic-adeno sine or intravenous anaesthetic-2-chloroadenosine administration produ ced similar effects to adenosine (p < 0.05). The adenosine antagonist theophylline, given before intravenous anaesthetic-adenosine or intrav enous anaesthetic-2-chloroadenosine administration caused a significan t delay in onset of sleep-time and shortening in the duration of sleep -time (p < 0.05). We conclude that central excitatory noradrenergic ne urones play an important role in adenosine, 2-chloroadenosine and dipy ridamole-induced hypnotic responses to intravenous anaesthetics and th eir inhibition by adenosine antagonists.