Sedative and electroencephalographic actions of erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA): relationship to inhibition of brain adenosine deaminase.

Parenteral administration of the adenosine deaminase (ADA) inhibitor erythro-9-(2-hydroxy-3-nonyl)-adenine (EHNA) results in a profound decrease in spontaneous motor activity in mice and rats. The inhibition of cortical ADA activity measured ex vivo parallels the decrease in spontaneous motor activity in a time-dependent manner. Nonetheless, a marked reduction in electroencephalographically defined sleep was observed in rats during a period when both spontaneous motor activity and ADA activity were profoundly inhibited. These data suggest that EHNA produces in rats a state of 'quiescent waking', which may be related to the observed inhibition of brain ADA activity.