Lack of effect of 1-methylisoguanosine on sleep in rats.

The dose-response effects of intracerebroventricular (i.c.v.) administration of 1-methylisoguanosine (MIG) on sleep in rats were examined. Not even the largest dose (100 nmol/rat) of 1-methylisoguanosine produced significant hypnotic effects, whereas doses of 10 and 100 nmol/rat suppressed rapid eye movement sleep in rats. The only statistically significant effect of 1-methylisoguanosine on sleep latencies was an increase in the latency of S2 after intracerebroventricular administration of 100 nmol/rat of the drug. These effects of 1-methylisoguanosine on sleep were unlike those of both adenosine and the benzodiazepines, suggesting that, contrary to earlier speculations, 1-methylisoguanosine does not interact with central adenosine or benzodiazepine receptors.