Hexobarbital blood levels and effects on EEG in the presence and absence of caffeine.

The interaction of caffeine and hexobarbital in the rat with spinal cord transection was studied. Duration of hexobarbital effect on the brain was taken as the time from the injection of hexobarbital (i.v.) to the return of pre-injection cortical voltage. Hexobarbital distribution and elimination was estimated by application of a two-compartmental model to values for blood hexobarbital concentration (determined by a direct gas chromatographic method after extraction). Caffeine caused a shift in the dose-response curve for hexobarbital but no changes in hexobarbital distribution and elimination. Results are interpreted on the basis of a central interaction of caffeine with hexobarbital at a brain receptor level.