Effects of gamma-aminobutyric acid agonist and antagonist drugs on local cerebral glucose utilization.

The [14C]2-deoxy-D-glucose method of Sokoloff et al. (Sokoloff, L., M. Reivich, C. Kennedy, M.H. Des Rosiers, C. S. Patlak, K. D. Pettigrew, O. Sakurada, and M. Shinohara (1977) J. Neurochem. 28:897-916) weas used to study local cerebral glucose utilization (LCGU) in rats treated with gamma-aminobutyric acid (GABA) agonist (muscimol and 4,5,6,7-tetrahydroisoxazolo[5,4-C]pyridin-3-ol, THIP) and antagonist (bicuculline) drugs. It was of interest to determine if the pattern of LCGU responses to GABA agonists and antagonists administered systemically in vivo would reflect the known distributions of markers for central GABAergic synapses. The patterns of LCGU responses to muscimol and THIP generally were similar. Most brain regions showed dose-dependent decreases in LCGU; others showed no effects; but the red nucleus showed an increase. The GABA antagonist bicuculline produced convulsions and variable LCGU responses, depending on the time of administration. Bicuculline also partially antagonized the depressant effects of muscimol of LCGU. The magnitudes and distribution of in vivo cerebral metabolic responses to specific GABA agonists were not correlated simply with markers for GABAergic synapses. This lack of correlation indicates that additional factors, such as neural circuitry, regulate the LCGU responses to GABAergic drugs.