ACTIVATION OF GABA-A RECEPTOR IN THE BRAIN SUPPRESSES NEOSTIGMINE OR HISTAMINE-INDUCED CENTRAL NERVOUS SYSTEM-MEDIATED HYPERGLYCEMIA

We investigated the effect of GABA receptor agonists on the central nervous system (CNS)-mediated hyperglycemia induced by neostigmine or histamine in anesthetized fed rats. The injection of muscimol, GABA(A) receptor agonist (1, 2.5 nmol) into the third cerebral ventricle suppressed the hyperglycemia induced by intraventricular injection of neostigmine (1x10(-8) mol) or histamine (5x10(-7) mol) . Baclofen, GABA(B) receptor agonist (1, 2.5 nmol) , however, did not suppress these hyperglycemia. Neither muscimol nor baclofen (2.5 nmol) affected plasma glucose levels. These findings suggest that activation of GABA(A) receptor in the CNS suppresses the hyperglycemia induced by the stimulation of cholinoceptive neuron or histaminergic neuron, but activation of GABA(B) receptor does not affect them.