Escape behavior produced by the blockade of glutamic acid decarboxylase (GAD) in mesencephalic central gray or medial hypothalamus.

Microinjections into the mesencephalic central gray (CG) or the medial hypothalamus (MH) of three drugs (L-allylglycine, Semicarbazide or 4,5 dihydroxy-isophtalic acid) known to block glutamic acid decarboxylase (GAD) produced a dose-dependent behavioral activation accompanied by jumps. These effects are qualitatively similar to those produced by microinjections of SR 95103 (a GABA-A receptor antagonist) at the same site. These findings suggest that, at both the level of the CG and the MH, gamma-aminobutyric acid (GABA) tonically inhibits a neuronal substrate involved in the generation of flight reactions.