BARBITURATE ANESTHESIA REDUCES THE NEUROTOXIC EFFECTS OF QUINOLINATE BUT NOT IBOTENATE IN THE RAT PEDUNCULOPONTINE TEGMENTAL NUCLEUS

We have previously demonstrated that ibotenate (IBO) injected into the pedunculopontine tegmental nucleus (PPTg) damages all neurones there while quinolinate (QUIN) makes relatively selective lesions of choline rgic neurones. We now compare the effects of two anaesthetics, sodium pentobarbitone and Avertin (tribromoethanol/tert-amylalcohol dissolved in ethanol, saline and phosphate buffer), on three doses of IBO and Q UIN in the PPTg. Diaphorase-positive cell loss after QUIN was attenuat ed under barbiturate, the relative selectivity of QUIN for diaphorase- positive neurones was lost and lesion volumes were uniformly small com pared with lesions made under Avertin anaesthesia. IBO toxicity was un affected by anaesthesia. These data are discussed with reference to th e actions of excitotoxins at glutamate receptor subtypes and interacti ons of barbiturates with the GABA(A) receptor.