SITE-SPECIFIC EFFECTS OF LOCAL PH CHANGES IN THE SUBSTANTIA-NIGRA PARS RETICULATA ON FLUROTHYL-INDUCED SEIZURES

Local cerebral changes of acid-base balance may interfere with neurona l communication. Acidosis enhances and alkalosis suppresses GABA(A) re ceptor neurotransmission while there are opposite effects on NMDA rece ptor transmission. In this study, we determined site-specific effects of acidified solutions of Na-HEPES-artificial cerebrospinal fluid infu sed into the anterior or posterior area of the substantia nigra pars r eticulata (SNR) in fats. Two levels of pH were compared: 6.7 and 7.4. Rats were challenged with flurothyl and the threshold for clonic and t onic-clonic seizures was determined, In the anterior SNR, there were n o differences between the effects of the solution with pH 6.7 and 7.4 on flurothyl seizures, In contrast in the posterior SNR, microinfusion s with pH 6.7 had proconvulsant effects. The results suggest that loca l pH changes may have site-specific effects on seizure susceptibility in vivo. (C) 1998 Elsevier Science B.V.