Cytophotometric analysis of magnocellular azure B-RNA and Feulgen-DNA following chronic GABA infusion into the nucleus basalis of rats.

This investigation was undertaken to examine possible cytopathic effects of GABA infusion on nucleus basalis (NBM) magnocellular neurons. Sixty-three male Long-Evans rats received unilateral, intra-NBM infusions of either GABA100 (100 micrograms/microliters/h), GABA10 (10 micrograms/microliters/h), or ultrafiltered saline (1 microliter/h) for a period of 24 hours. Rats from each of these groups were sacrificed at either 24 hours, 48 hours or 8 days following initiation of infusions. The sham operated hemisphere of each rat served as a control for the infused hemisphere. After stoichiometric azure B-RNA and Feulgen-DNA staining of brain sections, scanning-integrating microdensitometry was used to quantify GABA-induced alterations in these well established indices of neuronal toxicity. These results provide evidence that the neurotoxic effects of 24 hours of 100 micrograms/microliters-h GABA infusion are manifested within 48 hours post-initiation of infusions. Although 24 hours of 10 micrograms/microliters-h GABA infusion suppressed NBM neuronal metabolism, the lower magnitude and duration of this effect signified an impending recovery. GABA infusion resulted in little if any NBM neuronal chromatin template impairment (i.e., reduced Feulgen-DNA reactivity), irrespective of the dosage employed and the delay prior to sacrifice.