THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) GLYCOPROTEIN GP120 REDUCES THE EXPRESSION OF NEURONAL NITRIC-OXIDE SYNTHASE IN THE HIPPOCAMPUS BUT NOT IN THE CEREBRAL-CORTEX AND MEDIAL SEPTAL NUCLEUS OF RAT

`The expression of neuronal type of nitric oxide synthase (nNOS) has b een studied by immunocytochemistry in the brain of rats receiving a si ngle daily (for up to 14 consecutive days) intracerebroventricular (i. c.v.) injection of the HIV-1 recombinant protein gp120 (100 ng/day). T his treatment failed to affect nNOS expression in the cerebral cortex and medial septal nucleus whereas it reduced nNOS immunopositive neuro nes in the CA1 hippocampal cell layer of rats treated with gp120 for 1 4 days; the latter effect was accompanied by a parallel decrease in Ca 2+-dependent NOS enzyme activity in hippocampal brain tissue homogenat es. In conclusion, the present data demonstrate that in rats gp120 red uces the expression of nNOS in the hippocampus, an area of the brain i nvolved in memory formation. (C) 1997 Elsevier Science Ireland Ltd.