NERVE GROWTH-FACTOR INDUCES FOS-LIKE IMMUNOREACTIVITY WITHIN IDENTIFIED CHOLINERGIC NEURONS IN THE ADULT-RAT BASAL FOREBRAIN

Immunocytochemical techniques were used to examine and compare the eff ects of intracerebroventricular administration of nerve growth factor (NGF) on Fos expression within identified cholinergic and non-choliner gic neurons located in different regions of the adult rat basal forebr ain. Animals were killed 1, 3, 6, and 12 h after receiving NGF (0.5 or 5.0 mu g) or vehicle into the left lateral ventricle and sections thr ough the medial septum, diagonal band of Broca, nucleus basalis magnoc ellularis, and striatum were processed for the combined immunocytochem ical detection of Fos and choline acetyltransferase (a marker for chol inergic neurons), or Fos and parvalbumin (a marker for gamma aminobuty ric acid (GABA)-containing neurons). NGF produced a significant increa se in the percentage of cholinergic neurons containing Fos-like immuno reactivity within all four regions examined. The largest increases wer e detected in the medial septum (47.8%) and the horizontal limb of the diagonal band of Broca (67.7%). In these areas, NGF-mediated inductio n of Fos-like immunoreactivity was detected as early as 3 h, peaked at 6 h, and was reduced by 12 h, postinfusion. Small but significant inc reases in the percentage of cholinergic neurons containing Fos-like im munoreactivity were also detected in the striatum (4.2%) and in the nu cleus basalis magnocellularis (19.2%) 3-12 h following administration of the higher dose of NGF. No evidence for an NGF-mediated induction o f Fos within parvalbumin-containing neurons was detected in any of the four regions at any of the time-points examined; however, evidence fo r an NGF-mediated induction of Fos within epithelial cells lining the lateral ventricle was observed. These data demonstrate that NGF induce s Fos expression within cholinergic, and not parvalbumin-containing (G ABAergic), neurons in the basal forebrain, and furthermore that intrac erebroventricular administration of NGF influences the different subgr oups of basal forebrain cholinergic neurons to different degrees. (C) 1997 Elsevier Science B.V.