Selective cholinergic denervation inhibits expression of long-term potentiation in the adult but not infant rat hippocampus

The present study assessed the role of the cholinergic systems on the expre ssion of perforant path long-term potentiation (LTP) in rat hippocampal sli ces from the infant and adult brain. To denervate the cholinergic systems, 192 IgG-saporin was injected into the lateral ventricle of the infant (2-we eks-old) and adult (6-weeks-old) rat brain. There, choline acetyltransferas e-immunoreactive fibers were barely detectable 2 weeks and 2 months after i njection for both the groups. For the infant rats, perforant path LTP was n ot affected by selective cholinergic denervation; the probability of LTP de velopment was 0.83 (five out of six slices) and 0.78 (seven out of nine sli ces) at 2 weeks and 2 months later in 192 IgG-saporin-treated slices, as co mpared with 0.83 at each period in control saline-treated slices. In contra st, the expression of the LTP was blocked by selective cholinergic denervat ion for the adult rats; the probability of LTP development was 0 (zero out of 10 slices) and 0.38 (three out of eight slices) at 2 weeks and 2 months later in 192 IgG-saporin-treated slices, as compared with 0.8 (eight out of 10 slices) and 0.83 (five out of six slices) at each period in control sal ine-treated slices. The results of the present study thus suggest that the cholinergic systems play a crucial role in the expression of LTP in the adu lt brain and that the denervated systems in the infant brain could be compe nsated by the sprouting of non-cholinergic fibers. (C) 2001 Elsevier Scienc e B.V. All rights reserved.