Neonatal handling is an early experience which results in improved
function of the hypothalamic-pituitary-adrenal axis, increased
adaptability and coping as a response to stress, as well as better
cognitive abilities. In the present study, we investigated the effect of
neonatal handling on the basal forebrain cholinergic system, since this
system is known to play an important role in cognitive processes. We
report that neonatal handling results in increased number of
choline-acetyl transferase immunopositive cells in the septum/diagonal
band, in both sexes, while no such effect was observed in the other
cholinergic nuclei, such as the magnocellular preoptic nucleus and the
nucleus basalis of Meynert. In addition, neonatal handling resulted in
increased M1 and M2 muscarinic receptor binding sites in the cingulate
and piriform cortex of both male and female rats. A handling-induced
increase in M1 muscarinic receptor binding sites was also observed in
the CA3 and CA4 (fields 3 and 4 of Ammon’s horn) areas of the
hippocampus. Furthermore, a handling-induced increase in
acetylcholinesterase staining was found only in the hippocampus of
females. Our results thus show that neonatal handling acts in a sexually
dimorphic manner on one of the cholinergic parameters, and has a
beneficial effect on BFCS function, which could be related to the more
efficient and adaptive stress response and the superior cognitive
abilities of handled animals. (c) 2006 Published by Elsevier Ltd on
behalf of IBRO
