Age-Related Changes in the Central Cholinergic System and Learning Performance of Female Rats

Authors: Şakire PÖĞÜN, Lütfiye KANIT, Serdar DEMİRGÖREN, Berrin E. OKUR, Ersin 0. KOYLU, Fatma Z. KUTAY, Nuran I. HARİRİ

Abstract: The important role of the cholinergic system in learning processes and a decline in its function with aging are generally accepted principles, despite conflicting reports. The aim of the present study was to investigate the changes in the activity of the central cholinergic system in aging and to find out if a correlation exists between behavioral performance and cholinergic activity in various brain regions. Following active avoidance learning trials, muscarinic receptor binding (MRB) and acetylcholinesterase (AChE) levels were measured in seven brain regions of young adult (4 months) and aged (24 months) female Sprague Dawley rats. Aged rats had lower scores on learning trials, lower MRB, AChE and tissue weight in the temporal and parietal cortices, lower AChE and higher MRB in the striatum, and higher AChE and lower MRB in the cerebellum compared to the young. There was a negative correlation between learning performance and hippocampal AChE levels in aged rats. 0ur results show that learning performance declines with aging, and this decline is accompanied by an alteration in the postsynaptic cholinergic function.

Keywords: Aging, Active avoidance learning, Central cholinergic system, Muscarinic receptor binding, Acetylcholinesterase (AChE)