Evaluation of the effect of nicotine and O-acetyl-L-carnitine on testosterone-induced spatial learning impairment in Morris water maze and assessment of protein markers

Abstract

The hippocampus has an essential role in learning and memory and is a target for androgen actions. Thus, the effect of testosterone and its metabolites on learning and memory has attracted researchers' attention.The present study aimed to identify the effects of four-day bilateral intra-hippocampal infusion of nicotine and o-Acetyl L-carnitine alone and in combination on testosterone enanthate (TE)-induced spatial learning deficits using Morris water maze (MWM). The expression of CREB, pCREB and BDNF proteins was quantified using western blots.We observed that bilateral intra-hippocampal infusion of TE significantly impaired spatial learning and a significant decrease in CREB, pCREB and BDNF protein markers compared to a control group that did not receive TE. In addition, administration of O-acetyl L-carnitine and/or nicotine reversed TE-induced spatial learning impairment in behavioural and molecular assessments.Thus, our findings suggest that administration of TE in the hippocampus of adult male rats impairs memory function, possibly via down-regulation of cAMP/PKA-CREB-BDNF signaling pathway.