Effects of chronic intraventricular nerve growth factor treatment on vasoactive intestinal peptide and neuropeptide Y levels in the hippocampal formation and cerebral cortex following fimbrial transections

Abstract

The present study determined whether chronic intracerebroventricular (i.c.v.) nerve growth factor (NGF) treatment alters the hippocampal content of vasoactive intestinal peptide (VIP) or neuropeptide Y (NPY) in rats with unilateral fimbrial transections. In addition, effects of chronic NGF treatment on cortical VIP and NPY levels were determined. Following partial and full fimbrial transections, hippocampal choline acetyltransferase (ChAT) activity was reduced by 41% and 60% ipsilateral to the lesioned side, respectively. Chronic NGF treatment partially attenuated (by 48%) the reduction of ChAT following partial lesions, but not full lesions. Neither the hippocampal contents of VIP or NPY were altered by partial or full fimbrial transections nor by chronic NGF treatment. However, in the NGF-treated rats, significant increases not only in cortical ChAT activity (by 28%), but also cortical VIP levels (by 68%) were observed. Cortical NPY levels remained unchanged following chronic NGF administration. In summary, the results suggest that the increases in cortical VIP levels observed in chronic NGF-treated rats may be specific to this tissue and consequent to the enhanced cholinergic tone exerted by this neurotrophin in the basalocortical pathway. Additionally, it appears that NGF when administered in pharmacological doses is not involved in the regulation of NPY synthesis in the hippocampus or cortex despite the presence of an NGF-responsive element associated with the rat NPY gene.