The Effect of Intra-Hippocampal Injection of Growth Hormone on Spatial Learning and Memory in Animal Model of Alzheimer’s Disease

Abstract

The aim of this study was to evaluate the effect of intra-hippocampal injection of Growth Hormone (GH) on impaired spatial cognition in rats with Alzheimer's Disease (AD). Growth hormone replacement therapy leading to improved cognition and well-being has mainly been carried in GH-deficient patients. Nevertheless, relatively only a few studies have investigated the function of GH in the brain. Aged Wistar male rats (350-400 g, 18-20 months old) were randomly divided into 6 groups (7 in each): Control (healthy aged); L; L + Veh; L + GH10; L + GH20 and L + GH40. Rats with AD-like cognitive deficiency was induced by injection of ibotenic acid into Nucleus Basalis of Meynert (NBM) bilaterally (5 microg 0.5 microL(-1), each side). A guide cannula was implanted in the right hippocampus under stereotaxic surgery for injection of human recombinant GH (10, 20 and 40 microg 2 microL(-1), during 5 min, twice daily, 9:00 am and 3:00 pm, for 7 days). All rats were trained in Morris water maze to evaluate the spatial learning and memory. Escape latency, traveled distance to find hidden platform and percent time spent in gaol qudrant did not differ between L and L + Veh groups, while latency and distance were reduced significantly. But percent time spent in gaol quadrant (without hidden platform) was increased significantly in NBM-lesioned rats treated with GH (L + GH groups) dose dependently to compare with vehicle treated group. These results suggest that intra-hippocampal injection of GH to aged rats with dementia type of AD (with NBM lesioned) could improve spatial cognition.