The effect of peripheral administration of growth hormone on AD-like cognitive deficiency in NBM-lesioned rats.

This study aimed to evaluate the peripheral administration of growth hormone (GH) on AD-like cognitive deficiency in NBM-lesioned rats induced by ibotenic acid (5 microg/microl, in each side). Forty-eight male Wistar rats (20-24 months old; weighing 330+/-30 g) randomly divided into six groups (n=8). The groups include control group, which were intact rats; n-L+GH group: non-lesioned rats with GH treatment (1mg/kg, 9.00 am, for 10 consecutive days); n-L+Veh group: non-lesioned rats with vehicle treatment; L group: NBM-lesioned rats; L+GH group: NBM-lesioned rats with GH treatment and L+Veh group: NBM-lesioned rats with same volume of vehicle treatment. Peripheral administration of GH in control had no effect on learning and memory, while in L+GH group produced a significant enhancement in spatial learning and memory comparing to L and L+Veh groups. The percent of time spent in goal quarter during probe trial has decreased significantly in L and L+Veh groups compared to n-L groups. While it has increased significantly in L+GH group compared to L and L+Veh groups. No significant difference in percent of time spent was seen between the control and n-L groups. The GH has known as a mediate that effect through IGF-1. As the IGF-1 itself is earlier shown to improve cognitive function it is likely that the observed effect of GH is mediated through release of IGF-1 from peripheral tissue into the circulation for further transport across the BBB. This mechanism may result in the improvement of learning and memory in rats with NBM lesion.