Figure 3.

Overexpression of hippocampal GH rescues stress-related impairments in auditory trace conditioning. Two weeks of daily immobilization stress (STR) or handling (NS) were administered to rats. Twenty-four hours after the last session, GH or GFP virus was infused bilaterally into the dorsal hippocampus. (NS-GFP, n = 9; NS-GH, n = 7; STR-GFP, n = 7; STR-GH, n = 6). (A) After three days of recovery, auditory trace conditioning was administered. Neither stress nor GH administration affected conditional freezing during training. (B) Long-term contextual fear memory was measured the next day by returning rats to the conditioning context for 5 m. Stress impaired contextual fear memory, and intra-hippocampal GH expression partially reversed this impairment. (C) Long-term auditory fear memory was measured the following day by placing the rats in a novel context and presenting four tones in the absence of footshock. Stress impaired auditory fear memory, and intra-hippocampal GH expression fully reversed this effect. ^*Indicates p < 0.05 in a post-hoc comparison.