Figure 4
From: A ghrelin–growth hormone axis drives stress-induced vulnerability to enhanced fear
Ghrelin receptor antagonism during chronic stress abolishes stress-related enhancement of fear memory without affecting corticosterone release. Rats received either daily handling (no stress (NS)) or immobilization stress (STR). Each day, a systemic injection of either D-Lys3-GHRP-6 (DLys3), an antagonist of GHSR1a, or saline (VEH) was administered within 30 min of handling or stress initiation. (a) Animals received auditory fear conditioning 24 h after the last stress or handling session. (b) Fear memory was assessed 48 h after the conditioning session by placing the animals in a novel context and measuring conditional freezing during tone presentation. (c) In a subset of animals in the STR group, tail bleeds were performed during the final 30 min of the final stress session and plasma corticosterone levels were measured using enzyme-linked immunosorbent assay (ELISA). All data are mean±s.e.m. *P<0.05 in planned comparisons.
