The offspring of the high- and low-LG mothers also differ in behavioral responses to stress.40,41,68 As adults, the off spring of the high-LG mothers show decreased startle responses, increased exploration in novel, uncertain environments, and shorter latencies to eat food provided in a novel environment. The offspring of low-LG mothers also show greater burying of an electrified probe in the defensive burying paradigm,68 which involves an active response to a clearly defined threat. The offspring of the high-LG mothers exhibit decreased CRF receptor levels in the locus ceruleus and increased γ-aminobutyric acid (GABAA)/benzodiazepine (BZ) receptor levels in the basolateral and central nucleus of the amygdala, as well as in the locus ceruleus,41,69 and decreased CRF mRNA expression in the central nucleus of the amygdala (Francis, Diorio, and Meaney, unpublished data). BZ agonists suppress CRF expression in the amygdala.70 Predictably, stress-induced increases in PVNh levels of noradrenaline, which are normally stimulated by CRF, are significantly higher in the offspring of the low-LG offspring.71
