The offspring of rats selected for high or low ethanol intake at adolescence exhibit differential ethanol-induced Fos immunoreactivity in the central amygdala and in nucleus accumbens core

Abstract

Adolescents exhibit, when compared to adults, altered responsivity to the unconditional effects of ethanol. It is unclear if this has a role in the excessive ethanol intake of adolescents. Wistar rats from the third filial generation (F3) of a short-term breeding program which were selected for high (STDRHI) vs. low (STDRLO) ethanol intake during adolescence, were assessed for ethanol-induced (0.0, 1.25 or 2.5 g/kg) Fos immunoreactivity (Fos-ir) in the central (Ce), basolateral (BLA) and medial (Me) amygdaloid nuclei; nucleus accumbens core and shell (AcbC, AcbSh), ventral tegmental area (VTA), as well as prelimbic and infralimbic (PrL, IL) prefrontal cortices. Following i.p. administration of saline, and across the structures measured, Fos-ir was significantly greater in STDRHI than in STDRLO rats. Across both lines, baseline Fos-ir was significantly lower in BLA than in any other structure, whereas PrL, IL and Shell did not differ between each other and exhibited significantly greater level of baseline neural activation than Ce, Me, AcbC and VTA. STDRLO, but not STDRHI, rats exhibited ethanol-induced Fos-ir in Ce. STRDHI, but not STDRLO, rats exhibited an ethanol-induced Fos-ir depression in AcbC. Key maternal care behaviors (i.e., grooming of the pups, latency to retrieve the pups, time spent in the nest and time adopting a kiphotic posture) were fairly similar across lines. There were significant intergenerational variations in the amount self-licking behaviors in STDRHI dams as well as an increased amount of exploration of the cage in these animals, when compared to STDRLO counterparts. These results indicate that short term selection for differential alcohol intake during adolescence yields heightened neural activity at baseline (i.e., after vehicle) in STRDHI vs. STDRLO adolescent rats, and differential sensitivity to ethanol-induced Fos immunoreactivity in Ce and in AcbC. It is unlikely that rearing patterns explained the neural differences reported, between STDRHI and STDRLO rats.