Docosahexaenoic acid partially ameliorates deficits in social behavior and ultrasonic vocalizations caused by prenatal ethanol exposure

Abstract

Prenatal ethanol exposure disrupts social behavior in humans and rodents. One system particularly important for social behavior is the somatosensory system. Prenatal ethanol exposure alters the structure and function of this area. Docosahexaenoic acid (DHA), an omega 3 polyunsaturated fatty acid, is necessary for normal brain development and brains from ethanol-exposed animals are DHA deficient. Thus, we determined whether postnatal DHA supplementation ameliorated behavioral deficits induced by prenatal ethanol exposure. Timed pregnant Long-Evans rats were assigned to one of three groups: ad libitum access to an ethanol-containing liquid diet, pair fed an isocaloric isonutritive non-alcohol liquid diet, or ad libitum access to chow and water. Pups were assigned to one of two postnatal treatment groups; gavaged intragastrically once per day between postnatal day (P)11 and P20 with DHA (10 mg/kg in artificial rat milk) or artificial rat milk. A third group was left untreated. Isolation-induced ultrasonic vocalizations (iUSVs) were recorded on P14. Social behavior and play-induced USVs were tested on P28 or P42. Somatosensory performance was tested with a gap crossing test around P33 or on P42. Anxiety was tested on elevated plus maze around P35. Animals exposed to ethanol prenatally vocalized less, play fought less, and crossed a significantly shorter gap than control-treated animals. Administration of DHA ameliorated these ethanol-induced deficits such that the ethanol-exposed animals given DHA were no longer significantly different to control-treated animals. Thus, DHA administration may have therapeutic value to reverse some of ethanol's damaging effects.

Keywords: DHA; Fetal alcohol syndrome; Omega 3 polyunsaturated fatty acid; Social interaction.

Figure 1. Social behavior outcomes

(A) Prenatal exposure to ethanol decreased play fighting in both younger and older animals. DHA administration improved this behavior back to control levels. Younger animals play fought significantly more than older animals. (B) Time spent sniffing was not significantly affected by prenatal ethanol exposure, but was higher in younger animals than older animals. (C) Younger animals also spent more time chasing than older animals. At 28 days of age, DHA-treated animals spent more time chasing than NTC pups. No effects were seen in 42-day-old animals. (D) Social motivation was not significantly affected by prenatal ethanol exposure or postnatal treatment. Data are mean of 10–14 animals per group (see Table 2). T–bars are the standard error of the mean. *significantly (p<0.05) different to Ch (all), PF (all), and Et-DHA. # significantly (p<0.05) different to P28. & significantly (p<0.05) different to Ch (all) at same age. @ all DHA significantly (p<0.05) different to all NTC.

Figure 2. Gap crossing

At both ages, ethanol-exposed animals crossed a shorter gap than pups from pair-fed or chow-fed dams. Older ethanol-exposed animals crossed a longer gap than younger ethanol-exposed animals. Postnatal treatment with DHA improved the distance crossed for all ethanol-exposed animals. Data are mean of 11–14 animals per group (see Table 2). T–bars are the standard error of the mean. *significantly (p<0.05) different to Ch (all), PF (all), and Et-DHA. # significantly (p<0.05) different to P28.

Figure 3. Elevated plus maze

Prenatal exposure to ethanol did not alter behavior on the elevated plus maze. Postnatal treatment with DHA increased the number of entries into the closed arm compared with NTC pups. Arm preference was calculated as a ratio for the closed arm: [(time (s) in closed arm -time in open arm)/total time (s)]*100. Data are mean of 6–9 animals per group (see Table 2). T–bars are the standard error of the mean. @ all DHA significantly (p<0.05) different to all NTC.

Figure 4. Isolation-induced ultrasonic vocalizations

Prenatal exposure to ethanol increased the time until the first vocalization (latency) and the number of vocalizations. Within the ethanol-exposed group, treatment with DHA increased the number of vocalizations but did not alter latency to call. Data are mean of 10–14 animals per group. T–bars are the standard error of the mean. *significantly (p<0.05) different to Ch (all), PF (all), and Et-DHA. % significantly (p<0.05) different to Ch (all) and PF (all).

Figure 5. Play-induced 50 kHz ultrasonic vocalizations

Older animals emitted more 50 kHz USVs than younger animals (top). Prenatal exposure to ethanol increased the latency until the first 50 kHz vocalization (bottom). Data are mean of 10–14 animals per group. T–bars are the standard error of the mean. % significantly (p<0.05) different to Ch (all) and PF (all). # significantly (p<0.05) different to P28.

Figure 5. Play-induced 50 kHz ultrasonic vocalizations

There were no effects of treatments or age on the number of 22 kHz USVs (top) or on the latency to emit a 22 kHz USV (bottom). Data are mean of 10–14 animals per group. T–bars are the standard error of the mean.