12-P015 In vitro recognition of specific afferent axons by cerebellar granule cell dendrites

During development of the central nervous system, neurons pass through windows of vulnerability to environmental factors. Two windows are gestational day (G) 7 (during gastrulation) and G12 (early neuronal generation). The present study examined the effects of ethanol exposure at these times on social behavior and on the number of neurons in the central nucleus of the amygdala (Ce), which is important for social behavior. Pregnant Long-Evans rats were injected with 2.9 g/kg ethanol (peak blood ethanol concentrations of 300 mg/dl) or saline on G7 or G12. Male offspring from each of ten litters per treatment group underwent behavioral testing during early adolescence, late adolescence, or adulthood, i.e., on postnatal day (P) 28, P42, or P75, respectively. Social investigation, play fighting, social motivation, and overall locomotor activity were assessed using a modified social interaction test. Brains were collected on P28 and stereological analysis was performed on the Ce. Ethanol exposure on G7 resulted in mild changes of social behavior evident in young adolescents only. Animals exposed to ethanol on G12 showed a decrease in social investigation, play fighting behaviors, contact behavior, and social preference compared with controls across all three ages tested. Intriguingly, neuronal number in the Ce was significantly lower following exposure to ethanol on G12 compared with control or after exposure on G7. These findings show that a single exposure to ethanol alters behavior, that the timing of the exposure defines the behavioral outcome, and suggest that damage to the Ce may underlie the deficits in social behavior.