PHYSIOLOGICAL AND BEHAVIORAL-EFFECTS OF EARLY EMBRYONIC EXPOSURE TO ETHANOL AND COCAINE IN THE YOUNG CHICK

The physiological and behavioral effects of embryonic exposure to etha nol and cocaine, given during active neurogenesis (embryonic days E3 a nd E4), were studied in 1- and 2-day-old chicks. Broiler chicks (n = 1 31) from five embryonic treatment conditions were tested: incubative c ontrols (n = 28), vehicle (saline plus 50 mu g/ml bacitracin; n = 27), 10 mg ethanol(n = 20), 150 mu g cocaine (n = 25), or co-drug (10 mg e thanol and 150 mu g cocaine; n = 31). Compared with controls, embryo m ortality for the cocaine alone embryos was significantly increased. No significant embryonic treatment effects among chicks were found for h atching times, body weights at hatch and testing, and temperature regu lation when cold stressed. Behaviorally, chicks were first trained to key-peck for heat/light reward (autoshaping). Chicks in all groups inc reased responding from autoshape session 1 to session 2 (24 trials/ses sion). In an acquisition-extinction session (12 trials/phase), chicks in all groups except those in the co-drug group decreased responding f rom acquisition to extinction. In a second acquisition-extinction sess ion following a drug challenge of 0.5 mg/kg apomorphine, chicks in all embryonic treatment groups showed enhanced responding. Hence, in thos e chicks that survived, the selected doses of ethanol and cocaine prod uced minimal physiological and behavioral effects individually, but wh en given together did produce a significant deficit in extinction resp onding.