ETHANOL INFLUENCES ON THE CHICK-EMBRYO SPINAL-CORD MOTOR SYSTEM .2. EFFECTS OF NEUROMUSCULAR BLOCKADE AND PERIOD OF EXPOSURE

The study described below was performed as a continuation of a previou s study in which we found reduced motoneuron number in lumbar spinal c ord of the chick embryo following chronic ethanol administration from embryonic day 4 (E4) to Ell. We sought to determine whether this reduc tion was due to primary ethanol toxicity or to enhancement of naturall y occurring cell death (NOCD) and to determine whether administration of ethanol at a later period of development could also reduce motoneur on number. Earlier studies have shown that curare suspends NOCD in the chick embryo. By administering both ethanol and curare to these embry os from E4 to Ell and examining the lumbar spinal cord on E12, we dete rmined that ethanol was directly toxic to motoneurons and reduced moto neuron number in the absence of NOCD. By administering ethanol from E1 0 to E15 and examining the lumbar spinal cord on E16, we determined th at ethanol can reduce motoneuron number without altering spinal cord l ength during more than one stage of chick embryo development, and that ethanol toxicity is not dependent on NOCD. In addition, we demonstrat ed that ethanol does not affect the neurotrophic content of chick musc le when it is administered from E10 to E15. (C) 1997 John Wiley & Sons , Inc.