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Previous studies showed that in utero exposure to ethanol has an adverse effect on development of the central nervous system. Included among those abnormalities is the evidence that in utero exposure to ethanol alters the development of the cerebral cortex in terms of the arborization of pyramidal dendrites and the concentration of neurotransmitters and neurotransmitter receptors. However, limited information is available about the influence of in utero exposure to ethanol on synaptogenesis in the cortex. We examined the influence of chronic maternal ethanol consumption, prior to parturition, on synaptogenesis in layer I of the motor cortex of 19-day-old-rat offspring. Layer I (the molecular layer) was chosen because of the early timing of its development. The motor cortex was chosen because of the evidence of motor problems in children afflicted with the fetal alcohol syndrome. The results of these studies demonstrated that the 19-day-old offspring of rats that were pair-fed, using control or 6.6% (v/v) ethanol-containing liquid diets on a chronic basis prior to parturition, had a comparable density of synapses and distribution of paramembranous density lengths in layer I of the motor cortex as well as a comparable thickness of cortical layer I. Thus, evidence by this and other laboratories, of cortical neurotransmitter and dendritic abnormalities are not reflected in synaptic changes in layer I of the motor cortex at 19 days. It is possible that synaptogenesis is affected at another age or in other regions of the cerebral cortex.

Sprague-Dawley dams were fed either a protein-calorie deficient or control diet from day 5 to day 21 after parturition. The concentrations of seven amino acids (aspartate, glutamate, gamma-aminobutyric acid, glycine, glutamine, serine, and taurine) were determined in brain regions from 17-day-old undernourished offspring and from 35-day-old rehabilitated rats. The brain regions examined were the cortex, cerebellum, corpus striatum, hippocampus, hypothalamus, brainstem, and midbrain. At 17 days of age, taurine was the amino acid with the highest concentration, whereas at 35 days glutamate had the highest concentration. This change was due to the fact that the concentration of taurine decreased significantly in all brain regions between 17 and 35 days, whereas the concentration of glutamate remained high or increased somewhat in all brain regions except the hypothalamus and brainstem. When the age-matched offspring of control and undernourished rats were compared, several interesting and significant differences were found. The concentrations of glutamate and aspartate were significantly lower (decreased 16-34%) in the cerebellum, brainstem, cortex, and midbrain in 17-day-old undernourished rats. The aspartate level was also significantly decreased in the corpus striatum and hypothalamus in 17-day-old offspring. However, the deficiencies of aspartate and glutamate were transient and reversible. In contrast, the concentration of taurine was increased in the hypothalamus (31%) and hippocampus (12-33%) at both 17 and 35 days of age and in the midbrain (17%) at 17 days. Other transient abnormalities in amino acid levels were found in undernourished offspring. The results of these experiments suggest that undernutrition during lactation causes delayed CNS development, which is manifested in altered concentrations of the neurotransmitters aspartate, glutamate, and taurine.

The teleost pineal organ contains functional photoreceptors that synapse with pinealofugal neurons. This study examined the effects of environmental lighting on protein content and levels of putative amino acid transmitters, as well as structural components associated with protein synthesis and neurotransmission. Goldfish subjected to continual illumination for 3 days tended to have increased pineal levels of free amino acids and protein compared to dark adapted glands. Similar responses to environmental lighting occurred in cultured glands suggesting a functional relationship to photosensory mechanisms. Morphometric ultrastructural analyses of pineal photoreceptors showed an increased size of nucleoli (especially the fibrillar component), Golgi bodies, and synaptic ribbons when glands were subjected to continuous light both in vivo and in vitro. The good agreement between protein levels and nucleolar morphology indicates a general effect of environmental lighting on photoreceptor protein metabolism, which may be related to photoreceptor outer segment renewal. Parallel changes in levels of certain amino acids (e.g., glutamate) and size of synaptic ribbons is consistent with an hypothesized role of amino acids in photoreceptor neurotransmission.