Effects of ethanol on development of dorsal raphe transplants in oculo: a morphological and electrophysiological study

Effects of ethanol on development of locus coeruleus brain stem transplants in oculo

In this investigation, we studied the effects of ethanol (EtOH) on the development of noradrenergic (NE) neurons of the locus coeruleus. Fetal brainstem tissue from embryonic days 15-17 was grafted into the anterior chamber of the eye of adult rats. Two different experimental groups were exposed to 16% EtOH in the drinking water during different developmental windows. The first group received EtOH 24 h after transplantation and during the whole experimental period of 7 weeks (continuous EtOH), and the second group only during the last 5 weeks of the experimental period (delayed EtOH). The control group received water ad libitum. After 7 weeks, all the animals were sacrificed and morphological evaluations were performed. Immunohistochemical analysis showed that axon bundle formation and NE fiber outgrowth into the host iris was significantly reduced in the continuous EtOH-treated group compared to controls. We also studied the morphology of TH-positive neurons and processes in the intraocular transplants. A significant decrease in TH-positive staining intensity was observed in the continuous EtOH-treated group compared to controls. Moreover, we found a significant decrease in cell size and neuronal survival in both EtOH-treated groups compared to controls. The present results suggest that chronic EtOH exposure during development leads to an altered axonal outgrowth and decreased cell sizes and number of NE neurons in intraocular brain stem grafts. Furthermore, we found that NE neurons are more sensitive to EtOH exposure during the last prenatal days and the first postnatal week of development, compared to a later developmental period.

Newborn cerebrovascular responses after first trimester moderate maternal ethanol exposure in sheep

Fetal alcohol syndrome is one of the leading causes of mental retardation in the United States, but the pathogenesis of the associated brain damage is unknown. We tested the hypothesis that neonatal cerebrovascular responses to CO2 and/or hypoxia may be altered by moderate chronic maternal ethanol exposure early in gestation. We studied 26 newborn lambs (1-4 d old). Their mothers had received daily i.v. infusions of either ethanol (1 g/kg; ethanol concentration = 167 +/- 3 mg/dL; mean +/- SEM) or a similar volume of saline for 3 wk during the first trimester. In nine lambs, we studied cerebral responses to CO2 (saline, n = 4; ethanol, n = 5) and in 17 lambs, cerebral responses to hypoxia (saline, n = 7; ethanol, n = 10). Cerebrovascular responses to CO2 were not different between the groups. However, the cerebral vasodilatory response to hypoxemia was significantly attenuated in the ethanol lambs, such that cerebral O2 delivery was not maintained. During severe hypoxia (arterial PO2 = 30 mm Hg), cerebral blood flow increased 106 +/- 23% (mean +/- SEM) above baseline in the saline-treated group, but increased only 32 +/- 15% above baseline in the ethanol-treated group (p < 0.02). Similarly, cerebrovascular resistance in the saline group decreased 52 +/- 6% from baseline, but decreased only 16 +/- 11% in the ethanol group (p < 0.02). We conclude that moderate maternal ethanol infusion early in pregnancy attenuates neonatal hypoxic, but not CO2, cerebrovascular responsivity.

Serotonin and alcohol intake, abuse, and dependence: findings of animal studies

Despite a relatively large body of literature on the role of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) in the regulation of alcohol intake, the functional significance of serotonergic neurotransmission and its relationship to alcohol intake, abuse, and dependence remains to be fully elucidated. In part two of this review, the experimental (animal) data is summarized along two lines: the effects of serotonergic manipulations on the intake of alcohol, and the effects of acute and chronic alcohol intake, as well as the withdrawal of chronic alcohol, on the serotonergic system. It is concluded that serotonin mediates ethanol intake as a part of its larger role in behavior modulation, such that increases in serotonergic functioning decrease ethanol intake, and decreased serotonergic functioning increases ethanol intake. Ethanol produces transient increases in serotonergic functioning that activate the mesolimbic dopaminergic reward system. The results are discussed in light of recent theories describing the regulatory role of serotonin in general behavior.