A critical evaluation of the obstetric use of alcohol in preterm labor

Learning experiences comprising central ethanol exposure in rat neonates: Impact upon respiratory plasticity and the activity of brain catalase

Fetal ethanol exposure represents a risk factor for sudden infant death syndrome, and the respiratory effects of fetal ethanol exposure promote hypoxic ischemic consequences. This study analyzes central ethanol's effects upon breathing plasticity during an ontogenetic stage equivalent to the human third gestational trimester. Ethanol's unconditioned breathing effects and their intervention in learning processes were examined. Since central ethanol is primarily metabolized via the catalase system, we also examined the effects of early history with the drug upon this system. During postnatal days 3, 5, and 7 (PDs 3-7), pups were intracisternally administered with vehicle or ethanol (300 mg%). They were tested in a plethysmograph scented or not scented with ethanol odor. The state of intoxication attenuated the onset of apneas, a phenomenon that is suggestive of ethanol's anxiolytic effects given the state of arousal caused by the novel environment and the stress of ethanol administration. At PD9, pups were evaluated when sober under sequential air conditions (initial-normoxia, hypoxia, and recovery-normoxia), with or without the presence of ethanol odor. Initial apneic episodes increased when ethanol intoxication was previously associated with the odor. Pups then ingested ethanol, and brain catalase activity was determined. Pre-exposure to ethanol intoxication paired with the odor of the drug resulted in heightened enzymatic activity. Central ethanol exposure appears to exert antianxiety effects that attenuate apneic disruptions. However, during withdrawal, the cues associated with such effects elicit an opposite reaction. The activity of the catalase system was also dependent upon learning processes that involved the association of environmental stimuli and ethanol intoxication.

Co-existence of ethanol-related respiratory and motivational learning processes based on a tactile discrimination procedure in neonatal rats

In rats, high ethanol doses during early postnatal life exert deleterious effects upon brain development that impact diverse social and cognitive abilities. This stage in development partially overlaps with the third human gestational trimester, commonly referred to as the brain growth spurt period. At this stage in development, human fetuses and rat neonates (postnatal days [PD] 3-9) exhibit relatively high respiratory rates that are affected by subteratogenic ethanol doses. Recent studies suggest conditioned breathing responses in the developing organism, given that there are explicit associations between exteroceptive stimuli and the state of ethanol intoxication. Furthermore, studies performed with near-term rat fetuses suggest heightened sensitivity to ethanol's motivational effects. The present study was meant to analyze the unconditioned effects of ethanol intoxication and the possible co-occurrence of learning mechanisms that can impact respiratory plasticity, and to analyze the preference for cues that signal the state of intoxication as well as the effects of the drug, related with motor stimulation. Neonatal rats were subjected to differential experiences with salient tactile cues explicitly paired or not paired with the effects of vehicle or ethanol (2.0 g/kg). A tactile discrimination procedure applied during PDs 3, 5, 7, and 9 allowed the identification of the emergence of ethanol-derived non-associative and associative learning processes that affect breathing plasticity, particularly when considering apneic disruptions. Ethanol was found to partially inhibit the disruptions that appeared to be intimately related with stressful circumstances defined by the experimental procedure. Tactile cues paired with the drug's effects were also observed to exert an inhibitory effect upon these breathing disruptions. The level of contingency between a given tactile cue and ethanol intoxication also resulted in significant changes in the probability of seeking this cue in a tactile preference test. In addition, the state of intoxication exerted motor-stimulating effects. When contrasting the data obtained via the analysis of the different dependent variables, it appears that most ethanol-derived changes are modulated by positive and/or negative (anti-anxiety) reinforcing effects of the drug. As a whole, the study indicates co-existence of ethanol-related functional changes in the developing organism that simultaneously affect respiratory plasticity and preference patterns elicited by stimuli that signal ethanol's motivational effects. These results emphasize the need to consider significant alterations due to minimal ethanol experiences that argue against "safe" levels of exposure in a critical stage in brain development.

Brief ethanol exposure and stress-related factors disorganize neonatal breathing plasticity during the brain growth spurt period in the rat

RATIONALE

The effects of early ethanol exposure upon neonatal respiratory plasticity have received progressive attention given a multifactorial perspective related with sudden infant death syndrome or hypoxia-associated syndromes. The present preclinical study was performed in 3-9-day-old pups, a stage in development characterized by a brain growth spurt that partially overlaps with the 3rd human gestational trimester.

METHODS

Breathing frequencies and apneas were examined in pups receiving vehicle or a relatively moderate ethanol dose (2.0 g/kg) utilizing a whole body plethysmograph. The experimental design also considered possible associations between drug administration stress and exteroceptive cues (plethysmographic context or an artificial odor). Ethanol exposure progressively exerted a detrimental effect upon breathing frequencies. A test conducted at PD9 when pups were under the state of sobriety confirmed ethanol's detrimental effects upon respiratory plasticity (breathing depression).

RESULTS

Pre-exposure to the drug also resulted in a highly disorganized respiratory response following a hypoxic event, i.e., heightened apneic episodes. Associative processes involving drug administration procedures and placement in the plethysmographic context also affected respiratory plasticity. Pups that experienced intragastric administrations in close temporal contiguity with such a context showed diminished hyperventilation during hypoxia. In a 2nd test conducted at PD9 while pups were intoxicated and undergoing hypoxia, an attenuated hyperventilatory response was observed. In this test, there were also indications that prior ethanol exposure depressed breathing frequencies during hypoxia and a recovery normoxia phase.

CONCLUSION

As a whole, the results demonstrated that brief ethanol experience and stress-related factors significantly disorganize respiratory patterns as well as arousal responses linked to hypoxia in neonatal rats.

Brain Acetaldehyde Exposure Impacts upon Neonatal Respiratory Plasticity and Ethanol-Related Learning in Rodents

Prior studies indicate that neonates are very sensitive to ethanol's positive reinforcing effects and to its depressant effects upon breathing. Acetaldehyde (ACD) appears to play a major role in terms of modulating early reinforcing effects of the drug. Yet, there is no pre-existing literature relative to the incidence of this metabolite upon respiratory plasticity. The present study analyzed physiological and behavioral effects of early central administrations of ethanol, acetaldehyde or vehicle. Respiration rates (breaths/min) were registered at post-natal days (PDs) 2 and 4 (post-administration time: 5, 60, or 120 min). At PD5, all pups were placed in a context (plethysmograph) where they had previously experienced the effects of central administrations and breathing patterns were recorded. Following this test, pups were evaluated using and operant conditioning procedure where ethanol or saccharin served as positive reinforcers. Body temperatures were also registered prior to drug administrations as well as at the beginning and the end of each specific evaluation. Across days, breathing responses were high at the beginning of the evaluation session and progressively declined as a function of the passage of time. At PDs 2 and 4, shortly after central administration (5 min), ACD exerted a significant depression upon respiration frequencies. At PD5, non-intoxicated pups with a prior history of ACD central administrations, exhibited a marked increase in respiratory frequencies; a result that probably indicates a conditioned compensatory response. When operant testing procedures were conducted, prior ethanol or ACD central administrations were found to reduce the reinforcing effects of ethanol. This was not the case when saccharin was employed as a reinforcer. As a whole, the results indicate a significant role of central ACD upon respiratory plasticity of the neonate and upon ethanol's reinforcing effects; phenomena that affect the physiological integrity of the immature organism and its subsequent affinity for ethanol operationalized through self-administration procedures.

Fetal learning with ethanol: correlations between maternal hypothermia during pregnancy and neonatal responsiveness to chemosensory cues of the drug

BACKGROUND

Fetuses learn about ethanol odor when the drug is present in the amniotic fluid. Prenatal learning comprising ethanol's chemosensory cues also suggests an acquired association between ethanol's chemosensory and postabsorptive properties. Ethanol-related thermal disruptions have been implicated as a significant component of the drug's unconditioned properties. In the present study, ethanol-induced thermal changes were analyzed in pregnant rats subjected to a moderate ethanol dose. This thermal response was later tested for its correlation with the responsiveness of the progeny to ethanol and nonethanol chemosensory stimuli.

METHODS

During gestational day (GD) 14, pregnant rats were subjected to a minor surgical procedure to place a subcutaneous telemetric thermal sensor in the nape of the neck. During GDs 17 to 20, females received a daily intragastric administration of ethanol (2 g/kg) or water, using solutions kept at room temperature. Maternal body temperatures were recorded before and after (4 consecutive hours) the administration of water or ethanol. Newborns representative of both prenatal treatments were tested in terms of behavioral activity elicited by the smell of ethanol or of a novel odorant (cineole). A third group of pups were tested in response to unscented air stimulation.

RESULTS

Ethanol administration during late gestation induced reliable maternal hypothermia, a thermal disruption greater than that observed in water-treated females. It was systematically observed that maternal ethanol-induced hypothermia negatively correlated with neonatal motor reactivity elicited by ethanol olfactory stimulation. No other significant correlations were observed in terms of responsiveness to cineole or to unscented air in animals prenatally exposed to ethanol or water.

CONCLUSIONS

In conjunction with prior research, the present results indicate that fetal ethanol exposure may yield learning of an association between ethanol's sensory and unconditioned properties. Ethanol-induced hypothermia during late gestation seems to represent a significant component of ethanol's unconditioned consequences. Specifically, ethanol-related thermal disruptions in the womb are highly predictive of neonatal responsiveness to ethanol's chemosensory cues that are known to be processed by the near-term fetus.

Interactions between perinatal and neonatal associative learning defined by contiguous olfactory and tactile stimulation

Tactile stimulation of the neonate, as performed by the mother during and after delivery, has been described as an effective unconditioned stimulus during early ontogeny (Leon, 1987; Ronca & Alberts, 1994). The present experiments examined the interaction between perinatal and neonatal learning determined by the explicit association between alcohol odor and vigorous body stimulation of the perinatal organism. In Experiment 1, rat fetuses were exposed to either alcohol or saline 10 min prior to cesarean delivery. The alcohol administration procedure here employed was sufficient to provide sensory contamination of the amniotic fluid but avoid fetal alcohol intoxication. Pups in the two prenatal treatments later experienced the smell of alcohol, tactile stimulation, or both stimuli explicitly paired or unpaired. Other postnatal groups were composed of pups that had no explicit experience with either experimental stimulus. Pups subjected to alcohol odor in utero displayed more overall motor activity in response to that odor than saline controls. The increased motor responses were further potentiated in pups that experienced additional postnatal alcohol odor paired with tactile stimulation. In Experiment 2, pups were exposed to alcohol in the amniotic fluid 10 or 30 min prior to birth. As previously demonstrated the memory acquired in utero appears highly dependent upon contingency between exposure to this particular scent and delivery procedures. Pups in both prenatal treatment groups were then exposed to alcohol odor paired or unpaired with tactile stimulation. Some control animals received no further experience with either stimuli. Those pups exposed to alcohol odor paired with tactile stimulation both pre- and postnatally later showed maximum motor activity elicited by the odor of alcohol. The results support the notion of fetal associative learning comprising alcohol's chemosensory cues and behaviorally activating stimuli. Furthermore, the conditioned response under analysis is potentiated whenever neonates are reexposed to contingent presentations of the elements that defined the original associative memory.

Ethanol and parturition: a role for prostaglandins

A common pattern of birth defects was reported in children born to alcoholic women over 20 years ago. Shortly thereafter the constellation of defects became known as the Fetal Alcohol Syndrome, and reports from around the world served to acknowledge the pervasiveness of the disorder. Simultaneously with the clinical reports, animal models were developed to characterize the full spectrum of the teratogenic effects of ethanol. Not only did these animal models serve to define the actions of ethanol on fetal growth and development at the molecular pharmacological, neuroanatomical, and behavioral level, but unintentionally, they have resulted in renewed scientific interest in the effects of ethanol on pregnancy and parturition itself. The purpose of this review is twofold. First we will consolidate and summarize data from both clinical and basic research that pertains to ethanol and parturition. These data will demonstrate that ethanol consumption during pregnancy results in both delayed as well as premature delivery depending upon the pattern of consumption and timing of exposure. With these data as a background, the second objective will be to present a theoretical case for prostaglandins as possible mediators of ethanol-induced effects on the onset of parturition.

Preventing alcohol related birth damage: a review

Since 1974 numerous clinical studies have made it clear that heavy alcohol consumption during pregnancy (in excess of 80 g or 8 units daily) can result in a child being born with a specific combination of physical and mental disabilities known as the Fetal Alcohol Syndrome. More moderate levels of intake (as little as 10 g of 1 unit daily) are associated with other fetal problems known as Fetal Alcohol Effects. The most common of these is growth retardation. Reduction of alcohol consumption is beneficial to pregnancy outcome. However, despite this great clinical and research interest within the field there has been comparatively little attention paid to researching possible preventative strategies and appropriate policy development. This paper first describes the size of the problem posed by drinking in pregnancy in the U.S.A. and the U.K., detailing the contrasting policy response on either side of the Atlantic. It examines the difficulties of formulating appropriate advice and then assesses the available research reports on preventative measures. The strategies described include general publicity and counselling for pregnant women. In addition, attention has been paid to the problems of dissemination by emphasising professional education. One major shortcoming is that most of these studies appear to have been carried out with little reference to existing knowledge on health education and promotion, or educational work in the antenatal or alcohol fields. In addition, little attention appears to have been paid to the characteristics of the groups at whom intervention might be targeted or the underlying social or psychological factors which maintain drinking in these groups. The second part of this paper, therefore, attempts to suggest appropriate avenues for developing preventative strategies by presenting a wide-ranging review with special reference to British experience. Particular attention is given to the issues of form and content of appropriate messages, targeting of risk populations, the venue for intervention, and media and the actual mechanisms involved in implementing the programme. We conclude that women should be advised to limit their alcohol consumption to no more than one unit a day when they are either pregnant or planning a pregnancy. We recommend that pregnant women should be asked about their alcohol and given appropriate advice during routine antenatal clinic visits. We suggest that the form of advice should be designed with the characteristics of the risk population in mind.(ABSTRACT TRUNCATED AT 400 WORDS)

Organ growth and cellular development in ethanol-exposed rats

Effects of perinatal exposure to ethanol on growth and cellular development were investigated. Alcohol was administered in liquid diets designed to provide optimal nutrition during pregnancy. Pair-fed and ad lib control groups were included. The 3 groups of females were similar in body weight during gestation and lactation, and offspring weights were similar on gestation Day 21 and at birth. By Day 9 of lactation control pups weighted more than both alcohol and pair-fed pups which were similar in body weight. Weights of brain, heart, liver and kidney were reduced in alcohol pups compared to pair-feds and controls. Decreased liver weight reflected both decreased cell size and decreased protein content, but was primarily due to decreased caloric intake. Decreased heart weight appeared to result from a direct effect of ethanol on heart protein content. Even more marked were the adverse effects of ethanol on kidney protein content and kidney DNA (reflecting a decrease in cell number). In contrast, although both absolute brain weight and DNA content were decreased in ethanol-exposed offspring, relative brain weight was increased. Finally, maternal ethanol consumption significantly increased relative placenta weights as well as placental DNA and protein content.

Effect of ethyl alcohol infusions on glucose and hormone status in ovine pregnancy

Term pregnant ewes were given ethanol in dextrose water i.v. according to the usual 2-h loading dose recommended for premature labor. Glucose, insulin, cortisol, progestins, estrone and estradiol in maternal and fetal plasma were measured for 5 h. In both treated animals and controls (dextrose water only) there was reduction in maternal cortisol and a reduction followed by a rise in progesterone concentration. Mean concentration of insulin in maternal plasma across all sampling times was higher in ethanol treated animals.

Effects of alcohol ingestion in the pregnant rat on daily food intake, offspring growth and metabolic parameters

1. Daily food intake, fluid consumption, offspring growth and metabolic parameters were studied in rats receiving ethanol in the drinking water before, during and after gestation. 2. Ethanol treatment always reduced daily food, liquid and caloric intake in the rat, except during gestation when total daily caloric intake was greater in rats receiving ethanol than in control animals. The increase in both food and liquid intake during lactation in controls was also observed in alcohol-deprived mothers but was significantly reduced in mothers maintained under alcohol treatment. 3. Offspring from alcohol-treated mothers were retarded in body weight and size compared with controls, the differences becoming greater as the suckling period advanced. 4. The 15 day-old pups from alcohol-treated mothers had reduced glucose and augmented beta-hydroxybutyrate levels in blood, and markedly reduced liver glycogen concentrations, indicating their acutely malnourished state. 5. In pups from mothers that received alcohol until the 21st day of gestation, body weight and size were normalized at the 15th day but skeletal maturation and liver glycogen concentration were reduced and blood acetoacetate and beta-hydroxybutyrate were augmented as compared with values in pups from control mothers. If these parameters are interrelated, metabolic changes may be used for early diagnosis of fetal alcohol syndrome.

Teratogenic effects of acetaldehyde in the rat

Acetaldehyde, the proximal metabolite of ethanol, was administered intraperitoneally in single and triple doses (50, 75, 100 mg/kg) to pregnant CF rats on days 10, 11 and 12 of gestation and fetuses were collected on day 21. Besides significant fetal resorptions, malformations were found which included edema, microcephaly, micrognathia, micromelia, hydrocephaly, exencephaly, hemorrhages etc. Somatometric measurements of fetuses (i.e. crown rump length, transumbilical distance and tail length) revealed significant growth retardation. Alizarin red-stained skeletal preparations showed considerable stunting. The placental weight and umbilical cord length were also significantly reduced. The close similarity of the pattern of acetaldehyde-induced fetal malformations with those resulting from maternal alcohol consumption during pregnancy is suggestive of the possible implication of acetaldehyde in the fetal alcohol syndrome.