Chronic ethanol exposure during development: Disturbances of breathing and adaptation

Sexual dimorphic vulnerability of respiratory control in a neonatal rodent model of fetal alcohol spectrum disorder

Fetal alcohol spectrum disorder (FASD) has been linked to numerous poor neurological outcomes as well as impairments in respiratory neural control. Females are known to metabolize ethanol (EtOH) differently than males suggesting a sexual dimorphic sensitivity to EtOH exposure. We used a rodent model of FASD to investigate whether EtOH disrupts respiratory neural control. Rat pups received a single intraperitoneal injection of 2 different doses (0.8 mg/g or 4.4 mg/g) of EtOH. Whole-body plethysmography was used ∼24 h later to assess ventilatory responses to acute hypoxia (HVR) and hypercapnia (HCVR). Females treated with 4.4 mg/g of EtOH exhibited an attenuated HVR and HCVR, but there was no effect on males, and no effect of 0.8 mg/g on either sex. There was unexpected mortality of unknown causes, especially in females, that occurred 2-3 days after EtOH administration. These data suggest that important ventilatory defense responses in females are impaired following developmental EtOH exposure, and this may be associated with increased risk of later death.

Moderate ethanol exposure during early ontogeny of the rat alters respiratory plasticity, ultrasonic distress vocalizations, increases brain catalase activity, and acetaldehyde-mediated ethanol intake

Early ontogeny of the rat (late gestation and postnatal first week) is a sensitive period to ethanol’s positive reinforcing effects and its detrimental effects on respiratory plasticity. Recent studies show that acetaldehyde, the first ethanol metabolite, plays a key role in the modulation of ethanol motivational effects. Ethanol brain metabolization into acetaldehyde via the catalase system appears critical in modulating ethanol positive reinforcing consequences. Catalase system activity peak levels occur early in the ontogeny. Yet, the role of ethanol-derived acetaldehyde during the late gestational period on respiration response, ultrasonic vocalizations (USVs), and ethanol intake during the first week of the rat remains poorly explored. In the present study, pregnant rats were given a subcutaneous injection of an acetaldehyde-sequestering agent (D-penicillamine, 50 mg/kg) or saline (0.9% NaCl), 30 min prior to an intragastric administration of ethanol (2.0 g/kg) or water (vehicle) on gestational days 17–20. Respiration rates (breaths/min) and apneic episodes in a whole-body plethysmograph were registered on postnatal days (PDs) 2 and 4, while simultaneously pups received milk or ethanol infusions for 40-min in an artificial lactation test. Each intake test was followed by a 5-min long USVs emission record. On PD 8, immediately after pups completed a 15-min ethanol intake test, brain samples were collected and kept frozen for catalase activity determination. Results indicated that a moderate experience with ethanol during the late gestational period disrupted breathing plasticity, increased ethanol intake, as well brain catalase activity. Animals postnatally exposed to ethanol increased their ethanol intake and exerted differential affective reactions on USVs and apneic episodes depending on whether the experience with ethanol occur prenatal or postnatally. Under the present experimental conditions, we failed to observe, a clear role of acetaldehyde mediating ethanol’s effects on respiratory plasticity or affective states, nevertheless gestational acetaldehyde was of crucial importance in determining subsequent ethanol intake affinity. As a whole, results emphasize the importance of considering the participation of acetaldehyde in fetal programming processes derived from a brief moderate ethanol experience early in development, which in turn, argues against “safe or harmless” ethanol levels of exposure.

Maternal use of a combination of recreational and antiretroviral drugs (nyaope/whoonga): Case reports of their effects on the respiratory system in infants

Nyaope/whoonga is an indigenous street drug in South Africa (SA). It is made from a combination of neuro-stimulatory illicit drugs such as antiretroviral drugs, heroin, cannabis, opioids, cocaine as well as common household powders such as flat-screen television glass powder. It is a very addictive substance and is used even during pregnancy. Its effects on the developing fetus have been described as causing neonatal abstinence syndrome (NAS), intrauterine growth restriction (IUGR) and neurological complications. There are no data in the literature that report its effect on the respiratory system (RS) of the fetus or neonates. We describe two children who were prenatally exposed to nyaope and presented with upper and lower respiratory tract obstructions associated with recurrent pneumonias. Further studies are required to describe the adverse effects of whoonga on the developing RS of prenatally exposed fetuses.

Ethanol's disruptive effects upon early breathing plasticity and blood parameters associated with hypoxia and hypercapnia

Early ethanol exposure affects respiratory neuroplasticity; a risk factor associated with the Sudden Infant Death Syndrome. High and chronic ethanol doses exert long-lasting effects upon respiratory rates, apneic episodes and ventilatory processes triggered by hypoxia. The present study was performed in 3-9-day-old rat pups. Respiratory processes under normoxic and hypoxic conditions were analyzed in pups intoxicated with different ethanol doses which were pre-exposed or not to the drug. A second major goal was to examine if acute and/or chronic early ethanol exposure affects blood parameters related with hypercapnic or hypoxic states. In Experiment 1, at postnatal day 9, animals previously treated with ethanol (2.0 g/kg) or vehicle (0.0 g/kg) were tested sober or intoxicated with 0.75, 1.37 or 2.00 g/kg ethanol. The test involved sequential air conditions defined as initial normoxia, hypoxia and recovery normoxia. Motor activity was also evaluated. In Experiment 2, blood parameters indicative of possible hypoxic and hypercapnic states were assessed as a function of early chronic or acute experiences with the drug. The main results of Experiment 1 were as follows: i) ethanol's depressant effects upon respiratory rates increased as a function of sequential treatment with the drug (sensitization); ii) ethanol inhibited apneic episodes even when employing the lowest dose at test (0.75 g/kg); iii) the hyperventilatory response caused by hypoxia negatively correlated with the ethanol dose administered at test; iv) ventilatory long-term facilitation (LTF) during recovery normoxia was observed in pups pre-exposed to the drug and in pups that received the different ethanol doses at test; v) self-grooming increased in pups treated with either 1.37 or 2.00 g/kg ethanol. The main result of Experiment 2 indicated that acute as well as chronic ethanol exposure results in acidosis-hypercapnia. The results indicate that early and brief experiences with ethanol are sufficient to affect different respiratory plasticity processes as well as blood biomarkers indicative of acidosis-hypercapnia. An association between the LTF process and the acidosis-hypercapnic state caused by ethanol seems to exist. The mentioned experiences with the drug are sufficient to result in an anomalous programming of respiratory patterns and metabolic conditions.

Prevalence of positive toxicology analysis from the French national registry for sudden unexpected infant death (Tox-MIN)

BACKGROUND

Sudden unexpected infant death (SUID) remains the leading cause of postnatal mortality in many countries. French and international guidelines recommend a thorough examination with toxicology studies.

OBJECTIVES

The main objective was to determine the prevalence of toxic detection and positive analyses. The secondary objectives were to describe the different toxics and compare children with positive (Tox+) and negative results (Tox-) with other SUID risk factors.

DESIGN AND METHODS

We used the data registered from May 2015 to December 2018 by the French national SUID registry (OMIN). It collects data for all SUID cases admitted to any of the 35 participating French SUID referral centers.

RESULTS

Of the 624 SUID cases registered in the OMIN, a post-mortem toxicological analysis was performed in 398 infants. Thirty-six patients (9%) were positives for expected (Etox+ (n = 19 [53%], e.g., resuscitation drugs, regular treatments) and unexpected (UTox+) (n = 17 [47%]) toxics. The unexpected toxics were opioids (n = 8), cannabis (n = 4), cocaine (n = 3), cotinine (n = 2), carbon monoxide (n = 2), caffeine (n = 2), alcohol (n = 1) and GHB (n = 1). UTox + infants had a different seasonal distribution (p = .03), a higher incidence of inappropriate sleeping position and bedding at the time of death (respectively OR 3.8, p = .037 - OR 5.4, p = .026); inadequate body hygiene (OR 10.6, p = .0005), a younger maternal age (p = .045) and a higher rate of maternal drug abuse (OR 21.9, p = .0008).

CONCLUSION

The high rate of positive results warrants routine toxicology testing. The imputability of identified molecules is complicated by the presence of other known risk factors for SUID.

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.

Early ethanol pre-exposure alters breathing patterns by disruptions in the central respiratory network and serotonergic balance in neonate rats

Early ethanol exposure alters neonatal breathing plasticity. Respiratory EtOH's effects are attributed to central respiratory network disruptions, particularly in the medullary serotonin (5HT) system. In this study we evaluated the effects of neonatal pre-exposure to low/moderate doses upon breathing rates, activation patterns of brainstem's nuclei and expression of 5HT 2A and 2C receptors. At PD9, breathing frequencies, tidal volumes and apneas were examined in pups pre-exposed to vehicle or ethanol (2.0 g/kg) at PDs 3, 5 and 7. This developmental stage is equivalent to the 3^rd human gestational trimester, characterized by increased levels of synaptogenesis. Pups were tested under sobriety or under the state of ethanol intoxication and when subjected to normoxia or hypoxia. Number of c-Fos and 5HT immunolabelled cells and relative mRNA expression of 5HT 2A and 2C receptors were quantified in the brainstem. Under normoxia, ethanol pre-exposed pups exhibited breathing depressions and a high number of apneas. An opposite phenomenon was found in ethanol pre-treated pups tested under hypoxia where an exacerbated hypoxic ventilatory response (HVR) was observed. The breathing depression was associated with an increase in the neural activation levels of the raphe obscurus (ROb) and a high mRNA expression of the 5HT 2A receptor in the brainstem while desactivation of the ROb and high activation levels in the solitary tract nucleus and area postrema were associated to the exacerbated HVR. In summary, early ethanol experience induces respiratory disruptions indicative of sensitization processes. Neuroadaptive changes in central respiratory areas under consideration appear to be strongly associated with changes in their respiratory plasticity.

Respiratory and emotional reactivity to ethanol odor in human neonates is dependent upon maternal drinking patterns during pregnancy

BACKGROUND

Beyond the well-known deleterious effects of ethanol defining Fetal Alcohol Spectrum Disorders (FASD), the notion of fetal alcohol programming has gained scientific support. This phenomenon implies early neural plasticity relative to learning mechanisms comprising ethanol´s sensory cues and physiological effects of the drug; among others, its reinforcing properties and its depressant effects upon respiration. In this study, as a function of differential ethanol exposure during gestation, we analyzed neonatal physiological and behavioral responsiveness recruited by the odor of the drug.

METHODS

A factorial design defined by maternal ethanol intake during pregnancy (Low, n = 38; Moderate, n = 18 or High, n = 19) and olfactory stimulation (ethanol odor and/or or a novel scent) served as the basis of the study. Neonatal respiratory and cardiac frequencies, oxygen saturation levels and appetitive or aversive facial expressions, served as dependent variables.

RESULTS

Newborns of High drinkers exhibited significant physiological and behavioral signs indicative of alcohol odor recognition; specifically, respiratory depressions and exacerbated appetitive facial reactions coupled with diminished aversive expressions. Respiratory depressions were not accompanied by heart rate accelerations (cardiorespiratory dysautonomia). According to ROC curve analyses respiratory and behavioral reactivity were predictive of high maternal intake patterns.

CONCLUSIONS

These results validate the notion of human fetal alcohol programming that is detected immediately after birth. The reported early functional signs indicative of relatively high alcohol gestational exposure should broaden our capability of diagnosing FASD and lead to appropriate primary or secondary clinical interventions (Registry of Health Research N.3201- RePIS, Córdoba, Argentina).

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.

Central and peripheral chemoreceptors in sudden infant death syndrome

The pathogenesis of sudden infant death syndrome (SIDS) has been ascribed to an underlying biological vulnerability to stressors during a critical period of development. This paper reviews the main data in the literature supporting the role of central (e.g. retrotrapezoid nucleus, serotoninergic raphe nuclei, locus coeruleus, orexinergic neurons, ventral medullary surface, solitary tract nucleus) and peripheral (e.g. carotid body) chemoreceptors in the pathogenesis of SIDS. Clinical and experimental studies indicate that central and peripheral chemoreceptors undergo critical development during the initial postnatal period, consistent with the age range of SIDS (<1 year). Most of the risk factors for SIDS (gender, genetic factors, prematurity, hypoxic/hyperoxic stimuli, inflammation, perinatal exposure to cigarette smoke and/or substance abuse) may structurally and functionally affect the developmental plasticity of central and peripheral chemoreceptors, strongly suggesting the involvement of these structures in the pathogenesis of SIDS. Morphometric and neurochemical changes have been found in the carotid body and brainstem respiratory chemoreceptors of SIDS victims, together with functional signs of chemoreception impairment in some clinical studies. However, the methodological problems of SIDS research will have to be addressed in the future, requiring large and highly standardized case series. Up-to-date autopsy protocols should be produced, involving substantial, and exhaustive sampling of all potentially involved structures (including peripheral arterial chemoreceptors). Morphometric approaches should include unbiased stereological methods with three-dimensional probes. Prospective clinical studies addressing functional tests and risk factors (including genetic traits) would probably be the gold standard, allowing markers of intrinsic or acquired vulnerability to be properly identified.

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.

Understanding and managing sleep disruption in children with fetal alcohol spectrum disorder

Accumulating evidence has revealed high rates of sleep disruption among children with fetal alcohol spectrum disorder (FASD). Multiple animal and clinical studies have found a clear association between sleep problems and prenatal alcohol exposure, and recent research is beginning to characterize the types and extent of sleep disruption in FASD. Nevertheless, sleep disruption in children with FASD often goes unrecognized or is treated without referring to an evidence base. Children's disrupted sleep interferes with parental sleep and increases caregiver burden, which is of particular importance for families raising children with FASD, a group with very high levels of caregiving stress. The literature supporting an association between sleep problems and deficits in emotional, behavioral, and cognitive function in children is compelling, but needs further investigation in children with FASD. This paper will review the current state of knowledge on sleep in FASD and recommend a rational approach to sleep interventions for affected children and their families.

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.

Neonatal experiences with ethanol intoxication modify respiratory and thermoregulatory plasticity and affect subsequent ethanol intake in rats

Different studies have focused on the deleterious consequences of binge-like or chronic exposure to ethanol during the brain growth spurt period (third human gestational trimester) that in the rat corresponds to postnatal days (PDs) 3-10. The present study analyzed behavioral and physiological disruptions caused by relatively brief binge-like exposures (PDs 3, 5, and 7) with an ethanol dose lower (3.0 g/kg) than those frequently employed to examine teratological effects during this stage in development. At PD 9, pups were exposed to ethanol doses ranging between .0-3.0 g/kg and tested in terms of breathing patterns and thermoregulation. At PDs 11 and 12, ethanol intake was examined. The main findings were as follows: i) pre-exposure to the drug resulted in brief depressions in breathing frequencies and an exacerbated predisposition toward apneic episodes; ii) these effects were not dependent upon thermoregulatory alterations; iii) early ethanol treatment increased initial consumption of the drug which also caused a marked hypothermia that appeared to regulate a subsequent decrement in ethanol consumption; and iv) ethanol exposure retarded overall body growth and even one exposure to the drug (PD 9) was sufficient to reduce brain weights although there were no indications of microcephaly. In conjunction with studies performed during the late gestational period in the rat, the results indicate that relatively brief binge-like episodes during a critical window of brain vulnerability disrupts the respiratory network and exacerbates initial acceptance of the drug. In addition, ethanol treatments were not found to induce tolerance relative to respiratory and thermal disruptions.

Alcohol odor elicits appetitive facial expressions in human neonates prenatally exposed to the drug

Specific memories arise during prenatal life as a function of fetal processing of chemosensory stimuli present in the amniotic fluid. Preclinical studies indicate that fetal exposure to alcohol modifies subsequent neonatal and infantile responsiveness towards the sensory attributes of the drug. It has been previously demonstrated that 1-2day-old human neonates recognize ethanol odor as a function of moderate maternal alcohol consumption during gestation. In the present study 7-14day-old newborns were assessed in terms of behavioral responsiveness to alcohol's chemosensory attributes or to a novel odor (lemon). These newborns were representative of mothers that exhibited infrequent or frequent alcohol drinking patterns during pregnancy. Different clinical assessments indicated that all newborns did not suffer congenital or genetic diseases and that they were completely healthy when behaviorally evaluated. Testing was defined by brief presentations of ethanol or lemon odorants. Two sequences of olfactory stimulation were employed. One sequence included five initial trials defined by ethanol odor stimulation followed by one trial with lemon and five additional trials with the scent of the drug (EtOH-Lem-EtOH). The alternative sequence (Lem-EtOH-Lem) was primarily defined by lemon olfactory exposure. The dependent variables under analysis were duration and frequency of overall body movements and of facial expressions categorized as aversive or appetitive. The main results of this study were as follows: a) at the end of the testing procedure and independent of the sequence of olfactory stimulation, babies born to frequent drinkers exhibited signs of distress as operationalized through higher durations of aversive facial expressions, b) despite this effect, babies born to frequent drinkers relative to newborns delivered by infrequent drinkers exhibited significantly higher frequencies of appetitive facial responses when primarily stimulated with ethanol odor (EtOH-Lem-EtOH sequence) and c) when merging both samples of babies, a positive and significant correlation was found between overall maternal absolute alcohol consumption per month and frequency of appetitive facial expressions elicited by alcohol odor. In conjunction with previous preclinical research, the present results indicate that human prenatal exposure to the drug that yields no evident teratological effects is sufficient to modify the hedonic value of alcohol's chemosensory attributes.