### Neurotoxicology andTeratology,Vol. 12,pp. 231-237. ©PergamonPressplc, 1990.PrintedintheU.S.A. 0892-0362/90$3.00 + .00



# Prenatal Alcohol Exposure: Comparability of Effects in Humans and Animal Models

CYNTHIA D. DRISCOLL,* ANN P. STREISSGUTHt AND EDWARD P. RILEY:~



### *Haskell Laboratoryfor Toxicology and Industrial Medicine E.I. du Pont de Nemours & Co., Inc., Newark, DE 19714 1"Department ofPsychiatry & Behavioral Sciences, University of Washington, Seattle, WA and (cDepartment ofPsychology, San Diego State University, San Diego, CA

DRISCOLL, C. D., A. P. STREISSGUTH ANDE. P. RILEY. 

### Prenatalalcoholexposure:Comparabilityofeffectsinhumansand animalmodels.NEUROTOXICOL TERATOL 12(3) 231-237, 1990.--Much isknown about thepotential consequences ofprenatal alcoholexposure through datadeveloped inanimals andman. However, little attempthasbeenmadetocomparethehuman andanimal literature with respect to qualitative and quantitative similarities and differences. To this end, a comparison was made between the effects reported in humans following moderate levels of alcohol exposure and the neurobehavioral effects detected using animal models. A good deal ofcongruence was found with respect toqualitative endpoints. General functional categories, such asdeficits in learning, inhibition, attention, regulatory behaviors, and motorperformance werereported tobe affectedinboth animals andchildren. Quantitatively, although the doserequired toproduce aneffectdiffers across species, theresultant circulating blood alcohol levels are quite similar. Inaddition, while compelling data arelimited, the magnitude ofthe observed effects aregenerally dose-related forboth humans and animals.

Prenatal alcohol Developmental toxicity Behavioral teratogenesis Developmental neurotoxicity

EXPOSURE to ethanol during gestation has been associated with

a variety ofnegative outcomes including perinatal death, compromised growth, and behavioral deficits (62). The identification of the Fetal Alcohol Syndrome (FAS) in 1973 by Jones and coworkers (21) stimulated a great deal of research, while earlier work by Lemoine and colleagues (28) had described similar characteristics in children of alcoholic mothers. Although diverse methodologies have been utilized, the weight of the evidence implicates ethanol as a developmental neurotoxicant. The extensive clinical and experimental literature provides a wealth of data for assessing the qualitative and quantitative comparability of the neurobehavioral effects seen across species following prenatal alcohol exposure. Three major types of research have contributed to our understanding of alcohol-related developmental toxicity: case, epidemiologic, and animal studies. Case studies and case/comparison
group studies haveprovided a detailed clinicalprofileofFAS. The syndrome, recognized primarily in children of women with histories of heavy alcohol consumption, consists of pre- and postnatal growth retardation, distinctive facial anomalies, and central nervous system (CNS) abnormalities (21,22). While a diagnosis of FAS is specific to prenatal alcohol exposure, the term possible FetalAlcoholEffects (FAE) is used forpatients who have some of the characteristics, but not enough for a full diagnosis. Epidemiologic studies have provided information on the magnitude of neurobehavioral effects in groups of children following exposure to alcohol at levels which do not necessarily result in clinically significant morphological effects. In addition, other confounding factors which can influence development, e.g., smoking, nutrition, and other drug use, can be separated from the effects of alcohol exposure per se through the use of statistical adjustments. Animal studies and the development of appropriate animal models have provided a wealth ofinformation about the effects of gestational alcohol exposure. A variety ofneurobehavioral effects havebeen detected in animals followingprenatal alcoholexposure (12,34). Although a spectrum of study designs have been employed, effectswhich arequalitatively similartothose described in children with a history of gestational alcohol exposure have been detected with these animal models (6). While many factors impact the precision with which estimates of human exposure can be made, the clinical data generally support the notion of a dose-response continuum for neurobehavioral effects. The magnitude of the effects are generally greater among the more heavily exposed children relative to the children of social drinkers. However, while the magnitude may differ, the general categories of CNS dysfunction are similar. For example, children with a history of prenatal alcohol exposure without a diagnosis of mental retardation may still display impaired cognitive performance, hyperactivity, attentional deficits, and motor dysfunction (51). This paper will highlight data from the Seattle Longitudinal Prospective Study on Alcoholand Pregnancy to compare effectsin humans exposed to moderate doses of alcohol (54,64) to those

231232 DRISCOLL, STREISSGUTH AND RILEY

detected with animal models. Reference will also be made to clinical reports of children with FAS to provide a general basis of comparison for estimating dose-response relationships in humans. Although a comprehensive reviewofthe prenatal alcoholexposure literature is notprovided, severalrecent reviews are recommended [e.g., (34,51)].

RESEARCHMETHODOLOGIES

Alcohol teratogenesis has been a very popular subject of research. The expansive literature provides a rich resource for assessing the question of comparability between human and animal data. With quantity comes variety, and the literature also contains an abundance ofmethods. Factors such astime, dose, and duration ofexposure obviously can have a significant impact upon the results obtained, regardless of the species tested. Before comparing the neurobehavioral data, some points concerning the animal models that havebeen employed in thisresearch (5,41) and the assessment of exposure in humans will be discussed briefly. The primary method employed for administering alcohol to a pregnant animal has been by a liquid diet which serves as the animal's sole source of nutrition. Typically, in the rat, a diet providing 35% of the animal's daily caloric intake in the form of alcohol is administered during pregnancy. This design generally includes two control groups. The first is a group that is pairfed to the 35% group and receives a similar liquid diet with a carbohydrate substituted for the ethanol derived calories (EDC). This procedure equates the total daily caloric intake across groups and therefore, serves as a control for liquid diet administration and reduced caloricintake which istypicalinthe 35% EDC group. The second control group has continuous access to standard lab chow and water. If the alcohol group differs from both control groups, and the two control groups do not differfrom each other, theeffect may be attributed to alcohol or some interaction of nutrition and alcohol. Although with the liquid diet procedure the amount of ethanol intake is determined by how much the rat drinks, the average absolute alcohol intake typically varies between 10 and 14 g/kg/day using a 35% EDC diet. Blood alcohol levels (BAL) of

over 100 mg/dl (equivalent to 0.1% wt./vol.) are achieved during

a substantial portion of the dark cycle when the rats consume the majority of their daily intake. Another frequently employed method involves gastric intubation. In this procedure, alcohol is mixed with a vehicle and administered directly to the stomach via a tube. Control groups, similar to those outlined above, are typically incorporated into the design. In rats, the doses administered are generally 4 to 8 g/kg/day. Unlike the liquid diet method which produces a fairly consistent BAL throughout a goodportion ofeach 24-hour period, intubation produces higher peak, but more transient, levels of alcohol. To increase theportion ofthe day with measurable BALs, the absolute daily dose has occasionally been divided into two administrations. Following intubation, peak BALs are often well

over 200 mg/dl and the rats are obviously intoxicated. Since humans consume alcohol voluntarily, there is no experimental control (as there is in the animal studies) over the dose administered or the pattern of consumption. One way of dealing with this problem is to construct the most elementary summary

score: the AA (average ounces of absolute alcohol per day), for a basic calculation ofoverall consumption in humans. For example, the average AA score of mothers of the Seattle cohort was 0.63 prior to pregnancy recognition (a little over one drink per day on the average) and 0.25 atmidpregnancy (halfa drinkper day on the average). However, the AA score alone does not differentiate between the woman who drinks 2 drinks every night and the one who takes 14 drinks once a week. While the continuous AA scores

are useful in studying general dose-response questions, pattern

scores reflecting binge vs. regular patterns of consumption are also necessary to understand the full impact of prenatal alcohol
exposure on offspring development. Ways of dealing with this problem include characterizing patterns of consumption such as number ofdrinks peroccasion ornumber ofdrinking occasions per month. Although BAL data are generally not available in human studies, the BAL concept is useful for comparing exposure levels

across species. Due to differences in metabolism among species, the BAL, rather than the absolute dose ofalcohol, provides a more meaningful estimate of compound bioavailability. For example, although an ethanol dose of 12 g/kg/day for a rat, which would be consumed using the liquid diet technique, is considerably greater than that reasonably anticipated to be consumed by a woman on a body weight basis, the BAL produced is not unrealistic for comparisons with human levels. Even the BAL produced by the intubation method (over 200 mg/dl) is in line with the BAL estimated to be achieved in women who givebirth to infants with FAS (2). Therefore, BAL may provide a more useful basis for

cross species comparison than the amount consumed. In studying alcohol teratogenesis it is difficult to draw direct comparisons between human and animal research for several

reasons. In humans, actual dose is individually determined, not under experimental control, variable across days ofthepregnancy, and represents many patterns of consumption. Actual exposure is further modifiedby the individual maternal and offspring response to ethanol as determined by genetic factors. The numbers used in

our analyses to reflect "dose" can never reflect the true level of exposure to the fetus as it can in animal research. Findings from the Seattle Study are generally monotonic--the higher the presumed dose, the greater the effects on offspring (54). For some individual outcomes, we can take an arbitrary cutoff on some particular alcohol dimension and use this as a crude comparison with animal research. For example, there is a significant decrement in IQ between the group exposed at greater than AA 1.5 and the rest of the sample (53). This amount, which is not interpreted

as a biological threshold, would correspond to BALs of around 100 mg/dl ifconsumed within about an hour. This BAL would be similarto that achieved by a rat on the 35% EDC liquid diet. This is a levelknown to produce many ofthe neurobehavioral effectsto be discussed in the qualitative comparison to follow.

QUALITATIVE

COMPARISONS

The clinical data, in general, support the idea that prenatal alcohol exposure is associated with a continuum of effects, with heavier exposure being associated with more severe outcomes. Many of the animal studies conducted to date have focused on identifying and characterizing the potential effects of prenatal alcohol exposure. While dose selection has been narrow, concentrating on the upper end of the dose-response curve for neurobehavioral effects (e.g., 35% EDC), the animal data provide evidence for a continuum ofeffects. Similarities are also apparent among the clinical and animal data with respect to the types of effects detected for various functional categories of neurobehavioral assessment. The Seattle prospective longitudinal study has examined the effects of prenatal exposure related to levels of alcohol generally considered to be associated with social drinking. Less than 1% of these mothers reported alcohol-related problems. The children have been studied at a number of ages, including birth, 8 and 18 months, and at 4 and 7 years. Children of social drinkers demonstrated (on average) long-lasting neurobehavioral effects,

### PRENATAL ALCOHOL EXPOSURE 233

TABLE 1 BEHAVIORAL

EFFECTS FOLLOWING

PRENATAL

ALCOHOL

EXPOSURE

Humans Animals

Hyperactivity, Reactivity

Attention Deficits, Distractibility

Lack ofInhibition

MentalRetardation, Learning Difficulties

ReducedHabituation

Perseveration Feeding Difficulties

Gait Abnormalities

Poor Fineand Gross Motor Skills DevelopmentalDelay (Motor, Social, Language) HearingAbnormalities

Poor State Regulation Increased Activity, Exploration andReactivity

DecreasedAttention

InhibitionDeficits Impaired AssociativeLearning

Impaired Habituation

Perseveration FeedingDifficulties

Altered Gait

Poor Coordination

DevelopmentalDelay

AlteredAuditory Evoked Potentials

Poor State Regulation

particularlyon attention, memory, and motor development, while remainingwithintherangeofnormalintelligence.A widerangeof neurobehavioraleffectshave alsobeenfoundusingvariousanimal models including developmental delays, sensory-motor impairment, and learning dysfunctions. Qualitative examples of the continuumof effects associated with prenatal alcohol exposure in children and animals are numerous (Table 1).



### FeedingDifficulties

Infants with FAS are frequently described as being "poor feeders" in that they have poor sucking skills and are easily distractedorfatiguedwhile suckling(33, 35, 51). Thismaybeone indication of an early CNS dysfunction. In the epidemiologic studies of children of social drinkers, sucking parameters were systematically assessed and were found to be among the most sensitive indices of maternal alcohol use. With a pressure transducer attached to a nonnutritive nipple, the more alcohol the newborns were exposed to gestationally, the longer they took to initiate sucking and the lower their sucking pressure (33). While therehasbeen some speculationthatthese earlyfeedingproblems, which canbe quite severe in children with histories ofhigh levels of exposure, contribute to the postnatal growth deficiencies frequently seen in these individuals, these are more commonly regarded as independentCNS manifestationsof alcohol teratogenesis. Rat pups exposed to alcohol prenatally also often displaypreand postnatal growth deficits and feeding difficulties. Up until about 9 days of age, alcohol-exposed rats demonstrate longer latencies to attach to the nipple of a test dam when compared to control pups (13). Young animals with a history of prenatal alcohol exposure also show reduced suckling pressure and an altered pattern of suckling while attached to the nipple of an anesthetizeddam (44), althoughthese effects were notapparentin 15-day-old animals (43).



### StateRegulation

Tremulousness andjitteriness have been reported in neonates

across a range of prenatal exposures, from those diagnosed with FAStothosewhose mothers were socialdrinkers(16, 25, 36, 51). Sleep state disturbanceshave alsobeenreported inchildrenbornto mothers with histories of heavy alcohol consumption (45,47). Infants exposed to more moderate amounts of alcohol in utero demonstrated poor habituation as measured on the Brazelton Neonatal Behavior Scale, and were characterized by a cluster of

scores called "Low Arousal," representingfrequentstate changes
at the low end of the arousal continuum, primarily alternations between awake and drowsy (52). As determined by real-time scoring of naturally occurring behaviors, prenatal alcohol exposure inthe Seattle studies was alsorelated to increasedtremulousness, hand-to-face movements, time with eyes open, decreased vigorous bodily activity, and increased bead-tuming to the left (25). These are all behaviors that have been previouslydescribed

ascharacteristic ofinfantsatriskforpoordevelopmentaloutcome. The one infantinthis group with a diagnosisofFAS had extreme

scores on all of these behaviors compared to offspring of social drinkingmothers. Assessment of state regulation has been studied more systematically in the clinical setting than in animal model evaluations. There is, however, some indication that state regulation is also affected in exposed rats. For example, alcohol-exposed offspring thermoregulatepoorly until approximately 10 days of age and the difference relative to controls is not simply a function of their smallerbody size (65). Likehumaninfantsthey alsotake longerto habituatetoredundantstimuli.Ratpupstypicallyshow anincrease in respiration when a novel odor is presented. The polypnea decreases as the noveltyof the odor decreases. Rat pups exposed
to alcohol in utero also take longer to habituate to a novel odor than controls (9).



### ReflexDevelopmentandMotorFunction

Prenatal alcohol exposure has also beenrelated to deficiencies in reflex development, i.e., weak reflexes, particularly decreases in strength of movement, neck tone on the pull-to-sit, glabella reflex, knee-jerk reflex, extension of legs when supine, and increased frequency of spontaneous startles (50). Clinically significant delayed motor development is frequently observed in youngchildrenwithFAS/FAE(22, 24, 49). Smallbut statistically significantdelays in motor developmentduringinfancyhave also been observed in children of social drinkingmothers (55). On the Wisconsin Fine Motor Steadiness Battery, prenatal alcohol, atthelevelofsocialdrinking,was associated with several types ofperformancedecrementsincludingtotalerrors andlatency
to correct errors ongroove andmazeboards (8). Qualitativescores offinemotorfunctioningderivedfromexaminerratingswere also associated with prenatal alcohol exposure. Gross motor function deficits, particularly balance, were associated with prenatal alcohol exposure, but coordination and distance measures were not different from controls (8). Axial ataxia (particularly problems with balance and gait) and kinetic tremor have also been noted in children with FAS who were born to alcohol-abusing mothers (30). Rats exposed to alcohol prenatally also show deficits inreflex development and tasks that require balance and motor coordination. Developmental indices which require coordination such as the righting reflex (48) and negative geotaxis (27) are delayed.234 DRISCOLL, STREISSGUTH AND RILEY

Preweanling animals exposed to alcohol in utero also had more difficulty than controls in staying on a rotating drum, and fell off

an inclined plane at a less steep angle (3). Walking pattern or gait is also affected by prenatal alcohol exposure in rats. Alcoholexposed animals exhibited significantly shorter stride lengths, had

an increased angle of placement of the hind paws, and had less symmetry in their gait relative to controls (19).



### Hyperactivity andAttention Deficits
Hyperactivity is the most frequently reported behavioral problem in children with FAS (62). While hyperactivity is most marked during the preschool years, it is often superseded by attentional deficits in the early school years and restlessness and agitation in adolescence and adulthood. It seems likely that these

are all behavioral manifestations of the same pathological processes induced by prenatal alcohol. In the Seattle study, alcohol-related attentional deficits were noted on the first day of life on the habituation component of the Brazelton Scale (51). Attention and reaction time in the4-year-old children were evaluated with a computer-operated vigilance task. The child watched a large model of a Victorian house and had to respond whenever a cat appeared in a window. Prenatal alcohol
exposure was associated with more errors of omission (failure to press the key when the cat appeared), more errors of commission (pressing the key when the cat was not visible), and a smallerratio ofcorrect responses per total number ofresponses (63). Additionally, prenatal alcoholwas related to increased reaction time onthis vigilance task. The higher the exposure, the longer the reaction time and the less accurate the performance on all measures. Alcohol-related attentional deficits in four-year-old children born
to social drinking mothers have also been reported in a separate study which employed naturalistic observations in the children's homes (26). The vigilance findings in 4-year-old children have been replicated with the Seattle cohort at 7 years of age, suggesting that these attentional problems are persisting into the school age years (57). Errors of commission were most strongly related to prenatal alcohol exposure at 7 years. These are impulsive errors in which the child presses the response key when the target stimulus is not present; this may represent an underlying difficulty with response inhibition. Deficits inresponse inhibition havebeen well studied in animal models. When tested in a T-maze without any extrinsic rewards,
rats typically alternate between the two arms of the maze. This tendency to spontaneously alternate develops at the same time as cholinergicinhibitory systems are maturing in therat and therefore the tendency to spontaneously alternate is thought to reflect inhibitory tendencies. When tested at 21 days of age, alcoholexposed pups showed more perseverative behavior, taking more trials than controls prior to their first alternation (40). Testing at older ages did not discern alcohol-exposed offspring, suggesting that prenatal alcohol exposure delays the development of certain inhibitory systems (1). Other behavioral dysfunctions reported in animals following alcohol exposure during gestation can also be attributed to response inhibition deficits. Perhaps the most common finding following prenatal alcohol exposure is an increased level of activityorexploration. This has been reported in open-fields (11), running wheels (31), and in nose-poke and head-dip tests (42). The overactivity is thought to be due to an inability to inhibit activity and/or exploration or as a deficit in habituation to a novel environment. Alcohol-relatedoveractivity, at least as measured in the open-field, appears tobeboth dose and age-related. Weanlings and animals tested in old age typically are more active than controls, while adolescent or mature subjects are not (1,4). Many of the deficits in learning discussed below can also be interpreted

as inhibition deficits.


### Learning and Intelligence Indices
Mental retardation is a common manifestation ofchildren with

a diagnosis of FAS (62) and the more severe the diagnosis, the greater the level of retardation (60). Children with FAE may also be retarded, but their average intellectual functioning generally falls in the borderline range of intelligence (61). Even groups of children of alcoholic mothers, selected without respect to the physical manifestations ofFAS/FAE, have repeatedly been shown
to have significantly lower IQ scores than matched comparison
groups without alcoholic mothers (7, 18, 23, 61, 62). The Seattle study examined learning and intellectual functioning in children of social drinkers from day 2 through year 7. Two simple operant paradigms were used to study learning in neonates,

an operant head-turning paradigm and an operant sucking paradigm (32). In both paradigms, infants whose mothers were both drinking and smoking during pregnancy took longer to extinguish

a response once it was learned. Such infants continued to perseverate in making the conditioned response evenwhen theresponse

was no longer reinforced, thus prolonging the extinction period. At 8 months of age, small but statistically significant relationships between prenatal alcohol and mental development on the Bayley scales were observed. At 4 years of age, social drinking during pregnancy was related to significantly lower IQ scores on the WPPSI, although mean scores were well within the normal
range (53). Low birthweight alone was not a marker for those alcohol-exposed children who later demonstrated IQ decrements. However, children who had been classified at birth by a dysmorphologist as having FAE, based on the presence of microcephaly, certain minor physical anomalies, and growth deficiency (20),

were at increased risk for lower IQ at age four, compared to similarly exposed children without newborn characteristics of FAE (53). These findings continued to hold up when the Seattle cohort

was tested at approximately 7 years on the WISC-R. Prenatal alcohol exposure was again associated with lower, but still normal, IQ, Performance IQ and Verbal IQ (56). Two subtests from the WISC-R, Digit Span and Arithmetic, were most highly associated with prenatal alcohol, reflecting attention and memory deficits (46). On the Wide Range Achievement Test (WRAT-R), alcohol-related deficits in arithmetic skills were also observed (46). On a neuropsychological battery, prenatal alcohol was related to deficits in spatial memory and integration, verbal
memory and integration, flexible problem solving, and attention (58). Behaviorally, alcohol-exposed children were rated as more distractible by examiners (58). Classroom teachers alsorated them

as less cooperative and more impulsive. They also had more difficultywith grammar, informationretention and comprehension in their respective classrooms (46). These results from the Seattle study are consistent with studies

on children of alcoholic mothers and children with FAS, which have revealedpersisting problems with perceptual-motor development, academic achievement (particularly arithmetic), attention, and impulsivityduring the school-ageyears (7, 18, 24, 49, 59, 61, 62). The magnitude of the effects seen in the offspring of social drinkers is, however, generally smaller than reported in children diagnosed with FAS who have experienced higher levels of
exposure.

### PRENATAL ALCOHOL EXPOSURE 235

In young rats, exposure to alcohol in utero is associated with poorer associative learning (10,37). Alcohol-exposed pups tested

as youngas 3 days ofage showed deficits inassociating a specific odor with reward (10). Learning deficits in weanling rats were among the first effects reported using animalmodels to study the effects of prenatal alcohol exposure. Passive avoidance is a relativelyeasy task for even a youngrat to learn and requires the animalto remain in one locationto avoid shock. Youngrats with

a history ofprenatal alcoholexposure took longerthancontrolsto learn this task. When older animalswere tested, alcohol-exposed
rats no longer showed a deficit in learning (39). This is probably due, inpart, to the relatively simple nature ofthe test which does
not present a challenge to the typical adult rat, or even those known to have substantialbrain damage. Reversallearningisalsodisruptedbyprenatalalcoholexposure (40). Following the acquisition of a simple left-right discrimination, animalshad to learn to go to the side opposite that initially learned. Animalsexposed to alcohol inutero took more trials and made more mistakes per trial than did the controls. These effects have also been shown to be age-dependent. Alcohol-exposed offspring have been reported to show learningdeficits on numerous tests includingoperant learning paradigms, two-way active avoidance, and simple discriminations(38). More recently, deficits in spatial learningtasks, such as the Morris maze, have also been reported (17). Importantly, these more complex tasks have revealed deficits even in alcohol offspring tested as adult.



### Transient Effects: How Important Are They?

The animal data outlined above cited many examples of age-dependent effects. Similar examples exist from the Seattle Study where, for example, prenatal alcohol exposure was associated with smalldecrementsin mentaland motor developmentat 8 months, not at 18 months, but againat 4 and 7 years. Perhaps the Bayley scales at 18 monthsdidnotprovide a sensitiveenoughtest of the subtle effects of prenatal alcohol exposure at this age, or perhaps the most salient age-appropriate outcomes (such as language) were not measured adequately. These null findings demonstrate the importance of employing sensitive endpoints for behavioral teratology studies, the inconclusivenature of a single
set ofnegativeresults, and the necessityfor studies to incorporate longitudinal assessments of various outcomes. It should also be noted that such discrepancies are also more likely to be encountered at the lower end of the dose-response curve, i.e., children with FAS usually demonstrate delayed development across all ages ofassessment (51, 59, 61). Althoughthe effect ofalcohol on
some endpoints may be inconsistentacross time, the significance ofdeficitsdetected atearlierages shouldnotbeunderemphasized. Careful considerationofthe age and abilitiesofthe subject (rat or child) at the time of testing is paramount.

QUANTITATIVECOMPARISONS



### As mentionedpreviously, the quantitativedata forhumans and animal models are insufficient for clearly characterizing doseresponse relationships. The rat studies are limited because they typicallyhave concentrated on the upperendofthe dose-response

curve for studyingthe behavioralteratogenicityofethanoland the majority of studies have been conducted with only one level of alcohol exposure. However, in a few reports, dose-response effects of prenatal alcohol were detected after exposure to diets containing as little as 11% EDC (29,42). The human literature
cannot specify exposure levels with the exactness of the animal studies. Although the BAL index can onlybe applied to existing data in a general fashion, efforts should be made to incorporate quantitative assessment of alcohol exposure in future studies. In an attempt to establish dose-response data in a nonhuman primate model of prenatal alcohol exposure, macaques were exposed to oneof6 doses ofethanolonceweeklyduringgestation (14). Absolutealcohol administrationperexposure was withinthe range of possible human exposure (0.3-4.1 g/kg/week). In addition, measured BALs were also within the range of human exposure, albeitinthe 'abuse' zone atthe higher levels. Evidence ofCNS dysfunctionwas produced atlevelswhich didnotresultin obvious physical anomalies. Although the sample size of this study was small, the attempt to correlate BAL with specific dysfunctional outcomes is an important step in understanding dose-response relationships following prenatal exposure to alcohol. Additionalwork employingsimilardesigns shouldbeencouraged. Obviously,furtherconsiderationneedstobegiventotheuse of indices of exposure other than the administered dose, such as BAL, in the calculationof acceptable exposure measures.

CONCLUSIONS


### Researchers have characterized a great number of effects in offspring exposed to alcohol prenatally. Although a variety of neurobehavioral tools of varying sophistication have been employed, there is little doubt that ethanol could be detected as having the potential to produce adverse effects in exposed offspring at orbelow levels which would also be consideredtoxic to themother. Iflittleornothingwas knownofalcohol'spotentialto affect the developing offspring, simple assessments of body weight, activity, developmentandfunctioncouldbeusedtodetect developmentaltoxicity. The use of additionaltools couldprovide further characterizationof effects and elucidationofmechanisms, however, they would not be necessary for making the initial determinationoftoxicityvs. no toxicity. Sincethe developmental neurotoxicitybatteryoftestsproposedbythe U.S. EPA (see other papers from thisworkshop) includesvariousparameters ofgrowth and development prior to weaning, EtOH would have been detected as a developmental neurotoxicant. Other aspects of the EPA proposedbattery wouldhave furthercharacterized the effects ofEtOH, butwouldnothavebeennecessaryto implicateEtOH as
a developmental neurotoxicant. Prenatal alcohol exposure has been shown to affect a wide variety of neurobehavioral outcomes in humans, with effects of greatermagnitudeassociatedwithhigherlevelsofexposure. There is no indication that the effect of prenatal alcohol exposure attenuateswithincreasingage ofthechild, although somefindings may be more specific to certain ages. The epidemiologic studies have, in general, adjusted statistically for a wide variety of potentiallyconfoundingfactors that must be considered in human behavioral teratology studies, such as other prenatal exposures, maternal nutritionand socio-demographic variables that might be associated with either genetic or postnatal environmental influences on human development. The comparison between findings in humans and animals exposed to alcoholinutero are fairlycongruent. There is a sizable body of data indicatingdeficits in learning, inhibition,attention, regulatorybehaviors, and motor performance. While the comparisons between human and animal data are primarily qualitative in nature, the degree of correspondence is noteworthy. The doses reported to have effects in animals are representative of the blood alcohol levels achieved in humans and there appears to be a reasonable dose-response relationship in both humans and animals.236 DRISCOLL, STREISSGUTH AND RILEY

ACKNOWLEDGEMENTS

This work was supported, in part, by Research Scientist Development Award No. AA00077 (E.P.R.) andby the U.S. DepartmentofHealth and Human Services, Grant Numbers AA01455-14 (A.P.S.) and AA03249 (E.P.R.) from the National Institute on Alcoholism and Alcohol Abuse.

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