Alcohol exposure during the brain growth spurt promotes hippocampal seizures, rapid kindling, and spreading depression.

BACKGROUND: Epilepsy is a prominent sign of brain dysfunction and a cause of substantial disability in some children with fetal alcohol syndrome. The hippocampal formation is vulnerable to alcohol-induced pathologic changes and is the source of seizure activity in a variety of epileptic conditions. This study tests the hypothesis that developmental alcohol exposure facilitates epileptic activity and promotes kindling within hippocampal circuitry. METHODS: Rat pups received either a moderate dose (2.0 g/kg) or a high dose (3.75 g/kg) of alcohol via intragastric intubation over postnatal days 4 to 10. Intubated control and suckle control groups were also included. Upon reaching adulthood (postnatal days 85-100), the rats underwent electrophysiologic testing. A double-barrel potassium-sensitive microelectrode was placed into the right dentate gyrus stratum granulosum for the recording of extracellular field potential and extracellular potassium concentration. Stimuli were delivered via an electrode positioned in the CA3 subregion of the left hippocampus. To assess whether alcohol promotes hippocampal seizures and rapid kindling, the parameters of maximal dentate activation (MDA) were measured before, during, and after a series of stimulation-induced seizures. RESULTS: Developmental exposure to the high dose of alcohol permanently altered several parameters of MDA. Time to onset of MDA and stimulus threshold for afterdischarge production were both decreased, whereas the duration of the afterdischarge was increased. Although the moderate alcohol dose reduced time to onset of MDA, it did not affect any other MDA parameters. Over the course of the repeated induced seizures, spreading depression occurred more often and with fewer stimuli in the high-dose alcohol group than in any other group. The series of repeated electrographic seizures induced rapid kindling in all of the treatment groups. However, the kindling effect was enhanced in a dose-response manner by the previous alcohol exposures. CONCLUSIONS: These findings demonstrate that exposure to alcohol during brain development can permanently alter the physiology of the hippocampal formation, thus promoting epileptic activity, enhancing kindling, and facilitating spreading depression. The relative roles of alcohol intoxication and withdrawal in these abnormal physiologic responses remain unknown.

Reduced seizure threshold and hippocampal cell loss in rats exposed to alcohol during the brain growth spurt.

BACKGROUND: Epilepsy is a prominent sign of neurologic dysfunction in some children with fetal alcohol syndrome (FAS). However, it is unknown whether the epileptic disorders in these children are directly due to the neuroteratogenic effects of alcohol or to some other factor accompanying maternal alcoholism. The hippocampus is vulnerable to alcohol-induced pathologic changes, and dysfunction of the hippocampus often manifests as epilepsy. We examined the effect of alcohol exposure during development on the seizure threshold and examined the relationship between alteration of seizure threshold and alcohol-induced neuronal loss from the hippocampus. METHODS: Rat pups received 0.85, 2.5, or 3.75 g/kg of alcohol via intragastric intubation daily over postnatal days (PD) 4-9. An intubated control and a suckle control group were also included. To assess the effect of a single day of alcohol exposure, an additional group received 3.75 g/kg of alcohol on PD 4 alone. Behavioral seizure thresholds were determined by intravenous infusion of the proconvulsant, pentylenetetrazol (PTZ), on PD 31 or on PD 90. In addition, electrographic seizure thresholds were determined by recording extracellular field potentials from the dentate gyrus. The number of hippocampal CA1 pyramidal cells, CA3 pyramidal cells, and granule cells of the dentate gyrus were determined by stereology. RESULTS: Daily exposure to alcohol resulted in a dose-dependent decrease in the seizure threshold and in the selective loss of CA1 pyramidal cells. Reduction in the seizure threshold was significantly correlated with loss of CA1 pyramidal cells. Recordings of extracellular field potentials confirmed the alcohol-induced reduction in seizure threshold, demonstrated that PTZ-induced seizures involve hippocampal-parahippocampal circuitry, and provided evidence that the hippocampal formation is the generator of the PTZ-induced seizures in alcohol-exposed animals. CONCLUSIONS: These findings demonstrate that exposure of the developing brain to alcohol can permanently reduce the threshold for both behavioral and electrographic seizures and can selectively kill hippocampal CA1 pyramidal cells. Both the pathologic findings and the physiologic recordings support the concept that the reduced seizure threshold in alcohol-exposed animals is due to hippocampal pathology.

Subacute sclerosing panencephalitis, a measles complication, in an internationally adopted child.

A healthy 13-year-old boy who had spent the first 4.5 years of his life in an orphanage in Thailand before adoption by an American couple became ill with subacute sclerosing panencephalitis and died several months later. The boy had most likely contracted wild-type measles in Thailand. Measles complications are a risk in international adoptions.

An update on the treatment of hemangiomas in children with interferon alfa-2a.

OBJECTIVE: To report the benefits and complications of subcutaneous interferon alfa-2a therapy for hemangiomas in children. DESIGN: Prospective nonrandomized trial. SETTING: Tertiary care pediatric referral center. PATIENTS: Twenty-four pediatric patients diagnosed with massive or life-threatening hemangiomas. INTERVENTIONS: Each patient received daily subcutaneous injections of interferon alfa-2a to a target dose of 3 million U/m2 of body surface area for a minimum of 4 months. Nineteen patients completed therapy and have received adequate follow-up. MAIN OUTCOME MEASURES: Clinical and radiographic comparisons before, during, and after therapy. Reduction in hemangioma size was graded as complete (>90%), substantial (50%-80%), intermediate (20%-40%), or no response (<10%). RESULTS: Mean age at institution of therapy was 9.6 months, and mean duration of treatment was 10.2 months. Most patients (70%) had not received prior therapy. Responses were as follows: complete, 8 patients (42%); substantial, 3 patients (16%), intermediate, 5 patients (26%); and no response, 3 patients (16%) (n = 19). During therapy, 5 patients (26%) developed neurological abnormalities: 3 had an unsteady gait, and 2 had fine motor deficits. Only 1 of these 5 patients required premature termination from the study, and the neurological abnormalities in all 5 patients resolved after treatment was discontinued. Two of the 4 patients with neurological findings who completed therapy demonstrated complete resolution of their hemangiomas. Patients who developed neurological abnormalities began interferon alfa-2a therapy at an earlier age (4.7 months) than patients without neurological difficulties (aged 11.1 months). The mean time from initiation of therapy to the appearance of neurological complications was 4.8 months. CONCLUSIONS: In pediatric patients with massive or life-threatening hemangiomas, interferon alfa-2a therapy is an effective treatment option. However, neurological evaluation before and during therapy with interferon alfa-2a should be performed owing to a significant incidence of neurological abnormalities (28%). Although all children with neurological findings demonstrated neurological recovery after discontinuation of therapy, we have changed our protocol and now more gradually increase the dosage of interferon alfa-2a up to 3 million U/m2 per day. The effect of this modification on the development of neurological abnormalities has not yet been determined.

Congenital lymphocytic choriomeningitis virus syndrome: a disease that mimics congenital toxoplasmosis or Cytomegalovirus infection.

OBJECTIVE: To describe the clinical characteristics of intrauterine infection with lymphocytic choriomeningitis (LCM) virus, an uncommonly recognized cause of congenital viral infection. PATIENTS: Three infants born in the midwestern United States in 1994 and 1995 with clinical features and serologic studies consistent with congenital LCM virus infection and cases of congenital infection identified by review of the medical literature between 1955 and 1996. RESULTS: Twenty-six infants with serologically confirmed congenital LCM virus infection were identified. Twenty-two infants were products of term gestations, and birth weights ranged from 2384 to 4400 g (median, 3520 g). Ocular abnormalities, macrocephaly, or microcephaly were the most commonly identified neonatal features. Twenty-one infants (88%) had chorioretinopathy, 10 (43%) had macrocephaly (head circumference >90th percentile) at birth, and 3 (13%) were microcephalic (head circumference <10th percentile). Macrocephaly and hydrocephalus developed postnatally in one of the latter infants. Hydrocephalus or intracranial calcifications were documented in five infants by computed tomography or magnetic resonance imaging. Nine infants (35%) died, and 10 (63%) of the 16 reported survivors had severe neurologic sequelae, consisting of spastic quadriparesis, seizures, visual loss, or mental retardation. One-half of the mothers reported illnesses compatible with LCM virus infection, and 25% reported exposures to rodents during their pregnancies. CONCLUSIONS: These cases suggest that congenital LCM virus infection could be an underrecognized cause of congenital infection among infants born in the United States. Because of the clinical similarities of these congenital infections, cases of congenital LCM virus infection can be confused with infections with cytomegalovirus or Toxoplasma gondii.

Purkinje cell deficits in nonhuman primates following weekly exposure to ethanol during gestation.

The most serious features of fetal alcohol syndrome (FAS) are mental retardation and other behavioral problems resulting from alcohol-induced damage to the developing central nervous system (CNS). The mechanism by which alcohol induces its neuroteratogenic effects is unknown. One hypothesis is that gestational alcohol exposure results in a reduction in neuronal number. This study demonstrates that gestational exposure to ethanol in a non-human primate species induces permanent dose-related deficits in the number of cerebellar Purkinje cells. Ethanol was administered via nasogastric tube once per week to 15 gravid pigtailed macaques (Macaca nemistrina) in one of the following doses: 0.0 (intubated controls), 1.2, 1.8, 2.5, 3.3, and 4.1 g/kg/dose. Offspring were reared with parental surrogates and were sacrificed at 6 months of age; 8-microns-thick, parasagittal sections were cut through the paraffin-embedded cerebellar vermis. Purkinje cells were quantified, the length of the Purkinje cell line was determined stereologically, and Purkinje cell linear frequency was calculated. The number of Purkinje cells and their linear frequencies were significantly reduced in the alcohol-treated subjects, and the deficits were dose-dependent. The groups receiving 2.5 g/kg/dose and above were most severely affected and had an average deficit in Purkinje cell number of 11.8%, relative to controls. Alcohol had no effect on the length of the Purkinje cell line. The findings suggest that alcohol-induced reduction in neuronal number may be an important factor underlying the CNS dysfunction in FAS.

The role of extracellular ionic changes in upregulating the mRNA for glial fibrillary acidic protein following spreading depression.

While spreading depression has been shown to be a powerful stimulus in upregulating glial fibrillary acidic protein (GFAP) mRNA expression, the specific physiological signal underlying the upregulation is unknown. During spreading depression, extracellular ionic concentrations are altered markedly. The present study evaluates the role of these changes in extracellular ionic concentrations as potential signals influencing GFAP mRNA expression. Gel foam pledgets saturated with artificial cerebrospinal fluid (CSF) solutions in which [Na+], [Ca2+], [K+] and [H+] were altered one at a time to match concentrations seen in spreading depression were applied to exposed parietal cortex for one hour. Dot and in situ hybridization techniques were used to evaluate GFAP mRNA levels. We found that CSF containing 60 mM KCl produced a dramatic upregulation of GFAP mRNA levels throughout the cerebral cortex of the ipsilateral hemisphere without causing detectable tissue damage. The pattern and time course of the change were similar to those following application of 3 M KCl. Alteration of other ionic species did not affect GFAP mRNA levels. However, the upregulation of GFAP mRNA was not likely due directly to the increased [K+], but rather to the spreading depression that the elevated [K+] induced. This was demonstrated by the finding that the upregulation in GFAP mRNA induced by the potassium exposure was totally blocked by prior administration of MK-801, an NMDA antagonist that blocks spreading depression. These results demonstrate that an upregulation in GFAP mRNA can occur in the absence of degeneration debris and that the initiating events can be related to physiological changes, but that changes in extracellular ionic concentrations are not the likely molecular signals underlying the upregulation.

Spreading depression and reverberatory seizures induce the upregulation of mRNA for glial fibrillary acidic protein.

The present study evaluates the relative roles of seizure activity and spreading depression in upregulating glial fibrillary acidic protein (GFAP) mRNA expression. Stimulating electrodes were placed bilaterally in the angular bundle, and recording electrodes were placed bilaterally in the dentate gyrus of adult rats. Intense electrographic seizures were induced by delivering stimulus trains through one stimulating electrode. In some cases, spreading depression accompanied the seizures, while in other cases, the seizures occurred in the absence of spreading depression. Animals were killed 24 h following the last stimulus train, and the forebrains were prepared for quantitative in situ hybridization. Seizure activity and spreading depression led to significant increases in GFAP mRNA levels in the hippocampal formation. Seizure activity alone (without spreading depression) induced a 4-fold increase in GFAP mRNA levels in the hilus and molecular layer of the dentate gyrus and in stratum lacunosum-moleculare of the hippocampus. When seizure activity was accompanied by spreading depression, there was a 10-fold increase in GFAP mRNA levels in these same regions. Regional differences within the hippocampal formation in glial cell response were evident. While GFAP mRNA levels in stratum lacunosum-moleculare of the hippocampus were upregulated by seizure activity and spreading depression, levels in hippocampal stratum radiatum of the hippocampus remained unchanged. The results suggest that abnormal neuronal activity can influence glial cell gene expression and that spreading depression is a stronger signal than seizure activity in upregulating GFAP mRNA levels.

Induction of cortical spreading depression with potassium chloride upregulates levels of messenger RNA for glial fibrillary acidic protein in cortex and hippocampus: inhibition by MK-801.

The present study evaluates the time course and spatial extent of changes in GFAP mRNA expression following the induction of spreading depression. Spreading depression was elicited by applying filterpaper pledgets soaked in KCl (3 M) to exposed parietal cortex for ten minutes. Animals were killed 1.5, 3, 6, 12, 24, 48, 96 and 192 h post-KCl application, and the forebrains were prepared for quantitative in situ hybridization. The KCl treatment led to a many-fold increase in GFAP mRNA content in the ipsilateral hippocampus and neocortex and, to a lesser extent, in the contralateral hippocampus, but did not affect GFAP mRNA levels in the contralateral cortex or in the thalamus. The time course of increased expression of GFAP mRNA in the hippocampus differed markedly from that of the cortex. In the hippocampus, GFAP mRNA levels rose rapidly to a maximum at 24 h post-exposure, then fell rapidly. In the cortex, levels rose more slowly and did not reach a maximum until 4 days post-exposure. Analysis of GFAP mRNA levels by dot blot hybridization using samples from a separate set of animals killed at one and 4 days following the KCl exposure confirmed both the upregulation in GFAP mRNA levels and the regional time course differences. Intraperitoneal injection of MK-801, a non-competitive NMDA antagonist which prevents spreading depression, blocked the upregulation of GFAP mRNA in both the hippocampus and the cortex, as demonstrated by both in situ and dot blot hybridization. The results suggest that the physiological changes accompanying spreading depression have a powerful influence on glial cell gene expression.

Early postnatal alcohol exposure acutely and permanently reduces the number of granule cells and mitral cells in the rat olfactory bulb: a stereological study.

This study demonstrates that exposure to alcohol during a period of rapid brain growth can lead to severe and permanent deficits in the number of granule cells and mitral cells in the main olfactory bulb. Sprague-Dawley rat pups were reared artificially and were administered alcohol over postnatal days (PD) 4 through 9, a period of brain development comparable to part of the human third trimester. The daily alcohol dose of 6.6 g/kg was concentrated into two of the twelve daily feedings, producing high peak blood alcohol concentrations followed by near total clearance. Pups were either sacrificed on PD10 or were allowed to grow to adulthood and sacrificed on PD115. The total number of granule cells and mitral cells in the main olfactory bulb were estimated with the aid of unbiased stereological principles and systematic sampling techniques. Exposure to alcohol resulted in significant reductions in the number of both granule cells and mitral cells on PD10. Significant deficits in both neuronal populations remained on PD115. The results support the hypothesis that alcohol exposure can kill developing neurons and lead to permanent neuronal deficits. Substantial developmental changes also occurred in the total number of mitral cells and granule cells between PD10 and PD115 in the control groups. In untreated rats, the number of granule cells increased from 2.20 x 10(6) on PD10 to 5.06 x 10(6) on PD115, while the number of mitral cells decreased from 5.30 x 10(4) to 4.33 x 10(4) over the same time period. These results demonstrate that there is a natural loss of mitral cells during postnatal development at the same time that granule cell number is increasing.

Acute and long-term neuronal deficits in the rat olfactory bulb following alcohol exposure during the brain growth spurt.

This study demonstrates that there is a relative recovery in the number of olfactory bulb granule cells following an initial alcohol-induced deficit, while the number of mitral cells remains permanently and severely depressed. The importance of pattern of exposure in influencing the severity of alcohol-induced neuronal loss in the olfactory bulb is also demonstrated. Sprague-Dawley rat pups were reared artificially and were administered alcohol over postnatal days (PD) 4 through 9, a period of rapid brain growth comparable to part of the human third trimester. Two groups received a daily alcohol dose of 4.5 g/kg, administered either as a 5.1% or 10.2% solution. A third group received a higher daily alcohol dose of 6.6 g/kg administered continuously as a 2.5% solution. Pups were either sacrificed on PD 10 or were allowed to grow to adulthood and sacrificed on PD 90. The number of mitral cells and granule cells and the area of the subependymal zone were determined from single sections. On PD 10, immediately following the alcohol exposure, both the mitral cells and the granule cells were significantly reduced in number, relative to controls, in both of the groups receiving the concentrated (5.1% and 10.2%) alcohol treatments. On PD 90, however, only the mitral cell number remained significantly reduced in the groups receiving the concentrated solutions, while the number of granule cells no longer differed significantly from that of controls. The group receiving the higher daily dose (6.6 g/kg) in continuous fractions had no significant cell loss at 10 or 90 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Permanent neuronal deficits in rats exposed to alcohol during the brain growth spurt.

The purpose of this study was to determine whether developmental alcohol exposure could induce permanent neuronal deficits, whether the peak blood alcohol concentration (BAC) influences the severity of the effects, and whether the effects are gender related. Rat pups were reared artificially over postnatal days (PD) 4 through 11 (a period of rapid brain growth, comparable to part of the human third trimester). Alcohol treatments were administered on PD 4 through 9. Patterns of alcohol exposure that produce different peak BACs have been shown to affect differentially the amount of brain weight deficits and neuron loss shortly after the exposure period, so this study investigated whether the pattern of alcohol exposure was also effective in producing permanent deficits. Two groups received a daily alcohol dose of 4.5 g/kg, condensed into either four or two feedings. A third group received a higher daily alcohol dose of 6.6 g/kg administered in 12 uniformly spaced daily feedings. Pups were fostered back to dams on PD 11 and perfused on PD 90. Brain weights were measured, and Purkinje cells and granule cells were counted in each of the 10 lobules of the cerebellar vermis. In the hippocampal formation, cell counts were made of the pyramidal cells of fields CA1 and CA2/3, the multiple cell types of CA4 and the granule cells of the dentate gyrus. The groups receiving the lower daily dose (4.5 g/kg) condensed into either four or two feedings were exposed to higher peak BACs and suffered significant permanent brain weight deficits and neuronal losses, relative to controls. The group receiving the higher daily dose (6.6 g/kg) in continuous fractions had no significant brain weight reductions or neuronal loss. Vulnerability to alcohol-induced neuronal loss varied among regions and cell populations and as a function of peak BAC. In the hippocampus, only the CA1 pyramidal cells were significantly reduced in number and only in group receiving the most condensed alcohol treatment. In the cerebellum, the severity of Purkinje cell and granule cell losses varied among lobules, and Purkinje cell vulnerability appeared to depend on the maturational state of the neuron at the time of the alcohol exposure, with the more mature Purkinje cells being the more vulnerable.

Cell population depletion associated with fetal alcohol brain damage: mechanisms of BAC-dependent cell loss.

Neuronal death is one of the most serious consequences of alcohol exposure during development. Studies described in this paper used a neonatal rat model to address factors affecting neuronal death following alcohol exposure during the period of rapid brain growth, and relate them to possible mechanisms of damage. The profile of blood alcohol concentrations (BACs) is an important variable influencing both brain growth deficits and neuronal death--a smaller daily dose of alcohol can be more damaging than a larger daily dose, if it is consumed in a binge-like pattern that produces relatively higher BACs. Alcohol exposure for a single day also can be damaging, producing both brain growth deficits and neuron loss, if high BACs are obtained. Various brain regions and different neuronal populations within a given brain area exhibit different degrees of vulnerability. Some neuronal loss clearly is a function of cell death due to direct effects of alcohol, while other deficits may be due to either primary or secondary effects of the alcohol insult. In the cerebellum, a maturational or metabolic factor also appears to be involved with alcohol-induced neuronal death. Immunocytochemical studies using a monoclonal antibody against microtubule-associated protein 2 (MAP2) indicated that cerebellar lobules containing Purkinje cells that are in the process of extending dendrites are ones that are more vulnerable to alcohol than lobules containing Purkinje cells that mature later. Alcohol exposure during brain development may be producing neuron attrition in multiple ways, including disruption of membrane integrity, inhibition of protein synthesis or other alterations such as lipid solubility, or by disruption of cytoskeletal elements.

Alcohol-induced neuronal loss in developing rats: increased brain damage with binge exposure.

A rat model of third trimester fetal alcohol exposure was used to determine whether a smaller daily dose of alcohol can induce more severe microencephaly and neuronal loss than a larger dose, if the small dose is consumed in such a way that it produces higher blood alcohol concentrations (BACs). The possibility of regional differences within the developing brain to alcohol-induced neuronal loss was also investigated. Sprague-Dawley rat pups were reared artificially over postnatal Days 4-10 (a period of rapid brain growth similar to that of the human third trimester). Two groups received a daily alcohol dose of 4.5 g/kg, administered either as a 5.1% solution in four of the 12 daily feedings or as a 10.2% solution in two of the 12 feedings. A third group received a higher daily dose (6.6 g/kg) administered as a 2.5% solution in every feeding. Gastrostomy and suckle controls were also reared. On postnatal Day 10, the animals were perfused, and brain weights were obtained. In the hippocampal formation, cell counts were made of the pyramidal cells of fields CA1 and CA2/3, the multiple cell types of CA4 and the granule cells of the dentate gyrus. In the cerebellum, Purkinje cells and granule cells were counted in each of the ten lobules of the vermis. The lower daily dose (4.5 g/kg) condensed into two or four feedings produced high maximum BACs (means of 361.6 and 190.7 mg/dl, respectively) and significant microencephaly and cell loss, relative to controls. The higher daily dose (6.6 g/kg), administered continuously, resulted in low BACs (mean of 39.2 mg/dl) and induced no microencephaly or cell loss. Regional differences in neuronal vulnerability to alcohol were evident. In the hippocampus, CA1 neuronal number was significantly reduced only by the most condensed alcohol treatment, while CA3, CA4, and the dentate gyrus populations were not reduced with any alcohol treatment. In the cerebellum, some lobules suffered significantly greater Purkinje cell loss and granule cell loss than did others. The regions in which Purkinje cells were most mature at the time of the alcohol exposure were the most vulnerable to Purkinje cell loss.

Aspirin augments alcohol in restricting brain growth in the neonatal rat.

The purpose of this study was to determine whether the microencephaly in rats resulting from early postnatal alcohol exposure is altered by a concurrent administration of aspirin. Neonatal rats were artificially reared from postnatal day 4 to postnatal day 10, a period of the brain growth spurt in the rat that is similar to the third trimester of human brain development. The alcohol-treated groups received 6.6 g/kg/day of ethanol and either 0.0, 12.5, 25.0 or 50.0 mg/kg/day of aspirin in a milk solution. Control groups received either 0.0 (gastrostomy control), 12.5, 25.0 or 50.0 mg/kg/day of aspirin in a milk solution free of alcohol. Brainstem, cerebellum and total brain weights were measured on postnatal day 10. Alcohol alone significantly reduced the mean total brain weight, cerebellum and brainstem weight by 19.8%, 23.1% and 12.2%, respectively, relative to gastrostomy controls. A significant interaction between ethanol and aspirin was observed for total brain weight. The mean total brain weight of the group receiving both alcohol and 50 mg/kg/day aspirin was significantly lower than all other experimental groups and was reduced 29.5%, relative to gastrostomy controls. The highest dose of aspirin alone significantly reduced cerebellar weight, relative to gastrostomy controls but had no effect on brainstem or total brain weight.

Manipulating peak blood alcohol concentrations in neonatal rats: review of an animal model for alcohol-related developmental effects.

Fetal alcohol syndrome (FAS) is now well documented, but factors that affect the severity of the accompanying central nervous system damage are still not well understood. In a series of experiments, artificially reared neonatal rats were exposed to alcohol during postnatal days 4-10 (during the brain growth spurt of the rat) to evaluate the consequences of various patterns of alcohol consumption in contributing to the severity of alcohol-related brain damage. In the first experiment, groups of rat pups were given different doses of alcohol (6.6 to 9.8 g/kg) in a milk formula in eight 15-min feedings over each 24 hr. Measures of brain weight on day 10 indicated an inverse relationship between dose and brain weight. Re-evaluating the results with respect to blood alcohol concentration (BAC) revealed an even stronger correlation between BAC and microencephaly. A series of experiments followed in which various doses of alcohol were condensed into fewer and fewer hours each day. Condensing the dose produced higher BACs for a given dose and produced more severe microencephaly, greater neuronal loss, behavioral hyperactivity and impaired spatial navigation. Some of these effects were permanent with females more affected than males on some measures. These data suggest that patterns of alcohol consumption that produce high BACs, such as binge drinking, may be especially harmful to the brain of the developing fetus.

Blood alcohol concentration and severity of microencephaly in neonatal rats depend on the pattern of alcohol administration.

A rat model of third trimester fetal alcohol exposure was used to examine how the pattern of administration of a daily alcohol dose influences the pattern of blood alcohol concentrations (BACs) and the severity of brain growth restriction. Four groups of rats were artificially reared from postnatal days 4 to 10. Three of the groups received an equivalent daily dose of alcohol (6.6 g/kg/day) but in different daily patterns. To one group, the dose was administered continuously in a 2.5% (v/v) solution; in two other groups, the dose was condensed into either 7.5% or 15.0% (v/v) solutions. A fourth group (gastrostomy controls) received a formula containing maltose-dextrin, which was isocaloric to the 2.5% alcohol solution. BACs were determined twice daily at times designed to estimate the daily peak and minimum BACs. The rats were killed on postnatal day 10 and total brain weights, cerebellar weights and brainstem weights were measured. In each of the three groups given alcohol, the maximum BAC occurred on the afternoon of postnatal day 6. Thereafter, daily peak BAC declined progressively. The more concentrated the pattern of alcohol administration, the higher was the maximum BAC achieved and the more severe was the interference with brain growth. While the group receiving the alcohol dose in small continuous fractions (2.5%) did not exhibit any significant microencephaly, relative to gastrostomy controls, the groups receiving the dose in more concentrated forms (7.5% and 15.0%) exhibited significant brain growth restriction (reduced 19% and 31%, respectively, relative to controls).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood alcohol concentration and microencephaly: a dose-response study in the neonatal rat.

The relationships among microencephaly, peak blood alcohol concentration (BAC), and dose of alcohol were examined in a rat model of third-trimester fetal alcohol effects. Ethyl alcohol was administered to neonatal rats from postnatal day 4 to day 10 during the brain growth spurt via an artificial rearing technique. Groups of rats received one of nine doses of alcohol (0.0, 2.5, 3.3, 4.0, 4.5, 5.3, 6.6, 7.5, or 8.5 g/kg body weight) administered in 8 hours each day. BACs were determined on postnatal days 6 and 7 at times corresponding to peak and trough BACs, respectively. On postnatal day 10, brains were removed, and total brain weights, cerebellar weights and brainstem weights were measured. Pups receiving 4.0 g/kg/day or less had mean peak BACs below 150 mg/dl and did not exhibit significant microencephaly when compared with controls. Higher dosages further increased the peak BAC and produced significant microencephaly. While a dose of 4.5 g/kg/day was sufficient to decrease significantly both total brain weight and cerebellar weight, a minimum dose of 6.6 g/kg/day was required for significant restriction of brainstem weight. The dose of 7.5 g/kg/day yielded a mean peak BAC of 420 mg/dl and reduced total brain weight, cerebellar weight, and brainstem weight by 33%, 52%, and 22%, respectively, relative to controls. Exposure to 8.5 g/kg/day was uniformly lethal. Peak BAC and total brain weight were highly correlated (r = -.916). As peak BAC increased, total brain weight decreased linearly. Comparisons with previous studies indicate that condensing the daily dose of alcohol effectively reduced the threshold doses for microencephaly and lethality.

Developmental changes in alcohol pharmacokinetics in rats.

Developmental changes in the pharmacokinetics of alcohol could influence the outcome of alcohol exposure during different periods of postnatal development. Hence, the development of the ability to absorb and metabolize alcohol in the rat was examined by administering an acute dose (2.5 g/kg) of ethanol in milk formula by intragastric intubation to rats of 1, 2, 4, 6, 8, 10, 15, 21, 30, and 60 days of age. Each animal in a particular litter was assigned a different time point following intubation when its blood alcohol concentration (BAC) was determined from a tail blood sample. At all ages tested, maximum BACs occurred between 1.25 and 1.5 hr following intubation. However, maximum BACs decreased with age from 155 mg/dl in 1-day-old rats to 111 mg/dl in 60-day-old rats. Furthermore, the rate of alcohol clearance was slower in the younger rats. By linear regression analysis, the elimination rate of alcohol in 1-day-old rats was estimated to be 7.5 mg/dl/hr which increased to 42.2 mg/dl/hr in 60-day-old-rats. By 8 hr following intubation, rats that were 21 days of age and older had completely cleared the alcohol, whereas the younger rats (1-15 days of age) had not. No consistent sex differences were seen in either the maximum BAC or clearance rate. Since developmental changes in the ability to clear alcohol occur throughout the first 60 postnatal days in the rat, controlling for these changes is essential when looking for critical periods of an organ's vulnerability to damage by alcohol.