Prenatal ethanol exposure affects temperature responses of adult rats to pentobarbital and diazepam alone and in combination with ethanol

Fetal ethanol exposure alters pituitary-adrenal sensitivity to dexamethasone suppression

The present study investigated the hypothesis that a deficit in feedback inhibition of the hypothalamic-pituitary-adrenal (HPA) axis may underlie the hormonal hyperresponsiveness seen in fetal ethanol-exposed rats. Male and female Sprague-Dawley rats from prenatal ethanol (E), pair-fed (PF) and ad lib-fed control (C) treatment groups were tested in adulthood. The effects of dexamethasone (DEX) blockade on basal and stress corticosterone (CORT) levels and stress adrenocorticotropin (ACTH) levels were examined over a 36-h period. Stress CORT and ACTH levels after DEX administration at the trough (AM) and peak (PM) of the CORT circadian rhythm were compared. DEX administration significantly suppressed both resting and stress levels of CORT and ACTH in all animals, regardless of prenatal treatment. Importantly, E animals did not differ from PF and C animals in basal CORT. However, E males and females had significantly higher stress levels of CORT and/or ACTH than PF and C animals, and further, showed differential responsiveness following DEX administration depending on the time of day when testing occurred. At the trough of the CORT circadian rhythm. E males did not differ from PF and C males, whereas E females had increased stress levels of CORT compared to PF and C females. In contrast, at the peak of the circadian rhythm, E males showed increased stress levels of CORT but not ACTH, whereas E females showed increased stress levels of both CORT and ACTH compared to males and females in respective control groups. These data support the hypothesis that E animals may exhibit deficits in HPA feedback inhibition compared to controls and suggest a sex-specific difference in sensitivity of the mechanism underlying HPA hyperresponsiveness.

Early handling can attenuate adverse effects of fetal ethanol exposure

The effects of early handling on physiological and hormonal responses of rats exposed to ethanol prenatally were studied. Male and female Sprague-Dawley rats from prenatal ethanol (E), pair-fed (PF), and ad lib-fed control (C) prenatal treatment groups were either handled (H) or nonhandled (NH) during the preweaning period and tested in adulthood. Early handling eliminated the deficit in preweaning weight gain observed in E compared to PF and C offspring. In adulthood, early handling eliminated the increased hypothermia observed in E and PF compared to C males following an ethanol challenge (2.0 g/kg, IP). In addition, H males displayed marginally less hypothermia overall than NH males. In contrast, handling accelerated the return to preinjection temperature in PF and C females but had no effect on E females. There were no significant differences among E, PF, and C rats in corticosterone (CORT) responses to ethanol challenge (1.5 g/kg, IP), but both males (marginally) and females in the H condition displayed higher CORT levels overall than NH rats. Early handling also eliminated the increased peak CORT response to restraint stress in E compared to C females, but did not affect the more prolonged elevation of CORT in E compared to PF and C females. There were no differences among E, PF, and C females in hippocampal type I and type II glucocorticoid receptor density or affinity. However, binding affinity of type II receptors was slightly but significantly increased in H compared to NH females. Together, these data indicate that early handling may modulate or attenuate some, but not all, of the adverse effects of fetal ethanol exposure on offspring growth and physiological responsiveness.

The development of beta 1-adrenoceptors in brown adipose tissue following prenatal alcohol exposure

Prenatal alcohol exposure delays the development of thermoregulation in newborn rats. Newborns generate heat by the sympathetic nervous system's activation of nonshivering thermogenesis in brown adipose tissue (BAT). In this study, the effects of prenatal alcohol exposure on the development of the beta-adrenergic receptor system of BAT was investigated by assessing the number and pharmacological properties of beta-adrenergic receptors in BAT in 1-, 5-, 10-, and 20-day-old offspring. Pregnant dams were given either a liquid diet with 35% of the calories derived from alcohol, a liquid diet without alcohol for any effects of the liquid diet administration, or ad lib food and water. Offspring from the alcohol prenatal treatment group had a greater number of beta 1 adrenergic receptors compared to offspring from both from the pair-fed and lab chow control groups, which did not differ from each other. The greater number of receptor sites in 5-day-old subjects suggests that the number of binding sites in alcohol-exposed BAT cells continues to rise due to the absence of sufficient neurotransmitter, and perhaps reflects a delay in the arrival of sympathetic nervous system neurons. During the second and third postnatal weeks, when NE concentrations are rising and reaching asymptotic levels, the number of beta 1 adrenergic receptors in BAT of control subjects is decreasing. This expected compensatory "downregulation" response in receptor concentration was not seen in BAT from subjects exposed to alcohol prenatally. These findings may have important implications for understanding the effects of prenatal alcohol exposure on developing plasticity in the peripheral nervous system.

Prenatal ethanol exposure: susceptibility to convulsions and ethanol's anticonvulsant effect in amygdala-kindled rats

The present experiments assessed the effects of prenatal ethanol exposure on the susceptibility to convulsions and on the anticonvulsant effect of ethanol using the electrical kindling model of epilepsy in rats. Adult male Sprague-Dawley rats from prenatal ethanol (E), pair-fed (PF), and ad libitum-fed control (C) treatment groups were tested following the implantation of a stimulation electrode in the left amygdala complex. The same rats were tested in four consecutive experiments. Both E and PF rats showed a slightly slower rate of kindling than C rats, as measured by convulsion class but not as measured by forelimb clonus duration (experiment 1). However, the groups did not differ significantly in the electrical stimulation threshold for kindled convulsions (experiment 2). Furthermore, prenatal ethanol exposure had no significant effect on the dose-response curve for ethanol's (0, 0.9, 1.1, 1.3, and 1.5 g/kg, ip) anticonvulsant effect (experiment 3), or on the rate of tolerance development to ethanol's (1.5 g/kg, ip) anticonvulsant effect (experiment 4) on kindled convulsions. Thus, prenatal exposure to ethanol does not appear to have long-term effects on the susceptibility to convulsions or on the anticonvulsant effect of ethanol in adult male rats in the kindling model as used in the present experiments.

Reduction of rat pup ultrasonic vocalizations by the neuroactive steroid allopregnanolone

Several of the recently characterized neuroactive steroids have been proposed to have anxiolytic effects in behavioral models when subjects were tested as adults. In this experiment, the effects on infant subjects were examined using the isolation distress model of anxiety. The production of ultrasonic vocalizations in week-old rat pups after maternal separation was assessed after ICV injections of vehicle or allopregnanolone (1.25-5 micrograms), or sham injections. Subjects were also observed for activity and behavioral responses and tested on three measures of sedation. Allopregnanolone caused a dose-dependent decrease in ultrasonic vocalizations, with increasing motor incoordination, ataxia, and turning at the higher doses. Sex differences were not observed for any measure. These results suggest the GABAA receptor binding site for neuroactive steroids is behaviorally active in neonates as well as in adults, and that the anxiolytic effects of the neuroactive steroids at this site may be dissociable from their sedative effects at low doses.

Fetal alcohol exposure attenuates lipopolysaccharide-induced fever in rats

Exposure to alcohol in utero can lead to long-lasting impairments of immune functions and to decreased resistance to infectious agents. We studied the effects of fetal alcohol exposure (FAE) in rats on the core body temperature response to an exogenous challenge of the immune system with lipopolysaccharide (LPS). We report that FAE rats show markedly decreased LPS-induced fever [i.e., they require a higher dose than control rats to show any LPS-induced hyperthermia (50 micrograms/kg vs. 10 micrograms/kg)], and even with the higher LPS dose they manifest a weaker hyperthermia, which declines faster than in control animals. These results suggest that FAE produces an impairment in the release of endogenous pyrogens and/or in the neural substrate for body temperature regulation. This impairment may account for at least some of the decreased resistance to infections observed in FAE animals and humans.

Effects of prenatal alcohol exposure on uncoupling protein in brown adipose tissue in neonatal rats

Thermoregulatory deficits observed in neonatal rats exposed prenatally to alcohol may be due to peripheral and/or central dysfunction. One of the major mechanisms available to newborn mammals to generate heat is "nonshivering thermogenesis" in brown adipose tissue (BAT). In this study, the effects of prenatal alcohol exposure on the functional status of brown adipose tissue was assessed by immunoblot analysis of the content of mitochondrial uncoupling protein (UCP). BAT excised from 1- and 20-day-old male and female offspring from either alcohol-treated, pair-fed controls or standard control dams were analyzed. There were no effects of prenatal alcohol exposure on the UCP content. There was, however, a significant increase due to age. These results suggest that thermoregulatory deficits seen in alcohol-exposed offspring are not due to a deficiency in the concentration of mitochondrial UCP, and indicate a more central mechanism.

Effects of in utero administration of alcohol on alcohol sensitivity in adult rats

In utero exposure to alcohol has been associated with many physical deficits and behavioral abnormalities. The purpose of these studies was to determine the effects of in utero administration of alcohol on behaviors related to tolerance and sensitivity to alcohol in adult rats. Pregnant rats were maintained on a liquid diet containing alcohol [35% ethanol-derived calories (EDC)] throughout pregnancy. Offspring manifested physical characteristics of Fetal Alcohol Syndrome. The 35% EDC group was able to stay on a wooden dowel longer and at higher blood alcohol concentrations than were pair-fed controls. Following a hypnotic dose of alcohol, rats in the 35% EDC group slept longer than pair-fed controls. A greater alcohol-induced hypothermic effect was seen in females in the 35% EDC group than in controls. Treatment did not affect rate of metabolism of alcohol. These studies suggest that in utero administration of alcohol may be a factor in determining an individual's sensitivity and tolerance to alcohol and possibly their preference for alcohol.

Sex differences in sensitivity to pentylenetetrazol but not in GABAA receptor binding

Female rats have a higher threshold than males for seizures induced by the convulsant pentylenetetrazol, a GABAA receptor-chloride channel complex blocker. No sex difference was observed for the anticonvulsant activities of ethanol or diazepam to protect against pentylenetetrazol seizures. Ovariectomy reduces the pentylenetetrazol seizure threshold of females to that of males. In contrast, females have a lower threshold than males to electroshock seizures. Pentylenetetrazol receptors were compared in males and females and gonadectomized animals by binding of several radioligands to the GABAA receptor complex. No differences were found for these four groups of animals in the binding of [3H]flunitrazepam to the benzodiazepine sites and [35S]t-butyl bicyclophosphorothionate ([35S]TBPS) to the chloride channel/convulsant sites in membrane homogenates, nor for allosteric modulation of binding by GABA, the steroid anesthetic alphaxalone, or the benzodiazepine Ro 5-4864. In tissue section autoradiography, no difference was observed for these same assays nor for the binding of [3H]muscimol in the presence and absence of alphaxalone in several major regions. We conclude that circulating female sex hormones, possibly neurosteroid metabolites of progesterone, known to interact directly with the GABAA receptor complex, are involved in the sex differences in pentylenetetrazol seizure susceptibility.

Tolerance to ethanol-induced hypothermia in adult rats following postnatal ethanol exposure

Rat pups of both genders were treated during the entire postnatal brain growth spurt (postnatal days 1-20) with ethanol (EE) utilizing an intragastric intubation technique. Two other groups of pups included isocaloric vehicle and handled control pups. Beginning on postnatal day 43 (TD1), and every seventh day subsequently (TD's 2, 3 and 4), the rats received an intraperitoneal dose of 2.2 g/kg ethanol. Their body temperatures were recorded at 0, 30, 60 and 90 minutes postinjection by use of a rectal probe. On the six days between measurements of ethanol-induced hypothermia, all rats were administered a daily dose of ethanol by intragastric intubation. Body growth of male and female pups was inhibited throughout the early treatment period. Body growth of adult females, but not males, was also depressed on TD's 1 and 2. Basal body temperature of EE male rats was selectively depressed at TD2, compared to the other groups. Although all groups showed tolerance to ethanol-induced hypothermia by TD2, there was a significant difference between males and females. Specifically, EE female rats showed a greater degree of tolerance when compared to EE males or control females.

Differential actions of RO 15-1788 and diazepam on poikilothermia, motor impairment and sleep produced by ethanol

In adult male Sprague-Dawley rats kept at an ambient temperature of 23-25 degrees C, ethanol was injected intraperitoneally in a dose of 4.0 g/kg to produce a clear-cut impairment of autonomic and motorial functions. Following the injection of ethanol, motor coordination, measured on a rotorod, behavioral sleep, righting reflex and colonic temperature were monitored at predetermined intervals for 5.0-7.0 hr. In the first experiment, either 1.0 mg/kg RO 15-1788 (flumazenil), a benzodiazepine (BZ), receptor antagonist, or 1.0-5.0 mg/kg diazepam, a classical benzodiazepine receptor agonist, were injected intraperitoneally either alone or concurrently with ethanol's administration. In the second study, either RO 15-1788 (1.0 or 2.0 mg/kg) or diazepam (1.0 or 5.0 mg/kg) was injected at the nadir of the fall of body temperature induced by ethanol. Although RO 15-1788 alone failed to affect the rats' temperature, it did not prevent the characteristic ethanol-induced hypothermia but rather potentiated it in a dose-dependent manner. Further, this BZ receptor antagonist exacerbated motor incoordination and other behavioral effects when given either simultaneously with ethanol or at the nadir in the animals' core temperature. Although diazepam evoked a dose-dependent hypothermia, it did not enhance ethanol-induced hypothermia when both drugs were administered simultaneously. However, diazepam augmented motor incoordination and other effects and served to delay their recovery. When given to the rats at the nadir of ethanol hypothermia, diazepam did not potentiate ethanol's thermolysis but retarded the recovery from hypothermia; it caused also a dose-dependent delay in the recovery of motor coordination and other responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermoregulatory deficits following prenatal alcohol exposure: structural correlates

Prenatal exposure to alcohol delays the development of thermoregulation in newborn rats. This study examined two possible physiological correlates of this effect. In the first experiment, the effect of prenatal alcohol exposure on the availability of brown adipose tissue for nonshivering thermogenesis was investigated in rat pups from birth to weanling age. Male and female pups were chosen from independent litters with one of three prenatal treatment histories: 35% ethanol-derived calories (35% EDC), pair-fed control (0% EDC), or lab-chow control (LC). Prenatal alcohol exposure resulted in decreased body weight from postnatal (PN) day 1 to 20 compared to controls. Similarly, alcohol-exposed subjects had lighter interscapular brown adipose tissue pads than controls. However, the proportion of brown adipose tissue to body weight in alcohol-exposed pups was not different from controls. It appears that thermoregulatory deficits at birth due to prenatal alcohol exposure are not due to decreased substrate availability. In the second experiment, the relative growth rate of the tail compared to the growth rate of the body was measured in male and female pups from the three prenatal treatment groups. Five-day-old rat pups exposed to alcohol prenatally had relatively slower tail growth than control pups. Since tail growth rate has been associated with ambient temperature, these results suggest that alcohol-exposed rat pups may be experiencing transient periods of cold stress in the nest because of their thermoregulatory deficiencies, which, in turn, could have important implications for neural and body growth retardation seen in Alcohol Related Birth Defects.

Acute alcohol intoxication paired with aversive reinforcement: ethanol odor as a conditioned reinforcer in rat pups

Previous research has suggested that infant rats process ethanol sensory properties during acute alcohol intoxication. The present study was designed in order to examine if alcohol odor could act as an aversive conditioned stimulus after the organism experiences the state of intoxication paired with nociceptive stimulation (footshock). In a first experiment 11-day-old pups received intragastric alcohol administration (1.5 g/kg). At different postabsorptive intervals footshock was presented (0-30, 30-60, 60-90, or 90-120 min). An explicitly unpaired control group which experienced footshock prior to the state of intoxication was also employed. All animals were subsequently tested in terms of alcohol intake and ethanol locational odor preferences. Both assessments indicated that pups which were exposed to the unconditioned peripheral stimulus 30-60 min after receiving ethanol expressed strong alcohol aversions. In a second experiment pups were exposed to footshock during this postabsorptive interval. Twenty four hours later, pups experienced ambient ethanol odor paired with soft or rough texture surfaces. Differential texture aversions were registered in experimental animals when compared with controls which suffered the state of intoxication explicitly unpaired with footshock, or unpaired presentations of ethanol odor and the tactile stimuli under consideration. These results appear to support the hypothesis concerning orosensory processing during an acute state of intoxication. Additionally it seems that the hedonic value of sensory attributes of this drug varies as a function of associative processes occurring during such a state.

Voluntary beer drinking by pregnant rats: offspring sensitivity to ethanol and preference for beer

Female Long-Evans rats were allowed voluntary access to beer, food and water for three weeks prior to mating and throughout gestation; and were compared to controls. Offspring were tested for sensitivity to ethanol and preference for beer at 29 and 85 days of age. Offspring of beer drinkers had long-term alterations in sensitivity to ethanol as adults, although rates of ethanol metabolism were unaffected. The nature of responsivity to ethanol as adults was sex-dependent. Male offspring of beer drinkers were delayed in maintaining baseline body temperature at 29 days with recovery at 85 days; and were tolerant to the hypothermic effects of ethanol at 29 and 85 days. Female offspring had prolonged latency to respond to pain and temperature; and were tolerant to the effects of ethanol on motor coordination at 29 and 85 days. Although preference of the offspring for beer was not affected by maternal beer drinking, the pattern of fluid intake by offspring of beer drinkers differed from controls.

Diminished proliferative response of con A-blast cells to interleukin 2 in adult rats exposed to ethanol in utero

The fetal alcohol syndrome is associated with altered immunity. We attempted to delineate the mechanism of the decline in cell-mediated immunity observed by others by using rats which were exposed to alcohol in utero and tested for immune integrity 3 months after birth. We found that concanavalin A-stimulated T-lymphoblast (Con A T-blast) cells that were obtained from ethanol-exposed rats had significantly diminished proliferative responses to both crude and recombinant interleukin 2 compared to those obtained from normal and nutritional controls. The blunted response of Con A T-blast cells to interleukin 2 may be a biomarker of fetal exposure to alcohol.

Prenatal ethanol exposure impairs lesion-induced plasticity in a dopaminergic synapse after maturity

This study examined the consequences of alcohol (ethanol) exposure during fetal life on lesion-induced dopaminergic synapse responsiveness (plasticity) in the olfactory tubercle of the adult rat. Normally, in the olfactory tubercle, olfactory bulbectomy elicits alterations in pre- and postsynaptic dopaminergic markers, including, respectively, (1) increased tyrosine hydroxylase activity and immunoreactivity, which is associated with dopaminergic axon sprouting, and (2) increased dopaminergic receptor density and potentiated dopamine activation of adenylate cyclase. We have utilized biochemical and quantitative immunocytochemical methodology to examine these synaptic markers in olfactory bulbectomized or sham-operated adult rats. These animals were offspring of dams which were administered one of the following diets during pregnancy: (1) liquid diet containing 35% ethanol-derived calories ad libitum; (2) liquid diet containing an isocaloric amount of maltose-dextrin instead of ethanol, pair-fed; or (3) unaltered liquid diet ad libitum. The results show that prenatal alcohol exposure leads to suppression of the lesion-elicited dopaminergic synapse responsiveness in the olfactory tubercle. There were no significant differences between offspring born to control and pair-fed animals, indicating that the observed abnormalities were not due to alterations in their nutritional status. In conclusion, the present data are a biochemical and quantitative immunocytochemical demonstration of impaired lesion-induced synaptic responsiveness. This renders a new dimension in support of previous evidence indicating that prenatal alcohol exposure leads to altered neuroanatomical, neuroendocrinological and behavioral responsiveness to various challenges. Such impaired synaptic responsiveness may underlie brain functional abnormalities characteristic of fetal alcohol syndrome.

Prenatal ethanol weakens the efficacy of reinforcers for adult mice

Pregnant C57BL/6cr mice were fed a liquid diet containing 20% of the total calories from either ethanol (E) or sucrose (S) for gestation days 5-17. Adult male and female (six of each from both prenatal-treatment groups) offspring were tested under various schedules of food reinforcement. The first phase was a test of fixed-ratio (FR) acquisition in which the required number of responses per unit of reinforcement was increased from 1 to 20 to 100. Prenatal ethanol exposure interacted with other factors to produce an acquisition deficit. The second phase involved responding under extinction (Ext). Under standard Ext procedures there were no prenatal-ethanol effects; however, when a conditioned reinforcer was superimposed on an FR 5, the E males did not increase their rates as much as the S males. Finally, under a multiple FR 5 DRO 15-sec (differential-reinforcement-of-other-behavior) arrangement, prenatal-ethanol effects were found in each component. For the FR 5 component, prenatal ethanol eliminated the sex differences found in the S subjects. For the DRO 15-sec component, prenatal ethanol elevated response rates. The results indicate a general decreased efficacy of positive reinforcement in adult mice following prenatal ethanol exposure.