Fetal Ethanol Exposure: Hypothalamic-Pituitary-Adrenal and β-Endorphin Responses to Repeated Stress

Previous studies provide evidence that fetal ethanol exposure induces hypothalamic-pituitary-adrenal (HPA) and pituitary β-endorphin (β-EP) hyperresponsiveness to acute stressors. The present study demonstrates significant effects of in utero ethanol exposure on the parallel response patterns of the HPA axis and the pituitary β-EP system to repeated exposures to a stressor, restraint stress, and indicates sex differences in response. Together, data from the two experiments indicate that, after repeated restraint exposures, fetal ethanol-exposed (E) males and females both show significantly increased plasma levels of adrenocorticotropin (ACTH), and E males also show significantly increased plasma levels of β-endorphin-like immunoreactivity (β-EPLIR), compared with their respective pair-fed and control counterparts. Marginal increases in the corticosterone response of E males and the β-EPLIR response of E females, compared with their controls, were also observed. In addition, delayed or deficient habituation to restraint stress was observed in the β-EPUR response of E males and the ACTH response of E females. These data demonstrate that fetal E-exposed males and females both exhibit hormonal hyperresponsiveness and/or deficits in recovery after repeated exposures to restraint stress, but that the patterns of response may differ depending on the number and duration of restraint exposures, the time course measured, and whether the endpoint measured is corticosterone, ACTH, or β-EPLIR. In addition, the finding that E and pair-fed animals both differed from their respective controls in certain developmental and hormonal measures suggests that prenatal nutritional factors may play a role in mediating some of the changes that are observed.     

Effects of Alcohol on β-Endorphin and Reproductive Hormones in the Male Rat

In an attempt to examine the relationship between alcohol-induced alterations in immunoreactive beta-endorphin (i-beta E) levels in the hypothalamic-pituitary-gonadal axis and the synthesis and release of reproductive hormones, male rats were treated with either an acute intraperitoneal injection of alcohol or were chronically exposed to an alcohol-containing liquid diet. Hypothalamic, pituitary, serum, and testicular levels of immunoreactive beta-endorphin (i-beta E) and serum levels of luteinizing hormone (LH) and testosterone were measured at various times after initiation of these treatments. Testicular interstitial fluid (TIF) volumes and levels of TIF i-beta E and testosterone were also measured 4 hr after acute treatment as an index of testicular release of these substances. Acute alcohol decreased pituitary levels of i-beta E and increased serum levels of the peptide for up to 1 hr after its injection, but did not alter hypothalamic or testicular levels. Acute alcohol markedly increased TIF i-beta E and decreased TIF testosterone and TIF volume. Sharp decreases in serum LH and testosterone were observed in association with these acute changes in i-beta E levels in the pituitary, blood, and testes. During chronic alcohol exposure serum testosterone levels were substantially depressed, but tolerance appeared to develop quickly to the chronic effects of alcohol on serum LH. Similarly, tolerance to alcohol's effects on i-beta E levels in the pituitary and serum also appeared to develop during chronic alcohol administration. However, hypothalamic and testicular i-beta E levels were markedly suppressed by chronic alcohol administration in contrast to the lack of effect observed after acute alcohol administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differences in the Brain and Pituitary β-Endorphin System between the Alcohol-Preferring AA and Alcohol-Avoiding ANA Rats

The content of pro-opiomelanocortin (POMC) mRNA was determined in the hypothalamus, as well as in the anterior and intermediate lobes of the pituitary gland of the alcohol-preferring AA and alcohol-avoiding ANA rats under basal conditions. In addition the content of beta-endorphin-like immunoreactivity (beta-EPLIR) was measured in nine brain regions, the anterior and intermediate lobes of the pituitary gland and the serum. The content of beta-EPLIR was significantly higher in the septum and significantly lower in the amygdala, and periaqueductal gray matter of the AA rats, while there was no significant difference between the AA and ANA rats in the arcuate nucleus plus median eminence, nucleus accumbens, caudate, hippocampus, and cortex. HPLC analysis indicated no significant differences in the relative proportions of non-acetyl and acetyl forms of beta-endorphin peptides in the hypothalamus, distinct brain regions, and anterior and neurointermediate lobes of the pituitary gland, between the AA and ANA rats. The content of POMC mRNA but not of beta-EPLIR was significantly higher in the hypothalamus and neurointermediate lobe of the AA rats, while the content of both beta-EPLIR and POMC mRNA were significantly higher in the anterior pituitary of the AA than of the ANA rats. Thus, there are genetically determined differences in the pituitary and brain beta-endorphin system between the AA and ANA rats, which may be important in controlling the differences in the voluntary ethanol consumption exhibited by these animals.     

β-Endorphin Neuronal Cell Transplant Reduces Corticotropin Releasing Hormone Hyperresponse to Lipopolysaccharide and Eliminates Natural Killer Cell Functional Deficiencies in Fetal Alcohol Exposed Rats

Background: Natural killer (NK) cell dysfunction is associated with hyperresponse of corticotropin releasing hormone (CRH) to immune challenge and with a loss of β‐endorphin (BEP) neurons in fetal alcohol exposed animals. Recently, we established a method to differentiate neural stem cells into BEP neurons using cyclic adenosine monophosphate (cAMP)‐elevating agents in cultures. Hence, we determined whether in vitro differentiated BEP neurons could be used for reversing the compromised stress response and immune function in fetal alcohol exposed rats. Methods: To determine the effect of BEP neuron transplants on NK cell function, we implanted in vitro differentiated BEP neurons into the paraventricular nucleus of pubertal and adult male rats exposed to ethanol or control in utero. The functionality of transplanted BEP neurons was determined by measuring proopiomelanocortin (POMC) gene expression in these cells and their effects on CRH gene expression under basal and after lipopolysaccaride (LPS) challenge. In addition, the effectiveness of BEP neurons in activating NK cell functions is determined by measuring NK cell cytolytic activity and interferon‐γ (IFN‐γ) production in the spleen and in the peripheral blood mononuclear cell (PBMC) following cell transplantation. Results: We showed here that when these in vitro differentiated BEP neurons were transplanted into the hypothalamus, they maintain biological functions by producing POMC and reducing the CRH neuronal response to the LPS challenge. BEP neuronal transplants significantly increased NK cell cytolytic activity in the spleen and in the PBMC and increased plasma levels of IFN‐γ in control and fetal alcohol exposed rats. Conclusions: These data further establish the BEP neuronal regulatory role in the control of CRH and NK cell cytolytic function and identify a possible novel therapy to treat stress hyperresponse and immune deficiency in fetal alcohol exposed subjects.     

Hormonal (ACTH, Cortisol, β-Endorphin, and Met-Enkephalin) and Cardiovascular Responses to Hyperthermic Stress in Chronic Alcoholics

Chronic alcohol drinking causes profound alterations in hypothalamic-pituitary function. In the present study, endocrine [corticotropin (ACTH), β-endorphin, cortisol, and met-enkephalin] and cardiovascular (blood pressure) changes in response to hyperthermic stress (sauna at 90°C for 30 min) were evaluated in 25 normal men (25 to 50 years old) and in 48 male alcoholic subjects (34 to 56 years old) after 5 weeks of abstinence. Significantly lower increments in systolic blood pressure were observed in alcoholics than in control subjects. Furthermore, alcoholics showed lower ACTH, β-endorphin, and cortisol increments in response to sauna than normal controls. In contrast, sauna-induced hyperthermia did not change significantly the circulating met-enkephalin levels in either normal controls or chronic alcoholics. These data suggest that an impairment in the adaptive response to stress affects alcoholic men even after a few weeks of abstinence from alcohol.     

Effects of Ethanol on Basal and Prostaglandin E1-Induced Increases in β-Endorphin Release and Intracellular cAMP Levels in Hypothalamic Cells

Our recent studies determining the effect of cAMP-elevating agents forskolin and dibutyryl cAMP on ethanol-induced immunoreactive p-endorphin (IR-β-EP) release from hypothalamic cells in primary cultures suggested the possibility that both stimulatory and adaptive secretory responses of β-EP neurons after ethanol exposure may involve the cAMP system. To determine further the role of cAMP, the effects of prostaglandin E1 (PGE1) on basal and ethanol-regulated IR-β-EP secretion and cAMP productions were determined in primary cultures of hypothalamic cells. The results presented in this study show that a 50 mM dose of ethanol, which is within the EC₅₀ dose of ethanol required to elevate IR-β-EP release from hypothalamic cells, increased cellular levels of cAMP and elevated IR-β-EP release simultaneously from the cultured neurons for a period of 6 hr. The cAMP and IR-β-EP secretory responses developed desensitization to ethanol challenge after 24 hr of constant ethanol incubation. The cAMP-elevating agent PGE1 increased the cellular content of cAMP and IR-β-EP release in a dose-dependent manner. The EC₅₀ dose of PGE1 for elevation of IR-β-EP and cAMP was ∼0.5 μM. As with ethanol, chronic treatment with PGE1 desensitized the cAMP and IR-β-EP responses of hypothalamic neurons to PGE1. Acute exposure to ethanol increased the PGE1 -stimulated levels of cAMP and IR-β-EP, whereas chronic exposure to ethanol resulted in diminished cAMP responses to PGE1. These data provide evidence that the cAMP system may be involve in controlling hypothalamic β-EP secretion, as well in regulating the stimulatory and adaptive responses of β-EP neurons to ethanol.     

Prenatal Alcohol Exposure Blunts Interleukin-1-Induced ACTH and β-Endorphin Secretion by Immature Rats

The functional relationship between the immune and the hypotha-lamic-pituitary-adrenal (HPA) axis [and in particular the release of pro-opiomelanocortin (POMC)-related peptides and corticosteroids induced by interleukins (ILs)] is essential for coordinating the appropriate immune responses to pathogens. Exposure of pregnant mammalian females to alcohol results in abnormal immune functions in the offspring, as well as in altered HPA axis activity. We therefore tested the hypothesis that prenatal alcohol exposure might modify the stimulatory action of ILs on the HPA axis of the pups, thus providing a mechanisms through which this treatment results in increased rate of infectious or inflammatory processes. Pregnant dams were fed a liquid alcohol diet throughout gestation. Dams with free access to food (ad libitum group), or dams fed an isocaloric diet in which sucrose replaced alcohol (pair-feeding), were also included. At 22-24 days of age, the pups were injected intraperitoneally with IL-1β, corticotropin-releasing factor (CRF), or the vehicle. Blood samples obtained 1-2 hr later indicated that the alcohol diet resulted in significantly blunted adrenocorticotropic hormone (ACTH) and 0-endorphin, but not corticosterone release, in response to IL-1β. Pair-fed pups also showed some decrease in their pituitary response, although to a lesser degree. In contrast, there was no measurable difference in the ability of CRF to increase plasma ACTH levels. These results suggest that prenatal exposure to alcohol interferes with the stimulatory action of IL-1β on the secretion of POMC-related peptides, a phenomenon probably not caused by decreased pituitary responsiveness to CRF. As pups born to pair-fed dams also exhibited a measurable, although less significant, decrease in IL-induced ACTH and β-endorphin release, a possible synergism between caloric restriction and alcohol also needs to be ascertained. We propose that the ability of prenatal alcohol treatment to blunt the release of POMC-related peptides in response to IL-1/S may participate in the abnormal immune functions of the offspring.     

Effect of Alcohol, Acetaldehyde, and Salsolinol on β-Endorphin Secretion from the Hypothalamic Neurons in Primary Cultures

The effect of ethanol, acetaldehyde, and salsolinol on hypothalamic β -endorphin secreting neurons is studied by using rat fetal hypothalamic neurons in primary culture. Exposure of these neuronal cells to different concentrations of ethanol (12.5–50 mM) and acetaldehyde (12.5-50 μm) caused a concentration-dependent increase in the secretion of β -endorphin. Salsolinol (12.5–50 μm) did not cause any significant change in the secretion of β -endorphin. Ethanol's effect was short-lasting (2 hr). Acetaldehyde's effect on β -endorphin secretion was greater and longer lasting, as compared with ethanol. Ethanol and salsolinol do not have any effect on cell viability, whereas higher concentrations of acetaldehyde appear to reduce the number of viable cells after 6 hr of treatment. None of the above treatments has any effect on cellular DNA content. These results suggest that ethanol is a potent stimulator of hypothalamic β -endorphin. These results also show for the first time that ethanol's metabolite acetaldehyde is more potent in stimulating β -endorphin secretion and may be significant in the ethanol regulated β -endorphin secretion.     

Intravenous Self-Administration of Ethanol in β-Endorphin-Deficient Mice

Extensive research on both human alcoholics and in animal models of alcoholism has implicated the release of endogenous opioids in the consumption of ethanol. Various experiments using opioid antagonists have indicated that these drugs cause both humans and animals to decrease their consumption of ethanol. However, it remains unclear exactly which of the endogenous opioids mediates the rewarding effects of ethanol. The present experiment used intravenous self-administration of ethanol to determine whether β -endorphin (BE)-deficient mice differed from wild-type (WT) mice in ethanol self-administration. The BE-deficient mice completely lack BE, but are otherwise similar to the WT mice. By using intravenous self-administration, we were able to rule out any ability of BE to mediate differences in ethanol consumption via palatability factors alone. Both types of mice were 7 generations backcrossed onto a C57BL/6J inbred strain background. During nine daily, 2-hr free-operant sessions, 14 BE-deficient and 17 WT mice could nosepoke for 75 mg/kg ethanol infusions delivered intravenously on an fixed-ratio 3 schedule with a 2-sec time-out after each reinforcer delivery. Reinforcer delivery occurred following nosepokes in only one of two holes. Contrary to what was expected, BE-deficient mice acquired selective operant responding for ethanol, whereas WT mice did not. Although the two genotypes did not differ in either operant or locomotor behavior during the first session, by the end of the nine sessions, BE deficient mice were reliably nosepoking for ethanol, whereas WT mice were not. These findings may indicate that BE is not essential for the postingestive reinforcing effects of ethanol in these animals.     

Spontaneous and Ethanol-Stimulated In Vitro Release of β-Endorphin by the Hypothalamus of AA and ANA Rats

Previous studies demonstrated that both the spontaneous and ethanol-stimulated release of β-endorphin (β-EP) like-peptides (β-EPLPs) by the hypothalami of the ethanol-preferring C57BL/6 mice is more pronounced than by the hypothalami of the ethanol-avoiding DBA/2 mice. The objective of the present studies was to investigate the effects of various concentrations of ethanol on the in vitro release of β-EP peptides by the hypothalami of the ethanol-preferring Alko-Alcohol (AA) and ethanol-avoiding Alko Non-Alcohol (ANA) lines of rats. Results indicated that although the spontaneous release of hypothalamic β-EPLPs was higher by the ANA than by the AA rats, the percentage increase following exposure to various concentrations of ethanol was similar in both lines of rats. Furthermore, the release of hypothalamic β-EPLPs following exposure to 30 mM ethanol was significantly higher than the release following exposure to 10 mM ethanol in the AA, but not the ANA, rats. Analysis of the released β-EPLPs with Sephadex G-75 and reversed phase HPLC indicated that the nonacetylated β-EP1-31 was the major component in the hypothalamic perifusates of the AA rats, whereas the shorter and acetylated forms of β-EP were the predominant components in the hypothalamic perifusates of the ANA rats. Because the shorter and acetylated forms of β-EP are devoid of opioid activity, their pronounced release by the hypothalami of the ANA rats may be important in maintaining their low ethanol consumption, even after long-term access to ethanol solutions.     

Effect of Voltage-Dependent Calcium Channel Blockers on Ethanol-Induced β-Endorphin Release From Hypothalamic Neurons in Primary Cultures

The voltage-dependent calcium channel (VDCC) has been shown to mediate calcium entry into neurons that regulates neurotransmission in many neuronal cells. Four major types of VDCCs (three high-voltage-activated L-, N-, and P-types and one low-voltage-activated T-type) have been identified in neurons. Involvement of the VDCC in ethanol-stimulated beta-endorphin (beta-EP) release from hypothalamic neurons has not been studied. In the present study, the role of VDCC on basal and ethanol-induced beta-EP release was determined by using rat fetal hypothalamic cells in primary cultures. Treatments with a 50 mM dose of ethanol for 3 hr increased immunoreactive beta-EP (IR-beta-EP) release from hypothalamic cells maintained in cultures for 9 days. Ethanol-induced IR-beta-EP release was inhibited by a P/Q-type channel blocker omega-agatoxin TK (0.1-1 microM), an N-type channel blocker omega-conotoxin (0.1-1 microM), an L-type blocker nifedipine (1-10 microM), and a T-type blocker flunarizine (1-10 microM). The minimal effective doses of these blockers that blocked the ethanol response produced no significant effects on basal release of IR-beta-EP; neither did these doses of the blockers produce any significant effects on cell viability. These results suggest that ethanol-stimulated IR-beta-EP release is regulated by extracellular calcium involving P-, N-, L- and T-type channels.     

Forskolin Delays the Ethanol-Induced Desensitization of Hypothalamic β-Endorphin Neurons in Primary Cultures

Ethanol and its metabolite acetaldehyde have been shown to stimulate immunoreactive β-endorphin (IR-β-EP) secretion from hypothalamic neurons in primary cultures. Also, chronic ethanol and acetaldehyde have been shown to cause the development of tolerance and desensitization of these neurons. In this study, we determined some of the cellular events leading to desensitization of the function of β-endorphin (p-EP) Secretory neurons. The fetal hypothalamic cells were treated with various doses of ethanol (W and 50 mM) or acetaldehyde (6.25,12.5, and 25 mM) for 6 hr or treated with these drugs at 12 hr intervals for 72 hr. Determination of IR-β-EP concentrations in the media revealed that ethanol increased IR-β-EP secretion from these cultures for 12 hr; after this period, the cultured cells did not respond to ethanol. Acetaldehyde stimulated IR-β-EP secretion from this culture for a period of 48 hr, but the IR-β-EP secretory response to acetaldehyde reduced gradually with time during the first 48-hr period and reached the basal level at 72 hr. The desensitization of β-EP neurons 12 hr after treatment with alcohol did not seem to be related to the loss of viable cells, because chronic ethanol exposures did not produce any effect on cell viability. However, reduced IR- β-EP secretory response to acetaldehyde with time was associated with the time-dependent increase in cell death. Pretreatment of cultures with a cAMP analog, forskolin, increased the activity of functional β-EP neurons and delayed the ethanol desensitization effects on these neurons. Pretreatment of forskolin did not delay the acetaldehyde desensitization of β-EP neurons, but protected these cells from acetaldehyde toxicity. These results suggest that (i) chronic treatment with ethanol desensitizes β-EP-secreting neurons due to reduced cellular functions and (ii) chronic acetaldehyde reduces β-EP neurotransmission due to cell death. Furthermore, data suggest for the first time that cAMP pretreatments delay the ethanolinduced desensitization of opioid neurons and partly protect against the neurotoxic action of acetaldehyde on opioid neurons.     

The Role of cAMP in Ethanol-Regulated β-Endorphin Release from Hypothalamic Neurons

We have previously shown that ethanol acutely stimulates immuno-reactive β-endorphin (IR-β-EP) release from hypothalamic neurons, whereas chronic administration of ethanol desensitizes these neurons. In the study reported herein, the role of the intracellular cAMP system in the ethanol-regulated IR-β-EP release from hypothalamic cells in primary cultures was investigated. Acute treatment with ethanol or with the cAMP analog, dibutyryl cAMP, revealed that both agents stimulate the release of IR-β-EP from the hypothalamic cells. Combined treatment of ethanol and the cAMP analog produced a synergistic effect on IR-β-EP release. Treatment with ethanol and a cAMP-elevating agent, forskolin, increased cAMP levels in cultured hypothalamic cells. However, prior exposure to ethanol reduced the cAMP-elevating responses of these neurons to ethanol and forskolin. These results indicate that the stimulatory and adaptive responses of IR-β-EP neurons to ethanol may involve the cAMP system.     

Interaction of Stress and Ethanol: Effect on β-Endorphin and Catecholamines

To examine the interaction of ethanol (ET) and stress on beta-endorphin and catecholamine (CA) levels, male rats pretreated with ET (3.0 g/kg, i.p.) or saline were immobilized for 30 min and killed 90 min after the initial injection. Stress resulted in (a) an increase in plasma levels of norepinephrine (NE, 243%), epinephrine (E, 175%), beta-endorphin (220%) and corticosterone (CS, 151%) and a decrease in dopamine (DA, 54%); (b) a decrease in hypothalamic NE (15%) and beta-endorphin (33%) levels and an increase E (23%) and DA (58%) levels; (c) a decrease in pituitary beta-endorphin levels in both the neurointermediate (23%) and anterior (131%) lobes. Treatment with ET resulted in: (a) an increase in plasma NE (81%), E (53%), CS (71%), and beta-endorphin (33%) levels and decrease in DA (54%); (b) a decrease in the hypothalamic NE (12%) levels and an increase DA (27%) and beta-endorphin (46%) levels, and (c) a decrease in beta-endorphin (15.5%) in the intermediate lobe of the pituitary. Treatment with ET of stressed animals had only a small effect: (a) in plasma NE, E, CS, and beta-endorphin levels decreased by 30, 31, 14, and 36%, respectively; (b) in the hypothalamus DA levels decreased by 40% and beta-endorphin increased by 71%; (c) in the pituitary beta-endorphin increased in both the intermediate lobe (25%) and anterior (50%) lobes. Thus when the data of the stressed ET-treated group is compared to that of the nonstressed saline injected group, none of the measures differ significantly. These results confirm our earlier work indicating a significant interaction of ET and stress.     

Prenatal Exposure to Ethanol Alters the Ontogeny of the β-Endorphin Response to Stress

To determine whether prenatal exposure to ethanol alters the response of the β-endorphin (β-EP) system to stress, the effect of two types of stressful stimuli, ether and cold, was examined in the offspring of rats which during pregnancy were: (a) fed with an ethanol-containing diet; (b) pair-fed with an isocaloric sucrose diet; and (c) fed ad libitum with standard lab chow (basic control group). The effect of stress on the content of β-EP in the serum, pituitary gland and hypothalamus, as well as on the serum corticosterone and hypothalamic corticotropin-releasing factor (CRF) content was examined. Pups prenatally exposed to ethanol had significantly higher serum β-EP levels on Day 1 and higher serum corticosterone levels on Days 1-3 when compared to their pair-fed or basic controls. On all days tested pituitary β-EP content was lower in the offspring of the ethanol-treated rats than in the control groups. There was no difference in the total hypothalamic β-EP content between the three treatment groups; however, during the first 10 days of life a higher concentration (ng/mg protein) of β-EP was observed in the hypo-thalami of the ethanol and the pair-fed group when compared to the basic control pups. Hypothalamic CRF levels, though significantly lower in the pups exposed to ethanol in utero than in the control groups on Day 3, increased significantly in the ethanol group between Days 14 and 22, while no significant change was observed during this period in either of the control groups. From Days 1 to 10 significant elevations in serum corticosterone, levels were observed following both types of stress in the pair-fed and the basic control group, while no significant response, to either type of stressful stimuli, was observed prior to Day 14 in the pups exposed to ethanol prenatally. On Day 14 cold stress induced small increases in the serum β-EP and corticosterone levels of the offspring treated prenatally with ethanol which, however, were less pronounced than the elevations observed in both of the control groups. Furthermore, exposure to ether stress on Day 14 elicited no response by the β-EP system of the ethanol-exposed offspring. In contrast, the 22-day-old offspring of the ethanol-treated rats exhibited greater elevations in serum β-EP and corticosterone levels, following stress, than the offspring of the pair-fed and basic control groups. The elevations of serum β-EP levels following stress were associated with small decreases in the pituitary β-EP and hypothalamic CRF contents. Thus, the response of the β-EP system to stress was modified by prenatal exposure to ethanol, being suppressed at early postnatal life and enhanced at later stages of development. The transition from reduced to enhanced responsiveness seemed to occur during the third week of life.     

Effect of Prenatal Exposure to Ethanol on Body Growth and the Pituitary β-Endorphin

Pregnant rats were fed an ethanol diet from the first day of pregnancy until parturition. Control rats were either pair fed with an isocaloric sucrose diet, or fed with standard lab chow (basic control group). Rats fed with the ethanol diet and their pair-fed controls showed a similar increase in body weight during pregnancy, which was lower than the increase observed in the basic control group. At 10 days after ethanol withdrawal all three groups presented similar body weights. A lower body growth was exhibited by the offspring of both the ethanol and the sucrose pair-fed rats, implicating a prenatal nutritional factor on the postnatal growth. Furthermore, the rate of body growth was lower in the offspring of the ethanol-treated animals than in the offspring of both their pair-fed and the basic control rats, indicating the presence of an additional ethanol-associated factor. On day 4 of development, the concentration of beta-endorphin peptides (pmol/mg protein) in the pituitary gland and the anterior lobe, of the offspring of the ethanol-treated animals and their sucrose pair-fed controls, was significantly higher than that of the offspring of the basic control animals. However, a lower content of beta-endorphin-like peptides was noticed in the whole pituitary gland, the anterior lobe, and the intermediate lobe of the offspring of the ethanol-treated rats and their pair-fed controls on days 8, 14, and 22 postnatally.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction between Ethanol and Stress on ACTH and β-Endorphin Secretion

The intraperitoneal infusion of ethanol (EtoH) (1 g/hr/kg body weight for 3 hr) to intact rats blunted the secretion of adrenocorticotropic hormone (ACTH) and β-endorphin induced by a subsequent 10-min exposure to mild, inescapable electroshocks (1.5 mA; 2 sec; four shocks/min) or by corticotropin-releasing factor (CRF). Conversely, administration of the shocks for 3 hr diminished the pituitary response to an acute i.p. injection of EtoH. While we have previously shown (Rivier C, Vale W Endocrinology 121:1320–1328, 1987) that prolonged stress induces a loss of pituitary responsiveness due to the depletion of pituitary ACTH stores, the infusion of EtoH did not cause statistically significant changes in pituitary ACTH content. In adrenalectomized rats, the infusion of EtoH caused an elevation of ACTH plasma levels that was significantly ( p ≤ 0.01) larger than intact animals. These rats also showed a blunted pituitary response to the acute injection of CRF, possibly because they were already secreting ACTH at a maximal rate. These results support the hypothesis that CRF, stress, and alcohol do not potentiate each other on pituitary ACTH and β-endorphin secretion.     

Prenatal Ethanol Exposure Selectively Reduces the mRNA Encoding α-1 Thyroid Hormone Receptor in Fetal Rat Brain

Some of the developmental defects characteristic of congenital or experimental hypothyroidism are also observed in children or experimental animals prenatally exposed to ethanol, suggesting that a subset of neurological defects attributable to ethanol exposure are produced by interfering with thyroid hormone action. In this article, we tested whether an ethanol treatment regimen known to produce neurological damage in rats can alter the expression of the mRNAs encoding the thyroid hormone receptor isoforms (TR α-1, TR α-2, and TR α-1) in the fetal rat brain neocortex and hippocampus. Rats were fed an ethanol-containing diet beginning on gestational day (G) 6 and continuing until sacrifice on G15, G17, or G21; controls included animals pair-fed a liquid control diet or fed lab chow. Ethanol selectively reduced the expression of TR a-1 mRNA in the neocortex and hippocampus on G21, compared with pair-fed and control fetuses. In contrast, pair-feeding selectively reduced TR a-2 mRNA in both neocortex and hippocampus on G21, and increased TR 0–1 mRNA on G17. These data support the hypothesis that ethanol may interfere with thyroid hormone action during fetal brain development In addition, these data indicate that ethanol and pair-feeding exert independent effects on thyroid hormone receptor expression in the developing brain.