Ethanol differentially enhances adrenocortical response in LS and SS mice

Corticosterone Levels and Glucocorticoid Receptor Gene Expression in High Drinking in the Dark Mice and Their Heterogeneous Stock (HS/NPT) Founder Line

The High Drinking in the Dark (HDID-1) line of mice has been selectively bred for achieving high blood alcohol levels (BALs) in the Drinking in the Dark task, a model of binge-like drinking. Recently, we determined that glucocorticoid receptor (GR) antagonism with either mifepristone or CORT113176 (a selective GR antagonist) reduced binge-like ethanol intake in the HDID-1 mice, but not in their founder line, HS/NPT. Here, we examined whether the selection process may have altered glucocorticoid functioning by measuring (1) plasma corticosterone levels and (2) expression of the genes encoding GR (Nr3c1) and two of its chaperone proteins FKBP51 and FKBP52 (Fkbp5 and Fkbp4) in the brains (nucleus accumbens, NAc) of HDID-1 and HS/NPT mice. We observed no genotype differences in baseline circulating corticosterone levels. However, HDID-1 mice exhibited a greater stimulated peak corticosterone response to an IP injection (of either ethanol or saline) relative to their founder line. We further observed reduced basal expression of Fkbp4 and Nr3c1 in the NAc of HDID-1 mice relative to HS/NPT mice. Finally, HDID-1 mice exhibited reduced Fkbp5 expression in the NAc relative to HS/NPT mice following an injection of 2 g/kg ethanol. Together, these data suggest that selective breeding for high BALs may have altered stress signaling in the HDID-1 mice, which may contribute to the observed selective efficacy of GR antagonism in reducing binge-like ethanol intake in HDID-1, but not HS/NPT mice. These data have important implications for the role that stress signaling plays in the genetic risk for binge drinking.

Central effects of ethanol interact with endogenous mu-opioid activity to control isolation-induced analgesia in maternally separated infant rats

Endogenous opioid activity plays an important role in ethanol consumption and reinforcement in infant rats. Opioid systems are also involved in mediation and regulation of stress responses. Social isolation is a stressful experience for preweanling rats and changes the effects of ethanol through opioid-dependent mechanisms. The present study assessed effects of intracisternal (i.c.) administration of a selective mu-opioid antagonist (CTOP) and i.p. administration of a nonspecific opioid antagonist (naloxone) on voluntary intake and behavior in socially isolated 12-day-old (P12) pups treated with 0.5 g/kg ethanol. Voluntary intake of 0.1% saccharin or water, locomotion, rearing activity, paw licking and grooming were assessed during short-term isolation from littermates (STSI; 8-min duration). Thermal nociceptive reactivity was measured before and after this intake test, with normalized differences between pre- and post-test latencies of paw withdrawal from a hot plate (49°C) used as an index of isolation-induced analgesia (IIA). Results indicated several effects of social isolation and ethanol mediated through the mu-opioid system. Effects of low dose ethanol (0.5 g/kg) and voluntary consumption of saccharin interacted with endogenous mu-opioid activity associated with STSI. Blockade of mu-opioid receptors on saccharin consumption and paw licking-grooming affected intoxicated animals. Low dose ethanol and ingestion of saccharin blunted effects of CTOP on rearing behavior and nociceptive reactivity. Central injections of CTOP stimulated paw licking and grooming dependent on ethanol dose and type of fluid ingested. Ethanol selectively increased saccharin intake during STSI in females, naloxone and CTOP blocked ethanol-mediated enhancement of saccharin intake. We suggest that enhancement of saccharin intake by ethanol during STSI is the product of synergism between isolation-induced mu-opioid activity that increases the pup's sensitivity to appetitive taste stimulation and the anxiolytic effects of 0.5 g/kg ethanol that decreases behaviors otherwise competing with independent ingestive activity.

Effects of corticotropin-releasing factor 1 receptor antagonism on the hypothalamic-pituitary-adrenal axis of rodents

Corticotropin-releasing factor (CRF) is the major hypothalamic neuropeptide responsible for stimulation of the hypothalamic-pituitary-adrenal axis (HPAA), resulting in the synthesis and release of glucocorticoids from the adrenal cortex. In a recent study, we reported the discovery of the CRF1 receptor antagonist, 3-(4-chloro-2-morpholin-4-yl-thiazol-5-yl)-8-(1-ethylpropyl)-2,6-dimethyl-imidazo[1,2-b]pyridazine (MTIP), which has efficacy in preclinical models of stress-induced alcohol consumption. Because CRF1 is important in HPAA activation, we evaluated the effects of MTIP administration on rodent HPAA function. Initial studies established the MTIP doses required for brain and pituitary CRF1 occupancy and those associated with the inhibition of intracerebroventricular CRF on the HPAA in mice. Then, rat basal plasma corticosterone (CORT) concentrations were measured hourly by radioimmunoassay for 24 h after three daily doses of MTIP or vehicle. In these studies, the early phase of the nocturnal CORT surge was reduced; however, the area under the CORT curve was identical for the 24-h period. In subsequent studies, increases in plasma CORT due to direct pharmacological manipulation of the HPAA axis or by stressors were evaluated after MTIP treatment in mice. MTIP attenuated CORT responses generated by immediate bolus administration of insulin or ethanol; however, MTIP did not affect activation of the HPAA by other stressors and pharmacological agents. Therefore, MTIP can modulate basal HPAA activity during the CORT surge and reduced activation after a select number of stressors but does not produce a lasting suppression of basal CORT. The ability of MTIP to modulate plasma CORT after hyperinsulinemia may provide a surrogate strategy for a target occupancy biomarker.

Restraint stress and exogenous corticosterone differentially alter sensitivity to the sedative-hypnotic effects of ethanol in inbred long-sleep and inbred short-sleep mice

Decreased sensitivity to ethanol is a genetically mediated trait implicated in susceptibility to developing alcoholism. Here, we explore genotype by environment differences in ethanol sensitivity. The relationship between acute- and repeated-restraint stress, corticosterone (CORT) levels, and sensitivity to sedative-hypnotic properties of ethanol was explored using inbred long-sleep (ILS) and inbred short-sleep (ISS) mice. In ILS mice, acute restraint decreased ethanol sensitivity at a 4.1g/kg dose, as measured by a decrease in the duration of loss of the righting reflex (LORE) and an increase in blood ethanol concentration at regain of the righting response (BECRR). Repeated restraint also decreased LORE duration, but had no effect on BECRR. In the ISS mice, there was no effect of acute restraint on either LORE duration or BECRR. However, repeated restraint increased ethanol sensitivity at a 4.1g/kg dose; with an increase in LORE duration, but a decrease in BECRR. Differences in hypothalamic-pituitary-adrenal (HPA) axis responsiveness to restraint stress (as measured by plasma CORT) were also examined between genotypes. ILS mice displayed habituation to repeated restraint, whereas ISS mice did not. Lastly, the effect of enhanced CORT levels independent of psychological stress was examined for its effects on the sedative-hypnotic effects of ethanol. There were no effects of CORT pretreatment on LORE duration or BECRR in ILS mice compared to saline- or noninjected littermates. In contrast, ISS mice injected with CORT showed a decreased duration of LORE, but no effects on BECRR. These findings suggest that in addition to genetic susceptibility, environmental factors (e.g., restraint stress, exogenous CORT administration) also influence sensitivity to the sedative effects of ethanol through alteration of central nervous system sensitivity and pharmacokinetic parameters, and do so in a genotype-dependent manner.

Plasma catecholamines in ethanol tolerance and withdrawal in mice

Plasma levels of catecholamines (noradrenaline and adrenaline) as well as the ratio of the two catecholamines were measured in experimental mice during various stages of acute and chronic ethanol treatment. Acute intraperitoneal (i.p.) ethanol administration and acute per os (p.o.) ethanol ingestion resulted in a similar elevation of the plasma levels of both catecholamines. During the development of ethanol tolerance/dependence (ingestion of drinking water containing ethanol for 14 days), plasma catecholamine concentrations returned to the control levels. During subsequent ethanol withdrawal, a highly significant increase was observed in plasma noradrenaline. The withdrawal-associated elevation of plasma adrenaline was also significant; however, the rise in plasma noradrenaline during withdrawal appeared to be higher than that found for adrenaline. Thus, the ratio of plasma noradrenaline to adrenaline was higher during withdrawal, and this ratio also exhibited an association with the severity of ethanol withdrawal symptoms. Since plasma noradrenaline derives to a great extent from the sympathetic nervous system--and the alcohol withdrawal syndrome is characterized by symptoms of overactivity of this system--a positive correlation may exist between noradrenaline and the severity of withdrawal symptomatology.

Fine structure of hippocampal dendrites in the dentate fascia of LS/SS-mice after chronic ethanol treatment

1. The effect of ethanol and its withdrawal on the dendritic microtubules in the dentate fascia of male mice was studied in the ethanol-sensitive, long-sleep (LS) line and the ethanol-insensitive, short-sleep (SS) line. 2. Both mouse lines were treated with a liquid ethanol diet. Dendrites in the dentate molecular layer (DML) of the right hippocampus were examined. 3. They revealed marked changes in microtubule density as compared with the controls. While the microtubule density in LS mice was significantly reduced by 15% and 18% in the middle and distal third of the DML, respectively, in SS mice the reduction (by 12%) took place in the distal third only. During withdrawal a recovery of the microtubule density has been observed in both lines.

Chronic corticosterone treatment elicits dose-dependent changes in mouse brain alpha-bungarotoxin binding

Previous studies have shown that adrenalectomy results in a small increase in hippocampal alpha-bungarotoxin binding, whereas seven days of chronic treatment with high doses of corticosterone results in decreases in alpha-bungarotoxin binding in several brain regions. The studies reported here examined the effects of different doses of corticosterone on brain alpha-bungarotoxin binding. C3H mice were adrenalectomized and treated with corticosterone-containing pellets (0.5-60%) for four days. Alpha-Bungarotoxin binding was measured in eight brain regions. Chronic treatment with corticosterone resulted in plasma corticosterone levels ranging from the low levels observed in an unstressed mouse during the daytime to levels significantly above those observed in mice during the night or as a result of stress. Adrenalectomy resulted in small increases in binding in hippocampus which was reversed by low dose corticosterone treatment. Chronic high-dose corticosterone treatment resulted in significant decreases in binding in four of the eight brain regions examined. Similar, but not identical, results were obtained in two other mouse strains (C57BL and DBA/2). These results argue that corticosterone levels play an important role in modulating the level of the brain nicotinic receptors that bind alpha-bungarotoxin with high affinity.

Alcohol stimulates ACTH secretion in the rat: mechanisms of action and interactions with other stimuli

This review discusses some of the mechanisms through which alcohol (EtOH) alters the activity of the hypothalamic-pituitary-adrenal (HPA) axis. In adult rats, acute EtOH treatment increases plasma ACTH and corticosteroids levels primarily by stimulating the release of corticotropin-releasing factor (CRF) and possibly vasopressin (VP) from nerve terminals in the median eminence. Increased CRF gene transcription in the hypothalamus may also be important. The HPA axis remains activated during chronic EtOH exposure, although habituation may take place. Changes in the responsiveness of hypothalamic neurons, a phenomenon itself dependent in part on a number of intermediate secretagogues, as well as decreased pituitary responsiveness to VP, all play a role. Finally, the activity of the HPA axis is influenced by exposure to EtOH during embryonic development, with mature offspring showing hyporesponsiveness to many stimuli. These altered responses appear to be caused in part by changes in the synthesis/release CRF, possibly under the influence of nitric oxide. CRF, VP, ACTH, and corticosteroids are important regulators of the immune system, behavior, metabolic pathways, and reproductive parameters. Alcohol therefore may influence such functions through the pathological secretion of these hormones. A better understanding of the mechanisms through which the drug alters their release thus may permit the development of therapies designed to alleviate some of the consequences of alcoholism.

Use of transgenics, null mutants, and antisense approaches to study ethanol's actions

Behavioral and biochemical responses mediating ethanol's actions have been difficult to study in humans and animals because of their complex polygenic nature. Recent progress in the creation of new animal models using recombinant DNA technology has provided a set of genetic tools by which the role of specific candidate genes in ethanol's actions can be examined. These techniques include the creation of transgenic and null mutant mice, as well as manipulation of protein synthesis with antisense treatments. These techniques are reviewed, and their potential applications to alcohol research are discussed.

The effects of acute stress on ethanol absorption in LS and SS mice

Previously, our laboratory demonstrated that naive long-sleep (LS) mice absorb ethanol faster than short-sleep (SS) mice when administered 6.0 g/kg ethanol intragastrically (IG). We also demonstrated that the removal of the adrenal glands results in decreased absorption in both lines of mouse. The present study was designed to assess whether acute short-term elevations of corticosterone produced by exposure to a mild stressor could also alter ethanol absorption in LS and SS mice. Because a difference in ethanol absorption rates was observed in LS mice as a function of time of day, all stress experiments were performed in the morning. CCS elevation was induced by exposure to an elevated plus-maze for 45 min. LS mice demonstrated greater CCS release in response to this stressor than SS mice. This exposure to a mild stressor produced an increase in ethanol absorption in both lines of mice receiving a 6.0 g/kg intragastric dose of ethanol. Although this effect of stress on ethanol absorption could be prevented by adrenalectomy in SS mice, adrenalectomy alone did not completely block these effects of stress on ethanol absorption in LS mice. Dexamethasome treatment at the time of adrenalectomy was required to block the effects of stress on ethanol absorption in LS mice. These results suggest that exposure to mild stressors may alter ethanol pharmacokinetic parameters but that genetic factors may play a role in this response via regulation of the hypothalamic-pituitary-adrenal axis.

Biochemical and behavioral effects of steroids on GABAA receptor function in long- and short-sleep mice

The in vitro and in vivo effects of alphaxalone, a steroid anesthetic, and two physiological steroids, tetrahydrodeoxycorticosterone (THDOC) and pregnenolone sulfate (PS), on GABAA receptor function were evaluated in long-sleep (LS) and short-sleep (SS) mice. In vitro, both alphaxalone and THDOC enhanced GABAergic inhibition as measured by [3H]FNZ binding and GABA-stimulated 36Cl- flux. However, with the exception of alphaxalone potentiation of [3H]FNZ binding, which was greater in SS brain regions, LS and SS mice did not differ in their degree of enhancement. Pregnenolone sulfate produced mixed agonistic and antagonistic effects on GABAergic function, dependent upon brain region, with few differences between the lines of mice. In vivo effects of these steroids on sleep time indicated that, like other anesthetic agents, THDOC and alphaxalone induced longer sleep times in LS mice. Antagonism by PS of ethanol-induced sleep time was observed in LS mice only; however, this effect was dependent upon the dose of ethanol used and on the vehicle used to prepare the steroid. Pentobarbital-induced sleep time was not reduced by PS treatment in either line of mouse. These results demonstrate that few differences in sensitivity of the GABAergic receptor to these steroids exist between LS and SS mice. Thus, unlike the differences between LS and SS mice in GABAergic mediation of responses to ethanol and benzodiazepines, there is little genetic variability in subtypes of GABAA receptors capable of modulation by steroids in these lines of mice.

The rate of ethanol absorption is influenced by corticosterone in long-sleep and short-sleep mice

Ethanol was administered by intragastric (IG) injection and absorption was measured in long-sleep (LS) and short-sleep (SS) mice under various conditions that alter levels of adrenal steroids. In naive mice, LS mice absorbed ethanol more quickly than SS mice. Ethanol absorption was slower in both lines of mice after adrenalectomy (ADX). Short-term inhibition of corticosterone synthesis had no effect on ethanol absorption in either line of mice. The effect of ADX was most pronounced in SS mice at 24 hr after surgery and at 168 hr after surgery in LS mice. Therefore, the effects of various steroid replacements were examined at these times. At 24 hr after ADX, ethanol absorption was replaced to SHAM-operated values in SS mice receiving corticosterone treatments. Likewise, in LS mice at 168 hr after ADX, corticosterone implants reversed the effects of ADX while dexamethasome was ineffective. These results support a role for corticosterone in regulation of gastric ethanol absorption and suggest that the lack of repeatability for pharmacokinetic measures of ethanol absorption and metabolism in previous human and animal studies may relate to environmental impact on stress responses.

Hormone responses to sedative drugs and cold exposure in two rat lines with high and low alcohol sensitivity

Two rat lines bred for differences in motor impairment in the tilting plane test after a moderate dose of ethanol were compared for peripheral hormone responses. The alcohol-sensitive ANT rats had significantly lower plasma corticosterone concentrations than the alcohol-insensitive AT rats 30 min after an IP saline injection. Ethanol (2 g/kg, IP) and lorazepam (3 mg/kg, IP) injections increased the corticosterone concentration in ANT rats. Sodium barbital (160 mg/kg, IP) did not produce any increase in these rats; instead, it prevented any increase caused by a tilting plane test procedure 10 min before decapitation. Three trials on the tilting plane significantly elevated the corticosterone concentration in saline-treated ANT rats, but produced no additional increase in drug-treated ANT rats. In AT rats, drug injections caused no significant corticosterone increase but the tilting plane test procedure after barbital (lorazepam) treatment(s) elevated the corticosterone concentration. Cold exposure (+4 degrees C for 30 min) of the drug-naive animals elevated their concentrations of serum and adrenal corticosterone, thyrotropin, and growth hormone, but not of prolactin and luteinizing hormone. The increase in serum corticosterone was greater in AT than ANT rats, whereas the increase in serum thyrotropin was slightly greater in ANT rats. No differences between the rat lines were found in the growth hormone, prolactin, and luteinizing hormone levels. The results confirm and extend our earlier findings of the inability of ANT rats to produce additional stress responses to behavioral challenges when being intoxicated by sedative drugs, which may at least partly account for their increased sensitivity to sedative drugs.

Adrenalectomy and stress modulate GABAA receptor function in LS and SS mice

The effects of manipulation of adrenal steroids by adrenalectomy (ADX) or stress on GABAA receptor function were characterized in long-sleep (LS) and short-sleep (SS) mice. 36Chloride flux was not altered in either line of mouse after ADX; however, exposure to a behavioral stressor resulted in a highly significant inhibition of ion channel activity measured in cortical membranes from both LS and SS mice. Adrenalectomy also had no effect on [3H]FNZ binding; whereas exposure to stress differentially altered benzodiazepine binding in LS and SS mice. In LS cortex both Bmax and Kd values increased, whereas in SS cerebellum, Bmax and Kd values were decreased after stress. In SS mice ADX did not affect GABA-enhancement of [3H]FNZ binding. In LS mice, however, ADX resulted in a potentiation of GABA-enhanced [3H]FNZ binding in cortex and an inhibition of enhancement in cerebellum. Corticosterone (CCS) replacement in ADX-LS mice returned enhancement values to those of sham-operated mice, indicating a role for basal levels of CCS in maintaining normal receptor coupling function in this line of mouse. These results suggest that GABAA receptor sensitivity is more labile under stressful conditions. Differential receptor responses to adrenal manipulation between LS and SS mice may be due to genetic variation in GABAA receptor subunit combinations in these lines of mice.

Diminished stress responses in the alcohol-sensitive ANT rat line

During behavioral tests of alcohol sensitivity, rapid alcohol-opposing reactions may constitute an important mechanism in reducing the acute performance-impairing actions of alcohol. The alcohol-sensitive ANT (alcohol nontolerant) rats achieve lower plasma corticosterone concentrations after a tilting plane test of alcohol sensitivity (2 g ethanol/kg, IP) than the alcohol-insensitive AT (alcohol tolerant) rats, suggesting a dampening of activated stress mechanisms in the ANT rats. We have extended the comparison of these rat lines by examining central and peripheral stress responses to an acute 10-min swimming stress without ethanol administration. After the stress, plasma and adrenal corticosterone concentrations, adrenal dopamine concentrations, binding of [3H]Ro 5-4864 to adrenal membranes, and hypothalamic norepinephrine turnover were lower in the ANT than AT rats. Habituation to daily handling did not affect the stress effects or the differences between the rat lines. These results suggest that the alcohol-sensitive ANT rats have a diminished reaction to general stress, even in the absence of ethanol. This may impair their capacity to overcome the sedative and motor-impairing effects of moderate ethanol doses.

Hormonal tolerance to ethanol is associated with decreased expression of the GTP-binding protein, Gs alpha, and adenylyl cyclase activity in ethanol-treated LS mice

Using the proopiomelanocortin (POMC) system as a marker, long sleep (LS) and short sleep (SS) lines of mice were investigated to explore the cellular events that occur during the acquisition of hormonal tolerance to ethanol. Four-day ethanol exposure (1.8 g/kg/24 hr) increased anterior pituitary POMC mRNA levels 4-fold in the LS line and 2-fold in the SS line. Following 7 days of ethanol exposure (1.8 g/kg/24 hr), anterior pituitary POMC levels returned to basal values in the LS line but remained elevated (2-fold) in the SS line. In this setting, the loss of ethanol's ability to sustain elevated POMC mRNA levels in the LS line is defined as hormonal tolerance. Since POMC biosynthesis is primarily regulated through adenylyl cyclase, ethanol-induced alterations in this signal transduction system were explored. Paralleling the effects of ethanol on POMC mRNA levels, ethanol exposure reduced GTP-gamma-S, AIF3-, and MnCl2-stimulated adenylyl cyclase activity by 35%, 21%, and 24%, respectively, in the LS line without effecting adenylyl cyclase activity in the SS line. To determine whether ethanol-induced changes in adenylyl cyclase activity in LS mice could result from alterations in G proteins, protein levels of G, alpha and Gi alpha were determined by western analysis before and after ethanol exposure. Paralleling the effect on POMC mRNA levels and adenylyl cyclase activity, ethanol induced a 35% reduction in Gs alpha protein levels in LS mice but did not alter Gi alpha levels. Neither Gs alpha nor Gi alpha levels were altered in the SS line.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy increases bicuculline-induced seizure sensitivity in long-sleep and short-sleep mice

Susceptibility to bicuculline-induced seizure onset and tonus was increased in LS and SS mice after adrenalectomy (ADX). Replacement with 10% corticosterone (CCS) in ADX animals resulted in a return to seizure latencies equal to those of sham-operated (SHAM) mice. In SS mice, dexamethasone (DEX) and cholesterol-control replacement was as effective as 10% CCS in returning seizure thresholds to SHAM values. In LS mice, DEX was only effective at a low bicuculline dose. Within the sham-operated group SS mice were more susceptible to bicuculline-induced seizure onset than LS mice; however, after ADX latencies did not differ between the two lines. These results suggest that seizure thresholds are regulated to some extent by the hypothalamic-pituitary-adrenal (HPA) axis. The effects of ADX on GABA-related seizure activity may also be influenced by genotype, such that genetic differences in GABAA receptor function and adrenocortical responses in LS and SS mice may be responsible for the differential seizure latencies observed in sham-operated mice.

Corticotropin-releasing factor is altered in brains of animals with high preference for ethanol

Ethanol administered to rats has been shown to stimulate the hypothalamic-pituitary-adrenal axis. The present study describes alterations in brain CRF neuronal systems that accompanied the voluntary high consumption of ethanol by Wistar rats presented with a free choice between 6% ethanol and tap water. Hypothalamic CRF concentrations (outside median eminence) were significantly increased in animals with a high preference for ethanol whereas concentrations of CRF in neurointermediate pituitary and medulla-pons were significantly decreased. No changes of CRF levels were evident in median eminence, frontal cortex, midbrain, thalamus, or cerebellum. Brain CRF concentrations in two strains of mice with genetically determined differential alcohol preference were measured. In ethanol-naive mice, there were documented differences in CRF concentrations, with an increase in frontal cortex levels, and a decrease in medulla-pons levels in the ethanol-preferring strain (C57BL/6J) compared to the nonpreferring strain (C3H/CRGL/2). Thus, certain brain CRF neuronal systems are preferentially affected by high ethanol consumption, and pre-existing differences in these systems may even contribute to the development of a high preference for ethanol.

Differential regulation of anterior pituitary corticotrope function is observed in vivo but not in vitro in two lines of ethanol-sensitive mice

Anterior pituitary corticotrope function was analyzed in the long sleep (LS) and short sleep (SS) lines of mice selectively bred for differences in sensitivity to ethanol. In vivo challenge with acute ethanol or CRH administration or the stress of novel handling resulted in a more pronounced increase in serum corticosterone levels in LS mice compared with SS mice. Likewise, in vivo administration of ethanol resulted in 3-fold higher levels of anterior pituitary pro-ACTH/endorphin mRNA in LS mice compared with SS mice. However, this differential regulation of the HPA axis during in vivo analysis was not observed during in vitro studies of anterior pituitary corticotrope function. Primary cultures of LS and SS anterior pituicytes responded appropriately but equivalently to a variety of secretagogues known to stimulate anterior pituitary ACTH secretion. These secretagogues included CRH (10 nM), dibutyryl-cAMP (1 mM), vasopressin (100 nM), and phorbol 12-myristate 13-acetate (10 nM). Ethanol had no direct stimulatory effect on pituitary ACTH secretion. Quantitation of anterior pituitary corticotrope peptide biosynthesis was determined by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of extracts from [35S]methionine-labeled anterior pituitary explants and from [35S]methionine-labeled primary cultures of anterior pituitary cells. LS mice pro-ACTH/endorphin biosynthesis in pituitary explants was 2-fold greater than pro-ACTH/endorphin biosynthesis in SS mice pituitary explants. However, in culture, isolated from hypothalamic and adrenal factors, the LS anterior pituitary pro-ACTH/endorphin biosynthetic rate became equivalent to the SS anterior pituitary pro-ACTH/endorphin biosynthetic rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Low doses of ethanol reduce neurotensin levels in discrete brain regions from LS/Ibg and SS/Ibg mice

Studies were designed to examine the previously proposed hypothesis that some of the pharmacological actions of ethanol are mediated by neurotensinergic processes. Neurotensin-immunoreactivity (NT-ir) was extracted from various brain regions and shown by high performance liquid chromatography to possess the same retention time as authentic bovine NT1-13. The highest levels of NT-ir were observed in the hypothalamus with intermediate levels in the midbrain and striatum and lowest levels in the frontal cortex. Levels of NT-ir were higher in hypothalamus and midbrain from long-sleep (LS) than from short-sleep (SS) mice. Ethanol, in vivo, produced a dose-dependent decrease in NT-ir in several brain regions; low doses, 1.5 to 3.0 g/kg, but not high doses, 4.1 g/kg, of ethanol significantly decreased NT-ir in hypothalamus, midbrain, and striatum of LS and SS mice. Levels of NT-ir in the frontal cortex were not altered by ethanol administration. Ethanol-induced decreases in NT-ir were of rapid onset with a maximum decrease in 5 min after intraperitoneal (i.p.) injection, and they were of long duration with levels remaining depressed for 4 hr. These findings show that subhypnotic, intoxicating doses of ethanol enhance NT release, in vivo, and support the hypothesis that some of ethanol's actions are mediated by neurotensinergic systems.

Interaction of ethanol and stress with the GABA/BZ receptor in LS and SS mice

The interaction of stress and ethanol with the GABA/BZ receptor system was evaluated in LS and SS mice. The effects of two separate in vivo treatments, a 2.5 g/kg injection of ethanol or a behavioral stressor, on GABA-enhanced [3H]-FNZ binding were nearly identical in both lines of mice. A 2.5 g/kg ethanol- or stress-pretreatment resulted in increased enhancement in SS cortex, but not LS. In cerebellum, treatment effects were demonstrated in both SS and LS mice. Intraperitoneal injections of increasing doses of ethanol produced biphasic stimulation of GABA-enhanced [3H]-FNZ binding in LS brain regions, but not SS. Adrenalectomies performed one week prior to ethanol administration produced a loss of ethanol enhancement in cerebellum of both lines. However, in cortex, removal of the adrenals had no effect. The in vitro addition of 30 mM ethanol to brain preparations incubated at 37 degrees C from stressed and unstressed animals resulted in greater enhancement of binding in cortex, but not cerebellum of stressed mice. Differences in the degree of enhancement between the lines of mice were lost if the animals were stressed prior to sacrifice or if membrane preparations were incubated at 4 degrees C. The results of this study suggest that the interaction between ethanol and stress is mediated by the GABAergic system, but responses vary dependent on brain region, dose of ethanol, and degree of ethanol sensitivity.