Altered Ethanol Consumption in Osteocalcin Null Mutant Mice.

Osteocalcin (OC) is an abundant extracellular calcium-binding protein synthesized by osteoblasts. Although most OC is bound to hydroxyapatite mineral during bone formation, a consistent amount is released directly to circulation. Plasma OC (pOC) levels are highly sensitive to stressful stimuli that alter stress-responsive hormones, such as glucocorticoids (cortisol or corticosterone) and the catecholamines norepinephrine and epinephrine. To gain a better understanding of the apparent relationship of OC to the effects of ethanol (EtOH) and the stress responses, we compared mice that have OC (WT [OC+/+] and HET [OC+/-]) with OC null mutants (KO [OC-/-]), which have no OC in either plasma or in bone. One experiment included chronic unpredictable stress, a second was conducted in the absence of any known stressors other than EtOH, while a third imposed a more severe acute immobilization stress in addition to EtOH consumption. The data obtained confirmed significant differences in EtOH consumption in mice that previously experienced various stressful stimuli. We also determined that adrenal tyrosine-hydroxylase expression was inversely proportional to EtOH consumption and tended to be lower in KO than in WT. Data suggest that OC possesses the ability to modulate the adrenal gene expression of the catecholamine synthetic pathway. This modulation may be responsible for differences in EtOH consumption under stress.

Decreased sensory responses in osteocalcin null mutant mice imply neuropeptide function.

Osteocalcin, the most abundant member of the family of extracellular mineral binding gamma-carboxyglutamic acid proteins is synthesized primarily by osteoblasts. Its affinity for calcium ions is believed to limit bone mineralization. Several of the numerous hormones that regulate synthesis of osteocalcin, including glucocorticoids and parathyroid hormone, are also affected by stressful stimuli that require energy for an appropriate response. Based on our observations of OC responding to stressful sensory stimuli, the expression of OC in mouse and rat sensory ganglia was confirmed. It was thus hypothesized that the behavioral responses of the OC knockout mouse to stressful sensory stimuli would be abnormal. To test this hypothesis, behaviors related to sensory aspects of the stress response were quantified in nine groups of mice, aged 4-14 months, comparing knockout with their wild-type counterparts in six distinctly different behavioral tests. Resulting data indicated the following statistically significant differences: open field grooming frequency following saline injection, wild-type > knockout; paw stimulation with Von Frey fibers, knockout < wild-type; balance beam, knockout mobility < WT; thermal sensitivity to heat (tail flick), knockout < wild-type; and cold, knockout < wild-type. Insignificant differences in hanging wire test indicate that these responses are unrelated to reduced muscle strength. Each of these disparate environmental stimuli provided data indicating alterations of responses in knockout mice that suggest participation of osteocalcin in transmission of information about those sensory stimuli.

Amphetamine modifies ethanol intake of psychosocially stressed male rats.

Studies of socially housed rodents have provided significant information regarding the consequences of exposure to stressors. Psychosocial stressors are known to alter the ingestion of ethanol and the activity of the dopaminergic neuronal system. Since both stressors and ethanol are known to affect the function of dopaminergic neurons, we employed amphetamine to assess the role of this neural system on the ingestion of ethanol by psychosocially stressed male rats. Male rats housed two per cage were designated as dominant or subdominant rats based on evaluations of agonistic behavior and body weight changes. The dyad-housed rats and a group of single-housed rats were sequentially assessed for ethanol intake after injections of saline or amphetamine (0.3, 0.9 or 2.7 mg/kg i.p.) both prior to dyad housing and subsequently again during dyad-housing. Prior to dyad housing ethanol intake of future subdominant rats was higher than that of future dominant rats. Dyad-housing significantly increased ethanol intake of dominant rats. Pre-dyad the highest dose of amphetamine potently depressed ethanol ingestion. Sensitivity to amphetamine's depressant effect on ethanol intake was higher at the dyad test in all subjects, most prominently in single-housed rats. In contrast to the single-housed rats, the dyad-housed rats displayed saccharin anhedonia. It can be concluded that dopaminergic system modulates, at least partially, the psychosocial stress-induced changes in ethanol intake. Furthermore, the level of ethanol ingestion at the pre-dyad test was predictive of future hierarchical status.

Pairings of lever and food induce Pavlovian conditioned approach of sign-tracking and goal-tracking in C57BL/6 mice.

In rats, Pavlovian sign-tracking has been extensively evaluated as a model of compulsiveness in drug addiction and other addictive behaviors, but it remains unexplored in mice, a species with a wealth of genetically modified models, which makes it possible to examine gene-behavior relationships. In C57BL/6 mice, the most commonly used mouse strain for genetic studies, repeated pairings of lever conditioned stimulus (CS) with food unconditioned stimulus (US) induced Pavlovian conditioning of sign-tracking conditioned response (ST CR) performance of lever CS-directed approach, and Pavlovian conditioning of goal-tracking conditioned response (GT CR) performance of approach responses directed at the location of the food trough where the food US was delivered. The CS-US Paired group performed more ST CRs and more GT CRs during sessions 15-16 than did pseudoconditioning controls which received the lever CS and food US randomly with respect to one another. During sessions 15-16, all mice in the Paired group performed more GT CRs than ST CRs, and regression analysis revealed a positive relationship between an individual subject's tendency to perform ST CRs and GT CRs. The mice that performed more ST CRs during sessions 15-16 yielded higher plasma corticosterone levels. These data reveal stable and reliable acquisition and maintenance of ST CR performance and GT CR performance in mice; however, unlike in rats, ST CRs and GT CRs did not vary inversely within subjects. Corticosterone release, a pathophysiological marker of vulnerability to drug abuse, was positively related to ST CR performance.

Differential sensitivity to amphetamine's effect on open field behavior of psychosocially stressed male rats.

RATIONALE: Studies of socially housed rodents have provided significant information regarding the mechanisms of stress and of stress-related disorders. OBJECTIVE: Since psychosocial stress is known to alter the functional activity of dopaminergic system, we employed amphetamine (AMP) to evaluate the involvement dopamine in mediating the behavioral consequences of psychosocial stress. METHODS: Male rats housed two per cage were designated as dominant (DOM) or subdominant (Sdom) based on initial evaluations of agonistic behaviors and body weight changes. Diad-housed rats and a group of single-housed (SiH) rats were tested in an open field after injections of saline or amphetamine (0.9 or 2.7 mg/kg IP) prior to and again while diad-housing. RESULTS: Compared to future DOM rats, saline-injected future Sdom rats entered the open field center less frequently, spent less time in rearing behavior and groomed less. At the pre-diad test AMP treatment elevated locomotor activity of all rats, while stimulation of center entries was more marked in future DOM rats. At the diad test, AMP's locomotor stimulant effect was evident in all experimental groups with DOM rats showing higher effects compared to Sdom and SiH rats. Amphetamine's stimulation of center entries in DOM rats was similar to the pre-diad test, but it was diminished in Sdom rats, while stimulation of rearing behavior was most evident in diad-housed rats. CONCLUSION: The dopaminergic system modulates the psychosocial stress-induced differences in explorative and emotional behaviors. Furthermore, behavioral traits like frequency of grooming behavior and of center entries were predictive of future hierarchical status.

Effects of removing food on maintenance of drinking initiated by pairings of sipper and food.

Two experiments evaluated the effects of removing food presentations on the maintenance of drinking induced by experience with sipper - food pairings. In Exp 1, ethanol drinking was induced in non-deprived Long-Evans rats by Pavlovian conditioning procedures employing an ethanol sipper as conditioned stimulus (CS) and food pellet as unconditioned stimulus (US). The Paired/Ethanol group received presentations of the ethanol sipper CS followed immediately by the response-independent presentation of the food pellet US. The Random/Ethanol group received the ethanol sipper CS and food US randomly with respect to one another. For both groups, the concentration of ethanol in the sipper CS [(3%, 4%, 6%, 8% (vol./vol.)] was increased across sessions, and, as in previous studies employing low concentrations of ethanol in non-deprived rats (i.e., maintained with free access to food in their home cages), the two procedures induced comparable levels of sipper CS-directed ethanol drinking. Removing food US presentations had no effect on sipper CS-directed ethanol drinking in either group. In Exp 2, groups of non-deprived Long-Evans rats were trained either with water or ethanol in the sipper CS paired with food US. Removing food US presentations had no effect on ethanol drinking in the Paired/Ethanol group, but water drinking in the Paired/Water group declined systematically across sessions. Results indicate that food US presentations contribute to the maintenance of water drinking but not to the maintenance of ethanol drinking. Implications for accounts of ethanol drinking based on Pavlovian sign-tracking, behavioral economics and intermittent sipper procedures are considered.

Acute novel stressors modify ethanol intake of psychosocially stressed rats.

Psychosocial stressors are known to alter ingestion of ethanol in humans and experimental animals. We evaluated the effect of novel acute stressors on ethanol ingestion of male triad-housed rats. Based on behavioral and body weight assessments triad members were designated as dominant, subdominant or subordinate rats, housed in triads designated as aggressive or non-aggressive triads. The triad-housed, and a group of single-housed rats, were sequentially subjected to three stressors (novel open field arena, elevated plus maze, and modified resident-intruder test) at 1-2 week intervals. Ethanol intake was measured for 21-h before and after each stressor. Prior to stressor exposure, ethanol intake of the triad-housed rats was higher than that of single-housed rats. In triads overall intake of ethanol was lower in dominant compared to non-dominant rats. The modified resident-intruder test decreased ethanol intake in non-dominant rats in aggressive triads, but increased its intake in non-aggressive triads. Since in non-dominant rats this stressor also increased ethanol preference but not total fluid intake, its effect on ethanol intake was specific. In non-dominant rats ethanol intake and preference declined after the elevated plus maze stressor, without an effect on total fluid intake, but water intake was increased only in the subdominant rats. Compared to triad-housed rats, single-housed rats were more resilient to the novel stressors. It can be concluded that novel acute stressors have specific effects on ethanol intake that are dependent on the subject's psychosocial stress level.

Psychosocial stress and chronic ethanol ingestion in male rats: effects on elevated plus maze behavior and ultrasonic vocalizations.

Psychosocial stress is known to enhance anxiety levels in rodents. The present study evaluated the effect of long-term ingestion of ethanol (EtOH) on anxiety levels of male Long Evans rats housed either singly or in triads (three/cage). Based on measures of offensive and defensive behaviors, triad-housed rats were designated as being dominant, subdominant or subordinate. The effect of chronic ingestion of a 6% EtOH solution was assessed on behaviors in the elevated plus maze (EPM) test, and on air-puffs elicited 22 kHz ultrasonic vocalizations (USV). EtOH naïve dominant rats showed less anxiogenic-like (open arms time) and displacement behavior (grooming), but more risk assessment behavior (stretch-attend postures) than their cage-mates or the single-housed rats. Intake of EtOH prior to the EPM test was lower in dominant and single-housed rats compared to subdominant and subordinate rats. Triad-housed rats, but not the single-housed rats, decreased their intake of EtOH after the EPM test. Overall, EtOH intake had an anxiolytic effect in all rats, but the effect was most prominent in single-housed rats. Furthermore, EtOH intake decreased air-puff induced USVs of triad-housed rats, but increased USVs of single-housed rats. These data indicate that housing condition and rank status influence the emotional state of male rats. Furthermore, the anxiolytic effect of voluntarily ingested EtOH was depended on these variables.

Behavioral characteristics and neurobiological substrates shared by Pavlovian sign-tracking and drug abuse.

Drug abuse researchers have noted striking similarities between behaviors elicited by Pavlovian sign-tracking procedures and prominent symptoms of drug abuse. In Pavlovian sign-tracking procedures, repeated paired presentations of a small object (conditioned stimulus, CS) with a reward (unconditioned stimulus, US) elicits a conditioned response (CR) that typically consists of approaching the CS, contacting the CS, and expressing consummatory responses at the CS. Sign-tracking CR performance is poorly controlled and exhibits spontaneous recovery and long-term retention, effects that resemble relapse. Sign-tracking resembles psychomotor activation, a syndrome of behavioral responses evoked by addictive drugs, and the effects of sign-tracking on corticosterone levels and activation of dopamine pathways resemble the neurobiological effects of abused drugs. Finally, the neurobiological profile of individuals susceptible to sign-tracking resembles the pathophysiological profile of vulnerability to drug abuse, and vulnerability to sign-tracking predicts vulnerability to impulsive responding and alcohol self-administration. Implications of sign-tracking for models of drug addiction are considered.

Psychosocial stress and volatile compounds in preputial glands of rats.

Pheromones are volatile chemical cues that in rodents originate in large part from the preputial glands and influence various behavioral and physiological processes. We have examined the effect of psychosocial stress on volatile compound composition of preputial glands of male rats. Rats were housed three per cage or singly for 70 days. Dominants had heavier preputials compared to subdominant and subordinate rats. Capillary gas chromatographic mass spectrometry identified 55 volatile preputial compounds: 17 did not differ between groups, while 26 compounds were higher in single-housed compared to triad-housed rats. Six compounds were higher in dominant, while another six were higher in both dominant and single-housed rats. We conclude that both housing condition and rank status have significant differential effects on the preputial volatile compounds.

Ethanol and stress activate catecholamine synthesis in the adrenal: effects on bone.

Ethanol consumption and mental stress activate the sympathetic nervous system, which can adversely affect bone. We compared six groups of 10 young adult rats, three with and three without 2 h daily restraint stress. Two groups consumed food and water ad libitum, two received food and 6% (w/v) ethanol as drinking water, and two received the amount of food consumed by ethanol rats the previous day plus water ad libitum (pairfed). After 6 weeks, rats were killed. Plasma, femurs, lumbar vertebrae, and adrenals were harvested. Femoral dimensions were measured and biomechanical properties were tested by three-point bending. Plasma osteocalcin, vertebral osteocalcin mRNA levels, and adrenomedullary tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine N-methyl transferase (PNMT) mRNA levels were quantified. Daily restraint decreased weight gain and femoral length compared to dietary controls, and appeared to partially preserve bone strength, especially in calorie-restricted pairfed rats. Femoral strength was significantly affected by treatment in that bones of pairfed controls were weakest, ethanol drinkers were intermediate, and ad libitum restrained were strongest. Femoral yield load, displacement, and work at yield load were negatively correlated with TH and DBH mRNA levels, but not PNMT, suggesting a negative influence of norepinephrine. Plasma osteocalcin and dry weight of lumbar 3-5 vertebrae were unaffected; however, osteocalcin mRNA in second lumbar vertebrae was positively correlated with TH, DBH, and PNMT levels. Ethanol consumption at this level had little effect on femur morphology or strength. In contrast, the data suggested possible stimulation rather than inhibition of vertebral bone formation.

Intermittent exposure to a social stimulus enhances ethanol drinking in rats.

The present experiment evaluates the effects of intermittent exposure to a social stimulus on ethanol and water drinking in rats. Four groups of rats were arranged in a 2x2 factorial design with 2 levels of Social procedure (Intermittent Social vs Continuous Social) and 2 levels of sipper Liquid (Ethanol vs Water). Intermittent Social groups received 35 trials per session. Each trial consisted of the insertion of the sipper tube for 10 s followed by lifting of the guillotine door for 15 s. The guillotine door separated the experimental rat from the conspecific rat in the wire mesh cage during the 60 s inter-trial interval. The Continuous Social groups received similar procedures except that the guillotine door was raised during the entire duration of the session. For the Ethanol groups, the concentrations of ethanol in the sipper [3, 4, 6, 8, 10, 12, 14, and 16% (vol/vol)] increased across sessions, while the Water groups received 0% ethanol (water) in the sipper throughout the experiment. Both Social procedures induced more intake of ethanol than water. The Intermittent Social procedure induced more ethanol intake at the two highest ethanol concentration blocks (10-12% and 14-16%) than the Continuous Social procedure, but this effect was not observed with water. Effects of social stimulation on ethanol drinking are discussed.

Psychosocial stress alters ethanol's effect on open field behaviors.

Psychosocial stress, including social rank status, has been shown to alter spontaneously occurring behaviors in rodents as well as the behavioral effects of drugs of abuse. In this study, rats were repeatedly evaluated in a modified open field following: their initial exposure, and after intraperitoneal injections of saline and 0.75 g/kg ethanol (EtOH). All subjects were first tested while under single housing conditions, then again following 35 days of differential housing (singly or 3 rats/cage) with social status determined by scoring agonistic behavior at triad formation. The data suggest that (1) future subordinate rats differed with respect to specific aspects of behavior displayed in a 'novel' open field arena, (2) future subordinate rats were more emotional since they showed greater "anxiety-like" behavior and less exploratory behavior, (3) subordinate rats were more impaired by the saline injection stress, (4) subordinate rats were more sensitive to the depressant effects of EtOH, (5) grooming behavior did not show habituation, in contrast to the other behaviors, but showed sensitization on the second test. Overall, subordinate rats may have differed from their cage mates in innate anxiety, and this may underlie their distinct response to both stressors and EtOH. Furthermore, while EtOH had mostly stimulant effects in naive rats, psychosocial stress and/or repeated testing resulted in enhancement of EtOH's depressant effects.

Housing and rank status of male Long-Evans rats modify ethanol's effect on open-field behaviors.

RATIONALE: Psychosocial stress is known to alter behavior of rodents. While psychosocial stress may alter the response to some drugs, the response to ethanol (EtOH) has not been evaluated. OBJECTIVE: To examine open-field behaviors of triad- and singly housed rats treated acutely or voluntarily ingesting EtOH. METHOD: Triad-housed rats were categorized as dominant, subdominant, or subordinate based on assessments of offensive and defensive behaviors. Open-field behaviors were monitored during a 10-min test in rats voluntarily ingesting a 6% solution of EtOH for 2 weeks (1), and after an i.p. injection of saline, 0.5 or 1.0 g kg(-1) of EtOH (2). RESULTS: Daily intake of EtOH was highest in subdominant and lowest in dominant rats. Overall, open-field behaviors did not differ between water- and EtOH-consuming triad- or singly housed rats. The 0.5-g kg(-1) dose of EtOH enhanced locomotor activity only in triad-housed rats, center entries primarily in singly housed rats, and head-poke behavior in dominant and singly housed rats. Rearing behavior was not altered by the 0.5-g kg(-1) dose, but in singly housed rats, rearing behavior was depressed by the 1.0-g kg(-1) dose. This larger dose of EtOH had no effect on the other behaviors. CONCLUSIONS: EtOH's effects on open-field behaviors show behavioral specificity and vary with the subject's housing and/or rank status. EtOH's acute anxiolytic-like effect was primarily evident in singly housed rats.

An inter-gender effect on ethanol drinking in rats: proximal females increase ethanol drinking in males.

Three groups of male Long-Evans hooded rats were assessed for effects of social opportunity on drinking of ethanol or water. The ethanol/female group received intermittent presentations of a sipper containing ethanol that was followed by 15 s of social interaction opportunity with a female rat. The ethanol/male group received similar training except the social interaction opportunity was with a male rat. The water/female group received training similar to the ethanol/female group except that the sipper contained water. For the ethanol groups, the concentration of ethanol [3%, 4%, 6%, 8% and 10% (vol/vol)] in the sipper was increased across sessions. With 10% ethanol in the sipper, social opportunity with females induced more drinking and ethanol intake than did social opportunity with males. Social opportunity with females induced more intake of ethanol than water. Post-session plasma samples revealed social opportunity with females induced higher corticosterone and testosterone levels than did social opportunity with males, irrespective of the sipper fluid. This study documents, for the first time, an inter-gender effect on ethanol drinking in rats.

Intermittent presentations of ethanol sipper tube induce ethanol drinking in rats.

AIMS: Intermittent presentations of the ethanol sipper have been reported to induce more ethanol drinking in rats than when the ethanol sipper was continuously available during the session. This intermittent sipper effect was observed in a social drinking situation, in which subjects experienced intermittent opportunities to interact briefly with a conspecific rat. The objective of this study was to evaluate the effects of the intermittent sipper procedure in situations providing for intermittent presentations of food, and, in addition, in situations that do not provide for intermittent presentations of another rewarding event. METHODS: Four groups of male Long-Evans hooded rats, arranged in a 2 x 2 factorial design with two levels of Sipper Procedure (Intermittent vs Continuous) and two levels of Food procedure (Food vs No Food), were trained in drinking chambers. During each daily session, Intermittent Sipper groups received access to the ethanol sipper during each of 25 trials of 10 s each, while Continuous Sipper groups had access to the ethanol sipper during the entire session (approximately 30 min). During each session, Food groups received 25 presentations of food pellets while No Food groups received no food pellets. Ethanol concentrations in the sipper [3, 4, 6, 8, and 10% (vol./vol.)] increased across sessions. RESULTS: More rapid escalation of ethanol intake was observed in the Intermittent Sipper groups than in the Continuous Sipper groups, and this effect was observed in both the Food and No Food conditions (P's < 0.05), which did not differ from one another. CONCLUSIONS: Intermittent Sipper procedures provide less access to the ethanol sipper, yet induced more ethanol drinking than Continuous Sipper procedures. The intermittent sipper effect is not dependent on presentations of food. Implications for schedule-induced polydipsia and Pavlovian autoshaping are discussed.

Social interaction opportunity and intermittent presentations of ethanol sipper tube induce ethanol drinking in rats.

We evaluated the effects of social interaction opportunity (SIO) and intermittent presentations of the ethanol sipper tube (IS) on autoshaping of ethanol drinking in nondeprived rats. Rats were assigned to one of seven groups. Two groups experienced brief IS, either paired with or randomly related to the response-independent raising of a guillotine door (D) revealing the presence of a conspecific male rat in a holding cage (SIO). Two control groups received similar training, respectively, except that the D revealed an empty cage, whereas a third control group received IS but neither D nor SIO. For two additional control groups, the ethanol sipper tube was continuously available during the session, with and without SIO, with both groups receiving intermittent D. In IS conditions, procedures with SIO induced more ethanol intake than did non-SIO procedures, indicating that SIO contributed to ethanol intake, but D procedures did not differ from non-D procedures, indicating that ethanol drinking was not related to the operation of the door. Groups that received training procedures providing for both SIO and IS showed more rapid initiation of ethanol intake and more rapid escalation of ethanol intake as the concentration of ethanol in the sipper tube conditioned stimulus was increased across sessions. Theoretical accounts, which are based on cue at response manipulandum/autoshaping, schedule-induced polydipsia, incentive sensitization, and intermittency-induced arousal, are considered.

Anabolic androgenic steroid affects social aggression and fear-related behaviors in male pair-housed rats.

This study examines the effect of chronic administration of the anabolic androgenic steroid nandrolone decanoate (ND) on dominant and subordinate male rats in a pair-housed condition. Pair-housed rats were assessed for dominance status based on their behavior and alterations in body weights. Throughout the study the rats were allowed limited social interactions on a daily basis. At all other times, a Plexiglas divider kept the rats separated, allowing olfactory and visual contact between the cage mates while preventing significant physical contact. One week into the study all subjects were subcutaneously implanted with a pellet that continuously infused either ND (15 mg/kg/day) or placebo for 21 days. Following the pellet implant, behavioral tests including reassessment for dominance status, and a conditioned fear test were conducted over a period of approximately 2 months to investigate possible long-term changes. The main finding is that during the allowed social interactions, the dominant ND-pretreated rats spent more time on highly aggressive behaviors than the dominant placebo-treated rats. In addition, the probability for highly aggressive behaviors was maintained for the ND-treated rats throughout the study, whereas it was decreased for the placebo-treated rats. The ND-treated subordinate rats showed less fear in a potential threatening situation compared to placebo-treated controls. These findings support the relatively long-term behavioral changes that have been seen in humans after abuse of ND and other anabolic androgenic steroid compounds.

Autoshaping of chlordiazepoxide drinking in non-deprived rats.

Effects of autoshaping procedures (Paired versus Random) and sipper fluid [chlordiazepoxide (CDP) versus water] on sipper-directed drinking were evaluated in 32 male Long-Evans rats maintained with free access to food and water. For the Paired/CDP group (n = 16), autoshaping procedures consisted of the presentation of the CDP sipper conditioned stimulus (CS) followed by the response-independent presentation of the food unconditioned stimulus (US). The concentration of CDP in the sipper CS (0.05, 0.10, 0.15, 0.20, and 0.25 mg/ml CDP) was increased across sessions. The Paired/Water group (n = 8) received only water in the sipper CS. The Random/CDP group (n = 8) received the CDP sipper CS and food US randomly with respect to one another. The Paired/CDP group drank significantly more of the 0.20 mg/ml and 0.25 mg/ml CDP solutions than the Random/CDP control, and more fluid than the Paired/Water control group when the sipper CS for the Paired/CDP group contained the three highest concentrations of CDP. CS-Only extinction procedures reliably reduced sipper CS-directed drinking in the Paired/CDP and the Paired/Water groups, but not in the Random/CDP group. Data are consistent with the hypothesis that Pavlovian autoshaping procedures induce sipper CS-directed drinking of CDP in rats deprived of neither food nor fluid. Implications for the autoshaping model of drug abuse are discussed.

Ethanol consumption increases rat stress hormones and adrenomedullary gene expression.

Numerous reports document altered drinking behavior following acute stressors but few describe physiological responses to acute stress of chronic ethanol consuming subjects. We tested rats' responses to 120-min foot restraint immobilization (Immo) after 1 week of liquid diet containing 5% wt/vol ethanol (ethanol-fed). Controls consumed isocaloric liquid diet ad libitum (adlib-fed) or in amounts equal to that of ethanol-fed subjects on the previous day (pair-fed). Each rat was implanted with a tail artery cannula on day 7 to allow remote blood collection before and during Immo on day 8. Plasma epinephrine (Epi); norepinephrine (NE); corticosterone (Cort); prolactin (PRL); adrenomedullary gene expression of catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine-N-methyl transferase (PNMT); and TH protein levels were measured. Ethanol-fed rats had two to threefold higher basal plasma Epi and NE and tended to have increased Cort compared to adlib-fed or pair-fed rats. Immo increased Epi and NE in ethanol-fed rats more than twofold above those observed in controls, and also increased Cort more in ethanol-fed than in control rats. PRL was marginally affected. Ethanol potentiated the normal immobilization-induced increase in adrenomedullary TH, DBH, and PNMT messenger RNA (mRNA). TH protein increased only in ethanol-fed rats. Increased plasma catecholamine levels, adrenomedullary gene expression, and TH protein concentration in nonimmobilized ethanol-fed rats strongly suggest that ethanol consumption was itself a stressor, which potentiated the subsequent response to acute Immo. Moreover, the observed interaction of ethanol and stress on plasma catecholamine levels illustrates the importance of minimizing additional stressful stimuli when investigating ethanol's physiological effects.