Gamma-hydroxybutyric acid affects the acquisition and reinstatement of cocaine-induced conditioned place preference in mice

Cocaine addicts very often use different combinations of cocaine and other drugs of abuse such as gamma-hydroxybutyric acid. The objective of the present work was to evaluate the impact of gamma-hydroxybutyric acid administration on the rewarding actions of cocaine, using the conditioned place preference procedure. Cocaine-induced conditioned place preference (50 mg/kg) was studied after pairing this drug with different gamma-hydroxybutyric acid doses (6.25, 12.5, 25, 50 and 100 mg/kg) during either the acquisition or the expression phase of the procedure. After conditioned place preference had been established, and the preference was extinguished, a reinstatement was induced by a dose of cocaine half of that used to produce conditioning, or by gamma-hydroxybutyric acid alone or by both drugs together. The doses of 12.5 and 100 mg/kg of gamma-hydroxybutyric acid blocked the acquisition of cocaine-induced conditioned place preference, and no dose affected the expression of this conditioning. Reinstatement was abolished only with the dose of 25 mg/kg gamma-hydroxybutyric acid, which did not reinstate the preference by itself. This is the first study evaluating the effects of gamma-hydroxybutyric acid on the rewarding properties of cocaine using the conditioned place preference procedure. The principal conclusion of the study is that gamma-hydroxybutyric acid does not enhance the rewarding effect of cocaine, and within a narrow margin of effective doses, blocks the acquisition and reinstatement of cocaine-induced preference.     

Beta1 adrenergic receptors in the bed nucleus of stria terminalis mediate differential responses to opiate withdrawal.

The negative physical and affective aspects of opioid abstinence contribute to the prolongation of substance abuse. Withdrawal treatment is successful only in a subset of subjects, yet little is known about the neurobiological causes of these individual differences. Here, we compare the somatic and motivational components of opioid withdrawal in animals with high reactivity (HR) vs low reactivity (LR) to novelty, a phenotype associated with differential vulnerability to drug abuse. During withdrawal, HR relative to LR showed increased teeth chattering and eye twitching episodes, somatic signs associated with adrenergic modulation. Given the role of noradrenergic circuitry of the extended amygdala in opioid withdrawal, we examined adrenergic receptor gene expression in the bed nucleus of stria terminalis (BST) and central nucleus of the amygdala. Relative to LR, HR rats exhibit a selective increase in beta(1) adrenergic receptor expression in lateral and medial BST. To uncover the functional relevance of this difference, we microinjected betaxolol, a selective beta(1) receptor antagonist, into dorsal BST and assessed somatic and affective responses during withdrawal. Betaxolol microinjection dose-dependently decreased teeth chattering episodes in HR to levels observed in LR animals. Moreover, the antagonist blocked conditioned place aversion, a measure of negative affect associated with withdrawal, in HR but not in LR animals. Our results reveal for the first time that reactivity to novelty predicts somatic and affective aspects of opiate dependence, and that beta(1) receptors in BST are implicated in opiate withdrawal but only in novelty-seeking individuals.     

Attenuation of cocaine-induced reinstatement of cocaine conditioned place preference by acamprosate

Acamprosate (calcium acetylhomotaurinate) is a glutamatergic neuromodulator efficacious at reducing relapse in alcoholic patients. The effect of acamprosate on relapse to other drugs of abuse has received little attention, however, and given increasing evidence that glutamatergic transmission mediates relapse to cocaine-seeking behavior, the purpose of this study was to assess the effects of acamprosate on the reinstatement of a conditioned place preference for cocaine. Mice were conditioned daily with cocaine (15 mg/kg), tested for the establishment of cocaine conditioned place preference, and then retested once weekly to monitor the extinction of the place preference. Following extinction of cocaine conditioned place preference, animals were treated daily with saline or acamprosate (30 or 100 mg/kg) for 3 days, followed by a single injection of cocaine (15 mg/kg) to reinstate conditioned place preference. In mice treated with saline or the low (30 mg/kg) dose of acamprosate, cocaine induced a significant reinstatement of the previously extinguished conditioned place preference; however, this reinstatement was not observed in mice treated with the high (100 mg/kg) dose of acamprosate. These results indicate that acamprosate can attenuate relapse-like behavior in mice and suggest that this compound may be potentially useful in the treatment for cocaine addiction.     

Social experiences affect reinstatement of cocaine-induced place preference in mice

Rationale  

Drug addiction is a multifactorial disorder resulting from an interaction between genetic and environmental factors, and negative and positive environmental conditions may increase or reduce, respectively, vulnerability to drug addiction.     

Food-deprivation increases cocaine-induced conditioned place preference and locomotor activity in rats

 Food-deprivation increases the reinforcing efficacy of cocaine and other drugs within self-administration experiments. In this study, the effects of food-deprivation on cocaine-induced conditioned place preference were investigated. Male Sprague-Dawley rats were assigned to one of two feeding conditions: satiated (with ad libitum food) or deprived (maintained at 80% of free-feeding body weights). During conditioning trials, on alternate days, rats received IP injections of cocaine (0.0, 2.5, 5.0, or 10.0 mg/kg; n=12 per dose group) and were confined for 30 min in one of two distinct environments. On intervening days, the same rats were injected with saline and confined for 30 min in the opposite environment. After four cocaine and four saline trials, a 15-min choice test (with no injections) was given. During this time, the rats were able to move freely through a passageway between both environments. Relative to the food-satiated rats, the food-deprived rats showed a greater conditioned preference for the cocaine-paired environment during the choice test, greater cocaine-induced locomotor activity during conditioning trials, and a greater degree of sensitization to the activating effects of cocaine across conditioning trials. This study extends the general findings of food deprivation-induced increases in the reinforcing efficacy of cocaine to include the conditioned place preference paradigm. Received: 23 January 1996 / Final version: 4 December 1996     

D-serine facilitates the effectiveness of extinction to reduce drug-primed reinstatement of cocaine-induced conditioned place preference

Addiction is a disease that is characterized by compulsive drug-seeking and use despite negative health and social consequences. One obstacle in treating addiction is a high susceptibility for relapse which persists despite prolonged periods of abstinence. Relapse can be triggered by drug predictive stimuli such as environmental context and drug associated cues, as well as the addictive drug itself. The conditioned place preference (CPP) behavioral model is a useful paradigm for studying the ability of these drug predictive stimuli to reinstate drug-seeking behavior. The present study investigated the dose-dependent effects of D-serine (10?mg/kg, 30?mg/kg and 100?mg/kg) on extinction training and drug-primed reinstatement in cocaine-conditioned rats. In the first experiment, D-serine had no effect on the acquisition or development of cocaine-induced locomotor sensitization or CPP. In the second experiment, D-serine treatment resulted in significantly decreased time spent in the drug-paired compartment following completion of an extinction protocol. A cocaine-primed reinstatement test indicated that the combination of extinction training along with D-serine treatment resulted in a significant reduction of drug-seeking behavior. The third experiment assessed D-serine's long-term effects to diminish drug-primed reinstatement. D-serine treatment given during extinction was effective in reducing drug-seeking for more than four weeks of abstinence after the last cocaine exposure. These findings demonstrate that D-serine may be an effective adjunct therapeutic agent along with cognitive behavioral therapy for the treatment of cocaine addiction. This article is part of a Special Issue entitled 'Cognitive Enhancers'.     

Noradrenaline in the bed nucleus of the stria terminalis is critical for stress-induced reactivation of morphine-conditioned place preference in rats.

The effect of noradrenaline in the bed nucleus of the stria terminalis and locus coeruleus on maintenance and reactivation of morphine-conditioned place preference induced by footshock stress was investigated in rats. After receiving alternate injection of morphine (10 mg/kg) and saline for 6 consecutive days, the rats spent more time in the drug-paired compartment (morphine-conditioned place preference) on day 7. These animals did not show morphine-conditioned place preference on day 37 following sham-footshock once every 3 days from days 8 to 36 (28 days drug-free). However, 15 min of intermittent footshock once every 3 days could induce the maintenance of morphine-conditioned place preference on day 37 with significantly more time spent in the drug-paired compartment than on day 0. Microinjection of the alpha(2)-adrenoceptor agonist, clonidine (0.1 or 1 microg), into the locus coeruleus 30 min before footshock did not affect stress-induced maintenance of conditioned place preference. However, infusions of clonidine (1 microg) into the bed nucleus of the stria terminalis significantly attenuated the maintenance of conditioned place preference induced by footshock stress. In another experiment, after a 21-day extinction of morphine-conditioned place preference, a single footshock could reactivate the morphine place preference that was significantly blocked by pretreatment with infusion of clonidine (0.1 or 1 microg) into the bed nucleus of the stria terminalis but not the locus coeruleus. Reactivation of morphine-conditioned place preference elicited by footshock stress was significantly inhibited by 6-hydroxydopamine-induced lesions in the ventral noradrenergic bundle, most of the norepinephrine input to the bed nucleus of the stria terminalis arising from caudal brain stem noradrenergic cell groups. In contrast, chemical lesions of the dorsal noradrenergic bundle that arises from the locus coeruleus had no such effects. These findings suggest that noradrenergic neurons in locus coeruleus are not involved in stress-induced reinstatement of drug-seeking and further clearly demonstrate that noradrenaline in the bed nucleus of the stria terminalis plays a critical role in mediating this effect. Comprehension of the neurochemical events underlying the stress-induced and the bed nucleus of the stria terminalis-mediated reinstatement of drug-seeking may, therefore, throw more light on the biological bases of drug dependence and addictive behavior     

The role of mu- and kappa-opioid receptors in cocaine-induced conditioned place preference.

Effects of buprenorphine, U-50,488H, naltrexone and lithium chloride on cocaine conditioned place preference were examined. Buprenorphine, a mixed opioid agonist-antagonist, blocked the cocaine-induced place preference. Furthermore, the kappa-receptor agonist U-50,488H and the mu-receptor antagonist naltrexone both antagonized the cocaine preference. U-50,488H or naltrexone alone induced a place aversion in a dose-dependent manner. However, the cocaine-induced conditioned place preference was not blocked by lithium chloride, although the latter induced a conditioned place aversion, indicating that the antagonism of cocaine-induced place preference by U-50,488H or naltrexone does not result from a functional antagonism. These results suggest that mu- and kappa-opioid receptors may be involved in cocaine-induced conditioned place preference.     

Genetic liability increases propensity to prime-induced reinstatement of conditioned place preference in mice exposed to low cocaine

Rationale Relapse to drug use after periods of forced or self-imposed abstinence is a central problem in the treatment of addiction; therefore, identification of factors modulating the risk to relapse is a relevant goal of preclinical research. Objectives These experiments evaluated the influence of the amount of drug experienced, the duration of drug withdrawal, and individual liability on the propensity to cocaine-induced reinstatement of conditioned place preference (CPP). Materials and methods Mice from the inbred strains C57BL/6J and DBA/2J were trained for CPP with a high (20 mg/kg) or low (5 mg/kg) effective dose of cocaine. After CPP testing, all groups underwent extinction. Twenty-four hours after the extinction test, mice were challenged with saline, a cocaine dose unable to induce CPP (2.5 mg/kg) or an intermediate effective dose (10 mg/kg), and tested for CPP reinstatement. Additional groups of mice trained with the low cocaine dose were left undisturbed for 8 days after extinction test (long withdrawal), retested for extinction, and evaluated for prime-induced reinstatement (0, 2.5, 10 mg/kg of cocaine). Results Mice trained with the high cocaine dose, but not with the low one, showed prime-induced reinstatement 24 h after the extinction test; DBA/2J mice trained with the low dose showed reinstatement after long withdrawal. Conclusions These results indicate that reinstatement of CPP by cocaine prime depends on the amount of drug experienced and on an interaction between individual liability and duration of drug abstinence and suggest that the risk to relapse into drug seeking is not prevented by moderated drug consumption.     

Alcohol inhibits NR2B-containing NMDA receptors in the ventral bed nucleus of the stria terminalis.

Components of the mesolimbic dopamine system, in particular dopaminergic cells in the ventral tegmental area (VTA), have been implicated in the acute reinforcing actions of ethanol. The ventral bed nucleus of the stria terminalis (vBNST) potently regulates dopaminergic cell firing in the VTA, and has been implicated in the behavioral actions of ethanol. The N-methyl-D-asparate receptor (NMDAR) is a major molecular target of ethanol, however, current evidence suggests that ethanol regulation of NMDAR function is widely variable and likely depends on a number of factors. Thus, it is critical to investigate ethanol regulation of NMDAR function at synapses relevant to ethanol-regulated behaviors, such as in the vBNST. Here we show, using multiple techniques, that ethanol inhibits NMDAR function in vBNST neurons in a postsynaptic fashion. Further, we demonstrate the functional presence of both NR2A and NR2B-containing NMDARs in the vBNST. While genetic removal of NR2A did not alter the magnitude of ethanol inhibition, pharmacological blockade of NR2B rendered synaptically activated NMDARs insensitive to ethanol inhibition. Finally, we demonstrate that ethanol inhibits NMDARs in cells in the vBNST that project to the VTA, providing a direct means by which ethanol in the vBNST can modulate the dopaminergic system.     

Inactivation of the bed nucleus of the stria terminalis in an animal model of relapse: effects on conditioned cue-induced reinstatement and its enhancement by yohimbine

Rationale  

Drug-associated cues and stress increase craving and lead to greater risk of relapse in abstinent drug users. Animal models of reinstatement of drug seeking have been utilized to study the neural circuitry by which either drug-associated cues or stress exposure elicit drug seeking. Recent evidence has shown a strong enhancing effect of yohimbine stress on subsequent cue-elicited reinstatement; however, there has been no examination of the neural substrates of this interactive effect.     

Presynaptic muscarinic M(2) receptors modulate glutamatergic transmission in the bed nucleus of the stria terminalis

The anterolateral cell group of the bed nucleus of the stria terminalis (BNST(ALG)) serves as an important relay station in stress circuitry. Limbic inputs to the BNST(ALG) are primarily glutamatergic and activity-dependent changes in this input have been implicated in abnormal behaviors associated with chronic stress and addiction. Significantly, local infusion of acetylcholine (ACh) receptor agonists into the BNST trigger stress-like cardiovascular responses, however, little is known about the effects of these agents on glutamatergic transmission in the BNST(ALG). Here, we show that glutamate- and ACh-containing fibers are found in close association in the BNST(ALG). Moreover, in the presence of the acetylcholinesterase inhibitor, eserine, endogenous ACh release evoked a long-lasting reduction of the amplitude of stimulus-evoked EPSCs. This effect was mimicked by exogenous application of the ACh analog, carbachol, which caused a reversible, dose-dependent, reduction of the evoked EPSC amplitude, and an increase in both the paired-pulse ratio and coefficient of variation, suggesting a presynaptic site of action. Uncoupling of postsynaptic G-proteins with intracellular GDP-β-S, or application of the nicotinic receptor antagonist, tubocurarine, failed to block the carbachol effect. In contrast, the carbachol effect was blocked by prior application of atropine or M(2) receptor-preferring antagonists, and was absent in M(2)/M(4) receptor knockout mice, suggesting that presynaptic M(2) receptors mediate the effect of ACh. Immunoelectron microscopy studies further revealed the presence of M(2) receptors on axon terminals that formed asymmetric synapses with BNST neurons. Our findings suggest that presynaptic M(2) receptors might be an important modulator of the stress circuit and hence a novel target for drug development.     

Adolescents differ from adults in cocaine conditioned place preference and cocaine-induced dopamine in the nucleus accumbens septi

In humans, adolescent exposure to illicit drugs predicts the onset of adult drug abuse and suggests that early drug use potentiates vulnerability to drug addiction. Cocaine conditioned place preferences were measured in early adolescent [postnatal day (PND) 35], late adolescent (PND 45) and young adult (PND 60) rats by injecting either 0, 5 or 20 mg/kg cocaine and conditioning them to environmental cues. Cocaine preferences were found for all ages at the high dose. PND 35s were the only age group to have a preference at the low dose. To address whether age-related differences in cocaine place preferences were related to differences in the mesolimbic dopaminergic system, we measured extracellular dopamine levels in the nucleus accumbens septi of PND 35, PND 45 and PND 60 rats via quantitative microdialysis under transient conditions. Rats were injected daily with either 5 mg/kg/ip or saline for 4 days and surgically implanted with a microdialysis probe aimed at the nucleus accumbens. Rats were perfused with either 0, 1, 10 or 40 nM dopamine and the extracellular dopamine concentration was measured. Our results show that adolescents differ from adults in basal dopamine. All cocaine treated rats, regardless of age, showed a significant increase in dopamine over baseline in response to a cocaine challenge. Additionally, there were age-related differences in the extraction fraction (E_d), an indirect measure of dopamine reuptake. Together these findings suggest ontogenetic differences in extracellular dopamine and dopamine reuptake and that these differences may provide an explanation for adolescent vulnerability to addiction.     

The effect of phosphodiesterase inhibitors on the extinction of cocaine-induced conditioned place preference in mice

Several phosphodiesterase inhibitors (PDEis) improve cognition, suggesting that an increase in brain cAMP and cGMP facilitates learning and memory. Since extinction of drug-seeking behavior requires associative learning, consolidation and formation of new memory, the present study investigated the efficacy of three different PDEis in the extinction of cocaine-induced conditioned place preference (CPP) in B6129S mice. Mice were conditioned by escalating doses of cocaine which was resistant to extinction by free exploration. Immediately following each extinction session mice received (a) saline/vehicle, (b) rolipram (PDE4 inhibitor), (c) BAY-73-6691 (PDE9 inhibitor) or (d) papaverine (PDE10A inhibitor). Mice that received saline/vehicle during extinction training showed no reduction in CPP for >10 days. BAY-73-6691 (a) dose-dependently increased cGMP in hippocampus and amygdala, (b) significantly facilitated extinction and (c) diminished the reinstatement of cocaine CPP. Rolipram, which selectively increased brain cAMP levels, and papaverine which caused increases in both cAMP and cGMP levels, had no significant effect on the extinction of cocaine CPP. The results suggest that increase in hippocampal and amygdalar cGMP levels via blockade of PDE9 has a prominent role in the consolidation of extinction learning.     

Elevated extracellular CRF levels in the bed nucleus of the stria terminalis during ethanol withdrawal and reduction by subsequent ethanol intake

Corticotropin-releasing factor (CRF) is widely distributed throughout the brain and has been shown to mediate numerous endocrine and behavioral responses to stressors. During acute ethanol withdrawal, CRF release is increased in the central nucleus of the amygdala (CeA), and there is evidence to suggest that this activation of amygdala CRF systems may mediate the anxiogenic properties of the ethanol withdrawal syndrome. The present study was conducted to determine if another CRF-containing limbic structure, the bed nucleus of the stria terminalis (BNST), we would exhibit similar increases in CRF neurotransmission during ethanol withdrawal. Rats were administered an ethanol-containing (6.7% v/v) or control liquid diet for 2 weeks and subsequently implanted with microdialysis probes into the lateral BNST. A 50-75% increase in dialysate CRF levels was observed following removal of the ethanol-containing diet, while no changes were observed in control animals. When ethanol-withdrawn animals were given subsequent access to the ethanol-containing diet, dialysate CRF levels returned to basal levels. However, when ethanol-withdrawn animals were given subsequent access to the control diet, dialysate CRF levels increased further to 101% above basal levels. These data demonstrate that extracellular CRF levels are increased in the BNST during ethanol withdrawal, and that these increases are reduced by subsequent ethanol intake.     

Norepinephrine modulates glutamatergic transmission in the bed nucleus of the stria terminalis.

The bed nucleus of the stria terminalis (BNST) and its adrenergic input are key components in stress-induced reinstatement and maintenance of drug use. Intra-BNST injections of either beta-adrenergic receptor (beta-AR) antagonists or alpha2-adrenergic receptor (alpha2-AR) agonists can inhibit footshock-induced reinstatement and maintenance of cocaine- and morphine-seeking. Using electrophysiological recording methods in an in vitro slice preparation from C57/Bl6j adult male mouse BNST, we have examined the effects of adrenergic receptor activation on excitatory synaptic transmission in the lateral dorsal supracommissural BNST (dBNST) and subcommissural BNST (vBNST). Alpha2-AR activation via UK-14,304 (10 microM) results in a decrease in excitatory transmission in both dBNST and vBNST, an effect predominantly dependent upon the alpha2A-AR subtype. Beta-AR activation via isoproterenol (1 microM) results in an increase in excitatory transmission in dBNST, but not in vBNST. Consistent with the work with receptor subtype specific agonists, application of the endogenous ligand norepinephrine (NE, 100 microM) elicits two distinct effects on glutamatergic transmission. In dBNST, NE elicits an increase in transmission (62% of dBNST NE experiments) or a decrease in transmission (38% of dBNST NE experiments). In vBNST, NE elicits a decrease in transmission in 100% of the experiments. In dBNST, the NE-induced increase in synaptic transmission is blocked by beta1/beta2- and beta2-, but not beta1-specific antagonists. In addition, this increase is also reduced by the alpha2-AR antagonist yohimbine and is absent in the alpha2A-AR knockout mouse. In vBNST, the NE-induced decrease in synaptic transmission is markedly reduced in the alpha2A-AR knockout mouse. Further experiments demonstrate that the actions of NE on glutamatergic transmission can be correlated with beta-AR function.     

Chronic psychosocial stress causes delayed extinction and exacerbates reinstatement of ethanol-induced conditioned place preference in mice

Rationale

We have shown previously, using an animal model of voluntary ethanol intake and ethanol-conditioned place preference (EtOH-CPP), that exposure to chronic psychosocial stress induces increased ethanol intake and EtOH-CPP acquisition in mice.

Objective

Here, we examined the impact of chronic subordinate colony (CSC) exposure on EtOH-CPP extinction, as well as ethanol-induced reinstatement of CPP.

Methods

Mice were conditioned with saline or 1.5 g/kg ethanol and were tested in the EtOH-CPP model. In the first experiment, the mice were subjected to 19 days of chronic stress, and EtOH-CPP extinction was assessed during seven daily trials without ethanol injection. In the second experiment and after the EtOH-CPP test, the mice were subjected to 7 days of extinction trials before the 19 days of chronic stress. Drug-induced EtOH-CPP reinstatement was induced by a priming injection of 0.5 g/kg ethanol.

Results

Compared to the single-housed colony mice, CSC mice exhibited increased anxiety-like behavior in the elevated plus maze (EPM) and the open field tests. Interestingly, the CSC mice showed delayed EtOH-CPP extinction. More importantly, CSC mice showed increased alcohol-induced reinstatement of the EtOH-CPP behavior.

Conclusion

Taken together, this study indicates that chronic psychosocial stress can have long-term effects on EtOH-CPP extinction as well as drug-induced reinstatement behavior and may provide a suitable model to study the latent effects of chronic psychosocial stress on extinction and relapse to drug abuse.     

GABAA receptors modulate ethanol-induced conditioned place preference and taste aversion in mice

  Rationale: GABA_A receptor antagonists have been shown to reduce ethanol self-administration and ethanol-induced conditioned taste aversion (CTA) in rats, suggesting a role for the GABA_A receptor in modulating ethanol’s motivational effects. Objectives: The present experiments examined the effects of the GABA_A receptor antagonists, bicuculline and picrotoxin, on the acquisition of ethanol-induced conditioned place preference (CPP) and CTA in male DBA/2J mice. Methods: Mice in the CPP experiments received four pairings of ethanol (2 g/kg) with a distinctive floor stimulus for a 5-min conditioning session (CS+ sessions). During CS+ sessions, mice also received bicuculline (0, 1.0, 3.0, or 5.0 mg/kg) or picrotoxin (2.0 mg/kg) before an injection of ethanol. On intervening days (CS– sessions), the pretreatment injection was always vehicle followed by saline injections that were paired with a different floor type. For the preference test, all mice received saline injections and were placed on a half grid and half hole floor for a 60-min session. For the CTA experiments, mice were adapted to a 2-h per day water restriction regimen followed by five conditioning trials every 48 h. During conditioning trials, subjects received an injection of vehicle, bicuculline (0.5 and 2.0 mg/kg), or picrotoxin (0.75 and 2.5 mg/kg) before injection of 2 g/kg ethanol or saline following 1-h access to a saccharin solution. Results: Both picrotoxin and the lowest dose of bicuculline (1.0 mg/kg) significantly increased the magnitude of CPP relative to vehicle-treated controls. Picrotoxin alone did not produce place conditioning. Ethanol-stimulated locomotor activity was significantly reduced during conditioning trials with picrotoxin and the higher doses of bicuculline (3.0 and 5.0 mg/kg). Bicuculline did not alter ethanol-induced CTA; however, picrotoxin dose-dependently increased the magnitude of ethanol-induced CTA. Bicuculline and picrotoxin did not produce CTA when administered alone. Conclusions: Overall, these results suggest that blockade of GABA_A receptors with bicuculline and picrotoxin enhances ethanol’s motivational effects in the CPP paradigm; however, only picrotoxin enhances ethanol’s motivational effects in the CTA paradigm. Received: 12 September 1998 / Final version: 21 December 1998     

Anxiogenic and aversive effects of corticotropin-releasing factor (CRF) in the bed nucleus of the stria terminalis in the rat: role of CRF receptor subtypes

Rationale Corticotropin-releasing factor (CRF) produces anxiety-like and aversive effects when infused directly into the various regions of the brain, including the bed nucleus of the stria terminalis (BNST). However, the CRF receptor subtypes within the BNST mediating these phenomena have not been established.Objectives We used selective CRF receptor antagonists to determine the receptor subtypes involved in the anxiogenic-like and aversive effects CRF in the BNST.Materials and methods Male Long–Evans rats were bilaterally infused with CRF (0.2 or 1.0 nmol) either alone or in combination with the CRF₁ receptor antagonist CP154,526 or the CRF₂ receptor antagonist anti-sauvagine 30 (AS30) before behavioral testing in the elevated plus maze or place conditioning paradigms.Results Intra-BNST administration of CRF produced a dose-dependent reduction in open arm entries and open arm time in the elevated plus maze, indicating an anxiogenic-like effect. These effects were inhibited by co-infusion of CP154,526 but not of AS30, indicating that the anxiogenic-like effects of CRF in the BNST are mediated by CRF₁ receptors. Place conditioning with intra-BNST administration of CRF produced a dose-dependent aversion to the CRF-paired environment that was prevented by co-infusion of either CP154,526 or AS30, indicating that both CRF receptor subtypes mediate the aversive effects of this peptide. Intra-BNST infusions of the CRF receptor antagonists alone produced no effects in either behavioral paradigm.Conclusions CRF₁ receptors in the BNST mediate the anxiogenic-like effects of CRF in this region, whereas both CRF₁ and CRF₂ receptor subtypes mediate the conditioned aversive effects of this peptide within the BNST.