Adolescent Intermittent Ethanol (AIE) Enhances the Dopaminergic Response to Ethanol within the Mesolimbic Pathway during Adulthood: Alterations in Cholinergic/Dopaminergic Genes Expression in the Nucleus Accumbens Shell.

A consistent preclinical finding is that exposure to alcohol during adolescence produces a persistent hyperdopaminergic state during adulthood. The current experiments determine that effects of Adolescent Intermittent Ethanol (AIE) on the adult neurochemical response to EtOH administered directly into the mesolimbic dopamine system, alterations in dendritic spine and gene expression within the nucleus accumbens shell (AcbSh), and if treatment with the HDACII inhibitor TSA could normalize the consequences of AIE. Rats were exposed to the AIE (4 g/kg ig; 3 days a week) or water (CON) during adolescence, and all testing occurred during adulthood. CON and AIE rats were microinjected with EtOH directly into the posterior VTA and dopamine and glutamate levels were recorded in the AcbSh. Separate groups of AIE and CON rats were sacrificed during adulthood and Taqman arrays and dendritic spine morphology assessments were performed. The data indicated that exposure to AIE resulted in a significant leftward and upward shift in the dose-response curve for an increase in dopamine in the AcbSh following EtOH microinjection into the posterior VTA. Taqman array indicated that AIE exposure affected the expression of target genes (Chrna7, Impact, Chrna5). The data indicated no alterations in dendritic spine morphology in the AcbSh or any alteration in AIE effects by TSA administration. Binge-like EtOH exposure during adolescence enhances the response to acute ethanol challenge in adulthood, demonstrating that AIE produces a hyperdopaminergic mesolimbic system in both male and female Wistar rats. The neuroadaptations induced by AIE in the AcbSh could be part of the biological basis of the observed negative consequences of adolescent binge-like alcohol exposure on adult drug self-administration behaviors.

The Rewarding and Anxiolytic Properties of Ethanol within the Central Nucleus of the Amygdala: Mediated by Genetic Background and Nociceptin.

In humans, alcohol is consumed for its rewarding and anxiolytic effects. The central nucleus of the amygdala (CeA) is considered a neuronal nexus that regulates fear, anxiety, and drug self-administration. Manipulations of the CeA alter ethanol (EtOH) consumption under numerous EtOH self-administration models. The experiments determined whether EtOH is reinforcing/anxiolytic within the CeA, whether selective breeding for high alcohol consumption alters the rewarding properties of EtOH in the CeA, and whether the reinforcing/anxiolytic effects of EtOH in the CeA are mediated by the neuropeptides corticotropin-releasing factor (CRF) and nociceptin. The reinforcing properties of EtOH were determined by having male Wistar and Taconic alcohol-preferring (tP) rats self-administer EtOH directly into the CeA. The expression of anxiety-like behaviors was assessed through multiple behavioral models (social interaction, acoustic startle, and open field). Coadministration of EtOH and a CRF1 antagonist (NBI35965) or nociceptin on self-administration into the CeA and anxiety-like behaviors was determined. EtOH was self-administered directly into the lateral CeA, and tP rats self-administered a lower concentration of EtOH than Wistar rats. EtOH microinjected into the lateral CeA reduced the expression of anxiety-like behaviors, indicating an anxiolytic effect. Coadministration of NBI35965 failed to alter the rewarding/anxiolytic properties of EtOH in the CeA. In contrast, coadministration of the nociceptin enhanced both EtOH reward and anxiolysis in the CeA. Overall, the data indicate that the lateral CeA is a key anatomic location that mediates the rewarding and anxiolytic effects of EtOH, and local nociceptin receptors, but not local CRF1 receptors, are involved in these behaviors. SIGNIFICANCE STATEMENT: Alcohol is consumed for the stimulatory, rewarding, and anxiolytic properties of the drug of abuse. The current data are the first to establish that alcohol is reinforcing and anxiolytic within the lateral central nucleus of the amygdala (CeA) and that the nociceptin system regulates these effects of alcohol within the CeA.

Adolescent Intermittent Ethanol Increases the Sensitivity to the Reinforcing Properties of Ethanol and the Expression of Select Cholinergic and Dopaminergic Genes within the Posterior Ventral Tegmental Area.

BACKGROUND: Although not legally allowed to consume alcohol, adolescents account for 11% of all alcohol use in the United States and approximately 90% of adolescent intake is in the form of an alcohol binge. The adolescent intermittent ethanol (AIE) model developed by the NADIA consortium produces binge-like EtOH exposure episodes. The current experiment examined the effects of AIE on the reinforcing properties of EtOH and genetic expression of cholinergic and dopaminergic factors within the posterior ventral tegmental area (pVTA) in Wistar male and female rats and in male alcohol-preferring (P) rats. METHODS: Rats were exposed to the AIE or water during adolescence, and all testing occurred during adulthood. Wistar control and AIE rats were randomly assigned to groups that self-administered 0 to 200 mg% EtOH. Male P rats self-administered 0 to 100 mg%. RESULTS: The data indicated that exposure to AIE in both Wistar male and female rats (and male P rats) resulted in a significant leftward shift in dose-response curve for EtOH self-administration into the pVTA. TaqMan array indicated that AIE exposure had divergent effects on the expression of nicotinic receptors (increased a7, reduction in a4 and a5). There were also sex-specific effects of AIE on gene expression; male only reduction in D3 receptors. CONCLUSION: Binge-like EtOH exposure during adolescence enhances the sensitivity to the reinforcing properties of EtOH during adulthood which could be part of biological sequelae that are the basis for the deleterious effects of adolescent alcohol consumption on the rate of alcoholism during adulthood.

Reinforcing properties and neurochemical response of ethanol within the posterior ventral tegmental area are enhanced in adulthood by periadolescent ethanol consumption.

Alcohol drinking during adolescence is associated with increased alcohol drinking and alcohol dependence in adulthood. Research examining the biologic consequences of adolescent ethanol (EtOH) consumption on the response to EtOH in the neurocircuitry shown to regulate drug reinforcement is limited. The experiments were designed to determine the effects of periadolescent alcohol drinking on the reinforcing properties of EtOH within the posterior ventral tegmental area (pVTA) and the ability of EtOH microinjected into the pVTA to stimulate dopamine (DA) release in the nucleus accumbens shell (AcbSh). EtOH access (24-hour free-choice) by alcohol-preferring rats occurred during postnatal days (PND) 30-60. Animals were tested for their response to EtOH after PND 85. Intracranial self-administration techniques were performed to assess EtOH self-infusion into the pVTA. In the second experiment, rats received microinjections of EtOH into the pVTA, and dialysis samples were collected from the AcbSh. The results indicate that in rats that consumed EtOH during adolescence, the pVTA was more sensitive to the reinforcing effects of EtOH (a lower concentration of EtOH supported self-administration) and the ability of EtOH microinjected into the pVTA to stimulate DA release in the AcbSh was enhanced (sensitivity and magnitude). The data indicate that EtOH consumption during adolescence altered the mesolimbic DA system to be more sensitive and responsive to EtOH. This increase in the response to EtOH within the mesolimbic DA during adulthood could be part of biologic sequelae that are the basis for the deleterious effects of adolescent alcohol consumption on the rate of alcoholism during adulthood.

Selective breeding for high alcohol preference increases the sensitivity of the posterior VTA to the reinforcing effects of nicotine.

The rate of codependency for alcohol and nicotine is extremely high. Numerous studies have indicated that there is a common genetic association for alcoholism and nicotine dependency. The current experiments examined whether selective breeding for high alcohol preference in rats may be associated with increased sensitivity of the posterior ventral tegmental area (pVTA) to the reinforcing properties of nicotine. In addition, nicotine can directly bind to the serotonin-3 (5-HT3 ) receptor, which has been shown to mediate the reinforcing properties of other drugs of abuse within the pVTA Wistar rats were assigned to groups that were allowed to self-infuse 0, 10, 50, 100, 200, 400 or 800 µM nicotine in two-lever (active and inactive) operant chambers. P rats were allowed to self-infuse 0, 1, 10, 50 or 100 µM nicotine. Co-infusion of 5-HT3 receptor antagonists with nicotine into the pVTA was also determined. P rats self-infused nicotine at lower concentrations than required to support self-administration in Wistar rats. In addition, P rats received more self-infusions of 50 and 100 µM nicotine than Wistar rats; including a 5HT3 receptor antagonist (LY-278,584 or zacopride) with nicotine reduced responding on the active lever. Overall, the data support an association between selective breeding for high alcohol preference and increased sensitivity of the pVTA to the reinforcing properties of nicotine. In addition, the data suggest that activation of 5HT3 receptors may be required to maintain the local reinforcing actions of nicotine within the pVTA.

Identification of a novel perifornical-hypothalamic-area-projecting serotonergic system that inhibits innate panic and conditioned fear responses.

The serotonin (5-HT) system is heavily implicated in the regulation of anxiety and trauma-related disorders such as panic disorder and post-traumatic stress disorder, respectively. However, the neural mechanisms of how serotonergic neurotransmission regulates innate panic and fear brain networks are poorly understood. Our earlier studies have identified that orexin (OX)/glutamate neurons within the perifornical hypothalamic area (PFA) play a critical role in adaptive and pathological panic and fear. While site-specific and electrophysiological studies have shown that intracranial injection and bath application of 5-HT inhibits PFA neurons via 5-HT1a receptors, they largely ignore circuit-specific neurotransmission and its physiological properties that occur in vivo. Here, we investigate the role of raphe nuclei 5-HT inputs into the PFA in panic and fear behaviors. We initially confirmed that photostimulation of glutamatergic neurons in the PFA of rats produces robust cardioexcitation and flight/aversive behaviors resembling panic-like responses. Using the retrograde tracer cholera toxin B, we determined that the PFA receives discrete innervation of serotonergic neurons clustered in the lateral wings of the dorsal (lwDRN) and in the median (MRN) raphe nuclei. Selective lesions of these serotonergic projections with saporin toxin resulted in similar panic-like responses during the suffocation-related CO2 challenge and increased freezing to fear-conditioning paradigm. Conversely, selective stimulation of serotonergic fibers in the PFA attenuated both flight/escape behaviors and cardioexcitation responses elicited by the CO2 challenge and induced conditioned place preference. The data here support the hypothesis that PFA projecting 5-HT neurons in the lwDRN/MRN represents a panic/fear-off circuit and may also play a role in reward behavior.

Inhibitory and excitatory alcohol-seeking cues distinct roles in behavior, neurochemistry, and mesolimbic pathway in alcohol preferring (P) rats.

Cues associated with alcohol use can readily enhance self-reported cravings for alcohol, which increases the likelihood of reusing alcohol. Understanding the neuronal mechanisms involved in alcohol-seeking behavior is important for developing strategies to treat alcohol use disorder. In all experiments, adult female alcohol-preferring (P) rats were exposed to three conditioned odor cues; CS+ associated with EtOH self-administration, CS- associated with the absence of EtOH (extinction training), and a CS0, a neutral stimulus. The data indicated that presentation of an excitatory conditioned cue (CS+) can enhance EtOH- seeking while the CS- can inhibit EtOH-seeking under multiple test conditions. Presentation of the CS+ activates a subpopulation of dopamine neurons within the interfascicular nucleus of the posterior ventral tegmental area (posterior VTA) and basolateral amygdala (BLA). Pharmacological inactivation of the BLA with GABA agonists inhibits the ability of the CS+ to enhance EtOH-seeking but does not alter context-induced EtOH-seeking or the ability of the CS- to inhibit EtOH-seeking. Presentation of the conditioned odor cues in a non-drug-paired environment indicated that presentation of the CS+ increased dopamine levels in the BLA. In contrast, presentation of the CS- decreased both glutamate and dopamine levels in the BLA. Further analysis revealed that presentation of a CS+ EtOH-associated conditioned cue activates GABA interneurons but not glutamate projection neurons. Overall, the data indicate that excitatory and inhibitory conditioned cues can contrarily alter EtOH-seeking behaviors and that different neurocircuitries are mediating these distinct cues in critical brain regions. Pharmacotherapeutics for craving should inhibit the CS+ and enhance the CS- neurocircuits.

A pivotal role of lumbar spinothalamic cells in the regulation of ejaculation via intraspinal connections.

INTRODUCTION: A population of lumbar spinothalamic cells (LSt cells) has been demonstrated to play a pivotal role in ejaculatory behavior and comprise a critical component of the spinal ejaculation generator. LSt cells are hypothesized to regulate ejaculation via their projections to autonomic and motor neurons in the lumbosacral spinal cord. AIM: The current study tested the hypothesis that ejaculatory reflexes are dependent on LSt cells via projections within the lumbosacral spinal cord. METHODS: Male rats received intraspinal injections of neurotoxin saporin conjugated to substance P analog, previously shown to selectively lesion LSt cells. Two weeks later, males were anesthetized and spinal cords were transected. Subsequently, males were subjected to ejaculatory reflex paradigms, including stimulation of the dorsal penile nerve (DPN), urethrogenital stimulation or administration of D3 agonist 7-OH-DPAT. Electromyographic recordings of the bulbocavernosus muscle (BCM) were analyzed for rhythmic bursting characteristic of the expulsion phase of ejaculation. In addition, a fourth commonly used paradigm for ejaculation and erections in unanesthetized, spinal-intact male rats was utilized: the ex copula reflex paradigm. MAIN OUTCOME MEASURES: LSt cell lesions were predicted to prevent rhythmic bursting of BCM following DPN, urethral, or pharmacological stimulation, and emissions in the ex copula paradigm. In contrast, LSt cell lesions were not expected to abolish erectile function as measured in the ex copula paradigm. RESULTS: LSt cell lesions prevented rhythmic contractions of the BCM induced by any of the ejaculatory reflex paradigms in spinalized rats. However, LSt cell lesions did not affect erectile function nor emissions determined in the ex copula reflex paradigm. CONCLUSIONS: These data demonstrate that LSt cells are essential for ejaculatory, but not erectile reflexes, as previously reported for mating animals. Moreover, LSt cells mediate ejaculation via projections within the spinal cord, presumably to autonomic and motor neurons.

CNO Administration Increases Dopamine and Glutamate in the Medial Prefrontal Cortex of Wistar Rats: Further Concerns for the Validity of the CNO-activated DREADD Procedure.

The chemogenetic procedure DREADD (designer receptor exclusively activated by designer drugs) is an inventive way to selectively affect g-coupled protein receptors. In theory, DREADD receptors are only activated by administering inert compounds, primarily clozapine N-oxide (CNO). Research has shown that CNO does not cross the blood-brain barrier, and CNO is converted back to clozapine and N-desmethylclozapine (N-Des) in the brain. Clozapine and N-Des have many neurological effects including alterations in glutamate and dopamine (DA) levels in multiple brain regions. The current study examined the effects of peripheral administration of CNO on glutamate and DA levels in the medial prefrontal cortex (mPFC). Wistar rats were administered CNO, and microdialysis samples were collected from the mPFC. Administration of CNO significantly increased glutamate (31-87%) and DA (65-126%), CNO-induced increases in DA occurred for a longer duration than glutamate, and that for the two highest doses of CNO there was a significant correlation between the increase in glutamate and DA in the mPFC. In the mPFC, CNO-induced increases in DA occurred at 0.5 mg/kg, while increases in glutamate were observed at doses greater than 1.0 mg/kg. The source of the DA and glutamate could be caused by activation of projection neurons or local effects. The data replicate findings that CNO is not an inert compound and that interpretation of CNO-activated DREADD findings should be done with caution. The data indicate that low ('safe') doses of CNO still have neurochemical effects and that controlling for the actions of clozapine/N-Des in CNO-DREADD studies has many concerns.

Negative and positive allosteric modulators of the α7 nicotinic acetylcholine receptor regulates the ability of adolescent binge alcohol exposure to enhance adult alcohol consumption.

Rationale and Objectives: Ethanol acts directly on the α7 Nicotinic acetylcholine receptor (α7). Adolescent-binge alcohol exposure (ABAE) produces deleterious consequences during adulthood, and data indicate that the α7 receptor regulates these damaging events. Administration of an α7 Negative Allosteric Modulator (NAM) or the cholinesterase inhibitor galantamine can prophylactically prevent adult consequences of ABAE. The goals of the experiments were to determine the effects of co-administration of ethanol and a α7 agonist in the mesolimbic dopamine system and to determine if administration of an α7 NAM or positive allosteric modulator (PAM) modulates the enhancement of adult alcohol drinking produced by ABAE. Methods: In adult rats, ethanol and the α7 agonist AR-R17779 (AR) were microinjected into the posterior ventral tegmental area (VTA), and dopamine levels were measured in the nucleus accumbens shell (AcbSh). In adolescence, rats were treated with the α7 NAM SB-277011-A (SB) or PNU-120596 (PAM) 2 h before administration of EtOH (ABAE). Ethanol consumption (acquisition, maintenance, and relapse) during adulthood was characterized. Results: Ethanol and AR co-administered into the posterior VTA stimulated dopamine release in the AcbSh in a synergistic manner. The increase in alcohol consumption during the acquisition and relapse drinking during adulthood following ABAE was prevented by administration of SB, or enhanced by administration of PNU, prior to EtOH exposure during adolescence. Discussion: Ethanol acts on the α7 receptor, and the α7 receptor regulates the critical effects of ethanol in the brain. The data replicate the findings that cholinergic agents (α7 NAMs) can act prophylactically to reduce the alterations in adult alcohol consumption following ABAE.

Role of Basolateral Amygdalar Somatostatin 2 Receptors in a Rat Model of Chronic Anxiety.

Repeated exposure to stress has been implicated in inducing chronic anxiety states. Stress related increases in anxiety responses are likely mediated by activation of corticotropin-releasing factor receptors (CRFR) in the amygdala, particularly the basolateral amygdala (BLA). Within the BLA, acute injections of the CRFR agonist urocortin 1 (Ucn1) leads to acute anxiety, whereas repeated daily injections of subthreshold-doses of Ucn1 produces a long-lasting, persistent anxiety-like phenotype, a phenomenon referred to as Ucn1-priming. Relative gene expressions from the BLA of vehicle and Ucn1-primed rats were analyzed with quantitative RT-PCR using a predesigned panel of 82 neuroscience-related genes. Compared to vehicle-primed rats, only expression of the somatostatin receptor 2 gene (Sstr2) was significantly reduced in the BLA of Ucn1-primed rats. The contribution of Sstr2 on an anxiety phenotype was tested by injecting a Sstr2 antagonist into the BLA in un-primed rats. The Sstr2 antagonist increased anxiety-like behavior. Notably, pretreatment with Sstr2 agonist injected into the BLA blocked anxiety-inducing effects of acute Ucn1 BLA-injections and delayed anxiety expression during Ucn1-priming. However, concomitant Sstr2 agonist pretreatment during Ucn-1 priming did not prevent either the development of a chronic anxiety state or a reduction of BLA Sstr2 expression induced by priming. The data demonstrate that the persistent anxiety-like phenotype observed with Ucn1-priming in the BLA is associated with a selective reduction of Sstr2 gene expression. Although Sstr2 activation in the BLA blocks acute anxiogenic effects of stress and down-regulation of BLA Sstr2, it does not suppress the long-term consequences of prolonged exposure to stress-related challenges.

Psychosocial impairment following mild blast-induced traumatic brain injury in rats.

Traumatic brain injury (TBI) is associated with increased risk for mental health disorders, impacting post-injury quality of life and societal reintegration. TBI is also associated with deficits in psychosocial processing, defined as the cognitive integration of social and emotional behaviors, however little is known about how these deficits manifest and their contributions to post-TBI mental health. In this pre-clinical investigation using rats, a single mild blast TBI (mbTBI) induced impairment of psychosocial processing in the absence of confounding physical polytrauma, post-injury motor deficits, affective abnormalities, or deficits in non-social behavior. Impairment severity correlated with acute upregulations of a known oxidative stress metabolite, 3-hydroxypropylmercapturic acid (3-HPMA), in urine. Resting state fMRI alterations in the acute post-injury period implicated key brain regions known to regulate psychosocial behavior, including orbitofrontal cortex (OFC), which is congruent with our previous report of elevated acrolein, a marker of neurotrauma and 3-HPMA precursor, in this region following mbTBI. OFC of mbTBI-exposed rats demonstrated elevated mRNA expression of metabotropic glutamate receptors 1 and 5 (mGluR1/5) and injection of mGluR1/5-selective agonist in OFC of uninjured rats approximated mbTBI-induced psychosocial processing impairment, demonstrating a novel role for OFC in this psychosocial behavior. Furthermore, OFC may serve as a hotspot for TBI-induced disruption of psychosocial processing and subsequent mental health disorders.

Selective breeding for high alcohol preference is associated with increased sensitivity to cannabinoid reward within the nucleus accumbens shell.

RATIONALE: The rate of cannabinoid intake by those with alcohol use disorder (AUD) exceeds that of the general public. The high prevalence of co-abuse of alcohol and cannabis has been postulated to be predicated upon both a common predisposing genetic factor and the interaction of the drugs within the organism. The current experiments examined the effects of cannabinoids in an animal model of AUD. OBJECTIVES: The present study assessed the reinforcing properties of a cannabinoid receptor 1 (CB1) agonist self-administered directly into the nucleus accumbens shell (AcbSh) in female Wistar and alcohol-preferring (P) rats. METHODS: Following guide cannulae surgery aimed at AcbSh, subjects were placed in an operant box equipped with an 'active lever' (fixed ratio 1; FR1) that caused the delivery of the infusate and an 'inactive lever' that did not. Subjects were arbitrarily assigned to one of seven groups that self-administered either artificial cerebrospinal fluid (aCSF), or 3.125, 6.25, 12.5, or 25 pmol/100 nl of O-1057, a water-soluble CB1 agonist, dissolved in aCSF. The first four sessions of acquisition are followed by aCSF only infusates in sessions 5 and 6 during extinction, and finally the acquisition dose of infusate during session 7 as reinstatement. RESULTS: The CB1 agonist was self-administered directly into the AcbSh. P rats self-administered the CB1 agonist at lower concentrations and at higher rates compared to Wistar rats. CONCLUSIONS: Overall, the data indicate selective breeding for high alcohol preference has produced rats divergent in response to cannabinoids within the brain reward pathway. The data support the hypothesis that there can be common genetic factors influencing drug addiction.

Using loss- and gain-of-function approaches to target amygdala-projecting serotonergic neurons in the dorsal raphe nucleus that enhance anxiety-related and conditioned fear behaviors.

BACKGROUND: The central serotonergic system originating from the dorsal raphe nucleus (DR) plays a critical role in anxiety and trauma-related disorders such as posttraumatic stress disorder. Although many studies have investigated the role of serotonin (5-HT) within pro-fear brain regions such as the amygdala, the majority of these studies have utilized non-selective pharmacological approaches or poorly understood lesioning techniques which limit their interpretation. AIM: Here we investigated the role of amygdala-projecting 5-HT neurons in the DR in innate anxiety and conditioned fear behaviors. METHODS: To achieve this goal, we utilized (1) selective lesion of 5-HT neurons projecting to the amygdala with saporin toxin conjugated to anti-serotonin transporter (SERT) injected into the amygdala, and (2) optogenetic excitation of amygdala-projecting DR cell bodies with a combination of a retrogradely transported canine adenovirus-expressing Cre-recombinase injected into the amygdala and a Cre-dependent-channelrhodopsin injected into the DR. RESULTS: While saporin treatment lesioned both local amygdalar 5-HT fibers and neurons in the DR as well as reduced conditioned fear behavior, optical activation of amygdala-projecting DR neurons enhanced anxious behavior and conditioned fear response. CONCLUSION: Collectively, these studies support the hypothesis that amygdala-projecting 5-HT neurons in the DR represent an anxiety and fear-on network.

Differential effects of chronic ethanol consumption and withdrawal on homer/glutamate receptor expression in subregions of the accumbens and amygdala of P rats.

BACKGROUND: Homer proteins are constituents of scaffolding complexes that regulate the trafficking and function of central Group1 metabotropic glutamate receptors (mGluRs) and N-methyl-d-aspartate (NMDA) receptors. Research supports the involvement of these proteins in ethanol-induced neuroplasticity in mouse. In this study, we examined the effects of short versus long-term withdrawal from chronic ethanol consumption on Homer and glutamate receptor protein expression within striatal and amygdala subregions of selectively bred, alcohol-preferring P rats. METHODS: For 6 months, male P rats had concurrent access to 15% and 30% ethanol solutions under intermittent (IA: 4 d/wk) or continuous (CA: 7 d/wk) access conditions in their home cage. Rats were killed 24 hours (short withdrawal: SW) or 4 weeks (long withdrawal: LW) after termination of ethanol access, subregions of interest were micropunched and tissue processed for detection of Group1 mGluRs, NR2 subunits of the NMDA receptor and Homer protein expression. RESULTS: Within the nucleus accumbens (NAC), limited changes in NR2a and NR2b expression were detected in the shell (NACsh), whereas substantial changes were observed for Homer2a/b, mGluRs as well as NR2a and NR2b subunits in the core (NACc). Within the amygdala, no changes were detected in the basolateral subregion, whereas substantial changes, many paralleling those observed in the NACc, were detected in the central nucleus (CeA) subregion. In addition, most of the changes observed in the CeA, but not NACc, were present in both SW and LW rats. CONCLUSIONS: Overall, these subregion specific, ethanol-induced increases in mGluR/Homer2/NR2 expression within the NAC and amygdala suggest changes in glutamatergic plasticity had taken place. This may be a result of learning and subsequent memory formation of ethanol's rewarding effects in these brain structures, which may, in part, mediate the chronic relapsing nature of alcohol abuse.

Conditioned stimuli affect ethanol-seeking by female alcohol-preferring (P) rats: the role of repeated-deprivations, cue-pretreatment, and cue-temporal intervals.

RATIONALE: Evidence indicates that drug-paired stimuli can evoke drug-craving leading to drug-seeking and repeated relapse periods can influence drug-seeking behaviors. OBJECTIVES: The present study examined (1) the effect of an interaction between repeated deprivation cycles and excitatory conditioning stimuli (CS+) on ethanol (EtOH)-seeking; (2) the effects of EtOH-paired cue-exposure in a non-drug-paired environment on subsequent conditioning in a drug-paired environment; and (3) the temporal effects of conditioned cues on subsequent EtOH-seeking. METHODS: Adult female alcohol-preferring (P) rats were exposed to three conditioned odor cues; CS+ associated with EtOH self-administration, CS- associated with the absence of EtOH (extinction training), and a neutral stimulus (CS0) presented in a neutral non-drug-paired environment. The rats underwent four deprivation cycles or were non-deprived, following extinction they were maintained in a home cage for an EtOH-free period, and then exposed to no cue, CS+, CS-, or CS0 to assess the effect of the conditioned cues on EtOH-seeking behavior. RESULTS: Repeated deprivations enhanced and prolonged the duration of CS+ effects on EtOH-seeking. Presentation of the CS- in a non-drug-paired environment blocked the ability of a CS+ to enhance EtOH-seeking in a drug-paired environment. Presentation of the CS+ or CS- in a non-drug-paired environment 2 or 4 h earlier significantly altered EtOH-seeking. CONCLUSION: Results indicated an interaction between repeated deprivation cycles and CS+ resulted in a potentiation of CS+ evoked EtOH-seeking. In addition, a CS- may have therapeutic potential by providing prophylactic protection against relapse behavior in the presence of cues in the drug-using environment.

Assessment of fear and anxiety associated behaviors, physiology and neural circuits in rats with reduced serotonin transporter (SERT) levels.

Genetic variation in serotonin transporter (SERT) that reduces transcriptional efficiency is associated with higher anxiety and fear traits and a greater incidence of post traumatic stress disorder (PTSD). Although previous studies have shown that rats with no expression of SERT (SERT-/-) have increased baseline anxiety behaviors, SERT+/- rats with low SERT expression (and more relevant to the clinical condition with low SERT expression) do not. Yet, no systematic studies of fear acquisition/extinction or their underlying neural mechanisms have been conducted in this preclinical genetic SERT+/- model. Here we sought to determine if SERT+/- or SERT-/-, compared to wildtype, rats would show exacerbated panic responses and/or persistent conditioned fear responses that may be associated with PTSD or phobia vulnerability. Results: Only SERT-/- rats showed increased baseline anxiety-like behaviors with heightened panic respiratory responses. However SERT+/- (also SERT-/-) rats showed enhanced acquisition of fear and delayed extinction of fear that was associated with changes in serotonergic-related genes (e.g., reduced 5-HT1A receptor) and disrupted inhibition within the basolateral amygdala (BLA). Furthermore, the disrupted fear responses in SERT+/- rats were normalized with 5HT1A antagonist infusions into the BLA. Enhanced acquisition and failure to extinguish fear memories displayed by both SERT-/- and SERT+/- rats are cardinal symptoms of disabling anxiety disorders such as phobias and PTSD. The data here support the hypothesis that reduced SERT function is a genetic risk that disrupts select gene expression and network properties in the amygdala that could result in vulnerability to these syndromes.

Neural pathways underlying lactate-induced panic.

Panic disorder is a severe anxiety disorder characterized by susceptibility to induction of panic attacks by subthreshold interoceptive stimuli such as 0.5 M sodium lactate infusions. Although studied for four decades, the mechanism of lactate sensitivity in panic disorder has not been understood. The dorsomedial hypothalamus/perifornical region (DMH/PeF) coordinates rapid mobilization of behavioral, autonomic, respiratory and endocrine responses to stress, and rats with disrupted GABA inhibition in the DMH/PeF exhibit panic-like responses to lactate, similar to panic disorder patients. Utilizing a variety of anatomical and pharmacological methods, we provide evidence that lactate, via osmosensitive periventricular pathways, activates neurons in the compromised DMH/PeF, which relays this signal to forebrain limbic structures such as the bed nucleus of the stria terminalis to mediate anxiety responses, and specific brainstem sympathetic and parasympathetic pathways to mediate the respiratory and cardiovascular components of the panic-like response. Acutely restoring local GABAergic tone in the DMH/PeF blocked lactate-induced panic-like responses. Autonomic panic-like responses appear to be a result of DMH/PeF-mediated mobilization of sympathetic responses (verified with atenolol) and resetting of the parasympathetically mediated baroreflex. Based on our findings, DMH/PeF efferent targets such as the C1 adrenergic neurons, paraventricular hypothalamus, and the central amygdala are implicated in sympathetic mobilization; the nucleus of the solitary tract is implicated in baroreflex resetting; and the parabrachial nucleus is implicated in respiratory responses. These results elucidate neural circuits underlying lactate-induced panic-like responses and the involvement of both sympathetic and parasympathetic systems.

Selective breeding for high alcohol consumption and response to nicotine: locomotor activity, dopaminergic in the mesolimbic system, and innate genetic differences in male and female alcohol-preferring, non-preferring, and replicate lines of high-alcohol drinking and low-alcohol drinking rats.

RATIONALE: There is evidence for a common genetic link between alcohol and nicotine dependence. Rodents selectively bred for high alcohol consumption/responsivity are also more likely to self-administer nicotine than controls. OBJECTIVES: The experiments examined the response to systemic nicotine, the effects of nicotine within the drug reward pathway, and innate expression of nicotine-related genes in a brain region regulating drug reward/self-administration in multiple lines of rats selectively bred for high and low alcohol consumption. METHODS: The experiments examined the effects of systemic administration of nicotine on locomotor activity, the effects of nicotine administered directly into the (posterior ventral tegmental area; pVTA) on dopamine (DA) release in the nucleus accumbens shell (AcbSh), and innate mRNA levels of acetylcholine receptor genes in the pVTA were determined in 6 selectively bred high/low alcohol consuming and Wistar rat lines. RESULTS: The high alcohol-consuming rat lines had greater nicotine-induced locomotor activity compared to low alcohol-consuming rat lines. Microinjections of nicotine into the pVTA resulted in DA release in the AcbSh with the dose response curves for high alcohol-consuming rats shifted leftward and upward. Genetic analysis of the pVTA indicated P rats expressed higher levels of α2 and ß4. CONCLUSION: Selective breeding for high alcohol preference resulted in a genetically divergent behavioral and neurobiological sensitivity to nicotine. The observed behavioral and neurochemical differences between the rat lines would predict an increased likelihood of nicotine reinforcement. The data support the hypothesis of a common genetic basis for drug addiction and identifies potential receptor targets.

From anxiety to autism: spectrum of abnormal social behaviors modeled by progressive disruption of inhibitory neuronal function in the basolateral amygdala in Wistar rats.

RATIONALE: Social behaviors are disrupted in several psychiatric disorders. The amygdala is a key brain region involved in social behaviors, and amygdala pathology has been implicated in disease states ranging from social anxiety disorder to autism. OBJECTIVE: To test the effects of progressive disruption of the inhibitory function within the basolateral nucleus of the amygdala (BLA) on conspecific social interaction in rats and investigate functional networks from the ventral medial prefrontal cortex (mPFCv) to the BLA. MATERIALS AND METHODS: BLA inhibitory tone was disrupted by priming it with the stress-peptide corticotrophin releasing factor (CRF) receptor agonist urocortin 1 (Ucn 1, 6 fmol), or by selective lesioning of a subset of BLA-GABAergic interneurons containing neurokinin 1 receptors using the targeted toxin SSP-Saporin. The effects of the disruption of GABAergic tone in the BLA were examined using a repeated exposure and habituation paradigm of social interaction (SI/h). Lesions and selectivity of lesions were confirmed postmortem. Additionally, effects of stimulating mPFCv on cFos activity in interneurons of the BLA were examined. RESULTS: Rats primed with Ucn 1 showed persistent social inhibition, which could be overcome with habituation, putatively modeling social anxiety. Rats with a selective lesioning of a subset of GABAergic interneurons in the BLA exhibited persistent social inhibition that was not reversed by SI/h paradigm. We also demonstrate selective functional inputs to this subset of interneurons when mPFCv was activated. CONCLUSIONS: These models with different gradations of disrupted BLA inhibition could help to study social dysfunction in disorders ranging from social anxiety to autism spectrum disorders.