Effects of the 5-HT2C receptor agonist CP809101 in the amygdala on reinstatement of cocaine-seeking behavior and anxiety-like behavior.

Serotonin 2C receptor (5-HT2CR) agonists attenuate reinstatement of cocaine-seeking behavior. These receptors are found throughout the limbic system, including the basolateral amygdala (BlA), which is involved in forming associations between emotional stimuli and environmental cues, and the central amygdala (CeA), which is implicated in the expression of conditioned responding to emotional stimuli. This study investigated whether 5-HT2CRs in the amygdala are involved in cue and cocaine-primed reinstatement of cocaine-seeking behavior. Rats were trained to self-administer cocaine (0.75 mg/kg, i.v.) which that was paired with light and tone cues, and then subsequently they underwent daily extinction training. Rats then received bilateral microinfusions of the 5-HT2CR agonist CP809101 (0.01-1.0 µg/0.2 µl/side) into either the BlA or CeA prior to tests for cue or cocaine-primed (10 mg/kg, i.p.) reinstatement. Rats were also tested for CP809101 effects on anxiety-like behavior on the elevated plus-maze (EPM). Surprisingly, intra-BlA CP809101 had no effect on cue reinstatement, though it did increase anxiety-like behavior on the EPM. Intra-CeA infusions of CP809101 attenuated cocaine-primed reinstatement, an effect that was prevented with concurrent administration of the 5-HT2CR antagonist SB242084 (0.1 µg/0.2 µl/side). CP809101 had no effect on cue reinstatement or anxiety-like behavior on the EPM. These findings suggest that 5-HT2CRs in the BlA modulate anxiety, whereas those in the CeA modulate incentive motivational effects induced by cocaine priming injections.

Longitudinal stability of reward and relief drinking phenotypes in community and treatment-seeking individuals who engage in heavy drinking.

BACKGROUND: Precision medicine approaches aim to improve treatment outcomes by identifying which treatments work best for specific individual phenotypes. In the treatment of alcohol use disorder (AUD), precision medicine approaches have been proposed based on phenotypes characterized by individuals who drink primarily to enhance rewarding experiences (i.e., reward drinking) or those who drink primarily to relieve negative states (i.e., relief drinking). This study examined these phenotypes across treatment- and nontreatment-seeking individuals and the stability of the phenotypes over time. METHODS: We used latent profile and latent transition analyses to identify and assess longitudinal stability (over 3 or 4 months) of reward and relief drinking subgroups within a nontreatment-seeking community sample that engaged in hazardous drinking (n = 189) and two treatment-seeking samples of individuals with AUD enrolled in two large clinical trials (n = 1726, n = 1383). We examined prospective associations with alcohol consumption and consequences at long-term follow-up (15 or 18 months). RESULTS: Results supported four subgroups: low reward/low relief, low reward/high relief, high reward/low relief, and high reward/high relief. The community sample contained more individuals classified within the high reward/low relief subgroup than treatment-seeking samples. Subgroups were generally more stable over time in the community sample than in the treatment-seeking samples. Alcohol consumption and consequences decreased over time for the treatment-seeking samples, with consequences and drinking frequency decreasing for the community sample. Participants classified within the high reward/high relief and low reward/high relief groups reported the most consequences and consumption at long-term follow-up. CONCLUSION: Reward and relief drinking phenotypes can be identified within community and treatment-seeking samples of individuals who drink heavily. The phenotypic subgroups appear to be stable over time in the absence of treatment, change somewhat during treatment, and provide utility in predicting alcohol consumption and consequences.

Cortagine infused into the medial prefrontal cortex attenuates predator-induced defensive behaviors and Fos protein production in selective nuclei of the amygdala in male CD1 mice.

Corticotropin-releasing factor (CRF) plays an essential role in coordinating the autonomic, endocrine and behavioral responses to stressors. In this study, we investigated the role of CRF within the medial prefrontal cortex (mPFC) in modulating unconditioned defensive behaviors, by examining the effects of microinfusing cortagine a selective type-1 CRF receptor (CRF1) agonist, or acidic-astressin a preferential CRF1 antagonist, into the mPFC in male CD-1 mice exposed to a live predator (rat exposure test--RET). Cortagine microinfusions significantly reduced several indices of defense, including avoidance and freezing, suggesting a specific role for CRF1 within the infralimbic and prelimbic regions of the mPFC in modulating unconditioned behavioral responsivity to a predator. In contrast, microinfusions of acidic-astressin failed to alter defensive behaviors during predator exposure in the RET. Cortagine microinfusions also reduced Fos protein production in the medial, central and basomedial, but not basolateral subnuclei of the amygdala in mice exposed to the rat predatory threat stimulus. These results suggest that CRF1 activation within the mPFC attenuates predator-induced unconditioned anxiety-like defensive behaviors, likely via inhibition of specific amygdalar nuclei. Furthermore, the present findings suggest that the mPFC represents a unique neural region whereby activation of CRF1 produces behavioral effects that contrast with those elicited following systemic administration of CRF1 agonists.

Anxiety and Alzheimer's disease pathogenesis: focus on 5-HT and CRF systems in 3xTg-AD and TgF344-AD animal models.

Dementia remains one of the leading causes of morbidity and mortality in older adults. Alzheimer's disease (AD) is the most common type of dementia, affecting over 55 million people worldwide. AD is characterized by distinct neurobiological changes, including amyloid-beta protein deposits and tau neurofibrillary tangles, which cause cognitive decline and subsequent behavioral changes, such as distress, insomnia, depression, and anxiety. Recent literature suggests a strong connection between stress systems and AD progression. This presents a promising direction for future AD research. In this review, two systems involved in regulating stress and AD pathogenesis will be highlighted: serotonin (5-HT) and corticotropin releasing factor (CRF). Throughout the review, we summarize critical findings in the field while discussing common limitations with two animal models (3xTg-AD and TgF344-AD), novel pharmacotherapies, and potential early-intervention treatment options. We conclude by highlighting promising future pharmacotherapies and translational animal models of AD and anxiety.

5-HT(2A) receptor blockade and 5-HT(2C) receptor activation interact to reduce cocaine hyperlocomotion and Fos protein expression in the caudate-putamen.

Both the 5-HT(2A) receptor (R) antagonist M100907 and the 5-HT(2C) R agonist MK212 attenuate cocaine-induced dopamine release and hyperlocomotion. This study examined whether these drugs interact to reduce cocaine hyperlocomotion and Fos expression in the striatum and prefrontal cortex. We first determined from dose-effect functions a low dose of both M100907 and MK212 that failed to alter cocaine (15 mg/kg, i.p.) hyperlocomotion. Subsequently, we examined whether these subthreshold doses given together would attenuate cocaine hyperlocomotion, consistent with a 5-HT(2A)/5-HT(2C) R interaction. Separate groups of rats received two sequential drug injections 5 min apart immediately before a 1-h locomotion test as follows: (1) saline + saline, (2) saline + cocaine, (3) 0.025 mg/kg M100907 + cocaine, (4) 0.125 mg/kg MK212 + cocaine, or (5) cocktail combination of 0.025 mg/kg M100907 and 0.125 mg/kg MK212 + cocaine. Brains were extracted for Fos immunohistochemistry 90 min after the second injection. We next examined the effects of 0.025 mg/kg M100907 and 0.125 mg/kg MK212, alone and in combination, on spontaneous locomotor activity. While neither drug given alone produced any effects, the M100907/MK212 cocktail attenuated cocaine hyperlocomotion as well as cocaine-induced Fos expression in the dorsolateral caudate-putamen (CPu), but had no effect on spontaneous locomotion. The findings suggest that 5-HT(2A) Rs and 5-HT(2C) Rs interact to attenuate cocaine hyperlocomotion and Fos expression in the CPu, and that the CPu is a potential locus of the interactive effects between these 5-HT(2) R subtypes on behavior. Further research investigating combined 5-HT(2A) R antagonism and 5-HT(2C) R agonism as a treatment for cocaine dependence is warranted.

Environmental enrichment counters cocaine abstinence-induced stress and brain reactivity to cocaine cues but fails to prevent the incubation effect.

Environmental enrichment (EE) during a period of forced abstinence attenuates incentive motivational effects of cocaine-paired stimuli. Here we examined whether EE during forced abstinence from cocaine self-administration would prevent time-dependent increases in cue-elicited cocaine-seeking behavior (i.e. the incubation effect). Rats were trained to self-administer cocaine, which was paired with light/tone cues, for 15 days while living in isolated conditions (IC). Controls received yoked saline infusions. Subsequently, rats were assigned to live in either continued IC or EE for either 1 or 21 days of forced abstinence prior to a test for cocaine-seeking behavior. During testing, responding resulted only in presentation of the light/tone cues. Contrary to our prediction, cocaine-seeking behavior increased over time regardless of living condition during abstinence; however, EE attenuated cocaine-seeking behavior relative to IC regardless of length of abstinence. Brains were harvested and trunk blood was collected immediately after the 60-minute test and later assayed. Results indicated that short-term EE elevated hippocampal brain-derived neurotrophic factor and reduced plasma corticosterone compared with IC. Furthermore, 21 days of EE during forced abstinence prevented increases in the cue-elicited amygdala phosphorylated extracellular signal-regulated kinase expression that was observed in IC rats. These findings suggest that EE attenuates incentive motivational effects of cocaine cues through a mechanism other than preventing the incubation effect, perhaps involving reduction of stress and neural activity in response to cocaine-paired cues during acute withdrawal.

Characterizing the effects of 2-phenylethylamine and coyote urine on unconditioned and conditioned defensive behaviors in adolescent male and female Long-Evans hooded rats.

Predator odors provide critical information to prey species allowing them to gage potential threat via the detection of semiochemicals called kairomones. Recent reports indicate that the commercially available predator odor coyote urine (CU), and to a lesser extent 2-phenylethylamine (PEA), induce innate defensive behaviors in adult rats and mice. The aim of the present study was to see if the defense-inducing effects of CU and PEA would extend to adolescents. Specifically, we evaluated the ability of CU and PEA to induce unconditioned and conditioned defensive behavior in predator-odor naïve adolescent male and female Long-Evans hooded rats. An additional group of males were exposed to the non-predatory aversive odor formalin to control for potential general aversive properties of the odorants. The data revealed that in males, both CU and PEA, but not formalin induced measures of risk assessment, whereas CU and formalin produced avoidance of the odor source. In partial contrast, both CU and PEA produced avoidance of the odor source and increased measures of risk assessment in females. Surprisingly males failed to show any measures of defense during the cue+context conditioning test trial. In contrast, in females both odorants produced marginal effects during re-exposure to the conditioning context, with CU inducing conditioned avoidance and PEA inducing conditioned risk assessment. We conclude that commercially available CU and PEA elicit a moderate defensive profile compared to previous reports examining cat fur/skin odor in male and female adolescent rats. Future research needs to examine additional concentrations of the odorants to determine if a more robust unconditioned defensive profile (e.g., freezing) can be induced by these predator odors, and whether the defensive profile responds to standard anxiolytic drugs.

Differential effects of chronic stress on anxiety-like behavior and contextual fear conditioning in the TgF344-AD rat model of Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative brain disorder that leads to severe cognitive and functional impairments. Many AD patients also exhibit neuropsychiatric symptoms, such as anxiety and depression, prior to the clinical diagnosis of dementia. Chronic stress is associated with numerous adverse health consequences and disease states, and AD patients exhibit altered stress systems. Thus, stress may represent a causal link between neuropsychiatric symptoms and AD. To address this possibility, we examined the effects of chronic stress in the TgF344-AD rat model that co-expresses the mutant human amyloid precursor protein (APPsw) and presenilin 1 (PS1ΔE9) genes. Adult male transgenic (Tg+) and wild-type (WT) rats (6-7.5 months of age), with and without a history of chronic restraint stress, were tested for footshock-induced conditioned fear and for anxiety-like behavior in the elevated plus-maze. We found that non-stressed Tg+ rats showed increased anxiety-like behavior compared to non-stressed WT rats. In contrast, Tg+ and WT rats did not differ in levels of freezing immediately following footshock or during contextual re-exposure. Additionally, stressed Tg+ rats were not significantly different from stressed WT rats on any measures of anxiety or fear. Thus, while stress has been linked as a risk factor for AD-related pathology, it appears from the present findings that two weeks of daily restraint stress did not further enhance anxiety- or fear-like behaviors in TgF344-AD rats.

Chemogenetic inhibition of ventral hippocampal CaMKIIα-expressing neurons attenuates anxiety- but not fear-like defensive behaviors in male Long-Evans hooded rats.

Previous research has implicated the ventral pole of the hippocampus in regulating anxiety. However, most rat studies examining the specific contribution of the ventral hippocampus have utilized techniques that have nonspecific effects and/or create nonreversible damage to the region. The present study sought to characterize the role of ventral hippocampal CaMKIIα-expressing neurons in modulating anxiety- and fear-like behavior during exposure to a variety of threatening stimuli. Five weeks prior to testing, adult male Long-Evans hooded rats received ventral hippocampal viral-vector infusions expressing either AAV8-CaMKIIα-hM4D-mCherry (DREADD) or AAV8-CaMKIIα-EGFP (GFP). DREADD transfection allowed for the specific, noninvasive and temporary inhibition of the ventral hippocampus (vHC) immediately before threat presentation. Rats were evaluated for behaviors congruent with anxiety- or fear-like defensive states during testing in the elevated plus-maze (EPM) and light-dark test (LDT), or post footshock freezing and footshock-induced contextual freezing, respectively. Analyses revealed a significant effect of vHC inhibition that was dependent on the type of threat exposure. Specifically, DREADD-induced silencing of vHC neurons reduced anxiety-like behavior in the EPM and LDT, without reliably affecting footshock-induced fear. These data add to a growing literature implicating the vHC as a key region involved in controlling the expression of anxiety in rodents, primates and humans.

Coyote urine, but not 2-phenylethylamine, induces a complete profile of unconditioned anti-predator defensive behaviors.

Predator odors from various sources (e.g. fur/skin, urine, feces) provide prey animals valuable information that allows them to gage potential environmental threat via the detection of semiochemicals called kairomones. However, studies in rodents have revealed inconsistent and often conflicting results, which may occur from any combination of factors, including source and freshness of the odorant, sex, and genetic strain of the prey animal and/or predator. Regardless of cause, few odorants tested, if any, have lived up to the potent unconditioned predator odor stimuli - cat fur/skin odor - that induces a complete profile of innate unconditioned defensive behaviors (e.g., avoidance, risk assessment and freezing) and produces rapid aversive conditioned responses, both of which are sensitive to standard anxiolytic/anxiogenic drugs. Therefore, the present study investigated the effectiveness of coyote urine and 2-phenylethylamine (PEA), two commercially available predator odor cues, in satisfying the first of these criteria in predator odor naïve, adult male Long-Evans hooded rats. The data revealed that coyote urine, but not PEA, was effective in inducing a complete profile of anti-predator defensive behaviors characterized by avoidance, risk assessment, freezing and a reduction in exploratory behavior. We conclude that commercially available coyote urine satisfies the first criterion of a defense inducing unconditioned predator odor stimulus. In order to fully validate the use of coyote urine as an anxiety- and/or fear-like threat stimulus, future research needs to examine whether it produces aversive conditioning and whether the defensive profile induced by the odorant responds to standard anxiolytic drugs.

Methamphetamine and social rewards interact to produce enhanced conditioned place preference in male adolescent rats.

Elucidating the influence of social context on drug reward is critical for understanding substance use disorders. Adolescents demonstrate enhanced sensitivity to drug and social rewards. However, the extent to which methamphetamine interacts with social reward in adolescents has not been thoroughly examined. Therefore, the present study used the conditioned place preference (CPP) model to examine the relationship between methamphetamine and social rewards in adolescent male rats. Sprague-Dawley rats (PND 30) were randomly assigned to one of the following four conditioning groups: saline alone (SA), methamphetamine alone (MA), saline with a social partner (SS) or methamphetamine with a social partner (MS). Testing occurred in a two-chamber biased apparatus across seven consecutive days using parameters presumed to be sub-threshold for establishing social- and methamphetamine-induced CPP. Similar to previous reports for nicotine and cocaine, the present results indicate that rats receiving methamphetamine with a social partner (i.e., MS) during conditioning demonstrated a significantly greater preference shift compared to all other groups. These findings further highlight the importance of social context in influencing the magnitude of drug reward during adolescence.

Anxiety and Alzheimer's disease: Behavioral analysis and neural basis in rodent models of Alzheimer's-related neuropathology.

Alzheimer's disease (AD) pathology is commonly associated with cognitive decline but is also composed of neuropsychiatric symptoms including psychological distress and alterations in mood, including anxiety and depression. Emotional dysfunction in AD is frequently modeled using tests of anxiety-like behavior in transgenic rodents. These tests often include the elevated plus-maze, light/dark test and open field test. In this review, we describe prototypical behavioral paradigms used to examine emotional dysfunction in transgenic models of AD, specifically anxiety-like behavior. Next, we summarize the results of studies examining anxiety-like behavior in transgenic rodents, noting that the behavioral outcomes using these paradigms have produced inconsistent results. We suggest that future research will benefit from using a battery of tests to examine emotional behavior in transgenic AD models. We conclude by discussing putative, overlapping neurobiological mechanisms underlying AD-related neuropathology, stress and anxiety-like behavior reported in AD models.

Blocking serotonin 2A (5-HT2A) receptors attenuates the acquisition of methamphetamine-induced conditioned place preference in adult female rats.

Methamphetamine withdrawal can induce intense cravings leading to relapse. Contexts/cues paired with chronic methamphetamine use develop incentive motivational properties, promoting future drug-seeking and taking behavior. Research has shown that, in adult male rats, the selective 5-HT2A receptor antagonist M100907 attenuates the acquisition of methamphetamine-induced conditioned place preference (CPP), a measure that examines conditioned associations between the rewarding properties of drugs and contexts. However, these findings have not been extended to adult female rats. The present study investigated the effects of M100907 on the acquisition of methamphetamine-CPP in adult female rats. During conditioning, rats were administered M100907 (0, 0.025, 0.25 mg/kg, i.p.) 15 min before methamphetamine (1 mg/kg, i.p.) and then placed into their initially non-preferred chamber for 30 min, or administered saline and placed into their initially preferred chamber for 30 min. Conditioning sessions were separated by four hours. Following four days of conditioning, the effects of M100907 on the acquisition of methamphetamine-CPP were assessed during a 15 min drug-free test trial. Pretreatment with M100907 dose-dependently attenuated the acquisition of methamphetamine-induced CPP. Blocking 5-HT2A receptors with a low dose of the selective antagonist M100907 attenuated the rewarding effects of methamphetamine in adult female rats. These data provide further evidence that the 5-HT2A receptor subtype is involved in the behavioral effects of methamphetamine.

Maternal separation modulates short-term behavioral and physiological indices of the stress response.

Early-life stress produces an anxiogenic profile in adulthood, presumably by activating the otherwise quiescent hypothalamic-pituitary-adrenal (HPA) axis during the vulnerable 'stress hyporesponsive period'. While the long-term effects of such early-life manipulations have been extensively characterized, little is known of the short-term effects. Here, we compared the short-term effects of two durations of maternal separation stress and one unseparated group (US) on behavioral and physiological indices of the stress response in rat pups. Separations included 3h on each of 12days, from postnatal day (PND) 2 to 13 (MS2-13) and 3days of daily, 6-h separation from PND11-13 (MS11-13). On PND14 (Experiment 1), both MS2-13 and MS11-13 produced marked reductions in freezing toward an adult male conspecific along with reduced levels of glucocorticoid type 2 (GR) and CRF type-1 (CRF(1)) receptor mRNA in the hippocampus. Group MS2-13 but not MS11-13 produced deficits in stressor-induced corticosterone secretion, accompanied by reductions in body weight. Our results suggest that GR and/or CRF(1) levels, not solely the magnitude of corticosterone secretion, may be involved in the modulation of freezing. In a second experiment, we aimed to extend these findings by testing male and female separated and unseparated pups' unconditioned defensive behaviors to cat odor on PND26, and subsequent cue+context conditioning and extinction throughout postnatal days 27-32. Our results show that maternal separation produced reductions in unconditioned freezing on PND26, with MS2-13 showing stronger deficits than MS11-13. However, separation did not affect any other defensive behaviors. Furthermore, separated rats failed to show conditioned freezing, although they did avoid the no-odor block conditioned cue. There were no sex differences other than weight. We suggest that maternal separation may have produced these changes by disrupting normal development of hippocampal regions involved in olfactory-mediated freezing, not in mechanisms of learning and memory per se. These findings may have direct relevance for understanding the mechanisms by which early-life adverse experiences produce short-term and lasting psychopathologies.

Antagonizing serotonin 2A (5-HT2A) receptors attenuates methamphetamine-induced reward and blocks methamphetamine-induced anxiety-like behaviors in adult male rats.

BACKGROUND: Methamphetamine is a highly addictive and abused psychostimulant. Symptoms of methamphetamine withdrawal including drug craving and anxiety that can drive relapse. Currently, there is no FDA approved treatment for methamphetamine use disorder, highlighting the need for research examining the neural mechanisms underlying psychostimulant-induced behaviors. Research indicates that the 5-HT2A receptor antagonist M100907 attenuates several psychostimulant-induced behaviors, including conditioned place preference (CPP). However, these findings have not been extended to methamphetamine. The present study investigated the effects of M100907 on acquisition of methamphetamine-CPP and methamphetamine-induced anxiety-like behavior. METHODS: Adult male rats were tested across eight consecutive days. Prior to methamphetamine administration (0 or 1 mg/kg, i.p.), rats were pretreated with their assigned dose of M100907 (0, 0.0025 .025 or 0.25 mg/kg, i.p.) and were placed into their initially non-preferred chamber. After four methamphetamine conditioning sessions, the effects of M100907 on methamphetamine-induced CPP were assessed. Following CPP testing, rats were screened for anxiety-like behaviors in the elevated plus-maze. RESULTS: Pretreatment with M100907 attenuated methamphetamine-induced CPP without producing any observable rewarding or aversive effects in methamphetamine naïve rats. Additionally, M100907 blocked methamphetamine-induced increases in anxiety-like behavior and attenuated some indices of anxiety in methamphetamine naïve rats. CONCLUSIONS: Results suggest that blocking 5-HT2A receptors with the selective antagonist M100907 attenuates the rewarding effects of methamphetamine and does not produce any rewarding or aversive effects alone. Further, M100907 pretreatment blocked the anxiety-inducing effects of methamphetamine. Collectively, these data suggest that the 5-HT2A receptor subtype represents a novel target for treating methamphetamine use disorder.

Preclinical support for the therapeutic potential of zolmitriptan as a treatment for cocaine use disorders.

Serotonin 1B receptor (5-HT1BR) agonists enhance cocaine intake in rats during daily self-administration but attenuate cocaine intake after prolonged abstinence. Here we investigated whether the less selective but clinically available 5-HT1D/1BR agonist, zolmitriptan, produces similar effects. Male and free-cycling female Sprague-Dawley rats were trained to lever press for cocaine (0.75 mg/kg, i.v.) or sucrose (45 mg pellet) reinforcement until performance rates stabilized. Rats then received zolmitriptan (3.0, 5.6, and 10 mg/kg, s.c.) prior to testing for its effects on response and reinforcement rates. Under cocaine testing conditions, rats had access to the training dose for the first hour followed by a lower cocaine dose (0.075 mg/kg, i.v.) for the second hour. Zolmitriptan decreased cocaine intake at both cocaine doses and in both sexes even without a period of abstinence and without altering sucrose intake. A separate group of rats underwent identical training procedures and were tested for effects of the selective 5-HT1B and 5-HT1D receptor antagonists, SB224289 (3.2, 5.6, and 10 mg/kg, s.c.) and BRL15572 (0.3, 1.0, and 3.0 mg/kg, i.p.), respectively, alone or in combination with zolmitriptan (5.6 mg/kg, s.c.) under identical cocaine testing procedures as above. The zolmitriptan-induced decrease in cocaine intake was reversed by SB224289 and to a lesser extent by BRL15572, suggesting that the effects of zolmitriptan involve both 5-HT1B and 5-HT1D receptors. Neither zolmitriptan, SB224289, or BRL15572 altered locomotor activity at the doses effective for modulating cocaine intake. These findings suggest that zolmitriptan has potential for repurposing as a treatment for cocaine use disorders.

The Therapeutic Effectiveness of Full Spectrum Hemp Oil Using a Chronic Neuropathic Pain Model.

BACKGROUND: Few models exist that can control for placebo and expectancy effects commonly observed in clinical trials measuring 'Cannabis' pharmacodynamics. We used the Foramen Rotundum Inflammatory Constriction Trigeminal Infraorbital Nerve injury (FRICT-ION) model to measure the effect of "full-spectrum" whole plant extracted hemp oil on chronic neuropathic pain sensitivity in mice. METHODS: Male BALBc mice were submitted to the FRICT-ION chronic neuropathic pain model with oral insertion through an incision in the buccal/cheek crease of 3 mm of chromic gut suture (4-0). The suture, wedged along the V2 trigeminal nerve branch, creates a continuous irritation that develops into secondary mechanical hypersensitivity on the snout. Von Frey filament stimuli on the mouse whisker pad was used to assess the mechanical pain threshold from 0-6 h following dosing among animals (n = 6) exposed to 5 µL of whole plant extracted hemp oil combined with a peanut butter vehicle (0.138 mg/kg), the vehicle alone (n = 3) 7 weeks post-surgery, or a naïve control condition (n = 3). RESULTS: Mechanical allodynia was alleviated within 1 h (d = 2.50, p < 0.001) with a peak reversal effect at 4 h (d = 7.21, p < 0.001) and remained significant throughout the 6 h observation window. There was no threshold change on contralateral whisker pad after hemp oil administration, demonstrating the localization of anesthetic response to affected areas. CONCLUSION: Future research should focus on how whole plant extracted hemp oil affects multi-sensory and cognitive-attentional systems that process pain.

Moderate prenatal alcohol exposure reduces parvalbumin expressing GABAergic interneurons in the dorsal hippocampus of adult male and female rat offspring.

Prenatal alcohol exposure (PAE) negatively impacts hippocampal development and impairs hippocampal-sensitive learning and memory. However, hippocampal neural adaptations in response to moderate PAE are not completely understood. To explore the effects of moderate PAE on GABAergic interneuron expression, this study used a rat model of moderate PAE to examine the effects of PAE on parvalbumin (PARV)-positive cells in fields CA1, CA3 and the dentate gyrus (DG) of the dorsal hippocampus (dHC). Long-Evans dams were given daily access to 5 % (vol/vol) ethanol or saccharine (SAC) control solutions throughout the course of gestation. Offspring were divided into four separate groups: PAE (n = 7) or SAC (n = 7) males, or PAE (n = 8) or SAC (n = 8) females. All rats were aged to adulthood and, following testing in the Morris water task, their brains were analyzed for the expression of the GABAergic neuronal marker PARV. We report a main effect of PAE on GABAergic expression, with significant reductions in PARV-positive cells in area CA3 for males and the DG for females. There was also a trend for a reduction in PARV expressing neurons in fields CA1 and CA3 in females. The results are discussed in relation to hippocampal GABAergic interneuron function, PAE and behavior.

Anti-craving effects of environmental enrichment.

We hypothesized that environmental enrichment in rats may reduce cocaine-seeking behaviour elicited by cocaine-priming injections and by cocaine-associated cues. Rats trained to self-administer cocaine while housed in isolated conditions were then assigned to live in isolation or an enriched environment for 21 d of forced abstinence. Subsequently, extinction and reinstatement of cocaine-seeking behaviour (operant responses without cocaine available) were assessed. Expt 1 showed that enrichment resulted in less cocaine-seeking behaviour during extinction and cue-elicited reinstatement compared to continued isolation housing, but had no effect on cocaine-primed reinstatement. A subsequent experiment, which included a pair-housed group to control for potential isolation stress, again demonstrated that enrichment attenuated cocaine seeking during extinction, but not cocaine-primed reinstatement, relative to both isolation and pair-housed conditions. The findings suggest that enrichment reduces the impact of cocaine-associated environmental stimuli, and hence it may be a useful intervention for attenuating cue-elicited craving in humans.

Effects of acidic-astressin and ovine-CRF microinfusions into the ventral hippocampus on defensive behaviors in rats.

This study investigated a possible role for ventral hippocampal corticotropin-releasing factor (CRF) in modulating both unconditioned and conditioned defensive behaviors by examining the effects of pre-training ventral hippocampal ovine-CRF (oCRF) or acidic-astressin ([Glu(11,16)]Ast) microinfusions in male Long-Evans hooded rats exposed to various threat stimuli including the elevated plus-maze (EPM) (oCRF), cat odor (oCRF and [Glu(11,16)]Ast) and a live cat ([Glu(11,16)]Ast). Unconditioned defensive behaviors were assessed during threat exposure, while conditioned defensive behaviors were assessed in each predator context 24 h after the initial threat encounter. Pre-training infusions of the CRF(1) and CRF(2) receptor agonist oCRF significantly increased defensive behaviors during both the unconditioned and conditioned components of the cat odor test, as well as exposure to the EPM. In contrast to the behavioral effects of oCRF microinfusions, the CRF(1) and CRF(2) receptor antagonist [Glu(11,16)]Ast significantly decreased defensive behaviors during exposure to cat odor, while producing no discernible effects following a second injection in the cat exposure test. During conditioned test trials, pre-training infusions of [Glu(11,16)]Ast also significantly reduced defensive behaviors during re-exposure to both predator contexts. These results suggest a specific role for ventral hippocampal CRF receptors in modulating anxiety-like behaviors in several ethologically relevant animal models of defense.