Astrocytes in the ventral pallidum extinguish heroin seeking through GAT-3 upregulation and morphological plasticity at D1-MSN terminals

AbstractGABAergic projections from the nucleus accumbens core to the dorsolateral ventral pallidum are necessary for drug-conditioned cues to initiate relapse-like drug seeking. Astrocytes in the ventral pallidum are situated perisynaptically and regulate GABA transmission through expression of GABA uptake transporters, but whether they are involved in regulating drug seeking is unknown. To determine the contribution of ventral pallidal astrocytes to heroin seeking, we labeled astrocytes in male and female rats with a membrane-bound fluorescent tag and used confocal microscopy to quantify astroglial expression of the GABA transporter GAT-3 and astrocyte synaptic proximity after withdrawal from heroin self-administration and during 15 min of cued heroin seeking. We found that GAT-3 was upregulated in rats that had extinguished heroin seeking, but not in animals that were withdrawn from heroin without extinction training or in rats that extinguished sucrose seeking. When GAT-3 upregulation was reversed using a vivo-morpholino oligo, heroin seeking was restored in the extinguished context and extinction of cued heroin seeking was disrupted compared to control animals. Although astrocyte synaptic proximity was not altered overall after heroin withdrawal, examination of astrocyte proximity to accumbens D1- or D2-expressing afferents revealed a selective increase in astrocyte proximity with D1-expressing terminals during extinction of heroin self-administration. Experimentally-induced reduction of astrocyte synaptic proximity through knockdown of the astrocyte-selective actin-binding protein ezrin also markedly disrupted extinction of heroin seeking. Notably, GAT-3 or ezrin knockdown had no impact on context- or cue-induced seeking in sucrose-trained animals. These data show that astrocytes in the ventral pallidum undergo plasticity after extinction of heroin use that reduces seeking and highlight the importance of astrocyte-neuron interactions in shaping behaviors associated with opioid use disorder.

Download Full-text

Metformin in nucleus accumbens core reduces cue-induced cocaine seeking in male and female rats

10.1101/2021.09.05.458975 ◽

2021 ◽

Author(s):

Amy Chan ◽

Alexis Willard ◽

Sarah Mulloy ◽

Noor Ibrahim ◽

Allegra Sciaccotta ◽

...

Keyword(s):

Nucleus Accumbens ◽

Female Rats ◽

Therapeutic Effects ◽

Self Administration ◽

Nucleus Accumbens Core ◽

Male And Female ◽

Male And Female Rats ◽

Cocaine Seeking ◽

Ampk Activity ◽

Accumbens Core

This study investigated the potential therapeutic effects of the FDA-approved drug metformin on cue-induced reinstatement of cocaine seeking. Metformin (dimethyl-biguanide) is a first-line treatment for type II diabetes that, among other mechanisms, is involved in the activation of adenosine monophosphate activated protein kinase (AMPK). Cocaine self-administration and extinction is associated with decreased levels of phosphorylated AMPK within the nucleus accumbens core (NAcore). Previously it was shown that increasing AMPK activity in the NAcore decreased cue-induced reinstatement of cocaine seeking. Decreasing AMPK activity produced the opposite effect. The goal of the present study was to determine if metformin in the NAcore reduces cue-induced cocaine seeking in adult male and female Sprague Dawley rats. Rats were trained to self-administer cocaine followed by extinction prior to cue-induced reinstatement trials. Metformin microinjected in the NAcore attenuated cue-induced reinstatement in male and female rats. Importantly, metformin's effects on cocaine seeking were not due to a general depression of spontaneous locomotor activity. In female rats, metformin's effects did generalize to a reduction in cue-induced reinstatement of sucrose seeking. These data support a potential role for metformin as a pharmacotherapy for cocaine use disorder, but warrant caution given the potential for metformin's effects to generalize to a natural reward in female rats.

Download Full-text

Effects of the GluN2B antagonist, Ro 25-6981, on extinction consolidation following adolescent- or adult-onset methamphetamine self-administration in male and female rats

10.1101/2020.05.11.088732 ◽

2020 ◽

Author(s):

Sara R. Westbrook ◽

Joshua M. Gulley

Keyword(s):

Drugs Of Abuse ◽

Age Of Onset ◽

Drug Loading ◽

Female Rats ◽

Age Difference ◽

Adult Onset ◽

Self Administration ◽

Significant Group ◽

Drug Seeking ◽

Male And Female Rats

AbstractPrevious work suggests adolescent rats have deficient extinction consolidation relative to adults. Although the mechanisms underlying this age difference are currently unknown, studies in adult rats have implicated GluN2B-containing NMDA receptor function in extinction consolidation of drug-associated memory. Importantly, GluN2B neurotransmission emerges during adolescent development, and drugs of abuse during adolescence may delay the development of extinction consolidation by disrupting the ontogeny of GluN2B function. Here, we trained Sprague-Dawley rats of both sexes to self-administer methamphetamine (METH, 0.1 mg/kg/infusion i.v.) beginning during adolescence [postnatal (P) day 41] or adulthood (P91). Rats were given short access (2 h) to self-administer METH in seven daily sessions followed by fourteen sessions with long access (6 h). Subsequently, rats underwent four daily 30-min extinction sessions with immediate post-session injections of either a GluN2B antagonist (Ro25-6981; 6 mg/kg, i.p.) or a vehicle solution. After four daily 2-h extinction sessions, a priming injection (1 mg/kg METH, i.p.) was given prior to a final 2-h reinstatement session. During LgA, adolescent-onset rats earn more METH than adult-onset rats and display greater drug-loading behavior. Rats reduced their drug-seeking behavior across extinction sessions, with no significant group differences. Rats reinstated drug-seeking following the METH priming injection, with females displaying greater reinstatement than males. These results do not support our a priori hypothesis that adolescent-onset METH use disrupts the ontogeny of GluN2B transmission and contributes to age-of-onset differences in extinction of METH-seeking. However, our findings suggest that age-of-onset contributes to excessive METH-taking, while sex confers vulnerability to relapse to METH-seeking.

Download Full-text

Relapse to cotinine seeking in rats: Differential effects of sex

10.1101/2021.10.14.464393 ◽

2021 ◽

Author(s):

Xiaoying Tan ◽

Elizabeth Neslund ◽

Zheng-Ming Ding

Keyword(s):

Female Rats ◽

Male Rats ◽

Potential Mechanism ◽

Self Administration ◽

Drug Seeking ◽

Male And Female ◽

Rat Models ◽

Significant Challenge ◽

Male And Female Rats ◽

Future Treatments

Relapse is a defining feature of smoking and a significant challenge in cessation management. Elucidation of novel mechanisms underlying relapse may inform future treatments. Cotinine, the major metabolite of nicotine, has been shown to support intravenous self-administration in rats, suggesting it as one potential mechanism contributing to nicotine reinforcement. However, it remains unknown whether cotinine would induce relapse-like behaviors. The current study investigated relapse to cotinine seeking in two relapse models, the reinstatement of drug seeking and incubation of drug craving models. In the reinstatement model, rats were trained to self-administer cotinine, extinguished cotinine-associated responses, and underwent cue-, drug-, or stress-induced reinstatement. Conditioned cues associated with cotinine self-administration, cotinine (1-2 mg/kg), or the pharmacological stressor yohimbine (1.25-2.5 mg/kg) reinstated cotinine seeking. Female rats displayed more pronounced cue-induced, but not drug- or stress-induced reinstatement than male rats. In addition, an overall analysis revealed that female rats exhibited greater cotinine self-administration, but less extinction than male rats. In the incubation model, rats were trained to self-administer cotinine, and underwent forced withdrawal in home cages. Rats were tested for cue-induced cotinine seeking on both withdrawal day 1 and withdrawal day 18. Rats exhibited greater cotinine-seeking on withdrawal day 18 compared to withdrawal day 1, with no difference between male and female rats. These findings indicate that cotinine induces sex-dependent relapse to cotinine seeking in rats, suggesting that cotinine may be a novel mechanism contributing to relapse. These rat models are valuable preclinical tools for interrogation of neurobiological underpinnings of relapse to cotinine seeking.

Download Full-text

Sex Differences in Escalated Methamphetamine Self-Administration and Altered Gene Expression Associated With Incubation of Methamphetamine Seeking

The International Journal of Neuropsychopharmacology ◽

10.1093/ijnp/pyz050 ◽

2019 ◽

Vol 22 (11) ◽

pp. 710-723 ◽

Cited By ~ 8

Author(s):

Atul P Daiwile ◽

Subramaniam Jayanthi ◽

Bruce Ladenheim ◽

Michael T McCoy ◽

Christie Brannock ◽

...

Keyword(s):

Sex Differences ◽

Nucleus Accumbens ◽

Fixed Ratio ◽

Female Rats ◽

Male Rats ◽

Mrna Levels ◽

Self Administration ◽

Male And Female ◽

Orexin Receptors ◽

Male And Female Rats

Abstract Background Methamphetamine (METH) use disorder is prevalent worldwide. There are reports of sex differences in quantities of drug used and relapses to drug use among individuals with METH use disorder. However, the molecular neurobiology of these potential sex differences remains unknown. Methods We trained rats to self-administer METH (0. 1 mg/kg/infusion, i.v.) on an fixed-ratio-1 schedule for 20 days using two 3-hour daily METH sessions separated by 30-minute breaks. At the end of self-administration training, rats underwent tests of cue-induced METH seeking on withdrawal days 3 and 30. Twenty-four hours later, nucleus accumbens was dissected and then used to measure neuropeptide mRNA levels. Results Behavioral results show that male rats increased the number of METH infusions earlier during self-administration training and took more METH than females. Both male and female rats could be further divided into 2 phenotypes labeled high and low takers based on the degree of escalation that they exhibited during the course of the METH self-administration experiment. Both males and females exhibited incubation of METH seeking after 30 days of forced withdrawal. Females had higher basal mRNA levels of dynorphin and hypocretin/orexin receptors than males, whereas males expressed higher vasopressin mRNA levels than females under saline and METH conditions. Unexpectedly, only males showed increased expression of nucleus accumbens dynorphin after METH self-administration. Moreover, there were significant correlations between nucleus accumbens Hcrtr1, Hcrtr2, Crhr2, and Avpr1b mRNA levels and cue-induced METH seeking only in female rats. Conclusion Our results identify some behavioral and molecular differences between male and female rats that had self-administered METH. Sexual dimorphism in responses to METH exposure should be considered when developing potential therapeutic agents against METH use disorder.

Download Full-text