scholarly journals Effects of Kappa Opioid Receptor Agonists on Fentanyl vs. Food Choice in Male and Female Rats: Contingent vs. Non-Contingent Administration

2020 ◽  
Author(s):  
E. Andrew Townsend
Keyword(s):  
Opioid Receptor ◽  
Food Choice ◽  
Food Reinforcement ◽  
Abuse Liability ◽  
Kappa Opioid Receptor ◽  
Female Rats ◽  
Self Administration ◽  
Kappa Opioid ◽  
Male And Female ◽  
Male And Female Rats

AbstractRationaleStrategies are needed to decrease the abuse liability of mu opioid receptor (MOR) agonists. One strategy under consideration is to combine MOR agonists with kappa opioid receptor (KOR) agonists.ObjectivesThe effects of KOR-agonists (U50488, nalfurafine) on fentanyl-versus-food choice were compared under conditions where the KOR agonists were added to the self-administered fentanyl (contingent delivery) or administered as pretreatments (non-contingent delivery) in male and female rats. The effects of increasing and decreasing the magnitude of the alternative food reinforcer were also determined.MethodsRats were trained to respond under a concurrent schedule of fentanyl (0, 0.32-10 μg/kg/infusion) and food reinforcement. In Experiment 1, U50488 and nalfurafine were co-administered with fentanyl as fixed-proportion mixtures (contingent administration). In Experiment 2, U50488 (1-10 mg/kg) and nalfurafine (3.2-32 μg/kg) were administered as acute pretreatments (non-contingent administration). nor-BNI (32 mg/kg) was administered prior to contingent and non-contingent KOR-agonist treatment in Experiment 3. Experiment 4 evaluated the effects of increasing and decreasing the magnitude of the non-drug reinforcer.ResultsBoth U50488 and nalfurafine decreased fentanyl choice when administered contingently, demonstrating that KOR agonists punish opioid choice. Non-contingent U50488 and nalfurafine administration decreased rates of fentanyl and food self-administration without altering fentanyl choice. Both contingent and non-contingent U50488 and nalfurafine effects on fentanyl choice were attenuated by nor-BNI. Fentanyl choice was sensitive to increases and decreases in the magnitude of the non-drug reinforcer.ConclusionsThese results demonstrate that the effects of KOR agonists on fentanyl reinforcement are dependent upon the contingencies under which they are administered.

scholarly journals Adolescent intermittent ethanol exposure effects on kappa opioid receptor mediated dopamine transmission: Sex and age of exposure matter

2020 ◽  
Author(s):  
Mary B. Spodnick ◽  
Raymond T. Amirault ◽  
Trevor T. Towner ◽  
Elena I. Varlinskaya ◽  
Linda P. Spear ◽  
...  
Keyword(s):  
Opioid Receptor ◽  
Dopamine Release ◽  
Ethanol Exposure ◽  
Kappa Opioid Receptor ◽  
Female Rats ◽  
Male Rats ◽  
Kappa Opioid ◽  
Male And Female Rats ◽  
Dopamine Transmission ◽  
The Impact

ABSTRACTUnderage alcohol drinking increases the risk of developing alcohol use disorder (AUD). In rodents, adolescent ethanol exposure augments ethanol consumption and anxiety-like behavior while reducing social interaction. However, the underlying mechanisms driving these adaptations are not understood. The dopamine and kappa opioid receptor (KOR) systems in the nucleus accumbens (NAc) are implicated in affective disorders and AUD, with studies showing augmented KOR function and reduced dopamine transmission in ethanol-dependent adult animals. Thus, this study, we examined the impact of adolescent intermittent ethanol (AIE) exposure on dopamine transmission and KOR function. Rats were exposed to water or ethanol (4 g/kg, intragastrically) every-other-day during early (PD25–45) or late (PD45–65) adolescence. While AIE exposure during early-mid adolescence (early AIE) did not alter dopamine release in male and female rats, AIE exposure during late adolescence (late AIE) resulted in greater dopamine release in males and lower dopamine release in females. To determine the impact of AIE exposure on KOR function, we bath applied cumulative concentrations of KOR agonist, U50,488 (0.01–1.0 μM), and measured its effect on dopamine release. Early AIE exposure potentiated KOR-mediated inhibition of dopamine release in female rats, while late AIE exposure attenuated this effect in male rats. Together these data suggest that AIE-exposure impact on neural processes is dependent on sex and exposure timing. These differences likely arise from differential developmental timing in males and females. This is the first study to show changes in KOR function following AIE exposure.

scholarly journals Self-Administration of Entactogen Psychostimulants Dysregulates Gamma-Aminobutyric Acid (GABA) and Kappa Opioid Receptor Signaling in the Central Nucleus of the Amygdala of Female Wistar Rats

2021 ◽  
Vol 15 ◽  
Author(s):  
Sophia Khom ◽  
Jacques D. Nguyen ◽  
Sophia A. Vandewater ◽  
Yanabel Grant ◽  
Marisa Roberto ◽  
...  
Keyword(s):  
Opioid Receptor ◽  
Wistar Rats ◽  
Kappa Opioid Receptor ◽  
Female Rats ◽  
Central Nucleus ◽  
Self Administration ◽  
Kappa Opioid ◽  
Extended Access ◽  
Female Wistar Rats ◽  
Saline Vehicle

Male rats escalate intravenous self-administration of entactogen psychostimulants, 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxymethamphetamine (MDMA) under extended access conditions, as with typical psychostimulants. Here, we investigated whether female rats escalate self-administration of methylone, 3,4-methylenedioxypentedrone (pentylone), and MDMA and then studied consequences of MDMA and pentylone self-administration on GABAA receptor and kappa opioid receptor (KOR) signaling in the central nucleus of the amygdala (CeA), a brain area critically dysregulated by extended access self-administration of alcohol or cocaine. Adult female Wistar rats were trained to self-administer methylone, pentylone, MDMA (0.5 mg/kg/infusion), or saline-vehicle using a fixed-ratio 1 response contingency in 6-h sessions (long-access: LgA) followed by progressive ratio (PR) dose-response testing. The effects of pentylone-LgA, MDMA-LgA and saline on basal GABAergic transmission (miniature post-synaptic inhibitory currents, mIPSCs) and the modulatory role of KOR at CeA GABAergic synapses were determined in acute brain slices using whole-cell patch-clamp. Methylone-LgA and pentylone-LgA rats similarly escalated their drug intake (both obtained more infusions compared to MDMA-LgA rats), however, pentylone-LgA rats reached higher breakpoints in PR tests. At the cellular level, baseline CeA GABA transmission was markedly elevated in pentylone-LgA and MDMA-LgA rats compared to saline-vehicle. Specifically, pentylone-LgA was associated with increased CeA mIPSC frequency (GABA release) and amplitude (post-synaptic GABAA receptor function), while mIPSC amplitudes (but not frequency) was larger in MDMA-LgA rats compared to saline rats. In addition, pentylone-LgA and MDMA-LgA profoundly disrupted CeA KOR signaling such as both KOR agonism (1 mM U50488) and KOR antagonism (200 nM nor-binaltorphimine) decreased mIPSC frequency suggesting recruitment of non-canonical KOR signaling pathways. This study confirms escalated self-administration of entactogen psychostimulants under LgA conditions in female rats which is accompanied by increased CeA GABAergic inhibition and altered KOR signaling. Collectively, our study suggests that CeA GABA and KOR mechanisms play a critical role in entactogen self-administration like those observed with escalation of alcohol or cocaine self-administration.

scholarly journals Adolescent Intermittent Ethanol Exposure Effects on Kappa Opioid Receptor Mediated Dopamine Transmission: Sex and Age of Exposure Matter

2020 ◽  
Vol 10 (8) ◽  
pp. 472
Author(s):  
Mary B. Spodnick ◽  
Raymond T. Amirault ◽  
Trevor T. Towner ◽  
Elena I. Varlinskaya ◽  
Linda P. Spear ◽  
...  
Keyword(s):  
Opioid Receptor ◽  
Dopamine Release ◽  
Ethanol Exposure ◽  
Kappa Opioid Receptor ◽  
Female Rats ◽  
Kappa Opioid ◽  
Male And Female Rats ◽  
Dopamine Transmission ◽  
Underlying Mechanisms ◽  
The Impact

Underage alcohol drinking increases the risk of developing alcohol use disorder (AUD). In rodents, adolescent ethanol exposure augments ethanol consumption and anxiety-like behavior while reducing social interaction. However, the underlying mechanisms driving these adaptations are unclear. The dopamine and kappa opioid receptor (KOR) systems in the nucleus accumbens (NAc) are implicated in affective disorders, including AUD, with studies showing augmented KOR function and reduced dopamine transmission in ethanol-dependent adult animals. Thus, here we examine the impact of adolescent intermittent ethanol (AIE) exposure on dopamine transmission and KOR function in the NAc. Rats were exposed to water or ethanol (4 g/kg, intragastrically) every other day during early (postnatal day (PD) 25–45) or late (PD 45–65) adolescence. While AIE exposure during early adolescence (early-AIE) did not alter dopamine release in male and female rats, AIE exposure during late adolescence (late-AIE) resulted in greater dopamine release in males and lower dopamine release in females. To determine the impact of AIE on KOR function, we measured the effect of KOR activation using U50,488 (0.01–1.00 µM) on dopamine release. Early-AIE exposure potentiated KOR-mediated inhibition of dopamine release in females, while late-AIE exposure attenuated this effect in males. Interestingly, no differences in KOR function were observed in early-AIE exposed males and late-AIE exposed females. Together, these data suggest that AIE exposure impact on neural processes is dependent on sex and exposure timing. These differences likely arise from differential developmental timing in males and females. This is the first study to show changes in KOR function following AIE exposure.

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