Psychopharmacology
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Prescription opioid misuse and high-dose opioid use may result in allostatic dysregulation of hedonic brain circuitry, leading to reduced emotion regulation capacity. In particular, opioid misuse may blunt the ability to experience and upregulate positive affect from natural rewards. ⋯ Findings implicate the presence of reward processing deficits among chronic pain patients with opioid-misusing behaviors, and opioid dosage was associated with deficient emotion regulation, suggesting the presence of compromised top-down cognitive control over bottom-up hedonic processes. Emotion regulation among opioid misusers may represent an important treatment target.
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Cocaine produces significant aversive/anxiogenic actions whose underlying neurobiology remains unclear. A possible substrate contributing to these actions is the serotonergic (5-HT) pathway projecting from the dorsal raphé (DRN) to regions of the extended amygdala, including the bed nucleus of the stria terminalis (BNST) which have been implicated in the production of anxiogenic states. ⋯ Inhibition of 5-HT1B signaling within the BNST selectively attenuated the anxiogenic effects of cocaine, while leaving unaffected the positive incentive properties of the drug.
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The roles of group I metabotropic glutamate receptors, metabotropic glutamate receptor 1 (mGluR1) and mGluR5, in regulating synaptic plasticity and metaplasticity in the basolateral amygdala (BLA) remain unclear. The present study examined mGluR1- and mGluR5-mediated synaptic plasticity in the BLA and their respective signaling mechanisms. Bath application of the group I mGluR agonist, 3,5-dihydroxyphenylglycine (DHPG) (20 μM), directly suppressed basal fEPSPs (84.5 ± 6.3% of the baseline). ⋯ Nevertheless, blockade of protein kinase C (PKC), the downstream enzyme of PLC, with chelerythrine (5 μM) only prevented the transforming effect of DHPG on TBS-induced LTP and did not affect DHPG-induced long-term depression (LTD). These results suggest that mGluR1 activation induced LTD via a PLC-dependent and PKC-independent mechanism, while the priming action of mGluR5 receptor on the BLA LTP is both PLC and PKC dependent. The BLA metaplasticity mediated by mGluR1 and mGluR5 may provide signal switching mechanisms mediating learning and memory with emotional significance.