Probes for INS

Galanin receptor1 (GalR1) transcript levels are elevated in the rat ventral periaqueductal gray (vPAG) after chronic mild stress (CMS) and are related to depression-like behavior. To explore the mechanisms underlying the elevated GalR1 expression, we carried out molecular biological experiments in vitro and in animal behavioral experiments in vivo. It was found that a restricted upstream region of the GalR1 gene, from -250 to -220, harbors an E-box and plays a negative role in the GalR1 promoter activity. The transcription factor Scratch2 bound to the E-box to down-regulate GalR1 promoter activity and lower expression levels of the GalR1 gene. The expression of Scratch2 was significantly decreased in the vPAG of CMS rats. Importantly, local knockdown of Scratch2 in the vPAG caused elevated expression of GalR1 in the same region, as well as depression-like behaviors. RNAscope analysis revealed that GalR1 mRNA is expressed together with Scratch2 in both GABA and glutamate neurons. Taking these data together, our study further supports the involvement of GalR1 in mood control and suggests a role for Scratch2 as a regulator of depression-like behavior by repressing the GalR1 gene in the vPAG.

Ghrelin, an orexigenic hormone, has emerged as a critical biological substrate implicated in drug reward. However, the response of the ghrelin system to opioid-motivated behaviors and the role of ghrelin in oxycodone self-administration remain to be studied. Here, we investigated the reciprocal interactions between the endogenous ghrelin system and oxycodone self-administration behaviors in rats and the role of the ghrelin system in brain stimulation reward (BSR) driven by optogenetic stimulation of midbrain reward circuits in mice. Oxycodone self-administration significantly elevated plasma ghrelin, des-acyl ghrelin and growth hormone and showed no effect on plasma LEAP2, a newly identified endogenous ghrelin receptor (GHS-R1a) antagonist. Oxycodone self-administration produced significant decreases in plasma gastric inhibitory polypeptide and insulin. Acquisition of oxycodone self-administration significantly upregulated GHS-R1a mRNA levels in dopamine neurons in the ventral tegmental area (VTA), a brain region critical in drug reward. Pretreatment with JMV2959, a selective GHS-R1a antagonist, dose-dependently reduced oxycodone self-administration and decreased the breakpoint for oxycodone under a progressive ratio reinforcement in Long-Evans rats. The inhibitory effects of JMV2959 on oxycodone self-administration is selectively mediated by GHS-R1a as JMV2959 showed a similar effect in Wistar wildtype but not in GHS-R knockout rats. JMV2959 pretreatment significantly inhibited BSR driven by selective stimulation of VTA dopamine neurons, but not by stimulation of striatal GABA neurons projecting to the VTA in mice. These findings suggest that elevation of ghrelin signaling by oxycodone or oxycodone-associated stimuli is a causal process by which oxycodone motivates oxycodone drug-taking and targeting the ghrelin system may be a viable treatment approach for opioid use disorders.

Hypidone hydrochloride (YL-0919) is a novel antidepressant in clinical phase II trial. Previous studies show that YL-0919 is a selective 5-HT (serotonin) reuptake inhibitor, 5-HT1A receptor partial agonist, and 5-HT6 receptor agonist, which exerts antidepressant effects in various animal models, but its effects on neural function remain unclear. Medial prefrontal cortex (mPFC), a highly evolved brain region, controls highest order cognitive functions and emotion regulation. In this study we investigated the effects of YL-0919 on the mPFC function, including the changes in neuronal activities using electrophysiological recordings. Extracellular recording (in vivo) showed that chronic administration of YL-0919 significantly increased the spontaneous discharges of mPFC neurons. In mouse mPFC slices, whole-cell recording revealed that perfusion of YL-0919 significantly increased the frequency of sEPSCs, but decreased the frequency of sIPSCs. Then we conducted whole-cell recording in mPFC slices of GAD67-GFP transgenic mice, and demonstrated that YL-0919 significantly inhibited the excitability of GABAergic neurons. In contrast, it did not alter the excitability of pyramidal neurons in mPFC slices of normal mice. Moreover, the inhibition of GABAergic neurons by YL-0919 was prevented by pre-treatment with 5-HT1A receptor antagonist WAY 100635. Finally, chronic administration of YL-0919 significantly increased the phosphorylation levels of mTOR and GSK-3β in the mPFC as compared with vehicle. Taken together, our results demonstrate that YL-0919 enhances the excitability of mPFC via a disinhibition mechanism to fulfill its rapid antidepressant neural mechanism, which was accomplished by 5-HT1A receptor-mediated inhibition of inhibitory GABAergic interneurons.