Probes for INS

The dorsomedial striatum (DMS) is critically involved in motor control and reward processing, but the specific neural circuit mediators are poorly understood. Recent evidence highlights the extensive connectivity of low-threshold spiking interneurons (LTSIs) within local striatal circuitry; however, the in vivo function of LTSIs remains largely unexplored. We employed fiber photometry to assess LTSI calcium activity in a range of DMS-mediated behaviors, uncovering specific reward-related activity that is down-modulated during goal-directed learning. Using two mechanistically distinct manipulations, we demonstrated that this down-modulation of LTSI activity is critical for acquisition of novel contingencies, but not for their modification. In contrast, continued LTSI activation slowed instrumental learning. Similar manipulations of fast-spiking interneurons did not reproduce these effects, implying a specific function of LTSIs. Finally, we revealed a role for the γ-aminobutyric acid (GABA)ergic functions of LTSIs in learning. Together, our data provide new insights into this striatal interneuron subclass as important gatekeepers of goal-directed learning.

Summary

Endocannabinoids acting on the cannabinoid-1 receptor (CB1R) or ghrelin acting on its receptor (GHS-R1A) both promote alcohol-seeking behavior, but an interaction between the two signaling systems has not been explored. Here, we report that the peripheral CB1R inverse agonist JD5037 reduces ethanol drinking in wild-type micebut not in mice lacking CB1R, ghrelin peptide or GHS-R1A. JD5037 treatment of alcohol-drinking mice inhibits the formation of biologically active octanoyl-ghrelin without affecting its inactive precursor desacyl-ghrelin. In ghrelin-producing stomach cells, JD5037 reduced the level of the substrate octanoyl-carnitine generated from palmitoyl-carnitine by increasing fatty acid β-oxidation. Blocking gastric vagal afferents abrogated the ability of either CB1R or GHS-R1A blockade to reduce ethanol drinking. We conclude that blocking CB1R in ghrelin-producing cells reduces alcohol drinking by inhibiting the formation of active ghrelin and its signaling via gastric vagal afferents. Thus, peripheral CB1R blockade may have therapeutic potential in the treatment of alcoholism.

Sparse populations of neurons in the dentate gyrus (DG) of the hippocampus are causally implicated in the encoding of contextual fear memories. However, engram-specific molecular mechanisms underlying memory consolidation remain largely unknown. Here we perform unbiased RNA sequencing of DG engram neurons 24 h after contextual fear conditioning to identify transcriptome changes specific to memory consolidation. DG engram neurons exhibit a highly distinct pattern of gene expression, in which CREB-dependent transcription features prominently (P = 6.2 × 10-13), including Atf3 (P = 2.4 × 10-41), Penk (P = 1.3 × 10-15), and Kcnq3 (P = 3.1 × 10-12). Moreover, we validate the functional relevance of the RNAseq findings by establishing the causal requirement of intact CREB function specifically within the DG engram during memory consolidation, and identify a novel group of CREB target genes involved in the encoding of long-term memory