Biology subjects

Stapf, C. A.

Publications and source records attributed to Stapf, C. A..

3 recordsLinked to original sources

bioRxiv2024

Sex specific effects of dorsomedial striatal cannabinoid receptor-1 signaling on Pavlovian outcome devaluation.

Cannabinoid-1 receptor (CB1R) signaling in the dorsal striatum regulates the shift from flexible to habitual behavior in instrumental outcome devaluation. Based on prior work establishing individual, sex, and experience-dependent differences in Pavlovian behaviors, we predicted a role for dorsomedial striatum CB1R signaling in driving rigid responding in Pavlovian autoshaping and outcome devaluation. We trained male and female Long Evans rats in Pavlovian Lever Autoshaping (PLA). We gave intra-dorsomedial striatum (DMS) infusions of the CB1R inverse agonist, rimonabant, before satiety-induced outcome devaluation test sessions, where we sated rats on training pellets or home cage chow and tested them in brief nonreinforced Pavlovian Lever Autoshaping sessions. Overall, inhibition of DMS CB1R signaling prevented Pavlovian outcome devaluation but did not affect behavior in reinforced PLA sessions. Males were sensitive to devaluation while females were not and DMS CB1R inhibition impaired devaluation sensitivity in males. We then investigated how DMS CB1R signaling impacts local inhibitory synaptic transmission in male and female Long Evans rats. We recorded spontaneous inhibitory postsynaptic currents (sIPSC) from DMS neurons at baseline and before and after application of a CB1R agonist, WIN 55,212-2. We found that male rats showed decreased sIPSC frequency compared to females, and that CB1R activation reduced DMS inhibitory transmission independent of sex. Altogether our results demonstrate that DMS CB1Rs regulate Pavlovian devaluation sensitivity and inhibitory synaptic transmission and suggest that basal sex differences in inhibitory synaptic transmission may underly sex differences in DMS function and behavioral flexibility.

neuroscience↗

bioRxiv2022

Inducible CRISPR epigenome systems mimic cocaine induced bidirectional regulation of Nab2 and Egr3

Substance use disorder is a debilitating chronic disease and a leading cause of disability around the world. The nucleus accumbens (NAc) is a major brain hub that mediates reward behavior. Studies demonstrate exposure to cocaine is associated with molecular and functional imbalance in two NAc medium spiny neuron subtypes (MSNs), dopamine receptor 1 and 2 enriched D1-MSNs and D2-MSNs. Our previous reports showed that repeated cocaine exposure induced transcription factor early growth response 3 (Egr3) mRNA in NAc D1-MSNs, while reducing it in D2-MSNs. Here, we report our findings of repeated cocaine exposure inducing cell subtype specific bidirectional expression of the Egr3 corepressor NGFI-A-binding protein 2 (Nab2). Using CRISPR activation and interference (CRISPRa and CRISPRi) tools combined with Nab2 or Egr3 targeted sgRNAs, we mimicked these bidirectional changes in Neuro2a cells. Furthermore, we investigated D1-MSN and D2-MSN subtype specific expressional changes of histone lysine demethylases Kdm1a, Kdm6a and Kdm5c in NAc after repeated cocaine exposure. Since Kdm1a showed bidirectional expression patterns in D1-MSNs and D2-MSNs, like Egr3, we developed a light inducible Opto-CRISPR-KDM1a system. We were able to downregulate Egr3 and Nab2 transcripts and cause bidirectional expression changes in D1-MSNs and D2-MSNs similar to cocaine exposure in Neuro2A cells. In contrast, our Opto-CRISPR-p300 activation system induced the Egr3 and Nab2 transcripts and caused bidirectional transcription regulations in D1-MSNs and D2-MSNs. Our study sheds light on the expression patterns of Nab2 and Egr3 in specific NAc MSN subtypes in cocaine action and uses CRISPR tools to further mimic these expression patterns.

neuroscience↗

bioRxiv2022

Decreased ventral tegmental area CB1R signaling reduces sign-tracking and shifts cue-outcome dynamics in rat nucleus accumbens

Sign-tracking rats show enhanced cue sensitivity before drug experience that predicts greater discrete cue-induced drug-seeking compared to goal-tracking or intermediate-rats. Cue-evoked dopamine in the nucleus Accumbens (NAc) is a neurobiological signature of sign-tracking behaviors. Here, we examine a critical regulator of the dopamine system; endocannabinoids, which bind the cannabinoid receptor-1 (CB1R) in the Ventral Tegmental Area (VTA) to control cue-evoked striatal dopamine levels. We use cell-type specific optogenetics, intra-VTA pharmacology and fiber photometry to test the hypothesis that VTA CB1R receptor signaling regulates NAc dopamine levels to control sign-tracking. We trained rats in a Pavlovian lever autoshaping task (PLA) to determine their tracking groups before testing the effect of VTA[->]NAc dopamine inhibition. We found this circuit is critical for mediating the vigor of the ST response. Upstream of this circuit, intra-VTA infusions of rimonabant, a CB1R inverse agonist, during PLA decrease lever and increase foodcup approach in sign-trackers. Using fiber photometry to measure fluorescent signals from dopamine sensor, GRABDA, we tested the effects of intra-VTA rimonabant on NAc dopamine dynamics during autoshaping. We found that intra-VTA rimonabant decreased sign-tracking behaviors, which was associated with increases NAc shell, but not core, dopamine levels during reward delivery (US). We also observed a relationship between cue (CS)-evoked NAc dopamine activity and rigidity of behavior between rimonabant treatment sessions. Our results suggest that CB1R signaling in the VTA influences the balance between the CS- and US-evoked dopamine responses in the NAc and biases behavioral responding to cues in sign-tracking rats. SIGNIFICANCE STATEMENTSubstance Use Disorder is a chronically relapsing neurobiological disorder that affects a subset of individuals that engage in drug use. Recent research suggests that there are individual behavioral and neurobiological differences prior to drug experience that predict addiction and relapse vulnerabilities. Here, we investigate how midbrain endocannabinoids regulate a brain pathway that is exclusively involved in driving cue-motivated behaviors of sign-tracking rats. This work contributes to our mechanistic understanding of individual vulnerabilities to cue-triggered natural reward seeking that have relevance for drug motivated behaviors.

neuroscience↗