Neurons in the ventral tegmental area (VTA) and Nucleus Accumbens (NAc) play key roles in reward-seeking and are usurped in addiction. While most work has focused on dopaminergic projections from VTA to NAc, how opioids alter projections from NAc to VTA is largely unknown. The NAc to VTA connection deserves considerable attention since D1-MSN activity drives reward-seeking behavior, D1-MSNs directly modulate VTA neurons, and opioid receptors expressed specifically on D1-MSN to VTA synapses control dopamine release. Opioid-induced transcriptional changes in VTA neurons play an important role in opioid abuse and are likely sensitive to altered D1-MSN activity. However, no studies have examined transcriptional changes based on a specific synaptic input. It is further unknown if molecular adaptations in the VTA caused by D1-MSN activity alter dopamine release. We have adopted a technically innovative approach that combines next-generation single nuclei RNA sequencing with transsynaptic viral tagging to identify transcriptional changes based on synaptic input. RNAseq is a powerful tool for quantifying thousands of transcripts and can be used to identify changes in expression independent of a priori predictions.
We are currently profiling transcriptional changes in VTA neurons receiving D1-MSN input after fentanyl self-administration. We will then generate Cre-dependent viruses to manipulate our candidate molecules to block fentanyl self-administration and seeking. With in vivo fast-scan cyclic voltammetry, we are determining how fentanyl and molecular targets in VTA neurons influence NAc dopamine release after self-administration.