Cell type-specific neurotensin signaling in methamphetamine use disorder

About This Grant

Methamphetamine (METH) use disorder is chronic and progressive, and currently no therapeutic is approved by the FDA for its treatment. Dopamine (DA) neurons in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) are necessary for learning associated with drug reinforcers. Our published and preliminary work highlights a role for the peptide transmitter neurotensin in modulation of METH self-administration behavior and plasticity of inhibitory neurotransmission in the SNc/VTA. Neurotensin receptors in the SNc/VTA are localized not only on neurons but also on astrocytes, which are glial cells that can act through local circuits to affect DA neuron excitability and reward-related behavior. We have created floxed neurotensin receptor mouse lines that will enable, for the first time, the determination of the role of specific neurotensin receptors on individual cell types that contribute to METH self-administration and responding to related cues. Filling this knowledge gap is necessary to assess the feasibility of targeting cell type-specific neurotensin signaling and other forms of astrocyte glial modulation as a viable treatment for METH use disorder. The objective of this application is to identify the role of specific neurotensin receptors (NtsR1 and NtsR2), cell types, and circuits responsible for modulating inhibitory input to DA neurons and METH self-administration behavior in mice. Our central hypothesis is that repeated METH self-administration affects VTA circuits through NtsR1 on DA neurons and NtsR2 on astrocytes, which enhances METH intake and responding for METH-related cues. The experiments will combine intravenous METH self-administration in genetically-modified mice, brain slice electrophysiology, and virus-induced expression of Cre recombinase and designer ligand-sensitive proteins to determine the circuits responsible for neurotensin effects in the SNc and VTA. The studies in Aim 1 will elucidate the receptor subtypes and localization that are essential for inhibitory synaptic plasticity using patch clamp electrophysiology in mouse brain slices. The studies in Aim 2 will determine the consequences of METH self-administration, as well as forced abstinence, on neurotensin modulation of DA neurons. Experiments will combine intravenous self-administration of METH in mice with patch clamp electrophysiology, RNAScope, Patch-seq of previously-recorded dopamine neurons, and transcriptomics in midbrain astrocytes. The experiments in Aim 3 will combine chemogenetics and behavior to probe the effects of distinct receptors and neurotensin input on self-administration of METH and responding for METH-related cues after a forced abstinence. The knowledge gleaned from these studies will clarify the role of specific neurotensin receptors by identifying plasticity mechanisms for inhibitory input to DA neurons, and by determining how neurotensin contributes to multiple stages of METH self-administration (acquisition, maintenance, responding for cues after abstinence). The increased understanding of neurotensin and inhibitory circuits in the SNc/VTA could open the door to novel targets for the treatment of stimulant use disorders.