Neurotensin receptor 1 deletion suppresses methamphetamine self-administration and the associated reduction in dopamine cell firing

Abstract

We previously reported that pharmacological blockade of neurotensin receptors in the ventral tegmental area (VTA) decreases methamphetamine (METH) self-administration in mice. Here we explored the consequences of genetic deletion of neurotensin receptor 1 (NtsR1) in METH self-administration and VTA dopamine neuron firing activity. We implanted mice with an indwelling jugular catheter and trained them to nose-poke for intravenous infusions of METH. Mice with NtsR1 deletion (KO) acquired selfadministration similar to wildtype (WT) and heterozygous (HET) littermates. However, in NtsR1 KO and HET mice, METH intake and motivated METH seeking decreased when the response requirement was increased to a fixed ratio 3 and when mice were tested on a progressive ratio protocol. After completion of METH self-administration, single cell in vivo extracellular recordings of dopamine firing activity in the VTA were obtained in anesthetized mice. In WT METH-experienced mice, dopamine cell firing frequency dramatically decreases compared to WT drug-naïve mice. NtsR1 KO and HET mice did not exhibit this decline of dopamine cell firing activity after prolonged METH selfadministration. We also observed an increase in population activity following METH selfadministration that was strongest in the WT group. Our results suggest a role for NtsR1 in METH-seeking behavior, and ablation of NtsR1 receptors prevents the detrimental effects of prolonged METH self-administration on VTA dopamine cell firing frequency.Here we combined METH self-administration in mice with a genetic deletion of NtsR1 with in vivo single unit recordings of VTA dopamine neurons. We observed a decrease in METH self-administration and drug-seeking behavior in NtsR1 heterozygotes (HET) and knockouts (KO) versus wild type (WT) littermates. We also observed that METH self-administration increased the number of low firing rate dopamine neurons in vivo, an effect that was eliminated in mice lacking NtsR1. MATERIALS AND METHODSAnimals: Ntsr1 tm1Dgen mice (Jackson Stock #005826, Bar Harbor, ME) were generously provided by Dr. Gina M. Leinninger and were bred with C57Bl/6J mice, also from Jackson. A total of 36 adult male littermates were used, aged 6-8 months (KO, n= 10; HET, n=13; WT, n=13). Mice were group housed (3-5 per cage) in polycarbonate boxes with rodent bedding and shredding material and kept on a 12/12-hour reverse light-dark cycle (lights off at 0900 h) with ad libitum access to food and water. All procedures were approved by the Institutional Animal Care and Use Committee at the Oklahoma Medical Research Foundation.Genotyping: DNA from offspring was extracted from mouse ear punches using Extract-N-Amp® kit (Sigma, St. Louis, MO) and genotyped using a multiplex PCR reaction; primers at 1 µM final concentration used were: 5' CTC TAA TGT GCC ACA GCT CAG AGA G 3`, 5' CAG CAA CCT GGA CGT GAA CAC TGA C 3' and 5' CCA AGC GGC TTC GGC CAG TAA CGT T 3'. PCR conditions used were: 94ºC for 30 sec, 60ºC for 30 sec, and 72ºC for 2 min, for 35 cycles followed by a final amplif...

Depression of substantia nigra dopamine transmission is driven by retrograde neurotensin release and is enhanced by methamphetamine self-administration

“…This is consistent with previous reports of 2-to-3-fold higher NT levels in the SNc and dorsal striatum following methamphetamine self-administration (Frankel et al, 2011;Hanson et al, 2013). Furthermore, we have shown that blockade or ablation of NT receptors decreases methamphetamine selfadministration (Dominguez-Lopez et al, 2018;Dominguez-Lopez et al, 2019). Taken together, this suggests that methamphetamine use enhances NT-induced LTDDA, disinhibiting dopamine neurons and driving a further increase in reinforcing effects of the drug.…”

β-arrestin-biased Allosteric Modulator of Neurotensin Receptor 1 Reduces Ethanol Drinking and Responses to Ethanol Administration in Rodents

“…Neurotensin (Nts) systems have previously been explored in the context of and in circuitries related to AUD, stress disorders, and motivated behaviors [2][3][4][5][6][7] . Levels of neurotensin in the cortex are significantly lower in Alcohol Preferring P-rats as compared to their controls 8 .…”