REAGENT or RESOURCE	SOURCE	IDENTIFIER
Chemicals, peptides, and recombinant proteins
Naloxone methiodide (NLXM)	Sigma-Aldrich	Cat# N129
Naltrexone hydrochloride	Sigma-Aldrich	Cat# N3136
Norbinaltorphimine (norBNI)	Sigma-Aldrich	Cat# N1771
SR59230A hydrochloride	hydrochloride	Cat# 1511
U50,488H (U50)	Sigma-Aldrich	Cat# U111
Experimental models: Organisms/strains
Mouse: C57BL/6BJ	The Jackson Laboratory	RRID:IMSR_JAX:000664
Mouse: C57BL/6J DIO	The Jackson Laboratory	RRID:IMSR_JAX:380050
Mouse: Oprk1tm1.1(cre)Sros/J	Gift from Sarah Ross, Pitt	RRID:IMSR_JAX:035045
Mouse: B6.129S2-Oprk1tm1Kff/J	Gift from Sarah Ross, Pitt	RRID:IMSR_JAX:007558
Mouse: B6.129-Ucp1tm1Kz/J	Gift from Jonathan Brestoff, WashU	RRID:IMSR_JAX:003124
Software and algorithms
ResearchIR	Teledyne FLIR Systems Inc	N/A
FLIR E53 thermal imaging cameras	Teledyne FLIR Systems Inc	Cat# FLIR E53 24°
Leica Application Suite Advanced Fluorescence	Leica Microsystems	N/A
Wireless IPTT-300 temperature transponders	Bio Medic Data Systems	N/A
Phenomaster system	LabMaster System; TSE Systems	N/A
FED3 device	Open Ephys	N/A
GraphPad Prism	GraphPad Software	Version 9.3.1
Other
High fat diet (HFD) (60 kcal% fat)	Research Diets, Inc	Cat# D12492
Guide Cannula	P1 Technologies	N/A