behavioralmousewild-type and prepro-orexin knockout mice
Objective: Assessment of morphine-induced reward preference in wild-type and prepro-orexin knockout mice to investigate the role of orexinergic systems in dopamine-related behaviors
Materials & Equipment Checklist
8 items1 from ConductScience
Gather these items before starting the experiment. Check off items as you prepare.
Equipment3
Not specified • Not specified • Not specified • Not specified
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View Abstract
In this study, we investigated the role of orexinergic systems in dopamine-related behaviors induced by the μ-opioid receptor agonist morphine in rodents. Extensive coexpression of tyrosine hydroxylase with orexin receptors was observed in the mouse ventral tegmental area (VTA). The levels of dopamine and its major metabolites in the nucleus accumbens were markedly increased by the microinjection of orexin A and orexin B into the VTA. The subcutaneous morphine-induced place preference and hyperlocomotion observed in wild-type mice were abolished in mice that lacked the prepro-orexin gene. An intra-VTA injection of a selective orexin receptor antagonist SB334867A [1-(2-methylbenzoxazol-6-yl)-3-[1.5]naphthyridin-4-yl urea] significantly suppressed the morphine-induced place preference in rats. Furthermore, the increased level of dialysate dopamine produced by morphine in the mouse brain was significantly decreased by deletion of the prepro-orexin gene. These findings provide new evidence that orexin-containing neurons in the VTA are directly implicated in the rewarding effect and hyperlocomotion induced by morphine through activation of the mesolimbic dopamine pathway in rodents.
Protocol Steps
1
Morphine administration
Subcutaneous injection of morphine to induce place preference and hyperlocomotion in wild-type and prepro-orexin knockout mice
Not specifiedNot specified
Conditioned Place Preference - Mouse (Custom Order)
Note: Comparison made between wild-type mice and mice lacking prepro-orexin gene
View evidence from paper
“The subcutaneous morphine-induced place preference and hyperlocomotion observed in wild-type mice were abolished in mice that lacked the prepro-orexin gene”
2
Conditioned place preference assessment
Measurement of morphine-induced place preference in behavioral chamber
Not specifiedNot specified
Conditioned Place Preference - Mouse (Custom Order)
Note: Preference was abolished in prepro-orexin knockout mice
View evidence from paper
“The subcutaneous morphine-induced place preference and hyperlocomotion observed in wild-type mice were abolished in mice that lacked the prepro-orexin gene”
3
Hyperlocomotion measurement
Assessment of morphine-induced hyperlocomotion in wild-type and knockout mice
Not specifiedNot specified
Note: Hyperlocomotion was abolished in prepro-orexin knockout mice
View evidence from paper
“The subcutaneous morphine-induced place preference and hyperlocomotion observed in wild-type mice were abolished in mice that lacked the prepro-orexin gene”
4
Orexin A microinjection into VTA
Microinjection of orexin A into ventral tegmental area to measure effects on dopamine levels
Not specifiedNot specified
Note: Measured dopamine and metabolite levels in nucleus accumbens
View evidence from paper
“The levels of dopamine and its major metabolites in the nucleus accumbens were markedly increased by the microinjection of orexin A and orexin B into the VTA”
5
Orexin B microinjection into VTA
Microinjection of orexin B into ventral tegmental area to measure effects on dopamine levels
Not specifiedNot specified
Note: Measured dopamine and metabolite levels in nucleus accumbens
View evidence from paper
“The levels of dopamine and its major metabolites in the nucleus accumbens were markedly increased by the microinjection of orexin A and orexin B into the VTA”
6
SB334867A intra-VTA injection in rats
Intra-VTA injection of selective orexin receptor antagonist SB334867A to assess effects on morphine-induced place preference
Not specifiedNot specified
Conditioned Place Preference - Mouse (Custom Order)
Note: Conducted in rats; significantly suppressed morphine-induced place preference
View evidence from paper
“An intra-VTA injection of a selective orexin receptor antagonist SB334867A [1-(2-methylbenzoxazol-6-yl)-3-[1.5]naphthyridin-4-yl urea] significantly suppressed the morphine-induced place preference in rats”
7
Microdialysis measurement of dopamine
Measurement of dialysate dopamine levels in mouse brain following morphine administration
Not specifiedNot specified
Note: Compared wild-type mice with prepro-orexin knockout mice; deletion of prepro-orexin gene significantly decreased dopamine levels
View evidence from paper
“the increased level of dialysate dopamine produced by morphine in the mouse brain was significantly decreased by deletion of the prepro-orexin gene”
Subjects / Specimens
Species
mouse
Strain
wild-type and prepro-orexin knockout mice
Age
Not specified
Sex
unknown
Weight
Not specified
Study compared wild-type mice with mice that lacked the prepro-orexin gene
