The type 1 equilibrative nucleoside transporter regulates anxiety‐like behavior in mice

Abstract

Activation of adenosine receptors in the brain reduces anxiety-like behavior in animals and humans. Because nucleoside transporters regulate adenosine levels, we used mice lacking the type 1 equilibrative nucleoside transporter (ENT1) to investigate whether ENT1 contributes to anxiety-like behavior. The ENT1 null mice spent more time in the center of an open field compared with wild-type littermates. In the elevated plus maze, ENT1 null mice entered more frequently into and spent more time exploring the open arms. The ENT1 null mice also spent more time exploring the light side of a light-dark box compared with wild-type mice. Microinjection of an ENT1-specific antagonist, nitrobenzylthioinosine (nitrobenzylmercaptopurine riboside), into the amygdala of C57BL/6J mice reduced anxiety-like behavior in the open field and elevated plus maze. These findings show that amygdala ENT1 modulates anxiety-like behavior. The ENT1 may be a drug target for the treatment of anxiety disorders.

Nucleoside/nucleobase transport and metabolism by microvascular endothelial cells isolated from ENT1−/− mice

“…The ENT1 Ϫ/Ϫ mice had a consistently lower body weight. They were also notably easier to handle than WT mice (less distress because of handling), likely reflecting the anxiolytic phenotype reported previously (9 (Fig. 1), confirming the specificity of this radioligand for the ENT1 protein.…”

“…The ENT1 Ϫ/Ϫ mice are phenotypically normal with the only difference from wild-type (WT) littermates being a slight (Ͻ10%) decrease in body weight and some differences in their behavioral characteristics. The ENT1-null mice are less sensitive to the intoxicating effects of ethanol compared with their WT littermates (10), and they also display less anxiety-like behavior (9). It has been noted that there is less tonic A 1 adenosine receptor signaling in the brains of ENT1…”

“…Only ENT1 Ϫ/ϩ mice were crossed (producing ENT1 ϩ/ϩ , ENT1 ϩ/Ϫ , and ENT1 Ϫ/Ϫ offspring) to establish a breeding colony at the University of Western Ontario. Genotyping was done using isolated genomic DNA and standard PCR as previously described (9). All aspects of this study were conducted in accordance with the policies and guidelines set forth by the Canadian Council on Animal Care and were approved by the Animal Use Committee of the University of Western Ontario.…”

Adenosinergic Regulation of Striatal Clock Gene Expression and Ethanol Intake During Constant Light

“…In this regard, the present findings illustrate the pitfalls of relying on open-field locomotor testing, which is typically brief (p1 h) and performed during the daytime, when rodents sleep. The present data provide a relevant example: genotype differences in activity only occurred at night, whereas daytime circadian and open-field activity is comparable in ENT1 KO and WT mice (Chen et al, 2007;Choi et al, 2004;Ruby et al, 2011). As cellular timing controls the expression of many genes and proteins (Lowrey and Takahashi, 2004;Miller et al, 2007), the time of day at which experiments are performed may be critical in determining the contribution of genes and proteins to behavior.…”

Loss of equilibrative nucleoside transporter 1 in mice leads to progressive ectopic mineralization of spinal tissues resembling diffuse idiopathic skeletal hyperostosis in humans

“…ENT1 -/-mice have also been shown to exhibit reduced anxiety-like behaviors. (43) Levels of endogenous extracellular adenosine were not reported in these studies.…”