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  • AZ 10606120 dihydrochloride The present results revealed hig


    The present results revealed higher expression of delta opioid receptors (oprd1b) in bold relative to shy fish. To the best of our knowledge, this study is the first to relate opioid receptor gene expression to behavior in zebrafish. The delta opioid receptor has been implicated in mood and emotional responses [51], and previous research has shown that genetic AZ 10606120 dihydrochloride of the delta opioid receptor in mice is associated with anxiety-like behavior [52,53]. Bottom-dwelling behavior, low levels of exploration and low activity in the novel tank diving test, often used for interpretation about anxiety-like behavior in zebrafish [7,19], was a characteristic of the shy fish that also displayed lower expression of delta opioid receptors (oprd1b). Moreover, rats exposed to early life adverse experiences express increased exploration and risk-taking behavior in adulthood [54], accompanied by low immunoreactive levels of Met-enkephalin-Arg6-Phe7, a marker of proenkephalin [55,56], and increased expression of oprd1 [57], which is in line with the findings herein of bold fish having higher expression of delta opioid receptors.
    Conclusion The results of the current study show that boldness is associated with higher gene expression of drd2a, drd2b and oprd1b in zebrafish males. The results are correlational and additional experiments are needed to clarify the causal role of these receptors in zebrafish behavior.
    Conflict of interests
    Acknowledgements Part of the results in this manuscript has previously been presented in a Bachelor of Science in Biology project by SM ( This research was supported by the Swedish Research Council (to SW) and the FACIAS foundation (to SW and ER). The behavioral testing was carried out by support of the Uppsala University Behavioral Facility (UUBF), Disciplinary Domain of Medicine and Pharmacy, Uppsala University.
    Introduction The dopamine (DA) system is considered to be involved in most aspects of human behaviour, from motor control to cognitive and motivational domains. As a corollary, DA neurotransmission has been a central focus for research on the pathophysiology and treatment of major psychiatric disorders such as schizophrenia, affective disorders and substance use disorders. Positron emission tomography (PET) is a molecular imaging technique which allows for quantification of markers of brain neurotransmission in the living human brain, providing an opportunity to examine DA function in psychiatric populations. The majority of this work has focused on the dopamine D2/D3 receptor subtype (D2/D3-R) and the dopamine transporter [[1], [2], [3], [4]]. In contrast, the dopamine D1-receptor (D1-R), which is the most abundant receptor subtype in the brain, has received much less attention. D1-R belongs to the D1/D4/D5 receptor family, which shows opposing intracellular effects compared to D2/D3-R. Whereas D2/D3-R stimulation leads to blockade of cAMP cascade, stimulation of D1/D4/D5-R results in increased cAMP levels [5]. In the striatum, which is the most DA-rich region in the brain, these opposing effects of DA signalling are balanced by the distribution of D1-R predominantly on cells providing output via the direct nigrostriatal pathway whereas D2/D3-R expressing cells project via the indirect pathway [6]. D2/D3-R are found mainly in the striatum, in contrast the D1-R is widely distributed throughout the brain [7] (Fig. 1). Finally, D2/D3-R has high affinity for DA, and is AZ 10606120 dihydrochloride considered sensitive to tonic DA levels, whereas the relatively low affinity D1-R may primarily detect phasic changes [[8], [9], [10]]. These differences in downstream effects, connectivity and localization suggest that D1-R may serve as a functionally distinct marker of the DA system. Indeed, a specific role for D1-R has been suggested for cognitive performance [[11], [12], [13], [14]], reward signal processing [[15], [16], [17]] and response inhibition [18], all domains that are considered relevant for a range of psychiatric conditions [3,17,[19], [20], [21]].