Abstract
Neuropeptide Y (NPY) controls energy homeostasis including orexigenic actions in mammalians and non-mammalians. Recently, NPY has attracted attention as a mediator of emotional behaviour and psychosomatic diseases. However, its functions are not fully understood. We established npy gene-deficient (NPY-KO) zebrafish (Danio rerio) to assess the relationship between NPY and emotional behaviours. The NPY-KO zebrafish exhibited similar growth, but pomc and avp mRNA levels in the brain were higher as compared to wild-type fish. NPY-KO zebrafish exhibited several anxiety-like behaviours, such as a decrease in social interaction in mirror test and decreased locomotion in black-white test. The acute cold stress-treated NPY-KO zebrafish exhibited anxiety-like behaviours such as remaining stationary and swimming along the side of the tank in the mirror test. Moreover, expression levels of anxiety-associated genes (orx and cck) and catecholamine production (gr, mr, th1 and th2) were significantly higher in NPY-KO zebrafish than in wild-type fish. We demonstrated that NPY-KO zebrafish have an anxiety phenotype and a stress-vulnerability like NPY-KO mice, whereby orx and/or catecholamine signalling may be involved in the mechanism actions.
Highlights
Mammalian neuropeptide Y (NPY) consists of 36 amino acids, and is expressed both peripherally and in numerous brain regions, including the hypothalamus, amygdala, hippocampus, nucleus of the solitary tract, locus coeruleus, nucleus accumbens and cerebral cortex[1]
After microinjection of each gRNA/tracrRNA/rCas[9] in onecell-stage zebrafish embryos, genomic DNA was extracted from F0 embryos, and efficacy gRNAs for npy editing were estimated by conducting a heteroduplex mobility assay (HMA)
Zebrafish Neuropeptide Y (NPY) is upregulated during handling stress[30], and exogenous NPY injection into the brain increases food intake and suppresses anxious behaviour[21]
Summary
Mammalian neuropeptide Y (NPY) consists of 36 amino acids, and is expressed both peripherally and in numerous brain regions, including the hypothalamus, amygdala, hippocampus, nucleus of the solitary tract, locus coeruleus, nucleus accumbens and cerebral cortex[1]. Several rodent models have been used to study the mechanism underlying NPY-related psychiatric disorders, and the observed phenotypes are similar to those of human anxiety; as a result, NPY and its receptors have been targeted for depression therapy. Similar analytical methods of studying anxiety to those for mice have been developed for zebrafish, such as open field tank, black-white preference and t-maze tests[16]. The zebrafish is an excellent animal model for drug development[17], first-medicine screening[18], and studies on social behaviour[19]. ICV of NPY increases time spent in the bright white environment, a normally aversive region, in black-white preference tests that is decreased by BIBP-3226, which is a mammalian Y1 antagonist[23]. After establishing NPY-KO zebrafish, their behaviour and stress-related gene expression were analysed
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