Peer Review #1 of "Acute net stress of young adult zebrafish (Danio rerio) is not sufficient to increase anxiety-like behavior and whole-body cortisol (v0.2)"

In recent years, the zebrafish (Danio rerio) has become a popular model to study the mechanisms of physiological and behavioral effects of stress, due to the similarity in neural structures and biochemical pathways between zebrafish and mammals. Previous research in this vertebrate animal model has demonstrated an increase in whole-body cortisol resulting from an acute (30-second) net handling stress, but it remains unclear whether such a stressor will concomitantly increase anxiety-like behavior. In addition, as the previous study examined the effects of this acute stressor in adult zebrafish after a brief period of isolation, it is unclear whether this stressor would be effective in eliciting cortisol increases in younger aged subjects without isolation. In the current study, young adult zebrafish (approximately 90 days post-fertilization) were briefly exposed to a net handling stressor and were subsequently subjected to either the novel tank test or the light/dark preference test. The novel tank test was used to measure exploration and habituation in response to a novel environment, and the light/dark preference test was used to measure locomotor activity and scototaxis behavior. All subjects were sacrificed 15 minutes post-stressor and were analyzed for whole-body levels of cortisol. Contrary to expectations, there was no effect of acute net handling on cortisol levels. Similarly, acute net handling did not significantly induce anxiety-like behavior during the novel tank test or the light/dark preference test. Our findings demonstrate that there are possible developmental differences in response to an acute net handling stress, as we did not observe alterations in hormonal or behavioral measures of anxiety in young adult zebrafish. Alternatively, if zebrafish are not isolated before the stressor, they may be more resilient to a brief acute stressor. These results suggest the need for a different or more intense acute stressor in order further explore neuroendocrine mechanisms and anxiety-like behavior at this developmental stage in the zebrafish animal model.

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Peer Review #2 of "Anxiety-like behavior and whole-body cortisol responses to components of energy drinks in zebrafish (Danio rerio) (v0.2)"

10.7287/peerj.7546v0.2/reviews/2 ◽

2019 ◽

Author(s):

A Sachett

Keyword(s):

Peer Review ◽

Danio Rerio ◽

Energy Drinks ◽

Whole Body ◽

Cortisol Responses

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Evidence that SLC26 anion transporters mediate branchial chloride uptake in adult zebrafish (Danio rerio)

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00327.2009 ◽

2009 ◽

Vol 297 (4) ◽

pp. R988-R997 ◽

Cited By ~ 27

Author(s):

S. F. Perry ◽

B. Vulesevic ◽

M. Grosell ◽

M. Bayaa

Keyword(s):

Mrna Expression ◽

Danio Rerio ◽

Whole Body ◽

Mrna Levels ◽

Adult Zebrafish ◽

Chloride Uptake ◽

Anion Transporters ◽

Anion Transporter ◽

Normal Water

Experiments were performed to test the hypothesis that three members of the SLC26 anion transporter gene family (SLC26a3, A4, and A6; hereafter termed za3, za4, and za6) mediate branchial Cl−/HCO3− exchange in adult zebrafish ( Danio rerio). Real-time RT-PCR demonstrated that the gill expressed relatively high levels of za6 mRNA; za3 and za4 mRNA, while present, were less abundant. Also, za4 and za6 were expressed at relatively high levels in the kidney. The results of in situ hybridization or immunocytochemistry (za3 only) experiments performed on gill sections revealed that the SLC26 transporters were predominantly expressed on the filament epithelium (especially within the interlamellar regions) and to a lesser extent on the lamellar epithelium at the base of lamellae. This distribution pattern suggests that the SLC26 anion transporters are localized to mitochondrion-rich cells (ionocytes). Transferring fish to water containing low [Cl−] (0.02 mmol/l) resulted in significant increases in branchial SLC26 mRNA expression after 5–10 days of exposure relative to fish raised in normal water [Cl−] (0.4 mmol/l); transferring fish to Cl−-enriched water (2.0 mmol/l) was without effect on mRNA levels. Transferring fish to water containing elevated levels of NaHCO3 (10–12.5 mmol/l) caused marked increases in branchial SLC26 mRNA expression between 3 and 10 days of transfer that was associated with a significant 40% increase in Cl− uptake (as measured upon return to normal water after 7 days). A decrease in whole body net acid excretion (equivalent to an increase in net base excretion) in fish previously maintained in high [NaHCO3] water, concurrent with increases in Cl− uptake and SLC26 mRNA levels, suggests a role for these anion transporters in Cl− uptake and acid-base regulation owing to their Cl−/HCO3− exchange activities.

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