Late onset of NMDA receptor-mediated ventilatory control during early development in zebrafish (Danio rerio)

• Increased ventilation frequency (f(V)) in response to hypoxia in adult fish depends on ionotropic N-methyl-D-aspartate (NMDA) receptors. Nonetheless, the ontogeny of central control mechanisms mediating hypoxic ventilatory chemoreflexes in lower vertebrates has not been studied. Therefore, the aim of this study was to determine when the hypoxic ventilatory response during zebrafish (Danio rerio) development is mediated via NMDA receptors, by performing physiological experiments and western blot analysis of NMDA receptor subunits. Zebrafish larvae at stages 4-16 days post-fertilisation (dpf) were exposed to an hypoxic pulse in control groups and in groups treated with MK801 (NMDA receptor antagonist). The hypoxic increase in f(V) was present at all larval stages, and it matured during development. The reflex became MK801 sensitive at 8 dpf, but did not completely rely on a glutamatergic transmission until 13 dpf This, together with changing subunit composition during the different stages (increasing amounts of NMDAR1 subunits and appearance of NMDAR2A subunits in adults), suggests that the amount of functional NMDA receptors needed to achieve a fully developed reflex is not attained until later stages. Furthermore, our results suggest that other non-NMDA receptor mechanisms are responsible for the hypoxia-induced increase in f(V) during the earlier developmental stages. (c) 2005 Elsevier Inc. All rights reserved.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Keyword

teleost

fish

hypoxia

chemoreflex

respiration

nmda receptors

ontogeny

digital motion analysis

nucleus-tractus-solitarii

1st gill arch

glutamate receptors

excitatory actions

developing rat

in-vivo

gaba

expression

hypoxia

neurons

Publication and Content Type

ref (subject category)

art (subject category)