transparent gif


Ej inloggad.

Göteborgs universitets publikationer

Adenosinergic and cholinergic control mechanisms during hypoxia in the epaulette shark (Hemiscyllium ocellatum), with emphasis on branchial circulation

Författare och institution:
K. O. Stenslokken (-); Lena Sundin (Zoologiska institutionen); G. M. C. Renshaw (-); G. E. Nilsson (-)
Publicerad i:
Journal of Experimental Biology, 207 ( 25 ) s. 4451-4461
Artikel, refereegranskad vetenskaplig
Sammanfattning (abstract):
Coral reef platforms may become hypoxic at night during low tide. One animal in that habitat, the epaulette shark (Hemiscyllium ocellatum), survives hours of severe hypoxia and at least one hour of anoxia. Here, we examine the branchial effects of severe hypoxia (<0.3 mg oxygen 1(-1) for 20 min in anaesthetized epaulette shark), by measuring ventral and dorsal aortic blood pressure (P-VA and P-DA), heart rate (fH), and observing gill microcirculation using epi-illumination microscopy. Hypoxia induced a flow of blood in two parallel blood vessels, termed longitudinal vessels, in the outer borders of the free tip of the gill filament. Hypoxia also induced significant falls in fH, P-VA and P-DA, and a biphasic change in ventilation frequency (increase followed by decrease). Adenosine injection (1 mumol kg(-1)) also initiated blood flow in the longitudinal vessels, in addition to significant drops in P-VA, P-DA and fH, and a biphasic response in ventilation frequency (decrease followed by increase) indicating that adenosine influences ventilation. Aminophylline (10 mg kg(-1)), an A(1) and A(2) adenosine receptor antagonist, blocked the effects of adenosine injection, and also significantly reduced blood flow in the longitudinal vessels during hypoxia. In the second part of the study, we examined the cholinergic influence on the cardiovascular circulation during severe hypoxia (<0.3 mg 1(-1)) using antagonists against muscarinic (atropine 2 mg kg(-1)) and nicotinic (tubocurarine 5 mg kg(-1)) receptors. Injection of acetylcholine (ACh; 1 mumol kg(-1)) into the ventral aorta caused a marked fall in fH, a large increase in P-VA, but small changes in P-DA (suggesting increased R-gill. Atropine was able to inhibit the branchial vascular responses to ACh but not the hypoxic bradycardia, suggesting the presence of muscarinic receptors on the heart and gill vasculature, and that the hypoxia induced bradyeardia is of non-cholinergic origin. The results suggest that adenosine mediates increases in the arterio-venous circulation in the gill during hypoxia. This may serve to increase blood supply to heart and gill tissue.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
Biologiska vetenskaper
elasmobranch, blood pressure, cardiovascular, gill, shunt, bradycardia, dogfish scyliorhinus-canicula, carcharhinus-melanopterus carcharhinidae, lingcod ophiodon-elongatus, acid-base regulation, blacktip reef shark, squalus-acanthias, cardiovascular-responses, rainbow-trout, gadus-morhua, blood-flow
Postens nummer:
Posten skapad:
2007-04-23 10:32

Visa i Endnote-format

Göteborgs universitet • Tel. 031-786 0000
© Göteborgs universitet 2007