Intrinsic Vasomotion in the Dogfish Gill

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Abstract
1. The circulatory response of anaesthetized curarized Squalus acanthias to anoxia of 2 min. duration is described. Anoxia was evoked either by perfusing the pharynx with deoxygenated sea water or by stopping the flow of normal sea water. 2. Ventral aortic blood pressures increased (systolic: 29.6-37.9 mm. Hg; mean: 24.1-27.1 mm. Hg) during a period of 2 min. Concurrently dorsal aortic blood pressures fell (systolic: 17.3-14.1 mm. Hg; mean: 16.3-12.4 mm. Hg). The heart slowed from 38 to 20 per min. The opacity of the gill, recorded with a phototransducer, decreased. 3. Comparison of simultaneous pulse traces from the dorsal and ventral aortae demonstrated that the pressure drop across the gills was increased during anoxia and decreased after it. 4. In some, but not all, experiments the dorsal aortic pulse pressure diminished as the ventral aortic pulse pressure increased. 5. Neither cutting all the branchial nerves nor atropinization completely abolished these responses. 6. Possible explanations of these findings are discussed; it is concluded that anoxia evoked a constriction of some prelamellar elements in the branchial vessels and that the response was, at least in part, intrinsic to the gill