Mechanisms of Cardiovascular Compensation for Gravity in Bluefish (Pomatomus saltatrix)

¹ John B. Pierce Foundation Laboratory, New Haven, Connecticut 06519

Circulatory tolerance for gravity was examined in anesthetized and unanesthetized bluefish (Pomatomus saltatrix) tilted head up in air for short or prolonged periods. Blood pressure (BP) and heart rate (HR) were monitored using a ventral aortic catheter. During tilts in unanesthetized fish, BP decreased slightly, and tachycardia occurred. Anesthesia lowered resting BP while the response to tilting was similar to unanesthetized fish. Spinal cord transection 3 mm caudal to the obex was used to interrupt sympathetic outflow and paralyze the lower body. It produced a reduction and subsequent fall in BP during tilting. Spinal cord transection combined with vagotomy produced pronounced tachycardia, with a precipitous fall in BP with stable HR during tilting. Phentolamine mesylate (400 µg/kg) produced a fall in control BP and further reduction during tilting. When 80 µg/kg of atropine sulphate was given, tachycardia occurred and BP fell during tilting yet not below levels measured in control fish. Transient elevations of BP associated with body contractions during tilting were abolished with pancuronium bromide. Circulatory tolerance of bluefish for gravity depends upon integrity of the spinal cord and sympathetic innervation of peripheral vasculature as well as intact parasymathetic cardiac innervation. Muscular contraction of the lower body also contributes to maintaining BP during tilts.

This article has been cited by other articles:

				Y. Zhang, L. Weaver Jr., A. Ibeawuchi, and K. R. Olson Catecholaminergic regulation of venous function in the rainbow trout Am J Physiol Regulatory Integrative Comp Physiol, April 1, 1998; 274(4): R1195 - R1202. [Abstract] [Full Text] [PDF]