. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 186 0) £ 90 E in IT 111 cc D. Q o o CD u X 70 50 30 10 -^ 80 O. LU 20 CONTROL C. S. OGILVY ET AL 30° TILT RECOVERY. -30 1 0 20 30 50 60 TRANSECTION V -30 -20 -1 0 1 0 20 TIME (minutes) 30 50 60 Figure 8. Transection of the spinal cord 3 mm caudal to the obex 20 min prior to a 30° head-up tilt for 30 min in 5 anesthetized bluensh. tilts in phentolamine pretreated fish is higher than that seen in untreated fish, while pre-tilt heart rates are com- parable in each of these groups of animals. The increased tachycardia in tilts w
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 186 0) £ 90 E in IT 111 cc D. Q o o CD u X 70 50 30 10 -^ 80 O. LU 20 CONTROL C. S. OGILVY ET AL 30° TILT RECOVERY. -30 1 0 20 30 50 60 TRANSECTION V -30 -20 -1 0 1 0 20 TIME (minutes) 30 50 60 Figure 8. Transection of the spinal cord 3 mm caudal to the obex 20 min prior to a 30° head-up tilt for 30 min in 5 anesthetized bluensh. tilts in phentolamine pretreated fish is higher than that seen in untreated fish, while pre-tilt heart rates are com- parable in each of these groups of animals. The increased tachycardia in tilts with phentolamine may reflect a higher amount of baroreceptor feedback and subsequent increased suppression of vagal efferent discharge (Ab- boud and Thames, 1983). The tachycardia which occurs during tilts appears to provide the fish with a useful means of attempting to maintain cardiac output (Fig. 11). This tachycardia is typical in humans in response to tilts (Bie el ai. 1986). We used atropine sulfate to fix the pulse at a rapid rate. As noted in results, 80 Mg/kg of atropine sulfate produced a significant increase in heart rate and in blood pressure within 1 min after administration, in horizontal fish. In- creased blood pressure while horizontal is presumably related to the increased cardiac output secondary to a higher heart rate. Venous return in the horizontal posi- tion is sufficient to keep up with the increased cardiac output. In the tilted position, venous return, and hence blood pressure, is diminished. Heart rate during tilts was unchanged from pre-tilt values and blood pressure fell significantly (Fig. 7). Although blood pressure was re- duced, it did not approximate hypotensive levels, and as a result fish tolerated 30 min of 30° head-up tilting with- out any untoward effects. They swam well when returned to the holding tank. In atropine-treated fish, sympathetic arteriolar vasoconstriction as well as lower body muscle contractions can still occur, each of
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
