. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CIRCULATORY TOLERANCE FOR GRAVITY CONTROL 30° TILT RECOVERY 183 O) X til cr z> en en LLJ cr 0. Q O O _l CD E Q. UJ LU I 100 80 60 - Systolic Diaslolic VT * * M-4 •i—§—f. -20 10 20 30 40 50 60 PHENTOLAMINE (400 ng/kg) 100 80 60 40 20 •20 -1 0 1 0 20 30 40 50 60 TIME (minutes) Figure 5. Phentolamme mesylate (400 Mg/kg) was given in the ventral aorta 10 min prior to the 30 min. 30° head-up tilt in 5 anesthetized bluefish. In Figures 5 and 7 the single plus sign indicates P < and double plus P < for each fish
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CIRCULATORY TOLERANCE FOR GRAVITY CONTROL 30° TILT RECOVERY 183 O) X til cr z> en en LLJ cr 0. Q O O _l CD E Q. UJ LU I 100 80 60 - Systolic Diaslolic VT * * M-4 •i—§—f. -20 10 20 30 40 50 60 PHENTOLAMINE (400 ng/kg) 100 80 60 40 20 •20 -1 0 1 0 20 30 40 50 60 TIME (minutes) Figure 5. Phentolamme mesylate (400 Mg/kg) was given in the ventral aorta 10 min prior to the 30 min. 30° head-up tilt in 5 anesthetized bluefish. In Figures 5 and 7 the single plus sign indicates P < and double plus P < for each fish relative to the pre-drug, or in Figure 8 pre-transection, control. The standard error bars after the drug or transection but before the tilting are paired data related to the pre- treatment control values. over several minutes until ultimately permanent cardiac standstill occurred. These pauses were nonexistent in one bluefish in which the spinal cord was transected (vagi left intact) and 80 pg/kg of intraarterial atropine sulfate was given 10 min after transection. This fish exhibited the typical tachycardia observed in other fish following administration of this dose of atropine. Discussion The fact that bluefish can maintain blood pressure during head-up tilts has been documented in a previous study (Ogilvy and DuBois, 1982). However, the exact mechanism mediating this response has not previously been elucidated. In the present investigation we were able to examine the blood pressure and heart rate re- sponse during head-up tilts in unanesthetized fish, anes- thetized fish, and in fish pretreated with various pharma- cologic blockers or those subjected to selective or com- bined surgical lesions. Unanesthetized bluefish had the highest resting blood pressure of any group studied. In addition, the resting heart rate in these fish of 55 to 65 beats/min (Fig. 2) was higher than control values of 40 to 55 beats/min ob- served in groups of anesthetized fish (Figs. 3. 4
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
