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Cardiovascular responses to catecholamines at 12 degrees C in the American bullfrog (Rana catesbeiana)
- Source :
- The Journal of experimental zoology. 240(1)
- Publication Year :
- 1986
-
Abstract
- The effects of epinephrine, norepinephrine, phenylephrine, and isoproterenol on blood pressure and heart rate were studied in cannulated American bullfrogs, Rana catesbeiana. The bullfrogs were chronically cannulated with a T cannula in the right sciatic artery. In warm-acclimated (22 degrees C) bullfrogs, preinjection mean systemic arterial pressure (SAP) prior to experimental treatment was 13.1 +/- 0.7 mm Hg. Preinjection heart rate was 34.8 +/- 1.8 beats per minute. These parameters were lower in cold-acclimated (12 degrees C) bullfrogs. Cold-acclimated animals had mean SAP values of 8.2 +/- 0.3 mm Hg, and heart rate was 11.1 +/- 1.1 beats per minute. Epinephrine, norepinephrine, and phenylephrine increased blood pressure to an equivalent degree in warm- and cold-acclimated animals. Dose-related decreases in heart rate in response to these catecholamines were observed in warm- but not in cold-acclimated bullfrogs. Warm-acclimated animals were more responsive to isoproterenol from 0.03 micrograms/kg body weight (bw) to 10 micrograms/kg bw than were cold-acclimated animals. The response to isoproterenol was effectively blocked by propranolol (5 mg/kg bw) in both warm- and cold-acclimated animals. Propranolol alone decreased mean SAP in both warm- and cold-acclimated animals, suggesting blockade of endogenous sympathetic activity. Beta receptor response thus appears diminished, but not absent at 12 degrees C. However, the alpha receptors responsible for elevation of blood pressure equally responsive at 12 degrees and 22 degrees C.
- Subjects :
- Male
medicine.medical_specialty
Epinephrine
Acclimatization
Hemodynamics
Blood Pressure
Propranolol
Biology
Norepinephrine (medication)
Norepinephrine
Phenylephrine
Catecholamines
Heart Rate
Internal medicine
Heart rate
medicine
Animals
Rana catesbeiana
Isoproterenol
General Medicine
Cold Temperature
Endocrinology
Blood pressure
Catecholamine
Animal Science and Zoology
Female
medicine.drug
Subjects
Details
- ISSN :
- 0022104X
- Volume :
- 240
- Issue :
- 1
- Database :
- OpenAIRE
- Journal :
- The Journal of experimental zoology
- Accession number :
- edsair.doi.dedup.....de8a6b6f4a4c0a463e25a95f93583f2b