Paper Information

Title: 

SENSITIVITY IN RATS: TACHICARDIA RESPONSE TO HYPOTENSION

Type: POSTER
Author(s): DIANAT MAHIN*,FAHIM MOHAMMAD
 
 *DEPARTMENT OF PHYSIOLOGY, SCHOOL OF MEDICINE, AHVAZ JUNDISHAPUR UNIVERSITY OF MEDICAL SCIENCES, AHVAZ, IRAN
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2009Volume 19
 
 
Abstract: 

Role of arterial baroreceptors in the regulation of arterial pressure through reflex chronotropic effect and vasoconstriction is well established but mechanisms of action of epidural morphine on cardiac functions and baroreflex sensitivity (BRS) are unclear. The aim of this study was to examine the effect of epidural administration of morphine on baroreflex sensitivity. Male rats were assigned to two groups, Group I (0.2 ml/kg normal saline), Group II (200 μg/kg, morphine sulphate). In all groups, after baseline measurements, systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) were taken 30 minutes after administration of saline or morphine sulphate. 200μg/kg naloxone was administrated intravenously and measurements were repeated 5 minutes later in all groups. Baroreceptor reflex was examined after administration of saline or morphine sulphate. Baroreflex sensitivity (HR/SBP) was calculated from the dose-response curves of sodium nitroprusside (SNP) (2.5, 5, 7.5μg/kg). All values were expressed as mean±S.E.M. Comparisons between data were made using T-Test, one-way ANOVA (P<0.05). Results showed that epidural injection of morphine produced significant fall in HR and ABP (SBP, DBP, MAP) compared with control group. These depressant effects of epidural morphine were reversed by naloxone. Our data demonstrated that SNP in dose of5 and 7.5μg/kg produced a significant fall in SBP, DBP, MAP and BRS and rise in HR.
In conclusion, these results suggest that opioidergic system may influence the haemodynamic functions. There is considerable evidence that baroreflex activity can beblunted by opioid agonists, and this effect is thought to be mediated by central opioid mechanisms.

 
Keyword(s): MORPHINE, BAROREFLEX SENSITIVITY, TACHICARDIA, HYPOTENSION, RATS
 
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