Role of the central alpha-receptors in the modulation of carotid sinus reflex of rats
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abstract
To investigate the effects of the central alpha-receptors on the carotid sinus reflex, phenoxybenzamine (PBZ, 2 micrograms/20 microliters) or yohimbine (Y, 2 micrograms/20 microliters) was injected into the lateral cerebral ventricle (LCV) and intracarotid sinus pressure (ISP)-mean arterial pressure (MAP) relationship curve was constructed and fitted by a Logistic function. The results were as follows: (1) After injection of PBZ into LCV, the ISP-MAP relationship curve shifted upward at a higher ISP level with decreased peak slope and MAP range while the ISP-slope curve shifted downward. (2) After injection of Y into LCV, the ISP-MAP relationship curve shifted upward at a higher ISP level with decreased peak slope and MAP range and increased threshold. The ISP-slope curve shifted downward significantly at 10.64, 15.96 kPa. The peak slope and MAP range of Y group decreased significantly as compared with that of the PBZ group. These results indicated that after blockage of central alpha-receptors the sensitivity of the sinus reflex decreased significantly, and the blockage action of alpha 2-receptor is greater than that of alpha 1-receptor.
