抄録
The effects of baroceptor reflex on mean cardiac (MCSNA) and renal sympathetic nerve activity (MRNA) were analyzed before and after atropinized (0.1mg/kg, i.v.) states in conscious cats at rest. Resting values of MCSNA, MRNA, mean aortic pressure (MAP), and heart rate (HR) were 85±6imps/s, 76±11imps/s, 100±4mmHg, and 164±10beats/min, respectively. Both MCSNA and MRNA changed almost inversely to changes in the absolute MAP in the range of 90-140mmHg. Within this pressure range the gain of baroceptor-sympathetic system to the heart and kidney was 2.31 and 1.84, respectively. MCSNA as well as MRNA was reduced to the noise level at the MAP of 142 and 150mmHg, respectively. With atropine, MCSNA and MRNA were inhibited centrally whereas HR increased to 192beats/min. The increase in MAP caused by norepinephrine (2.1μg/kg, i.v.) was enhanced to 75±7mmHg by atropine from 31±4mmHg in control. The piecewise linear MAP-MCSNA and MAP-MRNA relationships changed to a remarkable clockwise hysteresis loop. During the rising MAP period, the gain of the baroceptor-sympathetic system decreased to 0.91 and 0.97 in MCSNA and MRNA, respectively. During the returning MAP period, a delayed activation in MCSNA and MRNA occurred centrally. We conclude that the baroceptor reflex effect on MCSNA is larger than those on MRNA, and that the baroceptor control of MCSNA and MRNA is modified centrally by atropine in the awake cat at rest.
