Daily spontaneous running attenuated the central gain of the arterial baroreflex

Chen, Chao-Yin, Stephen E. DiCarlo, and Tadeusz J. Scislo. Daily spontaneous running attenuated the central gain of the arterial baroreflex. Am. J. Physiol. 268 (Heart Circ. Physiol. 37): H662-H669, 1995. This is the second in a series of papers by this group addressing whether altered afferent sensitivity explains why physically active animals have differences in control of sympathetic outflow. In this follow up study, Steve DiCarlo and Tadek Scislo recorded from baroreceptor afferents while changing blood pressure in animals that had been on running wheels versus those that had been sedentary for 8-13 weeks. When they measureed responses in the aortic depressor nerve of rats from each group, they were not different. It is important to note that the aortic depressor nerve in the rat is made up of almost exclusively baroreceptor afferent fibers; whereas this is not true of the carotid sinus nerve which also contains chemoreceptor information. Even more interesting, they did not find a significant difference in the central gain of the lumbar sympathetic nerve whereas this group had shown that renal sympathetic nerve activity was different in rabbits and a Brazilian group (Negrao et al., 1993) had shown renal was also different in rats. This supports our contention that physically activity versus inactivity affects sympathetic outflow differently. Ultimately, though, since afferent activity of the aortic depressor nerve was not different these data further support the contention that changes in control of sympathetic outflow are not due to changes in the peripheral baroreceptors but due to changes in the brain. Again, this and their previous papers would be important to quote in a student's thesis on alteratons in control of sympathetic outflow in physically active verus sedentary rats (hint, hint: Mary, Dan, and Judy!). ~PJM