Daily spontaneous running did not alter vagal afferent reactivity

Scislo, Tadeusz J., Stephen E. DiCarlo and Heidi L. Collins. Daily spontaneous running did not alter vagal afferent reactivity. Am. J. Physiol. 265 (Heart Circ. Physiol. 34): Hl564-H1570, 1993. This is an important paper in our field since it is one of two by this group to address whether altered control of sympathetic outflow is due to peripheral adaptations in afferent sensitivity. In the present study, Tadek Scislo and Steve DiCarlo examined the sensivity of cardiopulmonary receptor afferents in wheel running rats and sedentary rats. They did so by recording directly from these afferents and producing two different types of stimuli to the animals. Since these afferents can be sensitive to stretch (i.e. low pressure volume receptors) they tested their sensitivity to increases in left atrial pressure. Since these afferents are also be sensitive to chemical stimuli during that produced during hypoxia, for example, they tested their responsiveness to the 5HT receptor agonist phenylbiguanide. The results were that spontaneously running rats had no difference in their afferent sensitivity to either stimuli compared to sedentary controls. These data suggested that alterations in cardiopulmonary reflex control were due to central adaptations (i.e. in the brain) rather than in the periphery at the level of the afferents themselves. This and the next paper would be good for students to quote in their thesis since it provides evidence of changes in the brain being responsible for difference in sympathetic output in physically active versus sedentary animals. ~PJM