TY - JOUR
T1 - Discharge properties of group III and IV muscle afferents
T2 - their responses to mechanical and metabolic stimuli.
AU - Kaufman, Marc
AU - Rybicki, K. J.
PY - 1987/10
Y1 - 1987/10
N2 - Static contraction of the hind limb muscles induced by electrical stimulation of the ventral roots has been firmly established to reflexly increase cardiovascular and ventilatory function. Moreover, Group III and IV afferents are known to compose the afferent arm of this reflex arc. The present experiments investigated the discharge properties of Group III and IV afferents whose activation is responsible for the pressor reflex response to static contraction. In general, we found that Group III afferents were more responsive to mechanical stimuli, such as distortion of their receptive fields and tendon stretch, than were Group IV afferents. In contrast, Group IV afferents were more responsive to ischemic contraction than were Group III afferents. In addition, equal percents of Group III and IV afferents were found to be stimulated by increasing interstitial potassium to levels that were similar to those found during muscular contraction. The afferents' response to potassium adapted within seconds, while the interstitial concentration of this ion remained elevated for several minutes. This rapidly adapting response casts doubt on the effectiveness of potassium as the metabolite that signals blood supply and demand in a working muscle are improperly matched.
AB - Static contraction of the hind limb muscles induced by electrical stimulation of the ventral roots has been firmly established to reflexly increase cardiovascular and ventilatory function. Moreover, Group III and IV afferents are known to compose the afferent arm of this reflex arc. The present experiments investigated the discharge properties of Group III and IV afferents whose activation is responsible for the pressor reflex response to static contraction. In general, we found that Group III afferents were more responsive to mechanical stimuli, such as distortion of their receptive fields and tendon stretch, than were Group IV afferents. In contrast, Group IV afferents were more responsive to ischemic contraction than were Group III afferents. In addition, equal percents of Group III and IV afferents were found to be stimulated by increasing interstitial potassium to levels that were similar to those found during muscular contraction. The afferents' response to potassium adapted within seconds, while the interstitial concentration of this ion remained elevated for several minutes. This rapidly adapting response casts doubt on the effectiveness of potassium as the metabolite that signals blood supply and demand in a working muscle are improperly matched.
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M3 - Article
C2 - 3652404
AN - SCOPUS:0023426041
SN - 0009-7330
VL - 61
SP - I60-65
JO - Circulation research
JF - Circulation research
IS - 4 Pt 2
ER -