Characteristics of brachiocephalic and carotid sinus baroreceptors with non-medullated afferents in rabbit.
The characteristics of brachiocephalic and carotid sinus baroreceptors with non-medullated afferents have been studied in rabbits. The conduction velocities of 18 non-medullated fibers arising from the brachiocephalic baroreceptors were 0.4-0.8 m/s (0.59 +/- 0.03 m/s, mean +/- SE) and their thresholds were 74-104 mmHg (84 +/- 2 mmHg). 29 non-medullated carotid sinus baroreceptor afferents had thresholds ranging from 60 to 125 mmHg (92 +/- 3 mmHg). Their conduction velocities were 0.5-1.1 m/s (0.65 +/- 0.05 m/s). Blood pressure-baroreceptor response curves of both the brachiocephalic and the carotid sinus baroreceptors were constructed. As the aortic arch non-medullated baroreceptor afferents, the brachiocephalic and the carotid sinus baroreceptors with non-medullated afferents exhibited thresholds about 30 mmHg higher than the medullated ones, considerably lower firing rates, comparatively rapid adaptation and remarkable irregular discharge pattern. It is suggested that the non-medullated baroreceptor afferents are of little importance for the cardiovascular regulation under normal conditions but are likely to play an important role during a sudden rise in arterial pressure.
D000222:Adaptation, Physiological; D000818:Animals; D001158:Arteries / Q000502:physiology; D001794:Blood Pressure; D016122:Brachiocephalic Trunk / Q000294:innervation*; D002346:Carotid Sinus / Q000294:innervation*; D005260:Female; D008297:Male; D009431:Neural Conduction; D009475:Neurons, Afferent / Q000502:physiology*; D011311:Pressoreceptors / Q000502:physiology*; D011817:Rabbits; D012684:Sensory Thresholds