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An afferent basis for sexual dimorphism in the aortic baroreceptor reflex of rat
Author(s) -
Chavez Grace Santa Cruz,
Li Bai-Yan,
Schild John H.
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.684.24
Subject(s) - baroreceptor , stimulation , sexual dimorphism , medicine , reflex , aorta , blood pressure , cardiology , anatomy , heart rate , chemistry , anesthesia
Our lab has shown that that female rats have a unique and functionally distinct class of low threshold, myelinated (Ah‐type) aortic baroreceptors (BR) rarely observed in males. Here, we quantify the functional role of these afferents in the parasympathetic mediated reduction of mean arterial blood pressure (MAP). Aged‐matched populations of urethane and alpha‐chloralose anesthetized naive male (n=14) and female (n = 15) rats were studied using a common protocol for bipolar electrical stimulation of the left aortic depressor nerve. The impact upon the MAP of the left femoral artery was measured in response to selective, repetitive stimulation (1–100 Hz) of myelinated (A‐type) and unmyelinated (C‐type) BR fibers. Across both populations the magnitude of the depressor response (% reduction in MAP) was similar, but for one robust and highly repeatable exception. In male rats, nerve stimulation rates below ~10 Hz failed to elicit a significant depressor response until the stimulus magnitude was increased beyond the electrical threshold for unmyelinated C‐type BR. In female rats, however, stimulation rates below ~10 Hz elicited a marked reduction in MAP at intensities well below the electrical threshold for unmyelinated C‐type BR fibers. We contend that low threshold Ah‐type BR afferents provide, at least in part, a neurophysiological basis for the sexual dimorphism in neurocirculatory control. HL072012 , HL081819