Neurochemical profile of dorsal root ganglion neurons innervating the canine ventricle

Abstract

Dorsal root ganglion (DRG) sensory neurons innervating the canine ventricle were identified by retrograde tracing with horseradish peroxidase (HRP and cholera toxin β subunit-conjugated HRP) injected into the anterior left ventricle and right ventricular outflow tract. DRG’s (T1-T4) were harvested 7 days post injection, sectioned and immunostained for HRP and combinations of calcitonin gene-related peptide (CGRP), substance P (SP), or neuronal nitric oxide synthase (nNOS). At the T3 level, 19+6% (mean ±SD) of the DRG neuronal population was immunolabeled for CGRP, 11%±3 for SP, and 6±3% were double labeled for CGRP and SP. Of this population, 2% were immunolabeled for HRP. Of these HRP-labeled DRG neurons, 23±17% exhibited positive staining for CGRP, 3±4% for SP (p<0.02 versus % SP positive in total population), and 13±9% were tripled labeled (HRP, SP and CGRP). Thirty-one percent of HRP-labeled DRG neurons exhibited nNOS immunoreactivity. These data support the emerging concept of afferent heterogeneity in sensory processing of the ventricular milieu. They also suggest that the neurochemical profile for DRG sensory afferents is differentially expressed, depending upon the target organ. (HL71830).