Chemosensitive neurons with C-fiber vagal afférents in the rat heart can he activated hy oxygen free radicals (OFR), and this activation is abolished by antioxidants (Circ.Res. 74: 895-903. 1994). Antioxidants also diminished the response of cardiac vagal afferent fibers 10 capsaicin. The question arouse if OFR formation modulates the sensitivity of afferent endings in the heart to chemical stimuli. We recorded the activity of cardiac Chemosensitive endings with vagal and sympathetic afférents in rats in response to topical applications of capsaicin and bradykinin to their receptive field. Capsaicin (1 μg) increased the activity of sympathetic fibers by 86±21% and bradykinin (1 μg) by 47±159,. Activation of OFR production hy iv administration of xanlhine+xanthine oxidase (1 μmol+30 mU) significantly increased the responses of sympathetic afferent fibers to the same doses of capsaicin and bradykinin by 279+43% and 152+2X91., respectively. Administration of the Superoxide radical scavenging enzymc Superoxide dismutase (20,000 U/kg. iv) or metal ion chelaior deferoxamine (20 mg/kg. iv), conversely, significantly diminished the responses of both sympathetic and vagal afférents to capsaicin and bradykinin. These data indicate that activation of OFR production increases the sensitivity of cardiac Chemosensitive endings to capsaicin and bradykinin. while inhibition of OFR production by antioxidants decreases the sensitivity of afferent fibers Hi these chemical agonists. Supported by HL-52190.
|Original language||English (US)|
|State||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology