| AimAtrial natriuretic peptides(ANP) is a cardiac hormone which exerts natriuretic, diuretic and vasorelaxant effects. Among the many organs and vascular beds populated with ANP receptors are the vestibular and auditory organs of the inner ear. The purpose of the current study was to provide morphologic basis for the function of atrial natriuretic peptides in the cochlear microcirculation through studying its distribution on the vessels . Further animal study was undertaken to assess the potential influence of ANP on cochlear blood flow in guinea pigs so as to provide the experimental basis for the clinical drug use.MethodDistribution characteristic of ANP immunohistochemical reaction was detected by immunohistochemical technique(ABC method). Thirty guinea pigs were divided into 2 groups at random, 20 for intravenous infusion(iv.) group,and 10 for perilympha application group. According to the prelimilary results, 3 subroups(n=5) were infused with 15, 150 and 300 ng/kg/min of ANP dissolved in physiologic saline at a rate of 10μl/min for 30 min. A seperate control group was treated equivalently and infused with 0.15M NaCl. Perilympha application groups had 2 subroups: control, 500 ng/μl (dissolved in artificial perilympha). 2μ1 vehicle were dropped through tiny bone hole on the lateral wall of cochlea. A control group was treated equivalently and infused with vehicle only(artificial perilympha). Mean arterial blood pressure (MABP), transferred by forcetransducers and preamplifier, was recorded simultaneously. The laser Doppler probe was placed on the lateral wall of cochlea and CoBF was recorded at the computer. Baseline measurements of MABP and CoBF were established. Measurements were recorded during the infusion and for a recovery period for 35 min.ResultsANP immunoreactive products were found in the strial vascularis, main stem of spiral modiolar artery and the branches of SMA near the basic turn of the cochlea. But no positive immunoreactive products were found in the small branches of SMA near the other turns. In control group cochlear blood flow and MABP had no significant changes.Infusion of ANP(5ng/kg/min) induced a mild drop of MABP followed by a small elevation. CoBF, however evidenced significant 67% elevation and decreased gradually 25 minute after infusion. Infusion of higher concentration of ANP(150ng/kg/min, 300ng/kg/min) induced a similar pattern of MABP change in a dose-dependent manner. CoBF of ANP(150ng/kg/min) showed a increase approximately 70% above baseline... |
