Moss, NG; Karastoianova, IV

Journal of the Autonomic Nervous System [J. AUTON. NERV. SYST.], vol. 63, no. 3, pp. 107-114, Apr 1997

Multiunit afferent renal nerve activity (ARNA) and single unit activity from R2 chemoreceptors were recorded in anesthetized male Sprague Dawley rats during rapid and graded increases in intrapelvic pressure. Multiunit ARNA in 9 rats was excited by rapid intrapelvic pressure increases to 20 mmHg with non-diuretic urine (285.5 plus or minus 76.2% above control) but not when isotonic saline was used to fill the pelvis (13.0 plus or minus 9.0%). Similar responses were recorded from 27 single R2 chemoreceptors. Multiunit ARNA showed a direct, linear relationship with ramp increases in intrapelvic pressure between 0 and 20 mmHg at rates of 0.05, 0.15 and 0.3 mmHg /s. The responses were dynamically linked to intrapelvic pressure and maximum activations showed a positive linear relationship with the rate of pressure increase. Individual R2 chemoreceptor activity showed a similar dynamic relationship with intrapelvic pressure. ARNA was also excited by intrapelvic backflow of diuretic urine (10% expansion of extracellular volume) but the response in impulses/s was depressed by 58.6 plus or minus 9% in multiunit preparations and 30.1 plus or minus 10.8% for R2 chemoreceptors. Basal activities were also reduced during diuresis by 49.0 plus or minus 16% and 36.7 plus or minus 12.3% for multiunit and single unit preparations, respectively, and the percent increases over background during urine backflow were not different in non-diuresis and diuresis. Both multiunit ARNA and R2 chemoreceptors were also activated by ramp increases in intrapelvic pressure during diuresis, but the dynamic component was lost and responses to each pressure ramp were not different. The similarity in responses between multiunit ARNA and individual R2 chemoreceptors indicates that the multiunit ARNA activation during intrapelvic pressure increases is largely composed of activity from R2 chemoreceptors.