Key result
Preventing arterial pressure changes during acute sympathetic activation yielded an SNA-nUF slope of -0.143 μL·min−1·kg−1·%−1 compared to 0.444 μL·min−1·kg−1·%−1 when pressure was variable.
Why the study?
During primary acute sympathetic activation, arterial pressure changes with sympathetic nerve activity, confounding the neurally mediated antidiuretic effect with pressure diuresis.
Does fixing mean arterial pressure during acute sympathetic activation allow direct estimation of the neurally mediated antidiuretic effect in anesthetized rats?
Does fixing mean arterial pressure during acute sympathetic activation allow direct estimation of the neurally mediated antidiuretic effect in anesthetized rats?
Absolute Event Rate: -0.143% vs 0.444%
Fixing mean arterial pressure during acute sympathetic activation reveals that the potency of the neurally mediated antidiuretic effect is 0.235 ± 0.014 relative to the effect of pressure diuresis.
Animal findings on neural antidiuresis require validation before clinical use; leaves open translation to human sympathetic volume control.
We examined urine excretion during primary acute sympathetic activation (PASA) in anesthetized Wistar-Kyoto rats. Since arterial pressure (AP) changes with sympathetic nerve activity (SNA) during PASA, urine excretion reflects a neurally mediated antidiuretic effect combined with an effect of pressure diuresis. We hypothesized that preventing AP changes under PASA would enable the direct estimation of the neurally mediated antidiuretic effect alone. We changed the isolated carotid sinus pressure stepwise from 60 to 180 mmHg and compared the relationship of normalized urine flow (nUF, urine flow normalized by body weight) versus SNA between conditions allowing and preventing baroreflex-mediated changes in the mean AP. The slope of the SNA-nUF relationship was [Formula: see text]nUF var = 0.444 ± 0.074 μL·min −1 ·kg −1 ·% −1 when the mean AP was variable, whereas it was [Formula: see text]nUF fix = −0.143 ± 0.032 μL·min −1 ·kg −1 ·% −1 when the mean AP was fixed at 100 mmHg ( n = 7 rats). The slope associated with the effect of pressure diuresis alone, calculated as [Formula: see text]nUF var − [Formula: see text]nUF fix , was 0.586 ± 0.105 μL·min −1 ·kg −1 ·% −1 . Hence, the potency of the neurally mediated antidiuretic effect |[Formula: see text]nUF fix |/([Formula: see text]nUF var − [Formula: see text]nUF fix ) was 0.235 ± 0.014 relative to the effect of pressure diuresis under PASA. Our findings would aid an integrative understanding of the effects of renal hemodynamic and sympathetic modulations on urine output function.
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Kawada et al. (2022) studied Primary acute sympathetic activation (n=7). Preventing baroreflex-mediated changes in mean arterial pressure (fixed at 100 mmHg) vs. Allowing baroreflex-mediated changes in mean arterial pressure (variable) was evaluated on Slope of the sympathetic nerve activity to normalized urine flow (SNA-nUF) relationship. Preventing arterial pressure changes during acute sympathetic activation yielded an SNA-nUF slope of -0.143 μL·min−1·kg−1·%−1 compared to 0.444 μL·min−1·kg−1·%−1 when pressure was variable.
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