Stimulation of the renal sympathetic nerve in young pigs with biphasic pulses of current (3 mA, 800 microseconds per phase, 5, 10 and 50 Hz) produced decreases in arterial and cortical blood flow in the kidney, with the greatest decreases occurring at the highest stimulus frequencies. The decrease in cortical flow lagged that in arterial flow by 1.53-1.99 s; the delay increased with decreasing frequency but was unaffected by captopril, an angiotensin-converting enzyme-blocking agent. This result was consistent with the hypothesis that stimulation of the sympathetic nerve causes constriction first in the afferent arteriole and then in the efferent arteriole. Systemic arterial pressure increased during stimulation of the nerve; the increase was greater in intact nerves than in nerves that had been crushed proximal to the point of the stimulus, indicating that pigs do have renal afferent nerves. Pressure increased after the stimulus ended, but the increase abated or changed to a decrease after administration of captopril. The changes in flow were unaffected by administration of captopril, but were markedly reduced by the blocking agent labetalol (renal arterial flow, 77 +/- 14 per cent; cortical flow, 70 +/- 12 per cent). Thus, the observed changes in flow resulted from direct stimulation of the sympathetic nerves and not from stimulation of the renin-angiotensin system, which affects the pressure response after the stimulus.
The conduction velocity of peripheral nerves is an indication of their growth.
Ulnar nerve conduction velocity, forearm length, postpartum age and weight were measured
in 25 monkeys (Macaco nemestrina) to determine the best way to estimate gestational age.
Correlation analysis showed that while conduction velocity is strongly correlated with
gestational age (r = 0.68), both forearm length (r = 0.91) and weight (r = 0.94) are more
strongly correlated. Of the three simple measurements made, weight provides the best
estimate of gestational age.
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