Received July 27, 2005
Revised September 9, 2005
Accepted after revision October 4, 2005

¹ Osaka University
² Kyushu University

^* To whom correspondence should be addressed. E-mail: naohayashi{at}ihs.kyushu-u.ac.jp.

	Abstract

We investigated the role played by the exercise pressor reflex in sympathetic regulation of renal circulation in rats. In mid-collicular decerebrate rats, mean arterial pressure (MAP), heart rate (HR), left renal cortical blood flow (RCBF), and left renal sympathetic nerve activity (RSNA) were recorded before and during 30 s of static contraction of the left triceps surae muscles evoked by electrical stimulation of the tibial nerve, which activates both metabo- and mechano- sensitive muscle afferents, and during 30 s of passive stretch of the left Achilles tendon, which selectively activates mechano- sensitive muscle afferents. Static contraction (n=17, +344 ± 34 g developed tension) significantly (p<0.05) increased MAP (+14 ± 3 mmHg), HR (+6 ± 1 bpm), and RSNA (n=11, +19 ± 5 %), and significantly decreased renal cortical vascular conductance (n=11, RCVC, -11 ± 2 %). Passive stretch (n=20, +378 ± 11 g) also significantly increased MAP (+11 ± 2 mmHg), HR (+7 ±2 bpm), and RSNA (n=15, +14 ± 4 %), and significantly decreased RCVC (n=11, -12 ± 3 %). RCBF showed no significant changes during static contraction or passive stretch. Renal denervation abolished the decrease in RCVC during contraction (n=12) or stretch (n=13). These data indicate that both the exercise pressor reflex and its mechanically- sensitive component, the muscle mechanoreflex, induced renal cortical vasoconstriction through sympathetic activation in rats.

Key Words: Exercise, Reflex, Sympathetic activity

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