The conduction velocity of the descending spinal pathway to the renal sympathetic nerve in the cat

Abstract

The conduction velocity of the descending spinal excitatory pathway to the renal sympathetic nerve was measured in five chloralose-anaesthetised, spinal cats (C1 transection). Electrical stimuli were delivered to the dorsolateral funiculus at three levels between segments C3 and T6, and responses recorded from the ipsilateral renal nerve. Spinal conduction velocity was calculated as 4.4 ± 0.4 m/s (mean ± SEM), from the latency difference of renal nerve volleys to stimulation at different cord levels. A contralateral pathway to the renal nerve was identified: this also ran in the dorsolateral funiculus, and crossed below segment T5. It conducted at 4.1 and 7.9 m/s (two cats). Renal preganglionic conduction velocity (greater splanchnic nerve) was 4.1 and 5.0 m/s (two cats). As the renal sympathetic nerve is functionally homogeneous [5], these conduction velocity measurements are of a functionally-defined sympathoexcitatory pathway.