Intrathecal administration of substance P enhances cutaneous plasma protein extravasation in pentobarbital anaesthetized rats

In pentobarbital-anaesthetized rats, the intrathecal administration of substance P (SP) at T9 spinal cord level enhances plasma protein extravasation (PE) in cutaneous tissues of the back, the hind paws and the ears. This vascular response is maximum at 15 min after administration of SP (6.5 nmol), and the most striking in the skin of the hind paws. Contrary to SP, neurotensin (NT) administered intrathecally failed to enhance PE. Both peptides are however potent enhancers of PE following intravenous injection. PE elicited by intrathecal administration of SP is significantly reduced in both spinal rats and in capsaicin treated animals. These results suggest that SP but not NT may play a role as a spinal chemical mediator in peripheral vascular permeability through a supraspinal reflex mechanism involving sensory afferents.