Substance p anatogue blocks sp-induced facilitation of a spinal nociceptive reflex

Intrathecal administration of 10 micrograms (6.5 nmoles) of substance P to the lumbar spinal cord of the awake, restrained rat had a biphasic effect on reaction time in the tail-flick test. This effect consisted of an initial decrease at one min after administration, followed five min later by a smaller increase in reaction time. When substance P was given after prior intrathecal administration of 1.55, 3.1 or 6.2 nmoles of [D-Pro2, D-Phe7, …