The effects of intrathecal sympathomimetic agents on neural activity in the lumbar sympathetic chain of rats.

Intrathecal injections of norepinephrine (0.30 mumol) and clonidine (0.035 mumol) produced decreases in neural activity recorded from the lumbar sympathetic chain and caused changes in rat thermoregulation consistent with a reduction in efferent sympathetic activity. These results support the conclusion that bulbospinal noradrenergic pathways inhibit sympathetic outflow. The data also indicate that the spinal cord is a potential site of action for clonidine.