abstract
- These experiments were performed to further elucidate the nature of the vasodilator fibers running in the sympathetic chain in the dog. The electrostimulation of the lumbar sympathetic trunk caused vasoconstriction in the perfused hind limb which inverted to vasodilatation after guanethidine was administered. This vasodilator response is mediated by cholinergic fibers since it was completely abolished by atropine. The observation, furthermore, that hexamethonium completely nullified both vasodilator and vasoconstrictor responses to the electrostimulation of the sympathetic chain indicates that both vasoconstrictor and vasodilator fibers, which are activated during the stimulation of the sympathetic chain, are preganglionic in nature.