Substance P(SP) has been known to be a peptide which may be plays a role as a neurotransmitter in central nervous system as well as peripheral autonomic nervous system. It has been reported that SP was widely destributed in the nerve of the
tracheal
smooth muscle and induced the muscle was not clear, yet.
Thus, present experiment was performed to elucidate an effect of substance P and an action mechanism on contraction of the smooth muscle in rabbits. In order to find a neural mechanism to the effect of SP on the tracheal smooth muscle
contraction,
atropine sulfate, tetrodotoxin, propranol and phentolamine were administered at 10 min before the addition of SP. Otherwise, to find effect of SP antagonists on the action of SP, (D-Pro2, D-Try7, 9)SP, (D-Argl, D-Pro2, D-Trp7.9, Leu11) SP and
(D-Pro4,
D-Trp7,9)SP were administered as a same fashion.
@ES These following results were obtained.
@EN 1) SP induced contraction of the tracheal smooth muscle under resting condition and the contraction was increased dose-dependently.
2) Cholinergic blocker(atropine), neural blocker(tetrodotoxin) and adrenergic blocker(propranol and phentolamine) didn't have an effect on the contractile response.
3) Three SP antagonists inhibited the contractile response.
4) Isoproterenol relaxed the contraction induced by SP.
The above results suggested that SP induced contraction of the tracheal smooth muscle directly act to the smooth muscle in rabbits. The autonomic nervous system did not seem to participate in the SP action. (Korean J Thoracic Cardiovas Surg 1994;
27:9-14)
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