RELEASE OF SUBSTANCE-P FROM THE ENTERIC NERVOUS-SYSTEM - DIRECT QUANTITATION AND CHARACTERIZATION

  • 1 January 1983
    • journal article
    • research article
    • Vol. 227  (2) , 365-368
Abstract
A dynamic system was developed in which in vitro release of substance P (SP) from 2 longitudinal muscle-myenteric plexus strips from the guinea pig ileum is obtained during continuous superfusion and measured directly by using a highly sensitive radioimmunoassay specific for SP. Electrical stimulation (0.5-40 Hz) produced a marked increase in the rate of release of SP. The magnitude of the increase in the rate of electrically evoked release was dependent on the frequency of stimulation, but this dependence did not appear to be linear over the entire range tested. Electrically-evoked release elicited by 20 Hz stimulation was reudced by 95% by omitting Ca2+ from the superfusion buffer or by cooling the preparation to 3.degree. C. Pretreatment with tetrodotoxin (1 .mu.g/ml for 15 min) substantially reduced the magnitude of the increase in the rate of release of SP but not abolish it. Despite tetrodotoxin pretreatment, a significant portion (53%) of the electrically-induced increase in SP release remained. The ability of electrical stimulation to release SP from the myenteric plexus in amounts sufficient to produce a physiological response in a Ca2+- and temperature-dependent fashion in combination with data provided by indirect pharmacological experiments strongly suggests that SP functions as a neurotransmitter in the enteric nervous system.

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