Inhibitory effects of peptide YY on basal and VIP-stimulated short-circuit current in the rat jejunum: influence of technical conditions on observed results

Abstract The interaction of PYY and VIP was studied in stripped and intact rat jejunum preparations mounted in Ussing chambers. PYY decreased basal Isc in intact as well as in stripped jejunum. Stripping was necessary to evidence a stimulation of basal Isc by VIP. When PYY and VIP were administered at the same time in the serosal bath, their effects seemed additive; VIP stimulation took over when VIP was present in ten times larger amounts than PYY, while PYY inhibition predominated at isomolar concentrations (10 −7 M) of both peptides. However, when PYY was administered three to six minutes before isomolar amounts of VIP, the VIP stimulation developed without being notably hampered. At this time, however, the amount of radioimmunoassayable PYY in the serosal compartment represented still 60% of the added amount. In conclusion, the experimental conditions can significantly change the results: stripping the longitudinal muscle/myenteric plexus impairs the effect of PYY and VIP in a different fashion, while the timing and order of administration of the peptides may change the apparent interaction between VIP stimulation and PYY inhibition.