Smooth-muscle effects of substance P.
The effects of substance P (SP) on smooth-muscle contractions induced by noradrenaline (NA) or by high- or low-frequency electrical stimulation (ES) were studied on isolated rat vas deferens and musculus anococcygeus. Neither the contractile effects of NA nor those of high-frequency ES were significantly changed by SP. The peptide in concentrations of 1 x 10(-7) M and 1 x 10(-6) M strongly potentiated (up to 70%) vas deferens contractions in response to low-frequency ES but slightly reduced those of musculus anococcygeus. Inhibition of the opiate receptors by 1 x 10(-6) M naloxone did not change the potentiating SP-effect on vas deferens contractions. Blockade of the prostaglandin (PG) receptors by polyphloretin phosphate (PPP), 5 micrograms/ml, or of the PGs synthesis by indomethacin, 5 x 10(-6) M, resulted in a slight increase of the SP-potentiating effect. The present results suggest that specific presynaptic SP-receptors (excitatory or inhibitory) play a major role in the mechanism of the potentiating action of substance P.
Zamfirova
R
R
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Todorov
S
S
D000818:Animals; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000494:pharmacology*; D013564:Sympathetic Nervous System / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects; D014649:Vas Deferens / Q000187:drug effects
D013373:Substance P; D007213:Indomethacin