Somatostatin potentiates cholinergic neurotransmission in ferret trachea.
We studied the effect of somatostatin on contractile responses to electrical field stimulation (EFS) in isolated ferret tracheal segments. Somatostatin (up to 10(-5) M) did not change resting tension, but it potentiated the contractile response to EFS dose dependently, with a maximum effect at 10(-6) M. Thus, at a concentration of 10(-6) M, somatostatin significantly decreased the mean log of EFS frequency producing 50% of maximum contraction from a control value of 0.52 +/- 0.07 to 0.24 +/- 0.06 (SE) Hz (P less than 0.01). The potentiating effect of somatostatin (10(-6) M) was not inhibited by hexamethonium, indomethacin, BW755C, pyrilamine, methysergide, or D,Pro2,D,Trp7,9-SP, but it was inhibited by atropine or by the somatostatin antagonist cyclo[7-aminoheptanoyl-Phe-D-Trp-Lys-Thr(Bzl)]. In contrast to EFS-induced contraction, contractions produced by acetylcholine (10(-9) to 10(-3) M) were not affected by somatostatin at a concentration of 10(-6) M. These results suggest that somatostatin potentiates contractions produced by EFS via presynaptic cholinergic mechanisms and probably through a specific somatostatin receptor.
Sekizawa
K
K
Cardiovascular Research Institute, University of California, San Francisco 94143-0130.
Graf
P D
PD
Nadel
J A
JA
D000818:Animals; D004558:Electric Stimulation; D005289:Ferrets; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D010275:Parasympathetic Nervous System / Q000187:drug effects*; D013004:Somatostatin / Q000494:pharmacology*; D009435:Synaptic Transmission / Q000187:drug effects*; D014132:Trachea / Q000187:drug effects* / Q000294:innervation / Q000502:physiology
D013004:Somatostatin