Airway response by neurokinin A.
We studied the effect of neurokinin A (NKA) on tracheal smooth muscle (TSM) contraction induced by the administration of acetylcholine (ACh) intra-arterially (ia) into the tracheal circulation or bilateral vagal stimulation in 18 mongrel dogs. In five dogs, 10(-12) to 10(-7) mol of NKA was injected selectively into the tracheal circulation. The tracheal contractile response to 10(-7) mol NKA was 3.12 +/- 0.48 g/cm, 6.3 +/- 0.7% AChmax. Plasma histamine concentration in the right atrium was measured at the peak response to NKA. Plasma histamine concentration was 3.33 +/- 2.05 ng/ml after 10(-7) mol NKA (vs 0.32 +/- 0.08 ng/ml for control, p > 0.10). In the other 5 dogs, dose-response was obtained with 10(-12) to 10(-7) mol ACh 10 min before and 10 min after administration of 10(-8) mol NKA. Frequency-response relationship also was induced by electrical stimulation of the distal cut ends of the cervical vagi in the range of frequencies 1-20 Hz (constant 30 V) at 15-s intervals 10 min before and after administration of 10(-8) NKA. Considerable potentiation of the tracheal contractile response to 10(-18) to 10(-7) mol ia ACh occurred 10 min after administration of 10(-8) mol NKA (p < 0.05). Significant potentiation of the tracheal contraction to vagal stimulation at 10-20 Hz was also observed 10 min after administration of 10(-8) mol NKA (p < 0.05). We demonstrate that the substantial contractile effects of NKA on canine tracheal smooth muscle are not related to histamine release from mast cells in the respiratory tract.(ABSTRACT TRUNCATED AT 250 WORDS)
Shioya
T
T
Second Department of Internal Medicine, Akita University School of Medicine.
Kagawa
M
M
Onodera
A
A
Miura
S
S
Miura
K
K
Miura
M
M
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D016535:Bronchial Hyperreactivity / Q000503:physiopathology; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D006632:Histamine / Q000097:blood; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D015288:Neurokinin A / Q000494:pharmacology*; D010275:Parasympathetic Nervous System / Q000502:physiology; D014132:Trachea / Q000187:drug effects; D014630:Vagus Nerve / Q000502:physiology
D006632:Histamine; D015288:Neurokinin A; D000109:Acetylcholine