Abstract
Electrical field stimulation (EFS), transmural nerve stimulation, was utilized to investigate autonomic nerve innervation of cat pulmonary artery. EFS (duration; 0.8 msec or 1.0 msec, frequency; 20 Hz, voltage; 70 V, for 15 sec) induced small fast constriction followed by large prolonged relaxation on prostaglandin H2 analog-precontracted cat pulmonary arterial strip which was suspended in a 10ml organ bath. The small fast constriction was blocked or considerably reduced by addition of phenoxybenzamine. The relaxation was partially blocked in some strips by addition of atropine and/or propranolol. Teterodotoxin or lidocaine not only blocked relaxation which was not blocked by atropine or propranolol, but also farther reduced or completely blocked the relaxation which was partially blocked by atropine and/or propranolol. It is concluded that (1) α-adrenergic nerve regulates pulmonary arterial constriction, (2) β-adrenergic and cholinergic regulations may be present, but their roles may be substantially small and (3) non adrenergic non cholinergic nerve may play major roles in inhibitory regulation of cat pulmonary circulation.
