ROLE OF SYMPATHETIC CHOLINERGIC PATHWAY IN THE NEUROGENOUS CONTROL OFTISSUE-TYPE PLASMINOGEN-ACTIVATOR RELEASE INTO THE BLOOD

The changes in conductivity of skeletal muscle vessels of the hind leg and tissue-type plasminogen activator (t-PA) activity in outflowing b lood after electrostimulation (5 V, 0.5 ms, 20 Hz, 30 s) at the L4-L5 level of the peripheral end of the transected isolated sympathetic cha in were studied in experiments on anaesthetized cats. Stimulation of t he sympathetic chain induced vasoconstriction and release of t-PA from the vascular wall into the blood. Pretreatment with the beta-adrenobl ocker propranolol neither changed the character of vascular reactions nor blocked t-PA secretion. Efferent stimulation of the sympathetic ch ain against a background of beta-adrenoceptor blockade by dihydroergot oxin increased blood flow and was accompanied by a rise in t-PA activi ty. The M-cholinergic blocker atropine suppressed both vascular relaxa tion and release of t-PA into the blood. Vasodilatation accompanied by t-PA secretion could be induced by intraarterial infusion of acetylch oline and blocked by atropine. The existence of a neurogenic mechanism controlling t-PA release from the vascular wall involving a sympathet ic cholinergic pathway and connected with excitation of vascular M-cho linoceptors by acetylcholine is suggested.