In vivo detection of endogenous acetylcholine release in cat ventricles.
To detect and monitor endogenous acetylcholine (ACh) release in the in vivo heart, we applied a dialysis technique to the hearts of anesthetized cats. Dialysis probes were implanted in the left ventricular myocardium and were perfused with Krebs-Henseleit solution containing Eserine (10(-4) M) at 3 microliters/min. Dialysate ACh concentration was measured with high-performance liquid chromatography. In four cats, the response to vagal stimulation was studied. Electrical stimulation of efferent vagal nerves (10 Hz) significantly increased dialysate ACh concentration from 596 +/- 118 (control) to 12,210 +/- 1,661 pM. After stimulation, dialysate ACh concentration significantly decreased to 382 +/- 80 pM below control. The influence of ganglionic blocker was determined in six cats. Control vagal nerve stimulation (10 Hz) increased dialysate ACh concentration from 582 +/- 136 to 9,102 +/- 754 pM. Local perfusion of hexamethonium (10(-4) M) did not affect this nerve stimulation-induced ACh increase (8,611 +/- 1,189 pM), and intravenous administration of hexamethonium (20 mg/kg) prevented this increase (340 +/- 88 pM). We examined the response to vagal nerve stimulation at different frequencies in three cats. Vagal nerve stimulation increased dialysate ACh concentration from a control of 588 +/- 211 to 1,227 +/- 195 pM at 2 Hz, 3,946 +/- 1,059 pM at 5 Hz, and 9,366 +/- 1,873 pM at 10 Hz. Dialysate ACh concentration reflects ACh release from postganglionic vagal nerves innervating the left ventricular myocardium; the dialysis technique permits estimation of relative changes in efferent cardiac vagal nerve activity.
Akiyama
T
T
Department of Cardiac Physiology, National Cardiovascular Center Research Institute, Osaka, Japan.
Yamazaki
T
T
Ninomiya
I
I
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002415:Cats; D002851:Chromatography, High Pressure Liquid; D004558:Electric Stimulation; D005260:Female; D005730:Ganglionic Blockers / Q000494:pharmacology; D006352:Heart Ventricles; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009994:Osmolar Concentration; D014630:Vagus Nerve / Q000502:physiology
D005730:Ganglionic Blockers; D006584:Hexamethonium Compounds; D018738:Hexamethonium; D000109:Acetylcholine