Action of potassium on neurochemical transmission at the cardiac adrenergic neuroeffector junction with aging.
The effect of age on potassium (K+)-induced norepinephrine release in the heart was studied in 6- and 24-month-old male Fischer-344 rats. Isolated hearts were perfused with Krebs-Ringer solution according to Langendorff method. K+ was employed as 2 ml bolus at the concentrations, of 70, 90, 100 and 120 microM. Norepinephrine content was measured by high pressure liquid-chromatography/electrochemical detection methodology. At each of the K- concentrations, the amount of norepinephrine released from preparations of 6-month-old animals was significantly greater than observed from preparations of 24-month-old animals. Since K(+)-induced release of norepinephrine is associated with calcium influx, the decrease in the capacity of K+ to cause norepinephrine release with age supports the hyothesis that diminution in transmitter release is due to altered calcium function.
Tumer
N
N
Department of Pharmacology, Medical College of Pennsylvania, Philadelphia, PA 19129.
Ryan
P J
PJ
Roberts
J
J
D000367:Age Factors; D000818:Animals; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000493:pharmacokinetics*; D051381:Rats; D011916:Rats, Inbred F344
D011188:Potassium; D009638:Norepinephrine