EFFECTS OF U50,488H ON ELECTRICALLY-INDUCED CYTOSOLIC CA2+ TRANSIENTS IN RAT VENTRICULAR MYOCYTES FOLLOWING CHRONIC TREATMENT WITH U50,488H
- 1 January 1995
- journal article
- research article
- Published by Cognizant, LLC in Analgesia
- Vol. 1 (4) , 723-726
- https://doi.org/10.3727/107156995819564013
Abstract
The effects of U50,488H, a specific k-opioid agonist, on the electrically-induced cytosolic Ca2+ (Ca2+ i) transients in ventricular myocytes of rat were studied. Ca2+ i transients, induced by electrical field stimulation at an intensity that elicited contraction of cardiac myocytes, were measured by a spectrofluorometric method using fura-2 as calcium indicator. During constant stimulation at 0.2 Hz, U50,488H at 3x10-5 to 3 x 10-5 M reduced the Ca2+ i transients dose- and time-dependently. The inhibitory effect of U50,488H on the Ca2+ i transient was blocked by Mr2266 (10-6 M), a specific k-receptor antagonist or pre-treatment of the myocytes with U50.488H at a subthreshold concentration (10-6 M) for 24 h (but not 16 h). In conclusion, the present study showed that chronic treatment of cardiac myocytes with U50,488H for 24 h induced tolerance to inhibitory effect of the agonist on Ca2+ i transients.Keywords
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