ISSN:
1432-1912
Keywords:
Temperature
;
β-Receptors
;
Guinea-Pig Atrium
;
Affinity
;
Adrenergic Drugs
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary Using electrically stimulated guinea-pig atria the influence of temperature on the contractility and on the efficacy of some β-sympathomimetic and-lytic drugs, was studied. The following results were obtained. 1. Raising the temperature of the bath fluid from 25–42°C decreased significantly the developed amplitude of contraction under control conditions, whereas dT/dt max values were not altered. The maximal developed tension induced by the sympathomimetic drugs decreased at 42°C. The corresponding dT/dt max values, on the other hand, were increased by elevation of the temperature. 2. The dose-response curves of the sympathomimetic drugs isoprenaline (IPN), Th 1165a and orciprenaline (OPN) were shifted to the right when the temperature was increased from 25–42°C. The affinity of IPN at 33°C was found about 30- and 100-times higher than that of Th 1165a and OPN, respectively. 3. The β-adrenolytic drug pindolol (LB 46), as well as the cardioselective β-blocker, practolol, antagonized the β-sympathomimetic effects evoked by IPN and Th 1165a in a competitive manner. As indicated by the pA2 values, pindolol had a 100-times higher affinity than practolol. The present results lead to the conclusion that, on the guinea-pig atrium, the agonist β-receptor reaction depends on the metabolic rate of this organ.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00505070
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