Effect of anesthesia on cardiac function and response in the perfused rat heart

In the present study we have examined the effect of the general anesthetic agent sodium pentobarbital (given i.p. to the intact animal) on the hemodynamic function of the isolated perfused heart and its response to treatments which affect calcium transsarcolemmal influx: extracellular calcium concentration and thyroid hormone. Perfused hearts (modified Langendorff system) isolated from anesthetized rats were found to respond differently to the two aforementioned effectors than hearts excised from non-anesthetized animals. Hearts of the two groups demonstrated a gradual increase in inotropic activity in response to step-wise increase in calcium concentration in the perfusion medium. However, cardiac contractility and the pattern of the response to the gradual increase in calcium concentration were different. At the lower Ca2+ concentrations of 0.5 and 1.0 mM, inotropic activity (left ventricular systolic pressure (LVP) and +dP/dt values) of hearts from anesthetized animals was significantly greater (P less than 0.05) than that of hearts from non-anesthetized animals: LVP values (mmHg, mean +/- S.E.M.) in hearts from anesthetized an non-anesthetized rats were: at 0.5 mM Ca2+, 19 +/- 3 and 9 +/- 2; and at 1.0 mM, 103 +/- 12 and 76 +/- 6, respectively. At the higher Ca2+ concentrations, hearts from anesthetized animals demonstrated maximal LVP at 1.75 mM calcium (139 +/- 9 mmHg), whereas the LVP values in hearts from non-anesthetized animals continued to increase throughout all the Ca2+ concentrations employed. A similar pattern of response was observed for +dP/dt values.(ABSTRACT TRUNCATED AT 250 WORDS)