Figure 7

Effect of desloratadine (DL), 4-DAMP, or methoctramine on oxotremorine-induced increase of left ventricular contractility in the pithed rat. Isoflurane-anesthetized animals (n = 6) were pithed after insertion of femoral and carotid arterial catheters. The carotid catheter was advanced into the LV to enable recording of contractility, which was expressed as the change in pressure over the change in time (dP/dt). Anesthesia was then discontinued. Following administration of atenolol (1.0 mg/kg, i.v.), oxotremorine was administered in random (n = 3) and ascending (n = 3) order of doses. The third generation antihistamine, DL (1.0 mg/kg, i.v.), the muscarinic M₃ receptor antagonist, 4-DAMP (1.0 mg/kg, i.v.), or the muscarinic M₂ receptor antagonist, methoctramine (0.5 mg/kg, i.v.) was then administered and the oxotremorine doses were repeated. No statistically significant differences were found between animals in which oxotremorine was given in random vs. ascending order of doses and both sets of data were pooled. Data are representative of the maximal percent increase in left ventricular contractility compared to control following the administration of each dose of oxotremorine. The highest dose tested for oxotremorine (0.04 mg/kg, i.v.) could not be given prior to treatment with 4-DAMP. Statistical analysis was done using the paired t-test with P < 0.05 denoting a statistically significant difference versus control as indicated by an asterisk.