Анотация: The aim of this study was to assess the effects of exogenous histamine and H1 and H2 central receptors on electrocardiographic (ECG) parameters, heart rate and mean electrical axis in broiler chickens. For this purpose, Ross broiler chickens (750-800 g weight) received intracerebroventricularly (ICV) histamine. Moreover, to determine the receptors involved in histamine-induced alterations in ECG changes, H1 and H2 blockers were administered to histamine-treated chickens. All ECGs were standardized at 1 mV = 20 mm, with paper speed of 50 mm/sec. Leads I, II, III, aVR, aVL and aVF were recorded. Injection of histamine (200 and 300 mg) decreased the duration of T wave and QRS complex and elevated the heart rate as compared to the control group (P<0.05). Chlorpheniramine (100 mg), an H1 receptor antagonist, increased the duration rate of T wave and QRS complex and reduced the heart rate (P<0.05). Cimetidine, an H2 receptor antagonist (100 mg) had no effect on ECG parameters. Pretreatment with chlorpheniramine (100 mg) significantly attenuated histamine effects (200 mg) on the duration of T wave, QRS complex and heart rate (P<0.05). Mean electrical axis, calculated from leads тт and ттт, did not differ between groups and it was between -93C and -99 C in all chickens. In conclusion, exogenous histamine intracerebroventricularly results in sinusoidal tachycardia in broiler chickens and central H1 receptors mediate the stimulatory effects of histamine on heart rate, but H2 receptors had no role in this manner