Effects of intracerebroventricular injection of histamine and H1, H2 receptor antagonists on electrocardiographic parameters in broiler chickens

ABSTRACT

The aim of this study was to assess the effects of exogenous histamine and H[1] and H[2] 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, H[1] and H[2] 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 micro g] 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 micro g], an H[1] receptor antagonist, increased the duration rate of T wave and QRS complex and reduced the heart rate [P<0.05]. Cimetidine, an H[2] receptor antagonist [100 micro g] had no effect on ECG parameters. Pretreatment with chlorpheniramine [100 micro g] significantly attenuated histamine effects [200 micro g] on the duration of T wave, QRS complex and heart rate [P<0.05]. Mean electrical axis, calculated from leads II and III, did not differ between groups and it was between -93 [degree sign] and -99 [degree sign] in all chickens. In conclusion, exogenous histamine intracerebroventricularly results in sinusoidal tachycardia in broiler chickens and central H[1] receptors mediate the stimulatory effects of histamine on heart rate, but H[2] receptors had no role in this manner