Segmental and age-dependent changes of histamine's affinity in the rabbit aorta

Affinities of contractile responses to histamine and H1-receptor agonists thiazolylethylamine (TEA) and pyridylethylamine (PEA) were evaluated in three segments of rabbit aorta and increase of affinity in the caudal direction was found. alpha-adrenergic affinity of noradrenaline did not possess such differentiation. Evaluation of the data with histamine receptor agonists and antagonists suggested H1-receptor liability of the phenomena. Affinities of histamine and noradrenaline were also investigated in relation to body weight which reflects age. Histamine's affinity was found to be age dependent, decreasing with the increase of age, while no correlation was found for noradrenaline between two parameters. Results are suggesting the presence of histamine specific vascular function in the rabbit which is receded by the advance of age.