The effects of thiamine (B1), its related substances and histamine liberators on blood pressure were studied by intraventricular injection to the rats. The results were as follows :
1) The lasting rise of blood pressure was observed by the injection of B1 (50 to 200μg/animal), thiaminic acid (200μg), desthiothiamine (200μg) and cocarboxylase (CoC, 10μg) . The similar effect was observed by the injection of histamine liberators such as compound 48/80 (0.01μg), polymyxin B (0.01μg) and d-tubocurarine (0.5μg) .
2) This pressure rising effect of B1, CoC and histamine liberators was inhibited by the pre-treatment with 20μg of antihistaminics (tripelennamine) . The pre-treatment of procaine (0.01 μg) did not inhibited effect of B1and CoC.
3) Each successive injections of B1, thiamine tetrahydrofurfuryl disulfide (TTFD), CoC and histamine liberators caused tachyphylaxis.
4) Polymyxin B and B1or d-tubocurarine produced cross-tachyphylaxis, which also occurred in the case of d-tubocurarine and B1, TTFD or polymyxin B.
From these results, it seemd that the blood pressure rising effect by the injection of B1and its related substances may be ascribed to the histamine releasing action of these substances.
