Horst M A, Robinson C P, Christiansen V J
Arch Int Pharmacodyn Ther. 1982 Apr;256(2):192-203.
On helically-cut strips of rabbit mesenteric artery contracted with phenylephrine, histamine in the presence of mepyramine caused a partial relaxation at 42 degrees C which was potentiated by reducing the temperature to 25 degrees C. However, under the same conditions, the selective H2 agonist, dimaprit, caused a smaller partial relaxation not enhanced by cooling the strips. Neither changing the temperature range (to 38 degrees and 22 degrees C), deleting the H1 blocker, nor substitution of another H1 blocker (pyribenzamine) resulted in an enhanced relation to dimaprit in the cold. Prior reserpinization of the rabbit did not abolish the cooling-enhanced relaxation to histamine, but did abolish the reversal of relaxation observed at high (10(-3) M) histamine concentrations. Metiamide (3 X 10(-4) M) blocked both histamine (H2)- and dimaprit-induced relaxations more effectively in cooled strips. Thus the H2 receptor activity observed in cooled strips differs in selectivity for the two agonists and antagonist from that observed at normal temperature.
在用去氧肾上腺素收缩的兔肠系膜动脉螺旋形切片上，在42℃时，组胺在有甲氧苄二胺存在的情况下引起部分舒张，将温度降至25℃可增强这种舒张。然而，在相同条件下，选择性H2激动剂二甲双胍引起的部分舒张较小，冷却切片不会增强这种舒张。改变温度范围（至38℃和22℃）、去除H1阻滞剂或替换另一种H1阻滞剂（吡苄明）均不会导致在低温下与二甲双胍的舒张关系增强。预先对兔进行利血平化处理并没有消除冷却增强的对组胺的舒张反应，但确实消除了在高（10⁻³ M）组胺浓度下观察到的舒张逆转。甲硫米特（3×10⁻⁴ M）在冷却的切片中更有效地阻断了组胺（H2）和二甲双胍诱导的舒张。因此，在冷却切片中观察到的H2受体活性在对两种激动剂和拮抗剂的选择性上与在正常温度下观察到的不同。
