Effect of histamine upon the dynamics of carbon dioxide

The dynamics of carbon dioxide in both gastric and peripheral circulation of rat were studied using H14CO3--. In the absence of histamine infusion the peripheral venous/arterial ratio Vp,/A rose from less than 1.0 to almost 1.2 while the gastric ratio VG/A fell from initial values of about 2.4 to 1.2. Steady histamine infusion speeded approach of both ratios to 1.2. During transient conditions after beginning or end of histamine infusion both ratios were initially depressed to values near zero. The ratios then both rose, showing damped oscillations with a twenty-minute period. The data show a marked effect of histamine on both peripheral and gastric CO2 dynamics, even though in the resting state the two circulations have very different dynamics.