DECREASE IN PLASMA-VOLUME FROM INTRAABDOMINAL TRAUMA IN RATS IS PREVENTED BY H-1 BUT NOT BY H-2 HISTAMINERGIC BLOCKADE

Intra-abdominal surgery causes plasma extravasation which, in the rat, is prevented by combined histaminergic H-1 and H-2 blockade. We evalu ated the relative importance of H-1 and H-2 blockade in this situation . Cloralose-anaesthetized Wistar rats were subjected to a standardized abdominal trauma. Mean arterial pressure (MAP), heart rate (HR) and h aematocrit (Hct) were monitored and plasma volume (PV) was determined before and 1 h after the trauma. Compared to non-traumatized rats (n=8 ), the trauma decreased PV and increased Hct (n=8). MAP decreased duri ng the actual trauma, whereas HR remained stable throughout. In animal s given cimetidine 25 mg kg(-1) i.v. just prior to the trauma (n=8), P V, Hct and MAP changed, as in the non-blocked rats. In contrast, pyril amine, 10 mg kg(-1), completely prevented the decrease in PV and the i ncrease in Hct (n=7), but not the decrease in MAP. The findings sugges t that a histaminergic H-1 mechanism is of importance for the plasma l oss elicited by intra-abdominal trauma.