This study examined the potential for histamine to cause cardiovascular reflexes when applied to the serosal or mucosal surface of the stomach. Thus, in chloralose-anesthetized cats, histamine was applied to the serosal surface of the stomach in concentrations ranging from 0.5 to 1,000 micrograms/ml. This resulted in graded increases in mean arterial pressure (MAP), maximal left ventricular pressure over time (dP/dt), and heart rate ranging from 9 +/- 4 to 30 +/- 3 mmHg, 450 +/- 103 to 1,710 +/- 610 mmHg/s, and 2 +/- 1 to 13 +/- 4 beats/min, respectively. Histamine stimulation of the gastric serosa evoked a greater pressor response than that observed when the same concentration of histamine (100 micrograms/ml) was applied to the gastric mucosa (43 +/- 7 vs. 13 +/- 3 mmHg, respectively). In six cats, celiac ganglionectomy abolished the previously observed cardiovascular response to histamine stimulation of the serosal surface of the stomach. When the gastric serosa was treated with the H1-receptor antagonist diphenhydramine (1 mg/ml) (n = 5), the cardiovascular response to histamine was abolished. In five other cats, administration of the H2-antagonist ranitidine (1 mg/ml) had no effect on the histamine-induced responses. When indomethacin (2-5 mg/ml), was applied to the serosal surface of the stomach (n = 6), histamine-induced increases in MAP and dP/dt were attenuated. However, application of PGE2 (1 microgram/ml) restored these two responses. These results suggest that histamine stimulates H1-receptors in the gastric wall to cause reflex cardiovascular responses that are dependent, in part, on the local production of prostaglandins.