The effect of histamine receptor antagonists on stress-induced catecholamine secretion: an adrenomedullary microdialysis study in the rat

The effects of pretreatment with selective histamine receptor antagonists o n changes in sympathoadrenal activity and haemodynamics, induced by 60-min immobilization stress, were studied in conscious rats. Using adrenomedullar y microdialysis, it was shown that ranitidine (5 mg/kg, i.v.), a histamine H-2 receptor antagonist, selectively suppressed stress-stimulated noradrena line secretion without affecting adrenaline response, whereas triprolidine (10 mg/kg, i.v.), a histamine H-1 receptor antagonist, had Little effect on stress-induced secretion of both catecholamines. Neither triprolidine nor ranitidine changed the presser response to 60-min stress. The stress-induce d increase in heart rate was not altered by triprolidine, whereas ranitidin e reduced it after 30 min of stress. To test whether the anti-secretory eff ect of ranitidine could be of peripheral origin, in a separate experimental series, a local catecholamine secretion was stimulated by histamine (0.5 m M) perfused through the adrenomedullary dialysis probe. It appeared that tr iprolidine, but not ranitidine, reduced this effect of histamine. Thus, the present results suggest that during stress, the activity of the central hi staminergic system, via histamine H-2-receptors, may selectively modulate n oradrenaline secretion by the adrenal gland. (C) 1999 Elsevier Science B.V. All rights reserved.