Pharmacological Studies on the effects of Histamine Centrally Administered in Rabbits

The effects of i.c.v. injection of histamine (100 ug, 200ug} mepyramine(25,50 ug)or cimetidine (25 ug, 50 ug ) alone and of histamine after mepyramineor cimetidine on blood. pressure,’ heart . rate, ECG pattern, body .t ernpe r at ur e , and electrolyte content, namely sodium, potassium and calcium in ser urn , heart and brain tissues of conscious rabbits was’ investigated in the present study.The level of brain andtn heart fpntents,’ of no r epinephr ine and dopamine were also de t e r rn ined, aft~! .histamine ’and its blockers adminsitraticn in the higher dose levels, only.The tinding s of this’ investigation can .Le’ summarized as , follow:-1- Effects on Blood Pressure:l.c.v. injection of hi sea mine induced dose dependent hyper-tension, that was blocked by mepYJar11in~ and not affected by the H2-blocker cirnetidine.Administ ration of either mepyramine or cimetidine i.c.v. in the two dose levels did not affect blood pressure.2- Effects on Heart’ Rate:Administration of histamine into the cerebral ventricle produced dose related tachycardia. This effect was antagonized.