Intracerebroventricular Injection of Histamine Induces State-Dependency through H1 Receptors

The aim of the present study was to investigate whether and by which mechanism; histaminecan induce state-dependent retrieval of passive avoidance task. the pre-training or pre-testintracerebroventricular (i.c.v.) injection of histamine (20flg/mouse) impaired retrieval, when itwas tested 24 h later. in the animals, which retrieval was impaired due to histamine pre-trainingadministration , pre-test administration of histamine, with the same dose, restored retrieval.the h] blocker, pyrilamine (20 ug/rnouse, i.e.v.), but not the h2 blocker; ranitidine preventedthe restoration of retrieval by pre-test histamine. a pre-test administration of histamine h)receptor antagonist, c1obenprobit, also reversed hitamine-induced impairment of memoryretention . in conclusion, histamine can induce state-dependent retrieval through the hi receptorhi mechanism.