Objective: In the present study the effect of histamine sensitization on the retrieval of passive avoidance memory was investigated.
Method: One-trail step-down passive avoidance task was used to assess memory in adult male NMRI mice.
Results: Post training administration of lithium (10 mg/kg) impaired the memory on the training day, and pre-test administration of lithium prevented the impairment of memory (p<0.001). Sensitization was induced using daily injections of 20 mg/mouse histamine in three consecutive days followed by five drug-free days. The lithium-induced impaired memory was restored better in mice sensitized with histamine than in non-sensitized mice (p<0.01). On the other hand, frequent injection (three days injection followed by five drug free days) of the H1 receptor antagonist pyrilamine (40 mg/mouse), and the H2 receptor antagonist ranitidine (6.25 and 12.5 mg/mouse), prevented the restoration of impaired memory.
Conclusion: Histamine sensitization affects memory impairment induced by lithium; therefore, it is postulated that signaling cascade from histamine receptors may mediate the effects of lithium on memory in passive avoidance task.