Effect of diazepam on stress induced changes in brain histamine.

Acute treatment with diazepam (2.5, 5 and 10 mg/kg) did not affect the basal histamine concentration in the hypothalamus, midbrain or in the cortex of the rat. The increase in the hypothalamic histamine level caused by 15 min of "platform stress" was significantly attenuated by diazepam (5 or 10 mg/kg) pretreatment, but the elevation induced by 15 min of air blasts remained unchanged. Diazepam significantly reduced the rise in plasma corticosterone concentration in response to air blast stress but did not affect the increase caused by "platform stress." Thus, in addition to the already known effects of diazepam on stress induced changes in other central neurotransmitters or neuromodulators, diazepam may also affect the hypothalamic histamine elevation induced by certain type of stress.