Brain histamine regulation following chronic diazepam treatment and stress

Chronic diazepam treatment (5 mg/kg intragastrically, twice daily for 14 days) did not influence either hypothalamic, midbrain or cortical histamine (HA) levels or histidine decarboxylase (HD) activity in male Sprague-Dawley (200-220 g) rats. However, a small but significant decrease in hypothalamic HA concentration and significantly increased HD activity was seen following diazepam withdrawal. Air blast stress induced a significant elevation in hypothalamic HA levels and HD activity in vehicle-treated controls, diazepam-treated and diazepam-withdrawn rats, but the change in HD activity was significantly greater in the last group. The latter group also displayed the greatest elevation in plasma corticosterone levels in response to stress. Hence, diazepam withdrawal in rats results in some changes in the basal hypothalamic HA regulation and may influence the hypothalamic HA and corticosterone response to stress.