Effects of different types of stress on histamine-H3 receptors in the rat cortex

The role of the histamine (HA) H3 receptor (estimated by binding of [3H]N-alpha-methyl HA in the brain cortex) in the response of male rats to four types of stress was evaluated: acute weak foot-shock stress (0.5 mA x 1 s x 5 times), acute intense foot-shock stress (1mA x 10 s x 5 times), acute restraint stress (60 min at 24 degrees C) and chronic variate stress. Two groups of rats received chronic treatment with a tricyclic antidepressant: amitriptyline (5 mg/kg i.p.); one group was also chronically stressed. HA-H3 receptor density rapidly decreased in acute intense foot-shock and chronic variate stress, but was unchanged in acute weak foot-shock and restraint stress. Amitripytline counteracted the chronic variate stress-induced decrease, and increased HA-H3 receptor density when chronically administered in the non-stressed control group. These results indicate that cortical HA-H3 receptor density is affected by the response to stress in function of the type, duration and intensity of the stressor.