Effects of a histamine H3 receptor antagonist on the development of sexually dimorphic behaviours

Histamine antagonists in developing rats delay puberty, disrupt sexual behaviour in males, and abolish sex differences in the open field test suggesting that this system may regulate sexual differentiation. The effects of histamine during the critical period for androgenic masculinization of the nervous system are currently unknown. Perinatal exposure to the H3 antagonist thioperamide on the development of sexually dimorphic behaviours in adult Sprague-Dawley rats was investigated. Pregnant dams (E14-E20) and their pups (PND1-PND7) were subcutaneously injected with thioperamide (5mg/kg) or saline and observed for changes in the elevated plus maze, open field test, sexual behaviour, and radial arm water maze. Thioperamide attenuated sex differences in the elevated plus maze and open field test but did not affect sexual performance or learning in the radial arm water maze. The present findings suggest evidence of long-term neurobehavioral consequences in anxiety and exploratory behaviours after developmental manipulation of the histaminergic system.