Effects of prenatal diphenhydramine exposure on dopaminergic function in adult rats.

Female pregnant rats were treated with 20.0 mg/kg diphenhydramine (DPH) or the same volume of saline solution (NaCl 0.9%), SC, daily during pregnancy. As adults, male pups were tested for stereotyped behavior in response to apomorphine (1 mg/kg, SC) administration. No differences between DPH-exposed and control rats were evident. In another group of rats, dopamine (DA) and homovanillic acid (HVA) levels were quantified in striatal samples. DA levels were equivalent, but increased levels of HVA were observed. Based upon these data we suggest that prenatal exposure to DPH, a histamine (H1) receptor antagonist, reduces presynaptic dopaminergic mechanisms without altering postsynaptic dopaminergic function in adulthood.