The diphenhydramine-induced decrease in general open-field activity of female rats is gonadal steroid dependent.
The effect of ovarian steroids on sedative effects of diphenhydramine (D), a histamine H1 receptor blocker, was determined. Seventy-five female Wistar rats were randomly divided into three groups: Group 1 (N = 54) was ovariectomized, group 2 (N = 7) was sham-operated, and group 3 (N = 14) was intact. The ovariectomized rats were then subdivided into 4 groups. Two groups received peanut oil 54 and 6 h before treatment with saline solution (group OS) or 20 mg/kg D (group OD). The other two groups received 50 micrograms/kg 17-beta-estradiol and 2 mg/kg progesterone, respectively, 54 and 6h before treatment with saline solution (group OHS) or 20 mg/kg D (group OHD). The sham-operated animals were treated as the OS group. Intact animals were injected with saline (group IS) or 20 mg/kg D (group ID) on the day of estrus, as determined by vaginal smears taken in the morning before the behavioral observations. Rats were observed for 6 min in the open field during the dark period of the cycle, 15 min after the administration of saline or D. There was a similar decrease in locomotion and rearing frequencies in OHS vs OHD and IS vs ID groups. Nevertheless, a lack of D sedative effect was observed in OD rats (locomotion and rearing frequencies, 56.0 +/- 3.3 vs 46.1 +/- 3.8 and 15.5 +/- 1.6 vs 15.2 +/- 1.6., for OS and OD groups, respectively). The results suggest that the sedative effect of diphenhydramine depends on the presence of ovarian steroids.
Bernardi
M M
MM
Disciplina de Farmacologia Aplicada e Toxicologia, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, Brasil.
de-Souza-Spinosa
H
H
Taricano
I D
ID
Richtzenhain
M H
MH
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004155:Diphenhydramine / Q000037:antagonists & inhibitors*; D004967:Estrogens / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D010052:Ovariectomy; D011374:Progesterone / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar
D004967:Estrogens; D011374:Progesterone; D004155:Diphenhydramine