Diazepam-induced cleft palate in the mouse and lack of correlation with the H-2 locus.

Cleft palate frequencies were studied in AJ and SW mice following either 1- or 2-day dosing schedules with the anxiolytic drug diazepam (DAZ). In all cases, mice were food and water deprived for 24 and 48 hours in the 1- and 2-day dosing schedules, respectively. High cleft palate frequencies in control mice of both strains resulting from 48-hour food and water deprivation (on days 13.5 and 14.5 of gestation) were reduced in mice deprived for 24 hours, indicating a stress related effect. Two-day dosing with DAZ (400 mg/kg) produced a net increase in cleft palate frequency in SW (33%) and AJ (18%) mice. Mice treated only on day 13.5 had reduced control and DAZ cleft palate frequencies, neither of which were significant. Clefting was significant but reduced following 1-day dosing on day 13/20 of gestation (13 days 20 hours) in SW mice (18%), whereas no clefting was seen in the AJ strain. This strain difference was shown not to be related to differences in developmental timing. Production of cleft palate seen in AJ mice after 2 days of dosing may be indicative of an interaction of DAZ with the stresses resulting from food and water deprivation. Genes of the major histocompatibility locus, H-2, have been shown to regulate cleft palate formation following glucocorticoid and phenytoin administration to mice. Despite pharmacological similarities between DAZ and phenytoin, comparison of cleft palate frequencies following administration of DAZ to various strains of mice of different H-2 haplotypes indicated that genes associated with the H-2 locus do not regulate DAZ-induced cleft palate in these strains.