Induction of Pseudopregnancy in Rats by Depletors of Endogenous Catecholamines

Abstract

A single subcutaneous injection of reserpine (0.2 mg/kg) or [alpha]-methyldopa (300 mg/kg) to rats on the first day of diestrus induced pseudopregnancy as confirmed by the development of deciduomata. A similar effect was produced by tetrabenazine (15 mg/kg). However, unlike reserpine or [alpha]-methyldopa, tetrabenazine injections were required every other day beginning with the first day of diestrus to maintain pseudopregnancy. Guanethidine sulfate (30 mg/kg), epsilon amino caproic acid (300 mg/kg) and p-chloro-N-methylamphetamine (25 mg/kg) failed to cause pseudopregnancy even when administered on a daily basis. These results suggested that depletion of brain norepinephrine was the basis for pseudopregnancy induced by reserpine. To test this hypothesis further, an attempt was made to prevent the pseudopregnancy caused by 0.2 mg/kg of reserpine with agents known to counteract the influence of reserpine on brain norepinephrine levels. Pretreatment with 150 mg/kg of iproniazid 18-24 hr. prior to the reserpine administration on the first day of diestrus prevented the induction of pseudopregnancy. A similar effect was produced by the injection of 750 mg/kg of 1-dopa 2 hr. after reserpine treatment. However, "false transmitter" formation by [alpha]-methyldopa, i.e., in vivo conversion to [alpha]-methylnorepinephrine, was apparently unable to prevent pseudopregnancy.