Diazepam facilitates acceptance of alien lambs by postparturient ewes

The aim of this study was to determine the effect of diazepam on the behavior of parturient ewes towards alien lambs. There is evidence that benzodiazepines cause behavioral changes during the lactation period in rats. In two independent experiments, it was found that the ewes acceptance of alien lambs significantly increased following a single injection of the benzodiazepine, diazepam, given either 1 or 12 h after parturition. In a third experiment, in which the alien lamb was not permitted to suckle during a period of 2 h after the injection, the diazepam treatment did not provoke significant differences in maternal behavior of the ewes, although in the ewes treated with diazepam, suckling clearly tended to increase. At the dose employed (20 mg), administered 1 h after birth, diazepam caused no signs of sedation as assessed in an open-field test carried out 3 h after parturition. This doesn't eliminate the possibility of diazepam having a sedative effect in the period of 2 h immediately after its administration and before the test and, in this way, facilitating suckling which could be responsible for the maternal behavior observed after this period. As diazepam gives rise to an enhanced GABAergic activity in the brain, these observations suggest that a GABAergic mechanism could also play a role in the process whereby ewes form a selective bond with their own offspring.