Transient and lasting effects of reproductive episodes on NaCl intake of the female rat.

Following recovery from experimental sodium depletion, both the need-free and the future need-induced NaCl intakes of the rat are increased. The present experiments asked whether a naturally occurring episode of sodium need, pregnancy and lactation, would also enhance NaCl intake. The daily 0.3 M NaCl intake of Long-Evans rats increased from 18.2 ml (prior to pregnancy) to 28.7 ml during pregnancy, and increased further to 36.2 ml during lactation. The daily intakes remained increased after the weaning of the second litter, at 28.5 ml/24h for females which had access to 0.3 M NaCl during the reproductive episodes (DAM + Na) and at 27.6 ml/24h for those which did not (DAM). When they were subsequently sodium depleted, the need-induced NaCl intake of the DAM, but not the DAM + Na group, was significantly increased compared to virgin female rats. The sodium depletion-induced water intakes of both groups were significantly increased. Neither the need-free nor the need-induced intakes of their offspring (as adults) were increased. In summary, pregnancy and/or lactation, in the absence of a sodium deficit, produced increased intakes of NaCl which persisted beyond the reproductive episodes.