Nutritional status, suckling behavior, and prolactin release during lactation.

This experiment was conducted to determine whether suckling-induced prolactin (PRL) values in chronically food-restricted lactating rats resulted from the inability of their litters to suckle vigorously. Rats were randomly assigned to be fed ad lib (AL) or to be chronically restricted (CR) to 50% of AL before and during pregnancy and lactation. Rats nursed their own litter (own) or a litter of the opposite dietary treatment group (other) for 90-min periods at early or peak lactation. Blood was collected regularly through a catheter implanted several days earlier. Suckling contributed to differences in PRL between AL and CR dams in early lactation as demonstrated by an interaction between dietary treatment and type of litter. However, tests of AL own vs. AL other and CR own vs. CR other were not significant. This is probably because the inattentive behavior of CR dams attenuated the PRL response in this group. At peak lactation, PRL values were related to recovery time from catheter implantation; therefore, determinants of PRL release change over the course of lactation.