Fig. 3.

Acute 1-h suckling stimuli suppressed pulsatile LH secretion in OVX + E2 dams deprived of their pups for 6 h during late lactation. (A) Schematic illustration of experimental schedule to investigate effects of pup removal and acute suckling on pulsatile LH secretion in OVX + E2 dams on day 16 of lactation. Blood samples were collected from free-moving conscious rats in the pup removal and acute suckling groups. Animals assigned to the pup removal group were deprived of their pups for 6 h immediately before the blood sampling on day 16 of lactation, and animals assigned to the acute suckling group received their pups for 1 h after the 6-h pup removal period immediately before the blood sampling on day 16 of lactation. (B) Plasma LH profiles of representative OVX + E2 dams in the pup removal and acute suckling groups. Blood samples were collected every 6 min for 3 h. Arrowheads indicate the peaks of LH pulses identified by the PULSAR computer program. (C) The mean LH concentrations, and the baseline, frequency, and amplitude of LH pulses were significantly lower in the acute suckling group than in the pup removal group (*, P < 0.05, Student’s t-test). Values in bar charts are means ± SEMs. Open circles on the bar chart indicate the individual values. The number in each column indicates the number of animals used.