Fig. 4.

Acute 1-h suckling stimuli failed to activate ARC enkephalin neurons in OVX + E2 rats deprived of their pups for 6 h during late lactation. (A) Schematic illustration of experimental schedule to investigate effects of acute suckling on ARC enkephalin neurons in OVX + E2 dams on day 16 of lactation. Animals assigned to the pup removal group were deprived of their pups for 6 h immediately before the brain 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 brain sampling on day 16 of lactation. (B) Penk (green)- and fos (magenta)-expressing cells in the ARC of representative OVX + E2 dams in the pup removal and acute suckling groups. The insets indicate magnified images of Penk- or fos-expressing cells (arrowheads). 3V, third cerebroventricle. Scale bars, 100 µm. (C) The number of ARC Penk-expressing cells (green) and fos-positive Penk-expressing cells (green and magenta striped) were comparable between the groups. Values in bar charts are means ± SEMs. Circles on the bar chart indicate the individual values of Penk-expressing cells (white) and fos-positive Penk-expressing cells (magenta). The number in each column indicates the number of animals used.