FIGURE 4. Relationship between the percent of LHRH neurons that 
expressed c-Fos and plasma LH values 30 to 60 minutes prior 
to sacrifice on the afternoon ofproestrus. Each point represents 
one animal. R=0.957; p<0.001. 
SOURCE: Modified from Lee et al M in press, copyright 1992, by permission of 
Oxford University Press (Oxford, England). 
hypothalamus, tonically inhibits prolactin release. Following the onset 
of suckling, prolactin release markedly increases, due at least in part to 
an inhibition of the dopamine’s inhibitory tone (Moore 1987). Groups of 
lactating rats (postpartum day 12) continually suckling their pups and 
diestrus rats were compared for the presence or absence of FRA proteins 
within dopamine neurons of the arcuate nucleus. An antiserum generated 
against the M-peptide region of c-Fos (generated by Dr. Michael ladarola) 
served as the FRA marker and was used at a concentration of 1 : 15,000. 
Staining for the enzyme tyrosine hydroxylase (TH) with an anti-TH serum 
served as a marker for dopamine in the hypothalamic neurons. Staining 
124 
