Fig. 6. Study IV: preoptic gonadotropin-releasing hormone 1 (GnRH1) expression is regulated by endogenous cues in females. Spawning (Sp), brooding (Br) and broodless (Br-) females were used to test the relative influence of social versus endogenous regulation of GnRH levels. Experimental groups are indicated on the lower x-axis and include two groups of broodless females, either fed (Br-F+) or fasted (Br-F-). (A) Normalized GnRH1 mRNA signals are plotted as their optical density (OD). Values are high in females that eat (Sp and B-/F+) and low in fasted females (Br and Br-F-). Soma sizes from spawning females are from White and Fernald (1993). (B) Brooding females have small ovaries indicated by their small gonosomatic index (GSI). Feeding increases ovary size, as does the absence of broods. The intermediate Sp value reflects egg release during capture while spawning. Values are means ± S.E.M. (N=6 Sp, 13 Br, 8 Br-F+, 6 Br-F-). Asterisks indicate P-values: ^*P<0.05; ^**P<0.005; ^***P<0.0005.