Hypothalamic gene expression of gonadotropin releasing hormone (GNRH), gonadotropin inhibitory hormone (GNIH), progesterone receptor (PGR), and estrogen receptors 1 and 2 (ESR1 and ESR2) in low egg producing hens (LEPH) and high egg producing hens (HEPH) sampled outside (basal) and inside (surge) of the preovulatory surge (PS). Normalized data are presented relative to LEPH basal expression for each gene. Significant expression differences denoted with an asterisk (*P ≤ 0.05, **P ≤ 0.01, and ***P ≤ 0.001). Solid lines indicate a significant difference between LEPH and HEPH for a given condition, whereas dotted lines indicate a significant difference between basal and surge for a given egg production level.