Estrogen receptor β and progesterone receptor mRNA in the intergeniculate leaflet of the female rat

The present study was undertaken to explore the possibility that the integration of hormonal cues in the regulation of neuroendocrine mechanisms may occur outside of the hypothalamus at the level of the lateral geniculate body. In situ hybridization for mRNA encoding estrogen receptor β and progesterone receptor was carried out on sections containing the lateral geniculate body using [³⁵S]-labeled antisense riboprobes. Labeled cells were present in different limbic and hypothalamic sites as described previously. Populations of cells distributed homogeneously in the ventral lateral geniculate nucleus and intergeniculate leaflet were also found to express mRNA for estrogen receptor β and progesterone receptor. The dorsal lateral geniculate nucleus lacked specific labeling for either type of gonadal steroid hormone receptor mRNA. The present observation together with the recent demonstration of a direct pathway between the intergeniculate leaflet and hypothalamic neuroendocrine cells indicate that integration of hormonal and photic stimuli in the central regulation of endocrine mechanisms occurs outside of the hypothalamus in the lateral geniculate body.