โ Scribed by Demski, Leo S.
No coin nor oath required. For personal study only.
Brain regions where photic stimuli and reproductive systems may interact in controlling both sexual development and reproductive behavior are considered in detail. Retinal input to the preoptic area and photic stimulation of pineal neural and endocrine systems appear to be major pathways for synchronization of reproductive development with environmental conditions. Both systems most likely influence gonadotropin-releasing hormone (GnRH) production and release and the feedback control of these processes via steroid-concentrating cells. In adult elasmobranchs, perceptions of visual stimuli are potentially important in certain aspects of mating, e.g., mate recognition and analysis of courtship displays, and the neural substrates for the perceptions are most likely conditioned by the hormonal status of the animal. Breeding fish may thus have visual mechanisms affected by synaptic input from GnRH and steroid-concentrating neurons. The central nucleus of the telencephalon (CN) provides high-level visual integration in elasmobranchs. Preoptic, terminal nerve, and perhaps midbrain reticular areas are suggested origins for hormonerelated CN afferents. The optic tectum contains GnRH-immunoreactive fibers in a variety of species. Thus, GnRH modulation of visual function probably occurs at this level. Visual centers of the midbrain tegmentum are near both GnRH-immunoreactive and sex-steroid-concentrating neurons. Sensory-hormonal integrative activity within the tegmental units could provide outputs for modulation of activity in both higher visual (e.g., the CN) and lower sex-related sensorimotor systems (e.g., spinal clasper control pathways) through ascending and descending pathways, respectively.
๐ SIMILAR VOLUMES
In elasmobranchs, seasonal and developmental changes in reproduction and sexual behavior appear to be regulated by gonadotropin-releasing hormone (GnRH). Circumstantial evidence indicates that GnRH control is primarily via the systemic circulation to pituitary gonadotrophs in the ventral lobe. Addit