ABSTRACT
I. Introduction................................................................................... 21 II. Brn-2-Knockout Mouse................................................................. 23
III. Nkx-2.1-Knockout Mouse............................................................. 24 IV. Pax-6-Deficient Rats...................................................................... 24 V. Concluding Remarks .................................................................... 26
References ............................................................................................... 27
In the vertebrate brain, the hypothalamus occupies the ventral half of the diencephalon and plays a role as a center for the autonomic nervous system and endocrine system as well as for feeding, sleep, biological rhythms, and reproductive function. The hypothalamus contains numerous neuronal clusters called nuclei which often work as distinct functional units. An example is the suprachiasmatic nucleus as a center for biological rhythms. Some hypothalamic nuclei contain special phenotypes of neurons that project their axons to terminate on and release neurohormones into blood vessels. Such cells are aptly named neurosecretory neurons, and are divided into two types: large neurons that send their axons to the posterior lobe of the pituitary to release neurohormones into the general circulation (magnocellular neurons), and small neurons projecting to the external layer of the median eminence to secrete neurohormones into the hypophysial portal vessels (parvocellular neurons). These neurons are localized in discrete hypothalamic nuclei.
