Hypophysiotropic Neurons in the Brain of Teleosts

The pituitary gland is primarily under the control of the hypothalamus, although a wealth of recent evidence supports the notion that intrapituitary chemical mediators themselves act as regulators of pituitary function. In teleosts several hypothalamic neuronal processes project into the pituitary forming an intricate association with the adenohypophysis. For several decades, two hypophysiotropic nuclei have been known to control the teleostean adenohypophysial functions. The first was the nucleus preopticus (NPO) and the second was the nucleus lateralis tuberis (NLT). Using classical neurosecretory stains such as aldehyde fuchsin (AF) or chrome alum-hematoxylin-phloxin (CAHP), the NPO neurons were selectively demonstrated in the teleostean brain. On the other hand, the perikarya of the NLT were AF- and CAHP-negative, but stained with the trichrome and tetrachrome stains. Different aspects pertaining to the hypothalamo-hypophysial system have been discussed in several reviews (Peter,1983, Peter,1986;Peter and Fryer, 1983;Schreibman, 1986).