LH-RH neuron system of the newt by immunohistochemical study

The location of LH-RH producing neurons, the pathways and terminal distributions of their fibers in the newt, Cynops pyrrhogaster were studied immunohistochemically. The LH-RH positive perikarya are located in the nucleus of the diagonal band of Broca and the medial septal nucleus. No LH-RH immunoreactive neuronal perikarya could be detected in the diencephalon. The pathways of fibers originating from the LH-RH reactive neurons were classified into three groups: the first project to the median eminence, the second to the olfactory bulb and the third to the habenular nucleus. The latter two pathways are extrahypothalamic, similar to those in mammals. These observations are briefly discussed and compared with those in other amphibian and mammalian species.