The term diffuse tuberomammillary nucleus refers to the central of three components of the magnocellular tuberomammillary nuclei that are identifiable by Nissl stain in the posterior hypothalamic region of the rat. It consists of large darkly stained neurons scattered across parts of the posterior periventricular nucleus, the lateral hypothalamic area and the ventral premammillary nucleus between the other two components of the magnocellular tuberomammillary nuclei: the dorsal tuberomammillary nucleus dorsomedially and the tuberomammillary nucleus ventrolaterally ( Koehler-1985 ).