The spiny cells, both cap-like and fusiform ones, were observed preponderantly, in the medial mamillary nucleus, whereas in the lateral mamillary nucleus there were mainly seen the triangular and fusiform neurones, either spiny or aspiny cells. 
In the brainstem, a strong NTR immunoreactivity was found in the lateral mamillary nucleus and the interstitial nucleus.
Injections of WGA-HRP into the medial mamillary nucleus resulted in dense anterograde and retrograde labeling in the ventral tegmental nucleus, while injections in the lateral mamillary nucleus resulted in dense anterograde labeling in the dorsal tegmental nucleus pars dorsalis and dense anterograde and retrograde labeling in the pars ventralis of the dorsal tegmental nucleus. The anterograde labeling in these two precerebellar relay nuclei was distributed near the midline such that projections from the lateral mamillary nucleus terminated mainly dorsomedial to the terminal fields of projections from the medial mamillary nucleus.
Inputs to LDTg were found from frontal cortex, diagonal band, preoptic areas, lateral hypothalamus, lateral mamillary nucleus, lateral habenula; the interpeduncular nucleus, ventral tegmental area, substantia nigra and retrorubral fields; the medial terminal nucleus, interstitial nucleus, supraoculomotor central grey, medial pretectum, nucleus of the posterior commissure, paramedian pontine reticular formation, paraabducens and paratrochlear region; the parabrachial nuclei and nucleus of the tractus solitarius.
It is noteworthy that no labeled cells were found in the dorsal thalamus, the hypothalamus (except for the lateral mamillary nucleus), the superior colliculus or the cerebellar nuclei..
Projections from the rostrodorsal and caudoventral subiculum terminated in a topographically organized laminar fashion in the medial mamillary nucleus bilaterally, whereas afferent projections from the presubiculum and parasubiculum terminated only in the lateral mamillary nucleus. Projections from the dorsal tegmental nucleus terminated in the ipsilateral lateral mamillary nucleus, whereas afferent projections from the anterior and posterior subnuclei of the ventral tegmental nucleus terminated topographically in the medial mamillary nucleus.
The largest perikarya are found in the lateral mamillary nucleus (cell area 257.0 microns2) and have 2-5 radially oriented aspiny dendrites that are often beaded. A quantitative analysis indicated that the numbers of RA terminals in the medial nucleus almost equals the numbers of PS terminals, whereas the lateral mamillary nucleus contains considerably more PS (64%) than RA terminals (36%)..
Furthermore, neurons of the dorsal and ventral premamillary nuclei, the lateral mamillary nucleus, the ventral tegmental area of Tsai, and the ventral tegmental nucleus of Gudden were found to project to the medial prefrontal cortex.
When such caudally placed injections also involved the lateral mamillary nucleus, the lateral division of the central amygdaloid nucleus was additionally labeled.
The lateral mamillary nucleus projects through the mamillothalamic tract bilaterally upon the anterodorsal nuclei of the thalamus, and through the mamillotegmental system to the dorsal tegmental nucleus; it also appears to contribute fibers to the medial forebrain bundle.
The nuclei identified include: the medial mamillary nucleus (in which at least three distinct subdivisions can be recognized--a pars medialis, a pars lateralis, and a pars basalis); the small-celled nucleus intercalatus; the large-celled lateral mamillary nucleus; a single premamillary nucleus; the tuberomamillary nucleus; the posterior hypothalamic nucleus; the caudal extension of the lateral hypothalamic area; the supramamillary area; and the paramamillary nucleus (which appears to correspond to the nucleus of the ansa lenticularis of other workers).
The cells of the medial mamillary nuclei send their axons to the ipsilateral AV and AM nuclei whereas the lateral mamillary nucleus projects bilaterally to the AD nuclei..
The mamillary peduncle ascending from the mesencephalon can be traced to the lateral mamillary nucleus.
The general mass of BA was shown to localize in the terminals of the lateral mamillary nucleus and in the supramamillary area. AChE is localized mainly in the neuropile and the cells of the medical nucleus and the cells of the lateral mamillary nucleus.
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