Mamillary Complex Research Articles

Mamillary complex of hypothalamus and efferent functions of capsaicin-sensitive neurons

Electrocoagulation in the region of mamillary complex of the hypothalamus induced disturbances in vascular permeability in the rat limb skin. This effect was prevented by pretreatment of the animals with the neurotoxin capsaicin, which indicates participation in the effect of the peptidergic capsaicin-sensitive neurons. The data are discussed in relation to possible mechanisms of central modulation of efferent function of the primary sensory neurons.

Immunocytochemical demonstration of DSIP-like immunoreactivity in the hypothalamus of the rat

The distribution of delta sleep-inducing peptide immunoreactivity (DSIP-IR) was studied in the rat diencephalon. Varicose nerve fibers exhibiting DSIP-IR were found throughout the mediobasal hypothalamus, most frequently in the hypothalamic arcuate nucleus and in the adjoining median eminence and pituitary stalk. This innervation provides a basis for the involvement of DSIP in neuroendocrine regulation at the hypothalamic level. In the hypothalamus, DSIP-IR innervation was also observed close to the third ventricle and within the mamillary complex. Despite pretreatment with colchicine, no evidence of immunoreactive cell bodies containing DSIP-IR could be found.

Connections linking the mamillary complex and hypothalamo-tegmental area of the brain with the brainstem in lizards

Connections between the hypothalamus and brainstem formations were investigated inOphisaurus apodus by locally injecting horseradish peroxidase (HP) or lectin-HP into the mamillary complex and the hypothalamo-tegmental area of the brain. Direct reciprocal connections were found linking mamillary complex nuclei and posterior and lateral hypothalamic structures with the following brainstem formations: central gray matter, parabrachial nucleus, raphe nuclei and the lateral loop, reticular formation of the caudal mesencephalon, pons, and medulla. It was concluded that direct bilateral hypothalamo-brainstem connections were already in place in reptiles, serving as the basis for sympatho-emotional nociceptive, and antinociceptive response.

Demonstration of a Mamillo-Ponto-Cerebellar Pathway.

The pathway from the mamillary complex to the cerebellum via the pontine nuclei has been studied using several anterograde and retrograde tracing techniques in the cat. We have also compared the pontine terminal regions of fibres from the mamillary complex and from the cingulate gyrus. Implantations of crystalline horseradish peroxidase wheat germ agglutinin (HRP-WGA) in the mamillary complex and lesions of the cingulate gyrus were combined in the same animal with injections of HRP-WGA, rhodamine-B-isothiocyanate (RITC), and Fluoro-Gold in different parts of the cerebellar hemisphere. Fibres from both the mamillary complex and the cingulate gyrus terminate mainly within a transversely oriented, c-shaped band in the ipsilateral, rostral pontine nuclei. Within this band the terminal fields of fibres from the mamillary complex and the cingulate gyrus form a mosaic-like pattern of partly overlapping patches. Pontine regions receiving a mamillary input project mainly to the ventral paraflocculus, and to a lesser degree to the dorsal paraflocculus, but apparently not to the uvula or crus II. Judging from the literature it seems highly unlikely that other parts of the cerebellar hemispheres received projections from these pontine regions. Fibres from the ventral paraflocculus were shown to terminate in the parvicellular part of the lateral cerebellar nucleus only. The present findings would seem to imply that inputs from the mamillary complex and a related cortical region, the cingulate gyrus, are partly integrated, partly kept separate at the precerebellar level. This would ensure that small groups of cells in the rostral pontine nuclei receive a specific set of afferents. Conceivably, the information transmitted to the cerebellum by these groups of pontine cells might be related to functions of the mamillary complex, such as learning, motivation, and spatial memory.

Neurons in the rat subiculum with transient postmamillary collaterals during development maintain projections to the mamillary complex.

We recently found that in developing rats large numbers of fibers extending through the fornix initially grow well past the mamillary bodies and into the mesencephalic and pontine tegmentum (Stanfield et al. 1987). This postmamillary component of the fornix is essentially completely eliminated during the first few postnatal weeks, although the cells of origin of this projection within the subicular complex of the hippocampal region persist. To determine if the subicular neurons which transiently extend post-mamillary axons maintain a projection to the mamillary complex after the elimination of the postmamillary component of the fornix, we employed a delayed double-retrograde labeling paradigm. The cells of origin of the postmamillary component of the fornix in rat pups were labeled with an injection of fast blue (FB) into the mesencephalic/pontine tegmentum, and, in the same animals, but at a stage after the elimination of the postmamillary component of the fornix, the cells of origin of the definitive fornix were labeled with an injection of diamidino yellow (DY) aimed at the mamillary complex. In these cases the FB labeled neurons within the subicular complex can be DY labeled as well, indicating that subicular neurons which transiently extend post-mamillary axons maintain projections to the definitive targets of the fornix within the caudal hypothalamus.

Connections between presumed diencephalic nuclei of the lizard limbic system using horseradish peroxidase axonal transport technique

Connections between the anterior thalamic and habenular nuclei were investigated in the lizard by administering horseradish peroxidase to these nuclei. They were shown to have overlapping locations of afferent sources, namely basotelencephalic structures, nuclei of anterior and hippocampal commissures, preoptic and lateral hypothalamic area, and superior raphe nucleus, as well as common projection zones, viz: the mamillary complex and the ventral tegmental area. Specific connections confined to individual nuclei were discovered, apart from those common to the nuclei: A reciprocal connection with the dorsolateral hypothalamic nucleus (for the anterior dorsolateral nucleus), a projection to the interpeduncular nucleus (for the habenular nucleus), and to the dorsal hypothalamic area (for the dorsomedial nucleus). No sources of afferent pathways to the anterior thalamic nuclei were found in the mamillary complex. All the thalamic nuclei studied, togetherwith their connections, are considered diencephalic relay links in pathways comparable with the dorsal (in the case of the habenular nuclei) and the ventral (with respect to the anterior thalamic nuclei) pathways of the mammalian limbic system.

Immunohistochemical demonstration of serotonin nerve fibers in the hypothalamus of the cat.

Distribution of serotonin nerve fibers in the hypothalamus of the cat was studied using the peroxidase antiperoxidase (PAP) immunohistochemical method. There was a heavy concentration of serotonin nerve fibers in the nucleus suprachiasmaticus, the nucleus ventromedialis and the nucleus dorsomedialis. The distribution pattern of the serotonergic fibers in the cat was principally similar to that of the rat and monkey. However, species differences were noted in the mamillary complex, the nucleus hypothalamicus anterior, the nucleus paraventricularis and the nucleus supraopticus.

The morphology and connections of the posterior hypothalamus in the cynomolgus monkey (Macaca fascicularis). I. Cytoarchitectonic organization.

The cytoarchitectonic organization of the posterior hypothalamus of the cynomolgus monkey (Macaca fascicularis) was analyzed in Nissl, Golgi, acetylcholinesterase, and reduced silver preparations. The region consists of a number of cell masses that differ considerably in their discreteness and in the homogeneity of their neuronal populations. 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). As a basis for the subsequent experimental study of the efferent connections of the posterior hypothalamus, the location of each of these cell masses is described and illustrated in a series of low-power photomicrographs, as are the form and distribution of the resident neuronal populations of the various components of the mamillary complex as seen in Golgi preparations.

The morphology and connections of the posterior hypothalamus in the cynomolgus monkey (Macaca fascicularis). II. Efferent connections.

The efferent connections of the posterior hypothalamus have been analyzed autoradiographically in a series of eight cynomolgus monkey (Macaca fascicularis) brains with injections of 3H-amino acids in different regions of the mamillary complex and the surrounding areas. The medial mamillary nucleus was found to project through the mamillothalamic tract to the ipsilateral anteroventral, anteromedial, and interanteromedial nuclei, and by way of the mamillotegmental tract principally to the deep tegmental nucleus (of Gudden). It also appears to contribute fibers to the medial forebrain bundle, some of which reach as far rostrally as the medial septal nucleus. 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 supramamillary area has extensive ascending and descending connections that are distributed with the medial forebrain bundle to the hypothalamus and rostral midbrain; in addition, it gives rise to an unusually well-defined projection to field CA2 of the hippocampus and to a narrow zone overlying the outer part of the granule cell layer and the adjoining part of the molecular layer of the dentate gyrus. We have not been able to distinguish the connections of the posterior hypothalamic nucleus from those of the caudal part of the lateral hypothalamic area: they both appear to contribute substantially to the ascending components of the medial forebrain bundle, and through its descending projection to the tegmental fields of the midbrain, the nucleus centralis superior of the raphe complex, the locus coeruleus, and the central gray as far caudally as the facial nerve. Their further projections to the spinal cord were not examined. Viewed broadly, and in the light of previous work, our observations confirm, once again, the constancy of the connections of the hypothalamus in the mammalian brain, and the pivotal position that the posterior hypothalamus occupies in the elaborate system of connections that links the limbic areas of the forebrain with the complex of structures that Nauta has aptly designated the "midbrain limbic region."

The distribution and concentration of thyrotropin-releasing hormone in discrete human hypothalamic nuclei.

TRH has been measured by RIA in 8 discrete human hypothalamic nuclei, the mammillary complex, the median eminence, and infundibular stalk. Tissues were derived from 13 subjects during autopsy after sudden death. Serial micropunch brain samples were secured from 300-μm frozen sections with stainless steel cannulae 1000 or 2000 μm in diameter. Pooled samples were extracted with 0.1 N HC1, lyophilized, and resuspended in phosphate-saline buffer for TRH determinations. Stability of TRH in postmortem tissues was assessed in rats sacrificed at varying time intervals before tissue extraction. TRH was detected in all structures examined. Highest concentrations of TRH were found in the median eminence area (3.139 ng/mg protein) and arcuate nucleus (2.034 ng/mg protein). Intermediate TRH concentrations, representing 5–10% of total TRH activity, were localized to the paraventricular and periventricular nuclei. Lowest TRH concentrations were found in the mamillary complex and the posterior, supraoptic, and anterior h...

Cell survival and architectonic differentiation of the hypothalamic mamillary region of the newborn mouse in culture.

AbstractThe development of the hypothalamic mamillary region of the newborn mouse has been studied in 519 cultures. The nuclear groups of the mamillary configuration as well as the infundibular nucleus may survive for at least 50 days. The surviving neuronal groups undergo in culture a further cytological and structural organization. The presence of ependymal tissue at the surface of the substrate enhances ependymal‐glial proliferation and this in turn supports the survival and new growth of the nerve cells in the adjacent areas. On the other hand, degeneration of white matter, especially if it occurs between the substrate and the overlying neuronal groups, has a highly detrimental effect leading to a profound regional neuronal loss. The survival of neuronal groups, the new axonal growth and the preservation of the cellular architectonics, which make possible their identification in culture, indicate that the mamillary complex has a capacity for regeneration during its development in isolation. The mamillary region and the infundibular nucleus display different developmental patterns and different structural organizations of their cells and axons. As a result, the culture seems to be divided morphologically into two distinctly separate regions.