Mammillary body

The ventral subgroup, situated at the ventral surface of the brain, rostral and caudal to the mammillary bodies, is the largest subgroup, containing approximately 2500 neurons (Kohler et a ., 1985). The ventral subgroup has fewer parvicellular neurons than the medial subgroup. 

The histaminergic neurons have several well-developed primary and secondary dendrites that overlap with each other. Furthermore, long dendrites from histaminergic neurons located close to the mammillary recess or to the basal surface of the mammillary body appear to penetrate into the ependymal layer and make contact with cerebrospinal fluid. Thus, it is likely that neuroactive substances such as cytokines, present in the cerebrospinal fluid, may influence the discharge activity of TMN neurons (Wada et al., 1991). Unlike the dopaminergic neurons, which are known to release dopamine from their dendrites, there is no evidence that these histaminergic dendrites store and/or release HA. 

Hypothalamus medial and lateral preoptic areas anterior, lateral, and posterior hypothalamic areas dorsomedial and ventromedial nuclei tuberomammillary nucleus medial and lateral preoptic areas, lateral hypothalamic area, dorsomedial nucleus, complex of mammillary bodies... 

Medium-high density of D2 receptors was found in the islands of Calleja, ventral pallidum, zona incerta, GP, central amygdala, in some cells of the anterior lobe of the pituitary, and at several sites in the forebrain the laterodorsal septal area, hippocampus, subiculum, lateral habenula, STh, lateral mammillary bodies. D2 receptors were also found with a medium-high density in various cortical fields prefrontal, anterior cingulate, entorhinal and perirhinal cortices. In the brain stem, medium-high density of D2 receptors was found in the VTA, SNc, ventral SNr, parabrachial nucleus, superior and inferior colliculi, dorsal raphe nucleus and locus coeruleus. 

Initially, there is a confused state, Korsakoff s psychosis, that is characterized by confabulation and loss of recent memory, although memory for past events may be unimpaired. Later, clear neurological signs develop - Wernicke s encephalopathy. This is characterized by nystagmus and extraocular palsy. Postmortem examination shows hemorrhagic lesions in the thalamus, pontine tegmentum, and mammillary body, with severe damage to astrocytes, neuronal dendrites, and myelin sheaths. 

The subiculum is an important area for hippocampal efferents. The brain target regions for subicular projections include, but are not limited to, thalamic nuclei (Aggleton et al., 2005), reunions nucleus(Herkenham, 1978), mammillary body of the hypothalamus (Aggleton et al., 2005) and amygdala (Kishi et al., 2006). The para-subiculum and pre-subiculum project heavily to the anterior thalamic nuclei (Sikes et al., 1977 Cohen and Eichenbaum, 1993). 

Aggleton JP, Vann SD, Saunders RC (2005) Projections from the hippocampal region to the mammillary bodies in macaque monkeys. Eur J Neurosci 22 2519—2530. 

The anterior hippocampal continuation (AHC) has been described in detail elsewhere (Wyss and Sripanidkulchai, 1983 Adamek et al. 1984). It is located just ventral to the rostrum of the corpus callosum and dorsal to the taenia tecta. The AHC has also been called ttj (Switzer et al. 1985) and has been described in detail in the rat (Wyss and Sripanidkulchai, 1983). The inputs to AHC are similar to IG as are its efferent connections with the outstanding difference that IG does not project to the olfactory bulb while there is a modest projection from AHC to the olfactory bulb (Wyss and Sripanidkulchai, 1983 Scheibel and Scheibel, 1978 De Olmos et al. 1978). Other major efferent projections of the IG and AHC are to the mammillary bodies and anterior thalamic nuclei. 

Rubio, S., Begega, A., Santin, L.J. and Arias, J.L. (1996). Ethanol- and diazepam-induced cytochrome oxidase activity in mammillary bodies. Pharmacol. Biochem. Behav. 55, 309-314. 

Ventricular dilatation (34%) MammiUary body atrophy (75%) Cerebellar vermal atrophy (34%) Cerebellar atrophy (21%) Paraventricular atrophy (5%) Mammillary bodies (99%) Third ventricular wall (61%) Thalamus (61%) Midbrain (50%) Pons (50%) MeduUa (33%)... 

Charness, M.E. (1999). Intracranial voyeurism revealing the mammillary bodies in tilcoholism. Alcohol. Clin. Exp. Res. 23 1941-1944. 

Shogry, M.E. and Curnes, J.T. (1994). Mammillary body enhancement on MR as the onlly sign of acute Wernicke encephalopathy. Am. J. Neuroradiol. 15 172-174. 

Human brains show symmetrical necrotic lesions most consistently in the mammillary bodies but also in the periaqueductal midbrain, thalamus, and along the floor of the fourth ventricle. These are the lesions of the acute disease, not necessarily associated with disordered memory. The changes in patients from the Korsakoff end of the spectrum differ by virtue of consistent involvement of the diencephalon, particularly the medial dorsal nucleus of the thalamus. This structural lesion, rather than a reversible biochemical process, appears to be responsible for the memory loss. Thus, patients with third ventricular tumors, resection of inferomed-ial portions of the temporal lobes, or sequelae of herpes encephalitis may demonstrate classical signs of Korsakoff s psychosis (Victor et al., 1971). 

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