Septal nucleus

Cingulate cortex Septal nuclei Occipital cortex Parietal cortex... 

The main projections of the DRN and the MRN ascend through the forebrain within the median forebrain bundle. The basal ganglia, substantia nigra, and amygdala are mainly innervated by the DRN, whereas MRN axons project densely to the basal forebrain, septal nuclei, thalamus, posterior hypothalamus, LDT, and DRN. The hippocampus receives an overlapping innervation from the DRN and the MRN (Hensler et al, 1994 Vertes et al, 1999) (Table 9.1). 

Limbic system amygdala (central, anterior, medial, and basolateral nuclei), medial and lateral septal nuclei medial septal nucleus... 

ACh is necessary for control of skeletal muscle in verterbrates, acting as the neurotransmitter at the neuromuscular junction. It is also involved in transmission in the autonomic nervous system (see below, under "Neuroanatomy"). Central ACh is produced in two general areas in the brain incuding the basal forebrain (medial septal nuclei, diagonal band... 

The intermediate length systems include the tuberoinfundibular system, which projects from the arcuate and periventricular nuclei into the intermediate lobe of the pituitary and the median eminence. This system is responsible for the regulation of such hormones as prolactin. The inter hypothalamic neurons send projections to the dorsal and posterior hypothalamus, the lateral septal nuclei and the medullary periventricular group, which are linked to the dorsal motor nucleus of the vagus such projections may play a role in the effects of dopamine on the autonomic nervous system. 

NK3 is also abundantly expressed in many limbic structures (Rothman et al. 1984 Shughrue et al. 1996 Spitznagel et al. 2001), while NKB is only produced in discrete areas, including the bed nucleus of the stria terminalis, the septal nuclei, and the central gray (Merchenthaler et al. 1992). It is conceivable that NKB is not the only ligand at NK3 receptors in the limbic system. 

The mesolimbic system, where the dopaminergic projections originate in the ventral tegmental area, the A10 region, and then spread to the amygdala, pyriform cortex, lateral septal nuclei and the nucleus accumbens. 

Immunohistochemical localization of 5-HT1A receptors has been accomplished by several groups with different antibodies (18-24). The highest 5-HT1A receptorlike immunoreactivity is detected in some septal nuclei, hippocampus,... 

The anatomical visualization of 5-ht1E receptor mRNA has been done in monkey and human brain by in situ hybridization histochemistry (75) see also Fig. 4) and in the guinea pig brain (Fig. 4). The strongest signals are seen in the caudate and putamen, islands of Calleja, external and internal cortical layers (layers II and V in the monkey brain), CA fields and dentate gyms of the hippocampal formation, dorsal and ventral parts of the lateral septal nuclei, and some hypothalamic nuclei. 

Other structures in this area make up the limbic system which is directly linked to the olfactory system. Areas called the septal nuclei and amygdala contain regions often called the pleasure centres, with the hippocampus concerned with motivational memory. Projections from the cerebral cortex connect with the thalamus, hypothalamus and posterior pituitary gland. The network of connections between all these different areas of the brain is highly complex. The role of the limbic system is significant in autonomic (involuntary or non-conscious) reactions that are implicated with emotional responses including fear, rage and motivation. 

Di receptor mRNA is most abundant in the olfactory tubercle, NAc and CPu. Cells expressing Di receptor mRNA were also found in the neocortex, lateral septal nuclei, amygdala, hypothalamus (and in particular in the suprachiasmatic nucleus), in the thalamus and in the retina. Di receptor mRNA was instead absent in the VTA, GP, SNr, SNc and EP (Mansour et al., 1990, 1992 Fremeau et al., 1991 Le Moine et al., 1991 Meador-Woodroff et al., 1991b Mengod et al., 1991 Weiner et al., 1991 Gaspar et al., 1995). 

Raisman G, Field PM (1973) A quantitative investigation of the development of collateral reinnervation after partial deafferentation of the septal nuclei. Brain Res 50 241-264. 

Besides the neuritic plaque, the other diagnostic lesion of AD is the neurofibrillary tangle. Tangles are non-membrane-bound masses of paired helical filaments, usually intermixed with straight filaments, found in the perinuclear cytoplasm of many limbic and cortical neuronal cell bodies. Smaller bundles of these abnormal filaments may occur in many, but not all, of the cortical dystrophic neurites found within and also separate from the neuritic plaques. Tangles are also observed in neurons of the subcortical nuclei (e.g., the cholinergic septal nuclei and nucleus basalis of Meynert) that project widely to limbic and association cortices rich in A/9 deposits. 

Mesolimbic Midbrain ventral tegmentum (At 0 area) Limbic areas (e.g., amygdala, olfactory tubercle, septal nuclei), cingulate gyrus Arousal, memory, stimulus processing, motivational behavior Relief of psychosis... 

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