Terminalis

The vomeronasal organ (VNO), located in the nose, is a small chemical sensing stmcture associated with odors and behavioral effects. The vomeronasal system, which is made up of the VNO and a portion of the brain s limbic system, is stmcturaHy independent of the olfactory and nervous terminalis systems in the nose. It may, however, interact with these systems in a manner dependent on prior experience or learning, and therefore be direcdy related to the association of smells and experiences. This independent chemosensory system in the nose may prove to open doors to new learning associated with the sense of smell and human behavior. 

The shell of the nucleus accumbens, the bed nucleus of the stria terminalis, and the central nucleus of the amygdala, together referred to as the extended amygdala, may play a role in diug addiction. 

Extrahypothalamic OX-B-like immunoreactivity, reminiscent to that of CRF, has been described in clustered GABAergic neuronal populations, in the lateral division of central nucleus ofthe amygdala, the bednucleus of the stria terminalis, and in the hippocampus. Moreover, ectopic expression of preproorexin mRNA in the gut, ependymal cells, neuroblastomas, and of orexin receptors in adrenal gland, cancer and hematopietic stem cells suggests yet unexplored roles of orexins as paracrine factors controlling blood-brain barrier, and tumor or stem cell function. 

Pali), P and Stamford, JA (1993) Real-time monitoring of endogenous noradrenaline release in rat brain slices using fast cyclic voltammetry. 2. Operational characteristics of the alpha2 autoreceptors in the bed nucleus of the stria terminalis, pars ventralis. Brain Res. 608 134-140. 

Absence from the first developmental stages as in whales and some Old World monkeys suggests that functional substitution is provided by other nasal chemoreceptors. The ganglia and fibres of the terminal nerve system (N. terminalis, Fig. 2.9) are the principal candidate (Wirsig and Leonard, 1987). The role of the trigeminal input, although a minor sensor, could well be expanded in a limited capacity (Tucker, 1971 Wysocki and Meredith, 1987 Westhofen, 1987). 

Fig. 2.9 Nasal chemoreceptive systems (Terminalis MOS and AOS) in neonate Rabbit. CP = cribriform plate F = forebrain GT = ganglion terminale NT(SNT) = Nervus terminalis ON = olfactory nvs. and F = forebrain (after Huber and Guild, 1913).

Fig. 4.4(a) Development of the N. terminalis in mammals and relationship to Vomeronasalis system (i) f = filia olfactoria (ii) induction of olfactory bulb and (iii) to (iv) separation of main/accessory systems (v,o) — from t, Nt system g, Nt ganglion + p/c, peripheral and t, central fibres (from Oelschlaeger, 1989). 

The ontogenesis of the AOS then, is closely bound up with the formation of its principal connection site within the mature brain. The sequence of events in mammals is revealed as a process which involves (1) early specialisation of presumptive GnRH cells (2) their attachment to and movement along specific (and transient) axonal bundles of the VN and N. terminalis tracts, and (3) coalescence of the neurocrine cells in the hypothalamus, where they complete differentiation as multi-axonal neurocrine cells. 

An early effort using this approach in Guinea-pigs reported variable results — attributable to incomplete nerve sectioning (Planel, 1953). Sectioning procedures may also produce some unwanted effects as intracranial nerve section will remove part of the animal s N. terminalis sensory capability (Devitsina and Cherova, 1992). 

Demski L.S. and Schwanzel-Fukada M., eds. (1987). The Terminal Nerve (Nervus Terminalis) — structure function and evolution. Ann NY Acad Sci 519, p. 531. 

Bojsen-Mpller F. (1975). Demonstration of terminalis, olfactory, trigeminal and perivascular nerves in the rat nasal septum. J Comp Neurol 159, 245-256. 

Huber G. and Guild R. (1913). Observations on the peripheral distribution of the Nervus terminalis in Mammalia. Anat Rec 7, 253-272. 

Larsell O. (1950). Studies on the Nervus terminalis mammals. J Comp Neurol 130, 3-68. 

Northcutt R.G. and Puzdrowski R. (1988). Projections of the olfactory bulb and Nervus terminalis in the Silver Lamprey. Brain Behav Evol 2, 96-107. 

Oelschlaeger H.A. (1989). Early development of the olfactory and N. terminalis systems in Baleen whales. Brain Behav Evol 34, 171-183. 

Oelschlaeger H.A. (1989). Development of the N. terminalis in mammals, including toothed whales and humans. Ann NY Acad Sci 519, 447-464. 

Oelschlager H.A. (1992). Development of the olfactory and terminalis systems in whales and dolphins. In Chemical Signals in Vertebrates 6 (Doty R.L. and Miiller-Schwarze D., eds), pp. 141-147. 

Schmidt A., Naujoks-Manteuffel C. and Roth G. (1988). Olfactory and vomeronasal projections and the pathway of the Nervus terminalis in ten species of salamanders — a whole mount study employing the horseradish-peroxidase technique. Cell Tissue Res 251, 45-50. 

Schwanzel-Fukuda M., Fadem B., Garcia M. and Pfaff D. (1988). Immunocytochemical localization of LHRH in the brain and Nervus terminalis of the adult and early neonatal Gray Short-Tailed opossum (Monodelphis domestica). J Comp Neurol 276, 44-60. 

Wirsig-Wiechmann C.R. (1993b). Nevus terminalis lesions, 1. No effect on pheromonally induced testosterone surges in male hamster. Physiol Behav S3, 252—255. 

Autoradiographic studies with [3H]R-(a)-methylhistamine have demonstrated the presence of high to moderate levels of H3 receptor binding in almost all layers of the cerebral cortex, striatum, bed nuclei of the stria terminalis, substantia nigra, amygdala, olfactory nucleus, hippocampus, and hypothalamus, especially on the cell somata, dendrites, and axonal varicosities of HA-containing TMN... 

Figure 7.4 Summary of some of the wide array of afferent and efferent connections of midbrain dopaminergic neurons (SN/A9, RRF/A8, and VTA/A10 in center of figure). This emphasizes their potential involvement in coordination of seemingly disparate behaviors inclusive of the sleep-wake state of the organism. Abbreviations BP, blood pressure BST, bed nucleus of the stria terminalis CEA, central nucleus of the amygdala MEA, midbrain extrapyramidal area NTS, nucleus of the solitary tract O2, oxygen tension PPN, pedunculopontine tegmental nucleus RRF, retrorubral field SN, substantia nigra VTA, ventral tegmental area.

Georges F., Aston-Jones G. (2001). Potent regulation of midbrain dopamine neurons by the bed nucleus of the stria terminalis. J. Neurosci. 21(16), RC160. 

Basal forebrain accumbens nuclei, ventral palbdum, bed nucleus of the stria terminahs, diagonal band bed nucleus of the stria terminalis, diagonal band, ventral pallidum... 

A major side-effect of morphine is respiratory depression. Opiates are believed to cause this effect via actions in brainstem nuclei, fi receptor immunoreactivity and mRNA were detected in neurons of the nucleus of the solitary tract, nucleus ambiguous, and parabrachial nucleus. mRNA was detected in the bed nucleus of the stria terminalis which projects to the nucleus of the solitary tract, fi receptor immunoreactivity is found in the nucleus of the solitary tract and dorsal rhizotomy reduced receptor immunoreactivity in the nucleus suggesting a presynaptic localization of the receptor. 

The amygdala is perhaps the best-studied, and most strongly implicated, brain structure in anxiety and fear. Electrical stimulation of the amygdala produces fear-like behavioral and physiological responses in animals, and increases the suggestive experience of fear in human subjects. Additionally, amygdala stimulation leads to corticosterone secretion and HPA-axis activation in animals, probably via outputs to the hypothalamus and the bed nucleus of the stria terminalis. It has been suggested... 

By contrast, the accessory olfactory system is thought to be involved in the detection of odors that influence a variety of reproductive and aggressive behaviors (Keverne 1999). Sensory neurons are located in the vomeronasal organ (VNO) and detect pheromones which gain access to the VNO by a pumping mechanism (Meredith and O Connell, 1979). VNO neurons send projections to the accessory olfactory bulb (AOB). Mitral cells of the AOB project in turn to the medial nucleus of the amygdala olfactory information is then dispatched to several hypothalamic regions such as the bed nucleus of the stria terminalis, the medial preoptic area and the ventromedial hypothalamus (Scalia and Winans 1975). 

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