Spinal cord and peripheral

Immunolabeling for GluRl, GluR5/6/7 and NRl is found in unmyelinated axons in glabrous skin of the rat hindpaw (Carlton et al., 1995). They are believed to act as autoreceptors for secreted glutamate that may regulate the response to pain. 

A number of organs have glutamate receptors. In the adrenal gland, (1) GluRl and GluR3 predominate in different parts of the cortex, (2) GluR2 is in medullary cells, (3) GluR4 

Taste bud cells in the mouth are believed to respond to the taste of glutamate through the metabotropic glutamate receptor, mGluR4 (Chaudhari and Roper, 1998). However, there is evidence for ionotropic glutamate receptors, probably NMDA receptors, in taste bud cells (Chaudhari and Roper, 1998). It is not clear whether the latter receptors participate in taste transduction at the apical (tasting) end of the cell or are involved in synaptic transmission at the basolateral (neural) end of the cell. 

GluR5 is expressed in rare cells of the GCL and in the outer two-thirds of the INL, while GluR6 and GluR7 are expressed more commonly in cells of the GCL and are expressed throughout the INL (Hamassaki-Britto et al., 1993). Another study indicates that in the INL, 

GluR6 is limited to a subset of amacrine cells, while GluR7 is expressed in most amacrine and bipolar cells (inner and middle INL, respectively), but probably not in horizontal cells (IS, Brandstatter et al., 1994). KAl is not expressed in the rat retina, although described in the mouse retina (Zhang et al., 1996) in contrast, KA2 is common in cells throughout the GCL and INL (IS, Brandstatter et al., 1994). Immunolabeling for delta 1/2 is restricted to the neuropil of the inner plexiform layer (IC, Brandstatter et al., 1997). 

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Three tachykinin GPCRs, NK, NK, and NK, have been identified and cloned. AH are coupled to phosphatidjhnositol hydrolysis. The NK receptor is selective for substance P (SP) and is relatively abundant in the brain, spinal cord, and peripheral tissues. The NK receptor is selective for NKA and is present in the gastrointestinal tract, urinary bladder, and adrenal gland but is low or absent in the CNS. The NIC receptor is selective for NKB and is present in low amounts in the gastrointestinal tract and urinary bladder, but is abundant in some areas of the CNS, ie, the spinal dorsal bom, soUtary nucleus, and laminae IV and V of the cortex with moderate amounts in the interpeduncular nucleus. Mismatches in the distribution of the tachykinins and tachykinin receptors suggest the possibility of additional tachykinin receptor subtypes. 

The neuraxis is the rostrocaudal extension of the nervous system including forebrain, midbrain, brainstem, spinal cord, and peripheral nerves. 

The actions of all clinically used opiates can now be explained in terms of their acting as agonists at one of the four opiate receptors found in the brain, spinal cord and peripheral nervous system. All four receptors are inhibitory (Table 21.2). 

Chicken (White Leghorn) once 2500 F 5000 F (increased incidence of unspecified spinal cord lesions) 10000 F (ataxia, increased incidence of unspecified spinal cord and peripheral nerve lesions) Mortensen and Ladefoged 1992 Fyrquel EHC... 

The histological investigation showed that these OPC did not produce degeneration and demyelinization in hen s spinal cord and peripheral nervous system. 

Histopathological examination of tissues representative of the nervous system, including the brain, spinal cord, and peripheral nervous system Quantitative observations and manipulative test to detect neurological, behavioral, and physiological dysfuntions. These may include general appearance body posture... 

Huang SM, Strangman NM, Walker JM. 1999. Liquid chromatographic-mass spectrometric measurement of the endogenous cannabinoid 2-arachidonylglcerol in the spinal cord and peripheral nervous system. Zhongguo Yao Li Xue Bao 20 1098. 

In the neurotoxicity study (OECD TG 424/EU Annex B.43), the animals are tested to allow the detection or the characterization of behavioral and/or neurological abnormalities. A range of behaviors that could be affected by neuro toxic ants is assessed during each observation period. At the end of the test, a subset of animals of each sex from each group are perfused in situ and sections of the brain, spinal cord, and peripheral nerves are prepared and examined. 

The nervous system consists of the brain, spinal cord, and peripheral nerves. Whereas the hormones generated by the endocrine system discussed in the preceding section direct longer-term activities of the body, the nervous system sends impulses very rapidly to direct movement and response of the body. At intervals that are generally of slightly less than 1 sec, a sequence of nerve impulses directs the heart to beat from before birth to death, 24 h each day, 7 days of the week. If just a few of these impulses fail, life ends. 

Application of in vitro test methods have become advantageous in specific cases, such as structurally defined compounds and delayed neuropathy, since target cell data and biochemical processes associated in delayed neuropathy are known. Microscopic studies reveal that cases of OPIDN have degeneration of axons followed by demyelination of the nervous system.25,26 Epidemiologic studies have indicated mild impairment of the brainstem, spinal cord, and peripheral nerve functions in Gulf War veterans.27 Such studies are consistent with the spectrum of OPIDN syndrome. The main nerve agents have been shown to inhibit NTE in vitro as well as in vivo. Sarin has been shown to produce delayed neurotoxicity when administered at higher doses in protected hens.25-27... 

No histological alterations were observed in the brains of rats exposed for 2 weeks to a dust of 4-nitrophenol sodium salt at concentrations of up to 2,119 mg 4-nitrophenol/m (Smith et al. 1988). Gross and histological examination of the brain, spinal cord, and peripheral nerves of rats exposed to up to 30 mg 4-nitrophenol dust/m for 4 weeks revealed no treatment-related effects (Hazleton 1983). However, since neurological tests were not performed in these studies, reliable NOAELs for neurological effects cannot be determined. 

A few OPs have been shown to cause OPIDN, a retrograde degeneration of long and large nerve fibers in the spinal cord and peripheral nerves of humans and experimental animals. Some OPs, such as GB, chlorpyrifos, and isofenphos, require very high doses to be acutely neuropathic (WHO 1986 Lotti 1991). Inhibition of approximately 70% or more of the carboxylesterase NTE often is associated with the disorder (WHO 1986 Lotti 1991). Onset of OPIDN is usually 10 days to several weeks after exposure. It is not clear whether OPIDN can occur after long-term exposure to low concentrations of OPs. 

Neurons are the core cell elements of the brain, spinal cord and peripheral nerves that process and hansmit information. Neurons are composed of a cell body (soma), dendritic hee (arbor. 

The limited neuropachologic information available from studies of affected persons deanonstrates that OP poisoning Induces degeneration of nerve fibers in spinal cord and peripheral nerves (122). 

Veronesi. B.,Arodentmodeloforganophosphateinduceddelayedneuropathy distribution of central (spinal cord) and peripheral nerve damage, Neuropathol. Appl. Neurobiol., 10, 357-368, 1984. 

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