Central nervous system axons

In humans, the hypothalamic-derived protein and the hormone noncovalent complexes are packaged in neurosecretory granules, then migrate along axons at a rate of 1 4 mm/h until they reach the posterior pituitary where they are stored prior to release into the bloodstream by exocytosis (67). Considerable evidence suggests that posterior pituitary hormones function as neurotransmitters (68) vasopressin acts on the anterior pituitary to release adrenocorticotropic hormone [9002-60-2] (ACTH) (69) as well as on traditional target tissues such as kidneys. Both hormones promote other important central nervous system (CNS) effects (9,70). 

Mode of Motion. The cyclodienes, like lindane and toxaphene, affect the nerve axon produciag hyperactivity, convulsions, prostration, and death. The biochemical lesion is the competitive inhibition of the y-aminobutyric acid (GABA) neurotransmitter binding site of the nerve axon. Spray workers with lengthy exposure to dieldrin have suffered from prolonged and repeated central nervous system disturbances produciag epileptiform coavulsioas. Similar disturbances occurred ia workers heavily exposed to chlordecoae. 

The nigrostriatal tract is one of the four main dopaminergic pathways in the central nervous system. About 75% of the dopamine in the brain occurs in the nigrostriatal pathway with its cell bodies in the substantia nigra, whose axons project in the corpus striatum. Degeneration of the dopaminergic neurons in the nigrostriatal system results in Parkinsons disease. 

The transport of information from sensors to the central nervous system and of instructions from the central nervous system to the various organs occurs through electric impulses transported by nerve cells (see Fig. 6.17). These cells consist of a body with star-like projections and a long fibrous tail called an axon. While in some molluscs the whole membrane is in contact with the intercellular liquid, in other animals it is covered with a multiple myeline layer which is interrupted in definite segments (nodes of Ranvier). The Na+,K+-ATPase located in the membrane maintains marked ionic concentration differences in the nerve cell and in the intercellular liquid. For example, the squid axon contains 0.05 MNa+, 0.4 mK+, 0.04-0.1 m Cl-, 0.27 m isethionate anion and 0.075 m aspartic acid anion, while the intercellular liquid contains 0.46 m Na+, 0.01 m K+ and 0.054 m Cl-. 

Tatagiba, M., Brosamle, C., and Schwab, M.E. 1997. Regeneration of injured axons in the adult mammalian central nervous system. Neurosurgery 40(3), 541-546. 

Hayashi, H., Campenot, R. B., Vance, D. E. and Vance, J. E. Glial lipoproteins stimulate axon growth of central nervous system neurons in compartmented cultures. J. Biol. Chem. 279 14009-14015,2004. 

McCarty, J. H, Lacy-Hulber, A., Charest, A., Bronson, R. T., Crowley, D., Housman, D., Savill, J., Roes, J. and Hynes, R. O. Selective ablation of (alpha)V integrins in the central nervous system leads to cerebral hemorrhage, seizures, axonal degeneration and premature death. Development 132 165-176,2005. 

Over the course of the last three decades, a variety of techniques have been used to characterize the circuitry of serotonergic neurons in the central nervous system. The density of serotonergic innervation in the forebrain was initially underestimated because the original histo-fluorescence method was limited in sensitivity and did not permit the detection of many fine axons and terminals. 

Neurotrophic factors promote both cell survival and axon growth after adult central nervous system injury in-vivo 524... 

Nogo-A is a potent inhibitor of neurite growth and blocks axonal regeneration in the central nervous system. Early in vitro experiments showed that neurite outgrowth was impeded across a culture dish coated with CNS myelin whereas neurites would actively grow on a... 

David, S. and Aguayo, A. J. Axonal elongation into peripheral nervous system bridges after central nervous system injury in adult rats. Science 214 931-933,1981. 

Avellino, A. M., Hart, D., Dailey, A. T., MacKinnon, M., Ellegala, D. and Kliot, M. Differential macrophage responses in the peripheral and central nervous system during wallerian degeneration of axons. Exp. Neurol. 136 183-198, 1995. 

---