Membrane continued neuronal

Low concentrations of solubilised jS-albumin inhibit ACh release in slices from rat hippocampus and cortex areas which show degeneration in AzD, but not in slices from the striatum which is unaffected. While not totally specific to ACh, since some inhibition of NA and DA and potentiation of glutamate release have been reported, this effect is achieved at concentrations of A/i below those generally neurotoxic. Since jS-amyloid can inhibit choline uptake it is also possible (see Auld, Kar and Quiron 1998) that in order to obtain sufficient choline for ACh synthesis and the continued function of cholinergic neurons, a breakdown of membrane phosphatidyl choline is required leading to cell death (so-called autocannibalism), /i-amyloid can also reduce the secondary effects of Mi receptor activation such as GTPase activity... 

Na+ channels to depolarize the membrane all the way to threshold however, it brings the membrane potential closer toward it. This increases the likelihood that subsequent stimuli will continue depolarization to threshold and that an action potential will be generated by the postsynaptic neuron. 

In certain neurons, a different type of synapse, called a gap junction, may be formed. Gap junction transmission occurs through membrane channels made of six subunits, which directly connect with other postsynaptic gap junction channels. When the channels open, there is a continuity of cytoplasm and exchange of ions between the two neurons. This mode of transmission is faster because it does not involve the time-consuming processes of neurotransmitter release, diffusion across the synapse, and receptor binding. 

The acute toxic properties of all the organochlorine pesticides in humans are qualitatively similar. These agents interfere with inactivation of the sodium channel in excitable membranes and cause rapid repetitive firing in most neurons. Calcium ion transport is inhibited. These events affect repolarization and enhance the excitability of neurons. The major effect is central nervous system stimulation. With DDT, tremor may be the first manifestation, possibly continuing to convulsions, whereas with the other compounds convulsions often appear as the first sign of intoxication. There is no specific treatment for the acute intoxicated state, and management is symptomatic. 

The bounding membrane of the neuron is typical of all cells. It is a continuous lipid bilayer sheet of thickness about 60-80 angstroms. Embedded in it, or passing through it, are numerous proteins and glycoproteins, many of which are found only in nerve cells. These have many functions. Some provide structural support to the membrane, but most form ion channels and receptor sites that are essential to nerve function. 

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