Neuronal receptors expression profiles

Sun H., Kawahara Y., Ito K., Kanazawa I., and Kwak S. (2005). Expression profile of AMPA receptor subunit mRNA in single adult rat brain and spinal cord neurons in situ. Neurosci. Res. 52 228-234. 

Some neurons are more sensitive than others to the effects of a variety of toxicants that is, they display a selective vulnerability to neurotoxicants. For example, mitochondrial respiratory complex inhibitors such as cyanide and 3-nitropropionic acid are toxic to all cell types yet within the CNS, neurons in the basal ganglia (a group of regions that collectively control motor behavior) appear to be particularly sensitive to these agents. In most cases, selective vulnerability to neurotoxicants arises because of a unique combination of factors that predispose a cell type or region to particular insults. These factors may include the presence of certain ion channels, receptors or uptake sites, the activity level of xenobiotic metabolizing or antioxidant enzymes, the expression profile of neurotrophic factors or their receptors, and so on. Three CNS sites highly vulnerable to neurotoxicant effects are described separately below. 

The fact that the differential sensitivity of young animals is end point specific, however,. shows that simple kinetic parameters will not provide a full explanation for all age-related differences. As mentioned previously, many cholinesterase-inhibiting pesticides act at other neuronal sites (e.g., muscarinic and/or nicotinic receptors) in addition to the AChE enzyme. Since the expression of these receptors and/or actions develops at different rates (Karanth and Pope. 2003 Tice et ai, 1996), the age-related differences in the behavioral profile of a specific pesticide may be a function of the cholinergic receptors, if any, that it directly affects, Thus, whereas the toxicokinetic factors for different pesticides predict age-related differences in cholinesterase inhibition, it appears that toxicodynamic differences may have a greater influence on the behavioral effects. 

It has been observed that the discriminatory capabilities of human olfaction are tremendous It was estimated that an untrained person could differentiate up to ten million odors, perhaps even significantly more than that. Information theory then shows that in order to encode the qualities of ten million odors in a simple binary mode (Monoosmatic components on or off, their intensity, albeit important, is in this connection disregarded) only 2h to 27 specific profiles, disregarding possible and probable redundancies, and therefore the same number of complementary receptor sites would be required. Assuming furthermore that said redundancy, in which the informational modalities of two different specific receptor sites of two different olfactory neurons are confluent in one collector cell and therefore contribute to the expression of only one monoosmatic component is indeed operational it becomes necessary to increase the total number of types of specific receptor sites to 2k-30. This means that only 2U-30 specific detector proteins are required for structure recognition in the transduction process. This compares to about UOOO enzyme systems in different stages of activity estimated to be present in a cell any time. 

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