Neurotransmitters microdialysis

Obviously, regulation of food intake depends on many neurotransmitters and hormones but this final section will outline the role played by central 5-HT transmission in this process. It had been the belief for some time that increased 5-HT transmission in the brain reduces food intake (Blundell 1977) and this certainly explains the satiety in rats that follows infusion of 5-HT into the paraventricular nucleus (PVN) of the hypothalamus. However, recent studies using microdialysis have found that 5-HT efflux in the lateral hypothalamus is itself increased by food intake, suggesting the existence of a feedback control system. In fact, because the increase in 5-HT efflux is greater in genetically obese rats than in their lean counterparts, it has been proposed that there is a deficiency in the 5-HT inhibition of food intake in obesity. 

O Brien KB, Esguerra M, Miller RF, Bowser MT (2004) Monitoring neurotransmitter release from isolated retinas using online microdialysis-capillary electrophoresis. Anal Chem 76 5069-5074... 

Klinker CC, Bowser MT (2007) 4-Fluoro-7-nitro-2, 1, 3-benzoxadiazole as a fluorogenic labeling reagent for the in vivo analysis of amino acid neurotransmitters using online microdialysis-capillary electrophoresis. Anal Chem 79 8747-8754... 

The effect of allethrin (a Type I pyrethroid), cyhalothrin, and deltamethrin (Type II pyrethroids) on neurotransmitter release from the hippocampus (acetylcholine, glutamate, and GABA release) and striatum (dopamine release) has recently been investigated using ex vivo microdialysis in freely moving rats exhibiting the symptoms of pyrethroid poisoning [94-97]. Deltamethrin increased the release... 

Neurotransmitters, peptides, and other endogenous substances in the extracellular space can be sampled using in vivo microdialysis. The dialysis membrane typically excludes the transport of larger molecules and enzymes that could otherwise interfere with analysis of the substances of interest. In the case of neurotransmitters, the levels in dialysates are the net result of the interaction between processes affecting release into and removal from the extracellular space. Consequently, in vivo microdialysis can only sample a neurotransmitter that has not yet been removed by clearing mechanisms and this method does not provide information regarding intracellular levels of substances. 

Bowser MT, Kennedy RT. 2001. In vivo monitoring of amine neurotransmitters using microdialysis with online capillary electrophoresis. Electrophoresis 22(17) 3668-3676. 

Zhou SY, Zuo H, Stobaugh JE, Lunte CE, Lunte SM. 1995. Continuous in vivo monitoring of amino acid neurotransmitters by microdialysis sampling with on-line derivatization and capillary electrophoresis separation. Anal Chem 67(3) 594-599. 

Toth E, Sershen H, et al (1992) Effect of nicotine on extraceUular levels of neurotransmitters assessed by microdialysis in various brain regions role of glutamic acid. Neurochem Res 17(3) 265-271... 

K. B. O Brien, M. Esguerra, R. F. Miller, and M. T. Bowser, Monitoring Neurotransmitter Release from Isolated Retinas Using Online Microdialysis-Capillaiy Electrophoresis, Anal. Chem. 2004, 76, 5069. 

If Ciniet has a value of zero, then equation (6.1) reduces to what is commonly called relative recovery and denoted in the literature as RR. The terms EE and RR are frequently interchanged and sometimes the general word, recovery, is used to describe the sampling efficiency of the microdialysis probe. It is important to note that the equivalence of EE versus RR under certain conditions such as with highly regulated concentrations of neurotransmitters has been debated in the literature 46... 

Justice JB. Quantitative microdialysis of neurotransmitters. Journal of Neuroscience Methods 1993, 48, 263-276. 

In vivo microdialysis is a technique that allows sampling of extracellular levels of neurotransmitters in discrete regions of the brain. The extracellular neurotransmitter levels provide an indication of the net activity of a particular set of neurons, including release, synthesis, and uptake, from conscious unanesthetized animals. For example, in vivo microdialysis studies have shown that extracellular 5-HT levels measured under appropriate conditions are dependent on the concentration of Ca2+ or K+ in the perfusion fluid, is inhibited by tetrodotoxin, and is predominately neuronal in origin (45). In addition, specific neural processes can be measured after the local application of agents through the microdialysis probe, such as release after application of hypertonic KC1, rate of synthesis after synthesis inhibitors, or the local effects of drugs (46). This technique has made it possible to more accurately quantitate and characterize the... 

The excitotoxic index was developed by our group as a composite descriptor of excitatory/inhibitory amino acid neurotransmitter balance as measured by microdialysis in the brain s extracellular space (66,102). This index is defined as ... 

Di Chiara G, Tanda G, Carboni E (1996) Estimation of in vivo, neurotransmitters release by brain microdialysis the issue of validity. Behav Pharmacol 7 640-657. 

The main target for microdialysis implantations is the ECF of various organs, predominantly the brain. The main objective of these studies is to find chemical correlations, as represented by measured neurotransmitter levels, to pharmaceutical, behavioral, pathological, or other stimuli. However, because of its small size a microdialysis probe allows sampling of fluids from other locations without first removing the fluid. Body fluids other than ECF to which the microdialysis technique has been applied are considered in Sections 6.3.1.1 to 6.3.I.6. 

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