Microdialysis probes

Cecchi, M., Passani, M. B., Bacciottini, L., Mannaioni, P. F. and Blandina, P. Cortical acetylcholine release elicited by stimulation of histamine HI receptors in the nucleus basalis magnocellularis a dual-probe microdialysis study in the freely moving rat. Eur. J. Neurosci. 13 68-78, 2001. 

S. Macha and A. K. Mitra. Ocular pharmacokinetics in rabbits using a novel dual probe microdialysis technique. Exp. Eye Res. 72 289-299 (2001). 

Enrico P, Bouma M, de Vries JB, Westerink BH. 1998. The role of afferents to the ventral tegmental area in the handling stress-induced increase in the release of dopamine in the medial prefrontal cortex a dual-probe microdialysis study in the rat brain. Brain Res 779(1-2) 205-213. 

Kawahara Y, Kawahara H, Westerink BH. 1999. Tonic regulation of the activity of noradrenergic neurons in the locus coeruleus of the conscious rat studied by dual-probe microdialysis. Brain Res 823(1-2) 42-48. 

Moor E, Schirm E, Jacso J, Westerink BH. 1998. Involvement of medial septal glutamate and GABAA receptors in behaviour-induced acetylcholine release in the hippocampus a dual probe microdialysis study. Brain Res 789(1) 1-8. 

Weikop P, Egestad B, Kehr J. Application of triple-probe microdialysis for fast phar-macokinetic/pharmacodynamic evaluation of dopamimetic activity of drug candidates in the rat brain. J Neurosci Meth 2004 140 59-65. 

Woo KL, Lunte CE (2008) The direct comparison of health and ulcerated stomach tissue a multiple probe microdialysis sampling approach. J Pharm Biomed Anal 48 85-91... 

The microdialysis sampling process which allows the monitoring of small molecules in circulation within an animal, is an example. An artificial capillary is placed in the tissue region of interest, and a sample is coUected via dialysis. In the case of a laboratory animal such as a rat, a probe is placed in the jugular vein under anesthesia. Elow rates ate of the order of 1 p.L/min. 

Figure 4.6 The tip of a microdialysis probe, expanded to show dialysis tubing around a steel cannula through the base of which fluid can flow out and then up and over the membrane. The length of membrane below the probe support can be altered (1-10 mm) to suit the size of the animal and the brain area being studied. Flow rates are normally below 2 pl/min...

Figure 4,7 The effect of perfusion of the microdialysis probe with a medium containing a depolarising (80 mM) concentration of K" ", or Ca +-free medium, for the periods indicated by the bars. The graph shows efflux of noradrenaline in the frontal cortex of anaesthetised rats. Increasing the concentration of K" " in the medium infused via the probe increases noradrenaline efflux whereas removing Ca reduces it...

Figure 4.8 Noradrenaline concentration in dialysis samples from probes implanted in the rat frontal cortex. Spontaneous efflux of noradrenaline is stable throughout a 4h sampling period ( extended basals ) but is increased markedly when either the noradrenaline reuptake inhibitor, desipramine (5 pM), or the a2-adrenoceptor antagonist, atipamezole (0.5 pM), is infused into the extracellular fluid via the microdialysis probe ( retrodialysis )...

Figure 1.6 (A) Changes in c-Fos IR in hypocretin/orexin(HCRT+)- containing neurons in response to BIC treatment as a function of distance from the microdialysis probe. The percentage of double-labeled cells was greatest closer to the probe (grids 1 and 2, compared with 3 and 4) and was greater with higher concentrations or exposure times. Contralateral cells were not affected. (B) Much lower percentages of melanin-concentrating hormone (MCH+) exhibited c-Fos IR activation in response to BIC. From Alam et al. (2005).

Flow sensors were also used coupled with microdialysis probe [236], providing several advantages the reaction took place in few minutes allowing continuous analysis the sensitivity was in the order of pmoles the microdialysis probe allowed biological specimens to be drawn without proteins or macromolecules. This technique can be extended to the analysis of analytes that need to be detected continuously such as during therapy monitoring, or in emergency care units. 

The technique consists of a microdialysis probe, a thin hollow tube made of a semi-permeable membrane usually around 200-500 /xm in diameter, which is implanted into the skin and perfused with a receiver solution that recovers the unbound permeant from the local area. In principle, the driving force of dialysis is the concentration gradient existing between two compartments separated by a semi-permeable membrane. For skin under in vivo conditions, these compartments represent the dermal or subcutaneous extracellular fluid (depending on the probe position) and an artificial physiological solution inside the probe [36-38],... 

The relative recovery (RR) of the probe, essential for data interpretation, is calculated using the retrodialysis method, which assumes that the net transport through the microdialysis membrane from the perfusate to the surrounding tissues equals the net transport from the tissues into the perfusate. The equation for calculation is represented as follows [39] ... 

F.-X. Mathy, A.-R. Denet, B. Vroman, P. Clarys, A. Barel, R. Verbeeck, and V. Preat. In vivo tolerance assessment of skin after insertion of subcutaneous and cutaneous microdialysis probes in the rat. Skin Pharmacol. Physiol. 16 18-27 (2003). 

In vivo microdialysis is based on the principle of dialysis, the process whereby concentration gradients drive the movement of small molecules and water through a semipermeable membrane. In vivo microdialysis involves the insertion of a small semipermeable membrane into a specific region of a living animal, such as the brain. The assembly that contains this semipermeable membrane is called a probe, which is composed of an inlet and an outlet compartment surrounded by a semipermeable membrane (see O Figure 9-1). Using a microinfusion pump set at a low flow rate (0.2-3 /rL/min), an aqueous solution known as the perfusate is pumped into the inlet compartment of the microdialysis probe. Ideally, the... 

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