Fundamental Knoweldge about Microdialysis

What is Microdialysis?

A microdialysis probe has a semi-permeable membrane. Our probes have a 220 µm outer diameter. The probe inlet is connected to a syringe pump which continuously perfuses thorough the probe. As the perfusate travels through the probe, analytes cross the membrane and travel out the probe outlet to sample vials on a fraction collector or to a sample loop of an analytical system via narrow tubing. This valuable tool enables sampling of relatively low molecular weight compounds from within the extracellular space of tissues. The efficient recovery can be obtained for the compounds having a molecular weight up to 1500.  In the particular case of the brain and spinal cord, neurotransmitters are released to the extracellular space and this measurement has more meaning as informational transmitting than total tissue content. The collected extracellular fluid (ECF) is used to determine the chemical composition with sub-nanomolar sensitivity and detect small changes due to manipulation, or related to a physiological/behavioral change. The microdialysis implanted animals behave very close to normal conditions.

Microdialysis features are summarized;

• Sampling of molecules from the extracellular space.
• Enables a time course of concentration changes of low molecular weight compounds.
• Subject animal can behave normally.

Basic Brain Microdialysis Fundamentals

A microdialysis probe with a membrane is slowly implanted into the tissue via a surgically implanted guide cannula. The guide cannula can be implanted into the specific brain region for sampling from within an exact area. A perfusion liquid (Ringer or artificial cerebral spinal fluid, aCSF) solution is slowly pumped through the microdialysis probe and allowed to equilibrate within the tissue. Neurotransmitters (such as serotonin, dopamine, norepinephrine, acetylcholine, GABA, histamine, glutamate, glycine and neuropeptiteds) are allowed to pass between the extracellular space and the probe membrane which are then collected for neurochemical analysis.

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