Push–pull perfusion is an

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, an ...

sampling method most commonly used for measuring

neurotransmitters A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotransmitters are rele ...

in the brain. Developed by J.H. Gaddum in 1960, this technique replaced the cortical cup technique for observing neurotransmitters. In order to analyze concentrations of

analytes An analyte, component (in clinical chemistry), titrand (in titrations), or chemical species is a substance or chemical constituent that is of interest in an analytical procedure. The remainder of the sample is called the matrix. The procedure ...

such as neurotransmitters, a probe consisting of two concentric tubes is implanted in the region of interest. A pump then pushes a neutral fluid such as saline or

Ringer's solution Ringer's solution is a solution of several salts dissolved in water for the purpose of creating an isotonic solutions, isotonic solution relative to the body fluids of an animal. Ringer's solution typically contains sodium chloride, potassium chlo ...

through one of the tubes, while another pump extracts the fluid through the other tube. While outside the tubes, the perfusion fluid picks up physiological substances such as neurotransmitters that are present in the area. The concentration of analytes of interest can then be measured in the expelled fluid, indicating in which concentration they are present at the site of interest at any given time. The advent of concentric

microdialysis Microdialysis is a minimally-invasive sampling technique that is used for continuous measurement of free, unbound analyte concentrations in the extracellular fluid of virtually any tissue. Analytes may include endogenous molecules (e.g. neurotra ...

probes in the 1980s resulted in push-pull sampling falling out of favor, as such probes require less monitoring, and are less invasive than the higher flow rate push-pull probes (>10 microliter/min), which could result in lesions if flow is unbalanced. With the advent of

microfluidics Microfluidics refers to a system that manipulates a small amount of fluids (10−9 to 10−18 liters) using small channels with sizes of ten to hundreds of micrometres. It is a multidisciplinary field that involves molecular analysis, molecular bi ...

and miniaturized probes, low-flow push–pull sampling was developed in 2002. By using flow rates of ~50 nL/min, this technique minimizes tissue damage while providing finer spatial resolution than

sampling.

References

External links

International Society for Monitoring Molecules in Neuroscience
Biochemistry methods Diagnostic neurology Neurochemistry Neurotechnology {{biochem-stub