Artificial cerebrospinal fluid (aCSF) is commonly used as a vehicle solution for administration of test agents to the central nervous system (CNS) of laboratory animals. Listed below is a suggested method for the preparation of artificial CSF. This solution closely matches the electrolyte concentrations and physiological compatibility of endogenous CSF.
1. Preparation of Solution A
Weigh appropriate amounts of each compound listed below and dissolve in 500 ml pyrogen-free, sterile water:
2. Preparation of Solution B
Weigh appropriate amounts of each compound listed below and dissolve in 500 ml pyrogen-free, sterile water:
3. Preparation of Artificial CSF
Combine solutions A and B in a 1:1 ratio. Equal volumes of each solution are required to end up with a multivalent physiological ion solution of aCSF.
Recomended Storage Conditions: The aCSF solution may be stored at 4 degrees Celsius for up to 4 weeks. If the solution becomes cloudy, or there is indication of precipitation, discard and make a fresh batch. To preserve the pH and quality of the aCSF solution, we recommend making a fresh batch of the mixed solution (A and B) as needed. Solution A is a mixture of salts, and solution B is a mixture of buffers. When separate, solutions A and B may be stored at 4 degrees Celsius for longer periods. When mixed together, the solution is more prone to microbiological growth, thus it is recommended to store solutions A and B separately, and mix as needed.
4. Composition of Cerebrospinal Fluid in Various Species 1
(Concentration in mM)
*Note : Only one reference listed a concentration level. Therefore, the listed value was used.
1 Ion concentrations (except for the levels indicated with an asterisk) are an average of the data listed in Davson, H. Physiology of the Cerebrospinal Fluid, J. & A. Churchill, Ltd., London, 1967 and Biology Data Book , Volume III, 2nd ed., Fed. Am. Soc. Exper. Biol., Washington D.C., 1974
5. Comparison of Real and Artificial CSF Electrolyte Concentrations
(Concentration in mM)
*Note : Cerebrospinal fluid concentrations are an average of the values listed for the various animal species shown in #4 above.
1 Ion concentrations (except for the levels indicated with an asterisk) are an average of the data listed in Davson, H. Physiology of the Cerebrospinal Fluid, J. & A. Churchill, Ltd., London, 1967 and Biology Data Book , Volume III, 2nd ed., Fed. Am. Soc. Exper. Biol., Washington D.C., 1974
6. Explanation for the Absence of HCO3
Bicarbonate was not added to the formula for artificial CSF for two reasons:
- Bicarbonate can cause shifts in the pH of the solution as it converts to CO2.
- As HCO3converts to CO2 , bubbles can develop inside the pump. The presence of a gas in the pump can then affect the pumping rate in unpredictable ways.
Therefore, unless there is an urgent need for using bicarbonate in a study, we strongly recommend that it not be added to the formula for artificial CSF.