Improved method for determination of catecholamines in rat brain by isolation on boric acid gel and high-performance liquid chromatography with electrochemical detection.

An improved sensitive, simple and time-saving method for determining catecholamine (CA) in rat brain is described. The method involves isolation on boric acid gel and high-performance liquid chromatography with electrochemical detection. Boric acid gel effectively adsorbs CA at weakly alkaline pH and the over-all recoveries of 5 ng and 10 ng samples of authentic norepinephrine (NE) and dopamine (DA) added to a homogenate of rat brain were 98.9 +/- 9.2% and 103.4 %/- 9.3% for NE and 96.2 +/- 4.6% and 99.4 +/- 4.8% for DA, respectively. Intra-assay variation was 5.3% (5 ng) and 3.0% (10 ng) for NE and 4.4% (5 ng) and 3.8% (10 ng) for DA. Inter-assay variation was 7.7% (1 ng) for NE and 5.0% (1 ng) for DA. With this analytical system, the lowest amount of NE or DA detectable was 40 pg. Application of this method to determination of the DA and NE contents of rat hypothalamus during estrous cycle revealed significant increases in the turnovers of both in the proestrus stage. This method should be useful for routine determination of plasma NE and DA because it is sensitive and inexpensive.