Monitoring Dopamine in Vivo by Microdialysis Sampling and On-Line CE-Laser-Induced Fluorescence

Abstract

Microdialysis sampling was coupled on-line to micellar electrokinetic chromatography (MEKC) to monitor extracellular dopamine concentration in the brains of rats. Microdialysis probes were perfused at 0.3 microL/min and the dialysate mixed on-line with 6 mM naphthalene-2,3-dicarboxaldehye and 10 mM potassium cyanide pumped at 0.12 microL/min each into a reaction capillary. The reaction mixture was delivered into a flow-gated interface and separated at 90-s intervals. The MEKC separation buffer consisted of 30 mM phosphate, 6.5 mM SDS, and 2 mM HP-beta-CD at pH 7.4, and the electric field was 850 V/cm applied across a 14-cm separation distance. Analytes were detected by laser-induced fluorescence excited using the 413-nm line of a 14-mW diode-pumped laser. The detection limit for dopamine was 2 nM when sampling by dialysis. The basal dopamine concentration in dialysates collected from the striatum of anesthetized rats was 18 +/- 3 nM (n = 12). The identity of the putative dopamine peak was confirmed by showing that dopamine uptake inhibitors increased the peak and dopamine synthesis inhibitors eliminated the peak. The utility of this method for behavioral studies was demonstrated by correlating dopamine concentrations in vivo and with psychomotor behavior in freely moving rats following the intravenous administration of cocaine. Over 60 additional peaks were detected in the electropherograms, suggesting the potential for monitoring many other substances in vivo by this method.

Molecular recognition with boronic acids—applications in chemical biology

“…Testing this system in a biological context, the authors were able to quantify the concentration of dopamine in a rat brain dialysate as 10 nM, a figure which agreed with previously reported values [35,69]. Moreover, upon adding a dopamine reuptake inhibitor to the sample, dopamine was released from the transporting proteins.…”

The Motivation to Self-Administer is Increased After a History of Spiking Brain Levels of Cocaine

“…Many self-administration studies have applied the equation to estimate brain concentrations of cocaine in live animals (Ahmed and Koob, 2005;Samaha et al, 2002;Zernig et al, 2007;Zimmer et al, 2011), and the equations have also been applied in studies using electrophysiology (Nicola and Deadwyler, 2000;Peoples and Cavanaugh, 2003;Peoples et al, 2004Peoples et al, , 2007, microdialysis (Wise et al, 1995) and voltammetry (Hermans et al, 2008;Stuber et al, 2005a, b). These studies have demonstrated that the modeled brain-cocaine concentrations are highly correlated with NAc dopamine levels (Hermans et al, 2008;Shou et al, 2006;Wise et al, 1995) as well as cocaine-induced locomotor behavior (Shou et al, 2006).…”

Capillary Electrophoresis in Bioanalysis

“…Recently, 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was used as a fluorogenic label for the online, high-speed microdialysis-CE analysis of amino acid neurotransmitters (29). Sixteen amino acids were identified and separated every 20 s with improved detection sensitivity.…”