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Vol. 18 No. 4
Bioanalytical Systems, Inc. / March 2000


Foreword (7k)
Happy Y2K! Time moves along quickly...

Four Channel Liquid Chromatography/ Electrochemistry (49k)
The new epsilon electrochemical detector is a potent analytical tool, as demonstrated by studies of natural anti-oxidants in green tea and honey.

The new epsilon™ family of electrochemical detectors from BAS can control up to four working electrodes simultaneously. There are several advantages to using multiple detector electrodes. By using four different applied potentials with electrodes placed in a parallel arrangement, a hydrodynamic voltammogram can be generated quickly through acquisition of four data points for every analyte injection. This speeds method development time. In addition, co-eluting compounds in complex mixtures can be resolved on the basis of their observed half-wave potentials by using the same arrangement of electrodes, also in parallel. This article presents a few examples of four-electrode experiments performed with epsilon detectors in the BAS R&D labs during the past few months, using both radial-flow and cross-flow thin-layer configurations.

The Effects of Melatonin Administration on the Release of Endogenous 5-HT and Its Metabolite
Kasuaki Yoshioka uses on-line brain microdialysis coupled to liquid chromatography to follow fluctuations in serotonin in the suprachiasmatic nuclei of the rat brain. Simultaneous animal activity measurements were correlated with neurochemical changes after melatonin administration.

The effect of melatonin administration on the release of 5-HT (5-hydroxytryptamine, serotonin), 5-HIAA (5-hydroxyindoleacetic acid), DOPAC (3, 4-dihydroxyphenylacetic acid), and HVA (homovanillic acid) in the suprachiasmatic nuclei (SCN) of freely-moving rats was studied by in vivo brain microdialysis coupled to liquid chromatography/electro-chemistry (LCEC). The extracellular concentration of 5-HT in the SCN was significantly increased, reaching a maximum dialysate concentration of 4 ng/mL between 60 and 180 min after oral administration of 10-mg melatonin at circadian time (CT) 18. In contrast, release of the 5-HT metabolite 5-HIAA, was significantly reduced by this treatment. Interestingly, those effects were only obtained after nighttime (CT 18) administration of melatonin, but not after daytime (CT 6) administration. These preliminary results suggest that melatonin stimulates the serotonergic system in the rat SCN. That this effect only occurred following nighttime (CT18), but not daytime (CT 6) melatonin administration further suggests that there may be a circadian element to melatoninís influence upon 5-HT. In addition, these experiments illustrate the simultaneous monitoring of rotational behavior and neurochemical changes using the Raturn™ awake animal system coupled to a Pollen-8™ on-line LC injector.

Pulsed Amperometric Detection with the epsilon™ LCEC Detector (30k)
Bruce Solomon demonstrates the utility of the new epsilon system for pulsed techniques, including sugars, carbohydrates and polyalcohols.

Controlled Current Techniques (25k)
Classical electroanalysis is also possible on the epsilon system, as discussed by Adrian Bott.

The epsilon™ instruments can perform both controlled potential (potentiostatic) and controlled current (galvanostatic) experiments. Although potentiostatic experiments are much more common, there are some applications for which a galvanostat is advantageous.

Electrochemical Titrations
Electrochemical titrations are among the most widely utilized applications of electrochemistry. Adrian Bott explains the principles of the technique.

One of the most widely used applications of electrochemistry is for determining the endpoint of titrations. Advantages of electrochemical methods over other methods (e.g., visual methods) include greater sensitivity, as well as increased accuracy and precision. These methods are based on simple electrochemical techniques, which are all available on epsilon™ instruments. Inexpensive motorized pipettes as well as stepper motor-controlled miniature syringe pumps (e.g., BAS Bee infusion pumps) can facilitate titrations in small volumes, both for research and teaching purposes.

Contingent and Non-Contingent Intracranial Electrical Stimulation Using the Raturn™
Prof. Garris discusses the use of the BAS Raturn as a tool for evaluating the behavior or rats receiving intracranial electrical stimulation.

We describe the use of the Raturn™ for investigation of behavior associated with contingent and non-contingent (or experimenter applied) intracranial electrical stimulation in the rat. The results support previous qualitative observations by our laboratory and may yield insight into the role of the neurotransmitter dopamine in the brain reward system.

Culex ABS Part I (119k)
Automated serial blood sampling from freely-moving rats is now possible because of a new robotic system developed by BAS.

At the National AALAS annual meeting (November, 1999) BAS introduced a new class of instrument. The Culex Automated Blood Sampler (Culex ABS) was designed to facilitate research in pharmacokinetics, drug metabolism and toxicology by automating the collection of whole blood from awake and freely-moving rats. This approach eliminated the extensive animal handling and restraints normally associated with manual blood sampling. In fact, rats in this system could roam freely in a cage, with food, water, and no interference in their normal activities while blood sampling was underway. A single animal could be used for studies ranging from a few hours to several days. The sampling times, and the blood volume removed at each time point, were programmable by the user. Four animals could be housed in the system with asynchronous sampling protocols.

Culex ABS Part II (236k)
The caging system in the automated blood sampler also provides animal activity measurements.

As a company involved with biomedical analysis for more than 25 years, BAS has processed all of the common body fluids including whole blood, plasma, serum, urine, bile, and CSF. It is more common for researchers in biomedical research to collect these biofluids than to conduct microdialysis, an alternate in vivo sampling method that we have offered since 1985. Yet, it was microdialysis, and one of the products we developed to support the technique, that lead us to design the Culex™ Automated Blood Sampler. The discussion offered here provides some background on our approach to managing the natural movement and activity of animals housed in the Culex. This approach derives from the BAS Raturn™ System for Awake Animals, which was originally developed to protect the integrity of inlet and outlet tubing lines used in microdialysis.

Pharmacokinetic and Pharmacodynamic Studies in Rats (56k)
The Culex ABS was used to monitor a psychoactive drug and its metabolite in the blood plasma and urine of a freely-moving rat. Post-dose behavioral changes were recorded by the system and compared with drug concentration.

A well-characterized prescription medication was used to demonstrate the utility of an automated blood sampling device for basic research in pharmacokinetics and pharmacodynamics. Both the parent drug and one of its major metabolites were monitored in plasma samples and urine collected simultaneously from the same animal. Animal activity measurements during the sampling period were used to evaluate behavioral changes after administration of the drug, and correlated both with observations by the investigators and drug concentrations in plasma.

Introducing epsilon. What does epsilon imply? (45k)
Craig Bruntlett introduces the epsilon concept for BAS instruments.

A highly-interactive approach to chemical analysis has been developed by BAS through the introduction of an instrument platform named epsilon. Experiments can be both monitored and controlled from any remote location with Internet access. Such worldwide connectivity enables global research collaborations, as well as the ability to select, purchase and take delivery of new analytical methods whenever they are needed. The epsilon-enabled instruments join the needs of the research laboratory with the convenience of e-business.

Products, In the EC Literature, In the MD Literature (88k)
Products: PM-90e pumps, desalter for LC/MS, pulse rate monitor for small animals
In the EC Literature: Reviewed by Adrian Bott
In the MD Literature: James Gitzen examines the microdialysis-mass spectrometry connection

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