in vivo Neurochemistry

Sygnature Discovery is a leading provider of intracerebral microdialysis services in rats and mice using passive methodologies and has just introduced the use of cerebral open flow microperfusion technology as part of its neurochemistry offering. Our dedicated team of experts have been conducting microdialysis studies for more than 20 years and can design bespoke studies to meet clients’ precise needs.

Microdialysis

Microdialysis is a technique which studies the effects of drugs on free concentrations of neurotransmitters and neuromodulators in different brain regions of freely moving or anaesthetized rodents. Typically, these studies evaluate the mode of action and/or efficacy of candidate compounds with potential for the treatment of CNS and metabolic disorders by characterizing their effects on neurochemistry in normal rodents and/or rodent models of a disease state.

Cerebral Open Flow Microperfusion (cOFM)

cOFM is an evolution of microdialysis that replaces the membrane at the tip of the probe with an open matrix, allowing direct sampling of the interstitial fluid as opposed to the passive diffusion method utilized by standard microdialysis. This in turn allows for greater recovery of analytes. The materials the cOFM probes are made from are designed to be as low bind as possible, allowing better recovery of lipophilic compounds and endogenous analytes. Their materials are also more inert than the membranes of traditional microdialysis probes meaning tissue reactivity to cOFM probes is minimal, significantly reducing glial scarring associated with long term implantation. This lends them to being ideal for PK/PD assessments as the disruption to the blood-brain barrier from implantation can be left to heal prior to sampling (recommended 2‑week recovery period for complete healing of BBB) leading to better compartmentalization between ISF, CSF and plasma.

Results are adjusted means; n=6 (CMA) n=5-6 (cOFM). SEMs are calculated from the residuals of the statistical model. Comparisons to vehicle for each probe are by the multiple t test. Significant differences vs vehicle: *p<0.05, **p<0.01, ***p<0.001.  Comparisons to the CMA probe (†p<0.05, ††p<0.01, †††p<0.001) are by a mixed linear model.

High-Sensitivity Neurochemical Analysis

Our experts use high sensitivity UHPLC and HPLC with electrochemical detection (ALEXYS™) or mass spectrometry (Thermo Scientific TSQ Altis) to measure:

• Dopamine
• Noradrenaline
• Serotonin
• Monoamine metabolites
• Gamma-aminobutyric acid (GABA)
• Glutamate
• Acetylcholine
• And others

Customizable Study Design

For either microdialysis or cOFM studies, the design is customizable to the clients’ needs including:

• Sampling can be conducted for up to 3 days following drug administration
• Single or dual probe studies in rats

Single-probe studies measure the effects of drugs on multiple neurotransmitters and their metabolites from a single region of interest in the same study.

Dual-probe studies allow investigation multiple brain areas simultaneously in the same study.

Integrated PK/PD and Behavioral Assessment

Our model also makes it possible to combine rat neurochemistry with behavioral assessment (using the Ethovision software, Noldus or Raturn, BASi) and automated stress-free blood sampling (using the Culex Bambino/Raturn System; BASi) for PK measurements to generate a detailed PK/PD assessment.

Maximizing Value From Neurochemistry Samples

Samples generated from neurochemistry studies can also be used to look at the recovery and measurement of free drug concentrations in the brain, or to measure drug and neurotransmitter levels in the same dialysate sample.

Applications in Abuse Liability Assessment

Neurochemistry plays a critical role in assessing abuse liability. Many drugs of abuse are associated with increased extracellular dopamine in the rat nucleus accumbens. Using microdialysis, we can monitor how novel treatments for substance use disorders influence this response, or whether a novel drug is likely to possess abuse potential.

Data are means; n=5-10. Vertical arrows indicate time of drug administration (0 min). Significant differences vs vehicle: *p<0.05, **p<0.01, ***p<0.001.

Contact us to discuss how intracerebral microdialysis or cOFM could support your CNS program.