title: In vivo dialysis setup with a loop injection valve facilitates retrodialysis studies.
abstract: BACKGROUND
  Retrodialysis, as used in neuropharmacological research, is a technique for in vivo delivery of neuroactive agents with concurrent monitoring of their effects on cellular activity with a separation between certain degree of spatial and temporal resolution. Typically, this is accomplished either by the use of a liquid-switch requiring multiple pumps, or by exchange of flow tubing requiring stopping and restarting dialysis. In the present study, we describe the use of a medium pressure injection valve for retrodialysis that overcomes these problems.
  
  
  METHODS
  The valve was configured with a loop to deliver 20μL of solution, and artificial CSF flow from the pump to the probe was established via this device. The application of this setup was evaluated in urethane anesthetized adult male C57BL/6J mice prepared with a CMA 11 probe implanted in the ventral hippocampus. By switching between the load and inject positions, the loop was filled with escitalopram solution (0.3μM) and delivered at a rate of 1μL/min at the probe for retrodialysis. Escitalopram (2mg/kg BW) was administered subcutaneously for microdialysis studies. During these treatments, dialysate fractions were collected for the determination of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA).
  
  
  RESULTS
  Irrespective of route of escitalopram administration, the pattern of dialysate 5-HT, and 5-HIAA response was comparable to that reported by other investigators. Accordingly, the in-line valve assembly did not compromise retrodialysis or microdialysis sampling. The manipulations to carry out retrodialysis using the valve setup are easy and simple.
  
  
  CONCLUSIONS
  An in-line injection valve is a promising adaptation for retrodialysis studies and can be incorporated as a standard part of in vivo dialysis instrumentation.
authors.affiliation: Department of Psychiatry & Behavioral Sciences, Emory University School of Medicine, Atlanta, GA 30322, USA. Electronic address: kthrivi@emory.edu.
authors.forename: K V
authors.initials: KV
authors.lastname: Thrivikraman
authors.affiliation: Department of Psychiatry & Behavioral Sciences, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Becky
authors.initials: B
authors.lastname: Kinkead
authors.affiliation: Department of Psychiatry & Behavioral Sciences, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Murray
authors.affiliation: Department of Psychiatry & Behavioral Sciences, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Owens
mesh_terms: D000818:Animals; D015283:Citalopram / Q000008:administration & dosage* / Q000494:pharmacology; D016503:Drug Delivery Systems; D006624:Hippocampus / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017551:Microdialysis / Q000295:instrumentation / Q000379:methods*; D012701:Serotonin / Q000378:metabolism; D017367:Selective Serotonin Reuptake Inhibitors / Q000008:administration & dosage* / Q000494:pharmacology
chemical_list: D015283:Citalopram; D006897:Hydroxyindoleacetic Acid; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors
keywords: 5-HT; Escitalopram; Medium pressure valve; Mouse; Reverse microdialysis; SSRI; Serotonin; Urethane