Simultaneous Measurement of Extracellular Morphine and Serotonin in Brain Tissue and CSF by Microdialysis in Awake Rats

Abstract

In this report, we describe an HPLC with electrochemical detection assay for the simultaneous measurement of levels of morphine, serotonin, 5-hydroxyindole-3-acetic acid, and homovanillic acid in dialysates of various brain areas and CSF in the awake rat. Morphine could be detected in the dialysates after a single intraperitoneal injection, with doses as low as 1.0 mg/kg. The time course of extracellular morphine content in the lateral hypothalamus, striatum, cerebellum, periaqueductal gray, and dorsal horn of the spinal cord and in CSF, from the ventricles and cisterna magna, was similar. We detected morphine in the first 15-min sample, and levels peaked 45-60 min after injection. Maximal dialysate levels, however, varied with the type of dialysis probe used and the area sampled. The most efficient in vivo recovery was in CSF dialysates from the cisterna magna, presumably because of minimal tissue interference with the dialysis probe. For this reason, the cisterna is an ideal region for sampling CSF. Morphine had no significant effect on the extracellular concentrations of serotonin in any of the areas studied and did not modify or only slightly increased levels of tissue metabolites; however, morphine markedly increased the CSF levels of 5-hydroxyindole-3-acetic acid and homovanillic acid. Because microdialysis in freely moving animals permits assessment of the behavioral effects of morphine while continuously monitoring the drug levels in discrete brain regions, this approach will greatly facilitate future studies of the neurochemical basis of morphine's effects in the brain.

Serotonin (5-HT) release in the dorsal raph� and ventral hippocampus: Raph� control of somatodendritic and terminal 5-HT release

“…Each rat was implanted with two microdialysis probes to allow the simultaneous measurement of 5-HT, 5-HIAA and HVA from the dorsal raph6 and ventral hippocampus. Microdialysis probes were made as previously described (Matos et al, 1992) using an acrylonitrile-sodium methallyl sulfonate membrane (AN6HF, Hospal, Uden, The Netherlands; inner diameter 230~tm, outer diameter 290 ~tm, MW cut-off 40,000). The dialysis membrane was coated with epoxy glue, except for a 2mm (dorsal raph6) or 4mm (hippocampus) dialysis tip.…”

Postmortem serotonin (5-HT) concentrations in the cerebrospinal fluid of medicolegal cases

“…Acute administration of morphine increased the synthesis of cerebral 5-HT and the formation of 5-hydroxyindolacetic acid (5-HIAA) [32][33][34], furthermore these effects are antagonised e.g. by naloxone and naltrexone [29,[35][36][37][38][39]. Otherwise, during withdrawal from substained morphine or heroine treatment the cerebral 5-HIAA levels are reduced in rats [40], in mice [31] and in man, too [29,41].…”

Measurement and pharmacokinetic analysis of imipramine and its metabolite by brain microdialysis

“…Recent advances in brain microdialysis techniques have enabled the direct measurement of various neurotransmitters in the brain (Ungerstedt & Hallstroem, 1987), but pharmacokinetic investigations of psychotropic agents by this method are limited (Dubey et al, 1989;Matos et al, 1992;Tellez et al, 1992). Since pharmacokinetic drug monitoring is crucial for the rational therapeutic use of drugs, the feasibility of employing the brain microdialysis method for pharmacokinetic studies is of particular importance.…”