[Study of neurological mechanism of lidocaine's suppression to tinnitus via microdialysis].

Objective: To elucidate the neurological mechanism of lidocaine's suppression to tinnitus.

Methods: Thirty-four Wistar rats weighing 300-350 grams were randomly divided into IC group (n = 17) and AC group (n = 17), according to microdialysis region. Each group was randomly subdivided into saline treatment group (n = 4), salicylate treatment group (n = 6), and salicylate + lidocaine treatment group (n = 7).

alpha-Sialylcholesterol enhances the depolarization-induced release of acetylcholine and glutamate in rat hippocampus: in vivo microdialysis study.

The effects of alpha-sialylcholesterol (alpha-SC), a synthetic ganglioside analogue, on synaptic neurotransmission were studied using in vivo microdialysis technique. Application of alpha-SC through a microdialysis probe enhanced high potassium-evoked release of acetylcholine and glutamate in the hippocampal CA3 region of Wistar rats. The experiments using synaptosomes and FM1-43, a fluorescent styryl dye used for studies of neurotransmitter release mechanisms, showed that alpha-SC increased depolarization-induced loss of dye but it did not evoke the dye loss at resting condition.

Perfusate oxygen and carbon dioxide concentration influence basal microdialysate levels of striatal glucose and lactate in conscious rats.

O(2) concentration ([O(2)]) in air equilibrated solutions at room temperature is three fold higher than that in brain extracellular fluid (ECF), and CO(2) concentration ([CO(2)]) is 100 times lower. Using microdialysis the ECF is routinely dialyzed against glucose free isotonic perfusates containing 200 microM O(2) and 10 microM CO(2). In conscious rats, 2 days after probe implantation, decreasing perfusate [O(2)] from 200 to 68 microM (physiologic level) for 60 min, while maintaining a low [CO(2)] (10 microM), increased striatal dialysate glucose and lactate by 12% and 33%, respectively.

Determination of carbohydrates as their 3-aminophthalhydrazide derivatives by capillary zone electrophoresis with on-line chemiluminescence detection.

A method based on pre-capillary derivatization with luminol (3-aminophthalhydrazide) for carbohydrate analysis using capillary electrophoresis with on-line chemiluminescence (CL) detection was developed. The derivatives of seven monosaccharides were separated and detected by using 200 mM borate buffer containing 100 mM hydrogen peroxide at pH 10.0 as separation electrolyte and 25 mM hexacyanoferrate in 3 M sodium hydroxide solution as post-capillary chemiluminescence reagent with separation efficiencies ranging from 160,000 to 231,000 plates per metre.

Analysis of glucose and lactate in hippocampal dialysates of rats during the operant conditioned reflex using microdialysis.

Changes of extracellular glucose and lactate in hippocampus for freely moving rats during the operant conditioned reflex were examined simultaneously. Samples of the dialysate were assayed for both glucose and lactate using in vivo microdialysis and a microbore flow injection analysis-immobilized enzyme reactor-electrochemical detection (FIA-IMER-ECD) system. Microdialysis samplings were conducted in a Skinner box where lights were delivered as conditioned stimuli (CS) paired with foot shocks as unconditioned stimuli (US).

Hyperoxia caused by microdialysis perfusion decreased striatal monoamines: involvement of oxidative stress.

Due to complex influence, such as utilization and permeability of arterial vessels to oxygen, there is a considerable difference of oxygen tension between extracellular fluid and perfusate usually used in microdialysis (30-60 Torr versus 145 Torr). Dialysate dopamine and monoamine metabolites-3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindoleacetic acid were measured under different kinds of oxygen tension solutions (145, 72, 48 Torr). In the acute and anesthetized group, dopamine, 3,4-dihydroxyphenylacetic acid, 5-hydroxyindoleacetic acid and homovanillic acid increased 72, 93, 86 and 65%, respectively when changing the perfusate from 145 Torr to near physiological 48 Torr, while in chronic and conscious group, carried out 72 h after surgery, these compounds showed obscure increases (only homovanillic acid produced a significant change of 14%).

Effects of salicylate on serotoninergic activities in rat inferior colliculus and auditory cortex.

In vivo microdialysis offers a unique approach to monitor biochemical events related to brain function and metabolism, and has been used extensively in many systems to measure the release of endogenous transmitters and other neuroactive substances during normal and pathological conditions. The characterization of neurotransmitters' changes induced by salicylate in the inferior colliculus (IC) and the auditory cortex (AC) may provide insight into the action of salicylate on the auditory system and, through this, provide a better understanding of neurological mechanism of salicylate-induced tinnitus. In the present study, the effect of salicylate on 5-HT system in IC and AC has been monitored by microdialysis in salicylate-induced tinnitus animal models.