ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: The effect of manipulating the activity of central 5-hydroxytryptamine (5-HT) neurones on extracellular 5-HT in ventral hippocampus of the chloral hydrate-anaesthetized rat was studied using the brain perfusion method, microdialysis. Basal levels of 5-HT in the dialysates were close to the detection limits of our assay using HPLC with electrochemical detection. However, addition of the selective 5-HT reuptake inhibitor citalopram (10−6M) to the perfusion medium produced readily measurable amounts of dialysate 5-HT. Citalopram, therefore, was used throughout our experiments. Hippocampal dialysate levels of 5-HT sharply declined over the first hour after dialysis probe implantation, but then became constant. This stable output of 5-HT was reduced by 57% in rats treated 14 days previously with intracerebroven-tricular injections of the 5-HT neurotoxin 5,7-dihydroxy-tryptamine. Electrical stimulation (1-ms pulse width, 300 μA, 2–20 Hz) of the dorsal raphe nucleus for 20 min caused a rapid rise in hippocampal 5-HT output, which immediately declined on cessation of the stimulus and was frequency-dependent. Addition of tetrodotoxin (10−6M) to the perfusion medium reduced 5-HT levels to 75% of predrug values. Injection of the 5-HT1A agonist 8-hydroxy-2-(di-n-propylami-no)tetralin (0.5 and 2.5 μg) into the dorsal raphe nucleus caused a dose-related fall in hippocampal output of 5-HT compared to saline-injected controls. We conclude from these data that the spontaneous output of endogenous 5-HT into hippocampal dialysates, measured under our experimental conditions, predominantly originates from central 5-HT neurones and changes in accordance with their electrical activity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1989.tb07319.x
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