Talk:Raphe nuclei

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"The nucleus raphe dorsalis is rich in 5-HT1a autoreceptors and is therefore a target of serotonin specific reuptake inhibitors, or SSRI’s. This nucleus is composed of small, medium and large cells, oddly enough it has been shown that the large cells contain norepinephrine (Steinbusch HW, Nieuwenhuys R, Verhofstad AA, Van der Kooy D. The nucleus raphe dorsalis of the rat and its projection upon the caudatoputamen. A combined cytoarchitectonic, immunohistochemical and retrograde transport study. Journal of Physiology (Paris). 1981;77(2-3):157-74). This is unusual because the raphe nuclei have traditionally been thought of as specifically serotonergic, and to have non-serotonin related neurons comes as quite a surprise"

I have not read this paper, nor do I currently have the time to dig it out, how did they label noradrenergic cells in the Steinbusch study? I ask because I am not aware of many cells in the dorsal raphe staining for NA, certainly it is my experience that very few stain for tyrosine hydroxylase in the human DR. It seems odd to single out NA cells for comment when the dopaminergic and substance P containing neurons are well characterised in the DR, and it has been well established that only about 70% of DR neurons are positive for tryptophan hydroxylase anyway (e.g. Baker et al 1991, Neuroscience 42: 757-775).--Coroebus 18:05, 15 December 2005 (UTC)

What is the threshold of detection for tryptophan hydroxylase? I seem to recall that transcription of this enzyme is reduced in the presence of high serotonin levels. This area has low monoamine oxidase activity, at least according to one before-after image which demonstrates the effect of tranylcypromine on MAO activity, which would result in a higher than usual level of serotonin.

Tryptophan hydroxylase is very robustly detected by standard immunohistochemical techniques, (an alternative approach would be in situ hybridisation to detect the mRNA). Tryptophan hydroxylase is not so strongly influenced by 5-HT that it would have much effect on staining. The dorsal raphe is where most forebrain serotonin is made, it wouldn't be inhibited to a huge extent by 5-HT --Coroebus 09:18, 28 September 2006 (UTC)

Also, staining for tyrosine hydroxylase exclusively when attempting to detect NA seems inadequate, as one should also attempt to get a measure of dopamine-β-hydroxylase. Zuiram 20:46, 27 September 2006 (UTC)

Tyrosine hydroxylase is specific for catecholamine synthesising cells, so if there are not many cells positive for it, there will be even less positive for NA (since most TH positive cells are dopaminergic in the raphe). --Coroebus 09:18, 28 September 2006 (UTC)

There are too many inline references in this page, I'm going to change them to endnotes along the lines of the Dorsal raphe section.

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Does anyone know of any drugs that specifically target the neurons of the raphe system? I know vagus nerve stimulation can directly affect this area, but I don't know of any drugs that are selective for this region. Zuiram 20:40, 27 September 2006 (UTC)

There aren't any, although 5-HT1A agonists would have a particularly strong effect here. --Coroebus 09:18, 28 September 2006 (UTC)

[edit] Distribution of 5HT

The article mentions "Their main function is to release serotonin to the rest of the brain". What does this mean exactly? I thought seratonin, and other NTs, were synthesized in each neuron. Am I mistaken? If the article is correct, this implies that seratonin is created in this center and distributed somehow to other parts of the brain for re-use. If this indeed happens, please elaborate on this process. --1000Faces (talk) 03:20, 18 November 2007 (UTC)