>Cites and three responses to GS Fraley's observations:
>>I do wonder if the authors have utilized techniques that would allow a
>conclusion that GnRH (aka LHRH) is not being produced in the mast cells.
>At least some precedent for such production is the fact that T-cells
>not only have receptors for GnRH but also can produce their own GnRH
>(1-4). Also, mast cells have a wide range of tissue-specific
>characteristics (5).
>Yes, as of my last conversation with Ray Silver, they were trying in situ
hybridization for GnRH mRNA. As of that time they were unsuccessful.
Certainly there is evidence for a great many cell types to produce GnRH,
including T cells. However, to the best of my knowledge no one has found
T cells within the CNS proper.Yes, mast cells localized everywhere from
the lung epithelium to lymph to being general granulocytes have various
characteristics....so what does that prove?
>>Habenula or habenular or habenulo... appears in more than 1100 titles and
>abstracts in Medline 1966-1996, and also has been studied and reported in
>many other articles that did not include the "habenu..." words in title
>or abstract. Possibly the best summary of the function of the habenula is
>the review by Reuven Sandyk (6). And GnRH has been reported to be found
>in the primate habenula since at least 1975 (7), and a sampling of
>habenula/primates cites is included (7-16).
>I in no way meant to imply that no one was researching the habenula. The
habenula has been shown to have strong inputs form the limbic and reticular
systems (Carpenter, 1991), from the basal ganglia (eg: Eisenberg, 1993;
Pontieri, 1992), from the cochlear nuclei (eg: Leake, 1993), and is generally
considered to be an important mediary step for many pathways leading from
the forebrain to the midbrain. A great many authors state in their papers
that lesion studies of the habenula are extremely difficult to ascertain
behavioral defecits. However some evidence points to a behavioral component
of the habenula in maintaining normal sleep patterns (Haun, 1992), in
specific learning sequelae (Thornton, 1991), and in certain types of motor
movement (Thornton, 1990). What I am getting at is the habenula cannot be
tied to any single system or behavior. Analysis of neurochemical components
of the habenula is extremely difficult to tie to a specific behavior/system.
And especially difficult when dealing with mast cell involvement in the
habenula since no one can ascertain any specific function for these mast
cells, although there certainly are postulates for their functionality.
>Given species differences between birds and mammals, I wonder whether
>"migration" is the most operative word when considering mast-cell
>contributions to neuronal function. Silver et al (0) write that
>"Alterations in the number of mast cells in response to age or
>environmental conditions have also been documented in other species
>(Hough LB 1988 Prog Neurobiol 30.469-505)." Also, "As noted above, mast
>cells are found in the medial habenula of several species."
>Ray Silver documents a movement of mast cells from the ependymal layer to
the habenular tissue proper. A general word for cell movement is "migration"
without having anything to do with a bird flying from point A to point B.
This word is quite useful even in dealing with different species.I do,
however, stand corrected in my statement regardig mammals. I was not aware
that mast cells within the habenula were becoming quite so common place.
>
>>Although the "habenula" has not graduated to the official recognition
>attentdant with its own Medline topic heading, 'tis a well studied
>nucleus whose role in behavior ought be no longer overlooked -- including
>its LHRH components, whether they be perikarya, neuronal processes, or
>(if at all) mast cells of the locally produced or visiting type.
>I certainly agree that there is a wide open field for understanding habenular
involvement in behavior. The mast cell aspect is also quite interesting.
Perhaps birds are a good place to start since they have no been shown to have
two to three different forms of GnRH, each in differnent areas (although some-
times mixed in the same areas) of the CNS. However, the behavioral component
of the habenula and in particular the mast cell component has a VERY LONG
way to go (as do many of our research interests!!!) and perhaps we should
avoid making grandiose statements/implications based upon Medline searches.
--Greg Fraley
"They say there's no devil, Jim,...but there is..."
