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In Vivo Measurement Using Microdialysis of the Release and Metabolism of 5‐Hydroxytryptamine in Raphe Neurones Grafted to the Rat Hippocampus
Author(s) -
Sharp T.,
Foster G. A.
Publication year - 1989
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1989.tb07329.x
Subject(s) - raphe , hippocampus , serotonergic , microdialysis , raphe nuclei , serotonin , neuroscience , transplantation , biology , lesion , endocrinology , medicine , central nervous system , chemistry , pathology , receptor
The overflow and metabolism of serotonin (5‐hydroxy‐tryptamine; 5‐HT) from transplants of embryonic medullary and mesencephalic raphe neurones in the previously 5‐HT‐denervated hippocampus have been analyzed in vivo using intracerebral dialysis. The average density of 5‐HT‐immunoreactive fibres in the grafted hippocampus was less than in nonlesioned hippocampus. Nonetheless, both basal and potassium‐stimulated levels of 5‐HT in the dialysates were restored to approximately normal after transplantation of medullary raphe cells, whereas mesencephalic implants resulted in over twice the 5‐HT output observed in control hippocampus. However, 5‐hydroxyindoleacetic acid (5‐HIAA) overflow was increased only after grafting of mesencephalic raphe and then only to normal levels; medullary implants, by contrast, failed to enhance 5‐HIAA output above that from lesion‐only hippocampus. The evidence of a relative hyperactivity of the grafted neurones may explain the disproportionate improvements in various lesion‐induced behavioural deficits after grafting of nervous tissue. In addition, differences in the presynaptic regulation of 5‐HT release and metabolism are also apparent in the transplants; these variations are dependent on the precise origin of the serotoninergic cells.