Erowid References Database
Bramwell GJ, Gonye T.
“Responses of midbrain neurones to iontophoretically applied 5-hydroxytryptamine”.
It has been reported that cells in the raphe system of the rat were always depressed by small quantities of serotonin (5-HT) applied iontophoretically, whereas other midbrain cells were un-affected. These findings differed from earlièr findings from the same laboratory' when it was reported that raphe neurones in cats were unaffected by iontophoretically applied 5-HT, but were generally excited by noradrenaline or that a great proportion of raphe cells in rats were excited by 5-HT. Therefore it was decided to re-examine the sensitivity of raphe and other cells to iontophoretically applied 5-HT. Male albino rats were anesthetized with ciSloral hydrate and the responses of 80 midline midbrain cells to iontophoretically applied 5-HT (25-100 nA) were studied. The response to nor-adrenaline was also examined. 5/7 Raphe neurones tested were depressed by lysergic acid diethylamide, in currents which had no effect on non-raphe neurones tested. In these latter neuronesexcitatory responses to noradrenaline and glutamate as well as to 5-HT were antagonized by lysergic acid diethylamide. Raphe neurones were not the only midline midbrain neurones to be depressed by 5-HT. However their sensitivity'as determined in terms of recovery time.,was greater than other midbrain units. Raphe neurones did not respond to noradrenaline with excitation as had previously been reported in cats.
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