Hippocampal 5-HT1A receptor binding site densities, 5-HT1A receptor messenger ribonucleic acid abundance and serotonin levels parallel the activity of the hypothalamo-pituitary-adrenal axis in rats.
Burnet PW., Mefford IN., Smith CC., Gold PW., Sternberg EM.
We have previously demonstrated that susceptibility of the Lewis rat to inflammatory disease, compared to the relatively resistant Fischer F344 rat, is related to a hyporesponsive hypothalamopituitary adrenal axis to inflammatory and other stress mediators. Since 5-HT and the 5HT1A receptor are important stimulators of this axis, we have investigated the levels of 5-HT1A receptor binding sites and encoding mRNA, 5-HT and 5-hydroxyindole acetic acid in various brain regions of Lewis, Harlan Sprague Dawley and Fischer F344 rats. Lewis rats expressed significantly less hippocampal and frontal cortical 5-HT1A receptor binding sites and mRNA than Harlan Sprague-Dawley and Fischer F344 rats. Adrenalectomy increased the number of 5HT1A receptor binding sites and mRNA expression in the hippocampus of all three strains. The levels of hippocampal 5-HT in Fischer F344 rats were significantly greater than levels detected in the same regions for the other two strains. Hypothalamic 5-HT and 5-hydroxyindole acetic acid levels in Harlan Sprague-Dawley rats were higher than the same area from the other two strains. Adrenalectomy increased the levels of 5-hydroxyindole acetic acid in the hypothalamus of all three strains. We conclude that hippocampal 5-HT1A receptor densities and 5-HT levels in the rat parallel the the activity and responsiveness of the hypthalamopituitary-adrenal axis. We have published these data in an earlier report.