Serotonin is localized in the neurogenic niche and serotonin receptor subtypes are expressed in hemocytes and brain. A. The neurogenic niche labels immunohistochemically for glutamine synthetase (blue) and serotonin (green). The vascular cavity is outlined by a rim of serotonin labeling, clearly seen in a higher magnification image shown in B. The additional serotonin labeling observed in (A) near the niche is localized in terminals in the accessory lobe. C. RT-PCR reveals the expression of 5-HT1α (left) and 5-HT2β (right) receptor subtype mRNAs in brain (lanes 1, 6), nerve (lanes 2, 7), hematopoietic tissue (HPT, lanes 3, 8), hemocytes (lanes 4, 9) and the negative control (lanes 5, 10). D. Western blot for 5-HT1α (top) and 5-HT2β (middle) receptor proteins, with actin control (bottom). Scale bars: A, 50 μm; B, 10 μm.