Enhanced synaptophysin immunoreactivity in rat hippocampal culture by 5-HT1A agonist, S100b, and corticosteroid receptor agonists (original) (raw)

Serotonin (5-HT) has been shown to modulate brain maturation during development and adult plasticity. This effect in the whole animal may be due to activation of 5-HTIA receptors and a corresponding increases in SlOOb and corticosterone. Synaptophysin, an integral protein of the synaptic vesicle membrane that correlates with synaptic density and neurotransmitter release, is reduced by depletion of 5-HT in the cortex and hippocampus of the adult rat. Injections of a 5-HTl~ agonist or dexamethasone can reverse the loss of synaptophysin immunoreactivity (IR). In this study we used morphometric analysis of synaptophysin-IR to study the effects of the 5-HTu agonist, ipsapirone, and the neuronal extension factor, SlOOb on hippocampal neurons grown in a serum and steroid free media. Both compounds increased the synaptophysin-IR at doses previously established to be highly specific. Ipsapirone (M) was more effective on neuronal cell bodies staining and SlOOb (10 ng/ml) was more effective in increasing the number of synaptophysin-IR varicosities on neuronal processes. In addition both types of corticosteroid receptor agonists, at previously established specific doses, Ru28362 M) and aldosterone (M) produced smaller increases compared to control groups in both the cell body staining and the number of varicosities. The effect of these differentiating factors on the expression of synaptophysin-IR suggests multiple regulation sites for producing and maintaining pre-synaptic elements in the brain. o 1996 Wiley-Liss, Inc.