Enhanced synaptophysin immunoreactivity in rat hippocampal culture by 5-HT 1A agonist, S100b, and corticosteroid receptor agonists.
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-HT1A receptors and a corresponding increases in S100b 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-HT1A 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-HT1A agonist, ipsapirone, and the neuronal extension factor, S100b 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 (10(-9)M) was more effective on neuronal cell bodies staining and S100b (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 (10(-8) M) and aldosterone (10(-9) 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.
Nishi
M
M
Department of Biology, New York University, New York 10003, USA.
Whitaker-Azmitia
P M
PM
Azmitia
E C
EC
D000818:Animals; D002478:Cells, Cultured; D006624:Hippocampus / Q000187:drug effects*; D007150:Immunohistochemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D011987:Receptors, Steroid / Q000819:agonists*; D009418:S100 Proteins / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*; D016708:Synaptophysin / Q000378:metabolism*
D011987:Receptors, Steroid; D009418:S100 Proteins; D017366:Serotonin Receptor Agonists; D016708:Synaptophysin