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

Abstract

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. © 1996 Wiley‐Liss, Inc.

S100β Increases Levels of β‐Amyloid Precursor Protein and Its Encoding mRNA in Rat Neuronal Cultures

“…Astrocyte-derived S 100/3 promotes neuronal survival in vitro (Winningham-Major et al, 1989;Barger et al, 1995) and in vivo (Bhattacharyya et al, 1992), induces increases in intraneuronal cytoplasmic free calcium levels (Barger and Van Eldik, 1991), stimulates neurite outgrowth (Kligman and Marshak, 1985;Winningham-Major et al, 1989), and increases the numbers of synaptophysin-immunoreactive varicosities on neuronal processes (Nishi et al, 1996). Our present results showing enhancement of neuronal viability, neurite outgrowth, and neuronal MAP2 expression by low doses of S 100/3 are consistent with these findings.…”

The response of synaptophysin and microtubule‐associated protein 1 to restraint stress in rat hippocampus and its modulation by venlafaxine

“…Therefore, we would attribute the accelerating effect of venlafaxine on post‐stress recovery mainly to its effect on 5‐HT re‐uptake. Together, these results lend support to the notion that serotonin modulates brain maturation during development and in adult plasticity (Nishi et al . 1996; Mazer et al .…”

St. John's wort may relieve negative effects of stress on spatial working memory by changing synaptic plasticity

“…Therefore, we attribute beneficial effects of H. perforatum on post-stress recovery mainly to its effect on 5-HT re-uptake. Together, these results lend support to the notion that serotonin modulates brain maturation during development and during adult plasticity (Nishi et al 1996;Mazer et al 1997). Xu et al (2004) found that restraint stress reduced the expression of SYP in the rat hippocampus by 50%.…”