Serotonin regulates synaptic connections in the dentate molecular layer of adult rats via 5-HT sub(1a) receptors: evidence for a glial mechanism

• Published in: Brain research 1998-01, Vol.782 (1-2), p.235-239
• Main Authors: Wilson, C C, Faber, K M, Haring, J H
• Format: Article
• Language: English
• ISSN: 0006-8993

The present study sought to verify effects of 5-HT on synaptic density at the ultrastructural level, to determine whether the 5-HT 1a receptor is important for the maintenance of synaptic connections and to obtain evidence implicating S100 beta in the apparent neurotrophic actions of 5-HT. Reduction of hippocampal 5-HT with para -chloroamphetamine (PCA) resulted in a significant decline in the synaptic density of the dentate molecular layer. Reduction of norepinephrine with DSP-4 produced a slight decrease in the number of molecular layer synapses, but this difference was not statistically different from control values. 5-HT 1a antagonist treatment resulted in a decline in synaptic density comparable to that observed following PCA treatment. These observations suggest that 5-HT functions to maintain synaptic connections in the dentate molecular layer via a 5-HT 1a mechanism. To determine whether the change in synaptic density was due to the action of 5-HT on neuronal receptors or astrocytic receptors, a monoclonal antibody against S100 beta was infused into the lateral ventricle for seven days. Controls received infusions of normal goat serum. Half of the rats from the anti-S100 beta and control groups also received daily injections of NAN-190. Anti-S100 beta infusion resulted in a significant (p