Serotonin 5-HT2A and 5-HT6 receptors in the prefrontal cortex of Alzheimer and normal aging patients

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>It has been hypothesized that alterations of the serotonergic system contribute to neuropsychiatric symptoms in Alzheimer disease (AD). Cellular expressions of the two serotonergic receptors 5-HT<jats:sub>2A</jats:sub>and 5-HT<jats:sub>6</jats:sub>have therefore been determined by immunohistochemistry in the prefrontal cortex of patients with AD (n=6) and normal age-matched controls (n = 7).</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>In normal aging patients, 5-HT<jats:sub>2A</jats:sub>label was mainly observed in large pyramidal cells, but to a lesser extent also in small pyramidal cells and in stellate cells of cortical layers II-VI. In AD, a similar distribution was observed, but density of positive cells was significantly reduced by 33%. In aging control patients, the 5-HT<jats:sub>6</jats:sub>receptor was expressed by pyramidal cells and occasional stellate cells, not only of layers II-V, but also of layer I, where a distinct label was observed in neurons and surrounding fibers. 5-HT<jats:sub>6</jats:sub>receptor expression in AD patients had the same pattern, but was significantly decreased by 40%.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>Our results indicate that a decline in neurons expressing 5-HT<jats:sub>2A</jats:sub>, but also 5-HT<jats:sub>6</jats:sub>receptors may play a role in the etiopathology of neuropsychiatric symptoms in AD.</jats:p></jats:sec>