ALPHA2 Adrenergic receptors in Alzheimer's disease and schizophrenic cortex frontal

m-CPP. In the second study, we compared the behavioral and neuroendocrine responses across age of 32 normal volunteers who received m-CPP (0.1 mg/kg iv) and found that behavioral but not neuroendocrine responsivity to m-CPP decreases with age. These data may help explain the functional significance of 5-HT abnormalities in Alzheimer’s disease and normal aging. The decrease in behavioral responsivity with age parallels the documented loss of cortical 5-HT, receptors, indicating a possible decline with age in 5-HT system function. Alzheimer patients appear to be more sensitive than age-matched controls to the effects of direct 5-HT receptor agonist stimulation. This increased behavioral responsivity could reflect the widespread disruption in neuronal 5-HT seen in Alzheimer’s disease or the lack of inhibitory drive of a defective cholinergic system on the 5-HT system, producing functionally hyperresponsive 5-HT, receptors. The discrepancy between behavioral and hormonal responses following m-CPP in Alzheimer’s disease might also be consistent with regional loss of some 5-HT receptors, with relative sparing of others.