Muscarinic binding in suicides.

Supersensitive muscarinic cholinergic receptors may underlie mood, neuroendocrine, and sleep disturbances in depression. To test this hypothesis, we examined muscarinic binding sites in the brains of suicides and controls in a matched-pair design, using the radioligand 3H-quinuclidinyl benzilate (QNB) and focusing on regions (frontal cortex, hypothalamus, and pons) mediating those functions. Receptor densities and binding affinities did not differ between suicide and control brains in any brain region studied, although there was a trend for both density and affinity to be lower in hypothalami from suicides. We discuss the implications of these findings for the cholinergic-adrenergic balance hypothesis of depression and the methodological limitations of our preliminary study.