QUANTITATIVE AUTORADIOGRAPHY OF ALPHA(1)-ADRENERGIC AND ALPHA(2)-ADRENERGIC RECEPTORS IN THE CEREBRAL-CORTEX OF CONTROLS AND SUICIDE VICTIMS

Alterations in both serotonergic and noradrenergic indices have been f ound in the brain of suicide victims. In order to better understand th e role of the noradrenergic system in suicide, we carried out quantita tive autoradiography of alpha1 and alpha2-adrenergic receptors using [ H-3]prazosin and [H-3]-p-aminoclonidine respectively. We compared the distribution and relative density of these receptors in the prefrontal (PFC) and alpha1-adrenergic receptors in the temporal cortex (TC) of suicide victims and controls matched for postmortem delay, age, side o f brain and sex. We found that: (1) the laminar patterns of alpha1-adr energic receptors in the PFC (n = 20) and the TC (n = 16) were differe nt (P = 0.022); (2) there was a 37% increase in alpha1-adrenergic bind ing corresponding to layers IV-V of PFC of suicide victims compared to controls (P = 0.029): (3) the TC had a greater density of alpha1-adre nergic binding sites than the PFC across all cortical layers (P = 0.00 6); (4) alpha1-adrenergic binding sites had a specific laminar distrib ution in the PFC (n = 24) which did not differ in controls and suicide victims; (5) binding to alpha2-adrenergic sites in the PFC of suicide victims did not differ from controls; and (6) norepinephrine concentr ations in the same brain areas were elevated in the suicide group comp ared to controls, but did not correlate with binding to alpha1- or alp ha2-adrenergic sites. The increase in [H-3]prazosin (to alpha1-adrener gic receptors) but not in [H-3]-p-aminoclonidine (to alpha2-adrenergic receptors), and in norepinephrine concentrations in the brain of suic ide victims provides further evidence for an association between suici de and altered brain noradrenergic function. Future studies must deter mine whether these changes in brain noradrenergic function indicate in creased or decreased transmission.