Dose-effect and concentration-effect relationships with new antidepressants

Interaction of paroxetine with mitochondrial proteins mediates neuroprotection

There are severe neurological complications that arise from HIV infection, ranging from peripheral sensory neuropathy to cognitive decline and dementia for which no specific treatments are available. The HIV proteins secreted from infected macrophages, gp120 and Tat, are neurotoxic. The goal of this study was to screen, identify and develop neuroprotective compounds relevant to HIV-associated neurocognitive disorders (HAND). We screened more than 2000 compounds that included FDA approved drugs for protective efficacy against oxidative stress-mediated neurodegeneration and identified selective serotonin reuptake inhibitors (SSRIs) as potential neuroprotectants. Numerous SSRIs were then extensively evaluated as protectants against neurotoxicity as measured by changes in neuronal cell death, mitochondrial potential, and axodendritic degeneration elicited by HIV Tat and gp120 and other mitochondrial toxins. While many SSRIs demonstrated neuroprotective actions, paroxetine was potently neuroprotective (100 nM potency) against these toxins in vitro and in vivo following systemic administration in a gp120 neurotoxicity model. Interestingly, the inhibition of serotonin reuptake by paroxetine was not required for neuroprotection, since depletion of the serotonin transporter had no effect on its neuroprotective properties. We determined that paroxetine interacts selectively and preferentially with brain mitochondrial proteins and blocks calcium-dependent swelling but had less effect on liver mitochondria. Additionally, paroxetine induced proliferation of neural progenitor cells in vitro and in vivo in gp120 transgenic animals. Therefore, SSRIs such as paroxetine may provide a novel adjunctive neuroprotective and neuroregenerative therapy to treat HIV-infected individuals.

Clinical impacts of single transcranial magnetic stimulation (sTMS) as an add-on therapy in severely depressed patients under SSRI treatment

Research on single and rapid transcranial magnetic stimulation (sTMS/rTMS) indicates an antidepressive efficacy of these methods. In our 4 week study of sTMS, 12 patients affected by severe non-psychotic major depression (DSM-III-R) were enrolled and put on standardized combined antidepressant medication with the serotonin re-uptake inhibitor citalopram, and the serotonin modulating drug, trazodone. They underwent sTMS in a specific method as an add-on therapy. Age, gender, illness and episode duration, episode number, Hamilton Rating Depression Scale-24 (HRDS), Mini-Mental State (MMS), drug levels assessed by HPLC, magnesium and thyroid stimulating hormone (TSH) were recorded. For each patient functional brain imaging was performed by (18)FDG and (99m)Tc HMPAO SPECT at the beginning of the study, as were EEG tracings which also were recorded at the end. Lorazepam was allowed as co-medication. Of the patients, 66.7 per cent (N=8) could be identified as sTMS responders. Possible predictors for sTMS response as add-on therapy may be duration, pattern of improvement in global and in specific single items of the HRDS, lorazepam dosage, functional involvement of basal ganglia and cortical temporal lobe and the initially lower mean frequency and lability of the alpha-activity of EEG. These variables possibly predict the clinical outcome of depressed patients treated by sTMS as an add-on therapy. Copyright 2000 John Wiley & Sons, Ltd.