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The lower 5-HT1A binding in the amygdala and mesiofrontal areas of SAD patients is consistent with 1) preclinical findings of elevated anxiety in 5-HT1A knockout mice, 2) a previous PET study in healthy volunteers showing an inverse correlation between 5-HT1A BP and state anxiety, and 3) another human PET study in patients with panic disorder showing reduced 5-HT1A binding, thus corroborating the potential validity of 5-HT1A receptors as targets in the treatment of human anxiety disorders.

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There is an increasing interest in the underlying mechanisms of the antidepressant and anxiolytic treatment effect associated with changes in serotonergic neurotransmission after treatment with selective serotonin (5-HT) reuptake inhibitors (SSRIs) in humans. The 5-HT 1A receptor is known to play a crucial role in the pathophysiology of affective disorders, and altered 5-HT 1A receptor binding has been found in anxiety patients. SSRI treatment raises the 5-HT level in the synaptic cleft and might change postsynaptic receptor densities. Therefore, our study in patients suffering from anxiety disorders investigated the effects of long-term treatment with escitalopram on the 5-HT 1A receptor. A longitudinal positrone emission tomography (PET) study in 12 patients suffering from anxiety disorders was conducted. Two dynamic PET scans were performed applying the selective 5-HT 1A receptor antagonist [carbonyl-11 C]WAY-100635. Eight regions of interest were defined a priori (orbitofrontal cortex, amygdala, hippocampus, subgenual cortex, anterior and posterior cingulate cortex, dorsal raphe nucleus and cerebellum as reference). After the baseline PET scan, patients were administered escitalopram (average dose of 11.2 ± 6.0 mg day À1 ) for a minimum of 12 weeks. A second PET scan was conducted after 109±27 days. 5-HT 1A receptor binding potentials in 12 patients were assessed by PET applying the Simplified Reference Tissue Model.There was a significant reduction in the 5-HT 1A receptor binding potential after a minimum of 12 weeks of escitalopram treatment in the hippocampus (P = 0.006), subgenual cortex (P = 0.017) and posterior cingulate cortex (P = 0.034). The significance of the hippocampus region survived the Bonferroni-adjusted threshold for multiple comparisons. These PET data in humans in vivo demonstrate a reduction of the 5-HT 1A binding potential after SSRI treatment.

SPECT and [123I]ADAM were used to investigate SERT occupancies after single doses of escitalopram or citalopram. The test-retest study revealed good reproducibility of SERT quantification. Similar SERT occupancies were found after administration of equal doses (in respect to mg) of escitalopram and citalopram, giving indirect evidence for a fractional blockade of SERT by the inactive R-citalopram.

Atypical antipsychotics have been linked to a higher risk for glucose intolerance, and consequentially the development of type 2 diabetes mellitus (DM2). We have therefore set out to investigate the acute effects of oral administration of olanzapine and ziprasidone on whole body insulin sensitivity in healthy subjects. Using the standardized hyperinsulinemic euglycemic clamp technique we compared whole body insulin sensitivity of 29 healthy male volunteers after oral intake of either olanzapine 10 mg/day (n ¼ 14) or ziprasidone 80 mg/day (n ¼ 15) for 10 days. A significant decrease (po0.001) in whole body insulin sensitivity from 5.7 ml/h/kg ( ¼ mean, SM ¼ 0.4 ml/h/kg) at baseline to 4.7 ml/h/kg ( ¼ mean, SM ¼ 0.3 ml/h/kg) after oral intake of olanzapine (10 mg/day) for 10 days was observed. The ziprasidone (80 mg/day) group did not show any significant difference (5.2 ± 0.3 ml/h/kg baseline vs 5.1 ± 0.3 ml/h/kg) after 10 days of oral intake. Our main finding demonstrates that oral administration of olanzapine but not ziprasidone leads to a decrease in whole body insulin sensitivity in response to a hyperinsulinemic euglycemic challenge. Our finding is suggestive that not all atypical antipsychotics cause acute direct effects on glucose disposal and that accurate determination of side effect profile should be performed when choosing an atypical antipsychotic.

The present study provides first-time evidence for a specific interrelation between the 5-HT(1A) receptor distribution, sex hormones, and aggression in humans. Our findings point to a reduced down-stream control due to higher amounts or activities of frontal 5-HT(1A) receptors in more aggressive subjects, which is presumably modulated by sex hormones.