Rivastigmine but not vardenafil reverses cannabis-induced impairment of verbal memory in healthy humans.

RATIONALE: One of the most often reported cognitive deficits of acute cannabis administration is an impaired recall of previously learned information. OBJECTIVE: The aim of the present study was to determine whether cannabis-induced memory impairment in humans is mediated via glutamatergic or cholinergic pathways. METHODS: Fifteen occasional cannabis users participated in a double-blind, placebo-controlled, six-way cross-over study. On separate test days, subjects received combinations of pretreatment (placebo, vardenafil 20 mg or rivastigmine 3 mg) and treatment (placebo or 1,376 mg cannabis/kg body weight). Cognitive tests were administered immediately after inhalation of treatment was finished and included measures of memory (visual verbal learning task, prospective memory test, Sternberg memory test), perceptual-motor control (critical tracking task), attention (divided attention task) and motor impulsivity (stop signal task). RESULTS: The results of this study demonstrate that subjects under the influence of cannabis were impaired in all memory tasks, in critical tracking, divided attention and the stop signal task. Pretreatment with rivastigmine attenuated the effect of cannabis on delayed recall and showed a trend towards significance on immediate recall. When cannabis was given in combination with vardenafil, there were no significant interaction effects in any of the tasks. CONCLUSIONS: The present data therefore suggest that acetylcholine plays an important role in cannabis-induced memory impairment, whereas similar results for glutamate have not been demonstrated in this study.

PDE2 and PDE10, but not PDE5, inhibition affect basic auditory information processing in rats.

Phosphodiesterase type 2 (PDE2), type 10 (PDE10), and type 5 (PDE5) have been considered as relevant targets for cognition enhancement. Although it is well established that PDE inhibitors (PDE-Is) improve memory functions in animals, the effects on auditory information processing are less clear. The aim of this study was to test the effects of PDE2 (BAY 60-7550), PDE5 (vardenafil) and PDE10 (PQ-10) inhibition on sensory gating in rats. Vehicle or 1mg/kg of a specific PDE-I was given orally 30min before testing. EEG was recorded from the hippocampus, striatum and vertex. Sensory gating was found for the N1 in the vertex and hippocampus, as revealed by diminished amplitudes to S2 compared to S1. Administration of PDE-Is did not affect sensory gating. However, PDE2 inhibition increased the P1 peak after presentation of S1 at the vertex and PQ-10 increased the N1 peak in general compared to vehicle treatment at the hippocampus. PDE2 and PDE10 inhibition affect auditory information processing in general, whereas PDE5 inhibition has no effect. These findings suggest that the positive effects of PDE5 inhibition on cognition previously found in animals are possibly the results of an effect on higher cognitive functioning specifically, whereas the cognition enhancing effects of PDE2 and PDE10 inhibition might also be influenced by effects on earlier stages of information processing.

Serum levels of brain-derived neurotrophic factor in major depressive disorder: state-trait issues, clinical features and pharmacological treatment.

Recent evidence supports 'the neurotrophin hypothesis of depression' in its prediction that brain-derived neurotrophic factor (BDNF) is involved in depression. However, some key questions remain unanswered, including whether abnormalities in BDNF persist beyond the clinical state of depression, whether BDNF levels are related to the clinical features of depression and whether distinct antidepressants affect BDNF levels equally. We addressed these questions and investigated serum BDNF levels in 962 depressed patients, 700 fully remitted persons (≥6 months) and 382 healthy controls. We found serum BDNF levels to be low in antidepressant-free depressed patients relative to controls (P=0.007) and to depressed patients who were treated with an antidepressant (P=0.001). BDNF levels of fully remitted persons (whether unmedicated or treated with an antidepressant) were comparable to those of controls. Analyzing the sample of antidepressant-free depressed patients showed that BDNF levels were unrelated to the core clinical features of depression such as its severity or first versus a recurrent episode. The antidepressant associated upregulation of serum BDNF in depressed patients was confined to selective serotonin reuptake inhibitors (SSRIs) (P=0.003) and St John's wort (P=0.03). Our results suggest that low serum levels of BDNF are a state abnormality that is evident during depression and normalizes during remission. Increases in serum levels of BDNF during antidepressant treatment appear to be confined to some antidepressants and do not parallel clinical characteristics, such as the severity of depressive symptoms.