Modulation of neurological pathways by Salvia officinalis and its dependence on manufacturing process and plant parts used.

BACKGROUND: Salvia officinalis has been used successfully for the treatment of hot flushes and excessive sweating during menopause. However, modes of actions have not been elucidated conclusively. We explored its pharmacology beyond any hormonal activity with a focus on neurologic impulse transmission. METHODS: A hydroalcoholic, thujone-free extract from freshly harvested Salvia officinalis leaves (A.Vogel Menosan®) was investigated in an acetylcholinesterase enzyme assay and several receptor binding assays (adrenergic alpha 2A, GABA (benzodiazepine site), GABAB; muscarinic M3, µ-opioid, serotonin 5-HT1A, serotonin 5-HT2B, serotonin 5-HT2C and serotonin transporter). The influence of the manufacturing process on additional extracts from different fresh or dry plant parts was studied. RESULTS: The Salvia officinalis extract replaced 50% of specific ligand binding to GABAA and GABAB receptors at an inhibitory concentration (IC50) of 89 and 229 µg/ml, respectively. Strong binding affinity was observed for the adrenergic α2A receptor, µ-opioid receptors, muscarinic M3 receptors, and serotonin 5-HT1A receptors, with IC50 values of 15 µg/ml, 20 µg/ml, 25 µg/ml and 19 µg/ml, respectively. Moderate interference with 5-HT2B, 5-HT2C receptors, and the human serotonin transporter was found, all with IC50 values above 32 µg/ml. Receptor binding data of Salvia extract were confirmed in native female hypothalamic tissue from two women (51 and 37 years old). Use of freshly harvested Salvia leaves resulted in 2- to 4-fold higher activity/lower IC50 values compared to extracts from dried plants or stipes. CONCLUSION: Our results suggest potent modulation of neuro-receptors and of serotonin transporters as mode of action for Salvia officinalis alcoholic extract, which may normalize thermoregulation and possibly also mental impairment during menopause.

Brain concentrations of mGluR5 negative allosteric modulator MTEP in relation to receptor occupancy--Comparison to MPEP.

BACKGROUND: To verify relation between brain free levels, receptor occupancy in vivo and in vitro affinity at the target for mGluR5 negative allosteric modulator (NAM) MTEP. METHODS: We evaluated plasma and brain extra-cellular fluid (ECF) concentration of MTEP at behaviourally active dose (5mg/kg) using in vivo microdialysis. These values were compared it to the affinity in vitro (receptor binding and FLIPR) and to receptor occupancy in vivo. Another, related substance, MPEP was used for comparison. RESULTS: MTEP and MPEP respectively inhibited mGluR5 receptors function in vitro with an affinity of 25.4 and 12.3 nM respectively. Accordingly peak ECF (extracellular fluid) levels were 1.3 and 0.14 µM, and peak total plasma levels were 7-11 and 2.6 µM. The ED50 for in vivo receptor occupancy was for both agents in the range of 0.8-0.7 mg/kg. CONCLUSIONS: At behaviourally active dose MTEP produced complete mGluR5 receptor occupancy but over 50 times higher ECF concentrations than affinity for mGluR5 receptor in vitro. This difference is seems lower for other mGluR5 NAM compounds such as MPEP. A possibly explanation could be different distribution in body compartments of both agents leading to errors of estimation with the microdialysis technique or different pharmacological activity at the receptor.

Effects of sarizotan in animal models of ADHD: challenging pharmacokinetic-pharmacodynamic relationships.

Sarizotan 1-[(2R)-3,4-dihydro-2H-chromen-2-yl]-N-[[5-(4-fluorophenyl) pyridin-3-yl]methyl] methenamine, showed an in vivo pharmaco-EEG profile resembling that of methylphenidate which is used in attention deficit/hyperactivity disorder (ADHD). In turn, we tested sarizotan against impulsivity in juvenile rats measuring the choice for large delayed vs. a small immediate reward in a T-maze and obtained encouraging results starting at 0.03 mg/kg (plasma levels of ~11 nM). Results from rats treated neonatally with 6-hydroxydopamine (6-OHDA), also supported anti-ADHD activity although starting at 0.3 mg/kg. However, microdialysis studies revealed that free brain concentration of sarizotan at active doses were below its affinity for 5-HT1A receptors, the assumed primary target. In contrast, electrophysiological experiments in mid-brain Raphé serotonergic cells paralleled by plasma sampling showed that there was ~60% inhibition of firing rate­indicating significant activation of 5-HT1A receptors­at a plasma concentration of 76 nM. In line with this, we observed that sarizotan concentrations in brain homogenates were similar to total blood levels but over 500 fold higher than free extracellular fluid (ECF) concentrations as measured using brain microdialysis. These data suggest that sarizotan may have potential anti-ADHD effects at low doses free of the previously reported side-effects. Moreover, in this case a classical pharmacokinetic-pharmacodynamic relationship based on free brain concentrations seems to be less appropriate than target engagement pharmacodynamic readouts.

Pharmacological characterization of MRZ-8676, a novel negative allosteric modulator of subtype 5 metabotropic glutamate receptors (mGluR5): focus on L: -DOPA-induced dyskinesia.

Subtype 5 metabotropic glutamate receptors (mGluR5) are abundant in the basal ganglia, amygdala, septum, hippocampus, peripheral sensory neurones and dorsal horn of the spinal cord. Thus, mGluR5 has been implicated in central processes underlying movement control, emotion, learning, and nociception. Different negative allosteric modulators (NAMs) of mGluR5 were repeatedly shown to be efficacious in models of L: -DOPA-induced dyskinesia (LID), anxiety, and some forms of pain. MRZ-8676 (6,6-dimethyl-2-phenylethynyl-7,8-dihydro-6H-quinolin-5-one) is a novel proprietary, selective, orally bioavailable mGluR5 NAM. MRZ-8676 (8.33, 25 and 75 mg/kg) showed a high efficacy in the rat model of LID, with the maximal effect size reaching ~80%. The antidyskinetic effects of MRZ-8676 (75 mg/kg) did not show tolerance as assessed after repetitive (6 days) treatment. MRZ-8676 (25 or 75 mg/kg) demonstrated moderate efficacy in two rat models of anxiety-contextual fear conditioning and the elevated plus maze. MRZ-8676 (25 mg/kg) was also effective in the formalin test, a rat model of persistent pain. The efficacious doses of MRZ-8676 did not produce any detrimental effects on motor performance of rats as determined by means of automated open field and rotarod. However, high doses of MRZ-8676 (75 or 150 mg/kg) disrupted learning in an aversive learning paradigm of the contextual fear conditioning test. In conclusion, MRZ-8676 is a new investigational agent with an efficacy profile similar to the widely published reference mGluR5 NAMs. The drug was demonstrated to possess a superior antidyskinetic efficacy with a sufficient therapeutic window. MRZ-8676 has also therapeutic potential as an anxiolytic and analgesic drug.