Several new 12-amino-6,7,10,11-tetrahydro-7,11-methanocycloocta[b]quinoline derivatives (tacrine-huperzine A hybrids, huprines) have been synthesized and tested as acetylcholinesterase (AChE) inhibitors. All of the new compounds contain either a methyl or ethyl group at position 9 and one or two (chloro, fluoro, or methyl) substituents at positions 1, 2, or 3. Among the monosubstituted derivatives, the more active are those substituted at position 3, their activity following the order 3-chloro > 3-fluoro > 3-methyl > 3-hydrogen. For the 1,3-difluoro and 1,3-dimethyl derivatives, the effect of the substituents is roughly additive. No significant differences were observed for the inhibitory activity of 9-methyl vs 9-ethyl derivatives monoor disubstituted at positions 1 and/or 3. The levorotatory enantiomers of these hybrid compounds are much more active (eutomers) than the dextrorotatory forms (distomers) as AChE inhibitors. Compounds rac-20, (-)-20, rac-26, (-)-26, rac-30, (-)-30, and rac-31 showed human AChE inhibitory activities up to 28.5-fold higher than for the corresponding bovine enzyme. Also, rac-19, (-)-20, (-)-30, and rac-31 were very selective for human AChE vs butyrylcholinesterase (BChE), the AChE inhibitory activities being 438-871-fold higher than for BChE. Several hybrid compounds, specially (-)-20 and (-)-30, exhibited tight-binding character, showing higher activity after incubation of the enzyme with the inhibitor than without incubation, though the reversible nature of the enzyme-inhibitor interaction was demonstrated by dialysis. The results of the ex vivo experiments also supported the tight-binding character of compounds (-)-20 and (-)-30 and showed their ability to cross the blood-brain barrier. Molecular modeling simulations of the AChE-inhibitor complex provided a basis to explain the differences in inhibitory activity of these compounds.

Neuropathic pain is a clinical manifestation of nerve injury difficult to treat even with potent analgesic compounds. Here, we used different lines of genetically modified mice to clarify the role played by CB 2 cannabinoid receptors in the regulation of the central immune responses leading to the development of neuropathic pain. CB 2 knock-out mice and wild-type littermates were exposed to sciatic nerve injury, and both genotypes developed a similar hyperalgesia and allodynia in the ipsilateral paw. Most strikingly, knock-outs also developed a contralateral mirror image pain, associated with an enhanced microglial and astrocytic expression in the contralateral spinal horn. In agreement, hyperalgesia, allodynia, and microglial and astrocytic activation induced by sciatic nerve injury were attenuated in transgenic mice overexpressing CB 2 receptors. These results demonstrate the crucial role of CB 2 cannabinoid receptor in modulating glial activation in response to nerve injury. The enhanced manifestations of neuropathic pain were replicated in irradiated wild-type mice reconstituted with bone marrow cells from CB 2 knock-outs, thus demonstrating the implication of the CB 2 receptor expressed in hematopoietic cells in the development of neuropathic pain at the spinal cord.

Epidemiological studies help to establish the health status in a country and allow a better allocation of economic resources. This survey estimated pain prevalence in Catalonia (Spain), analysed its relationship with demographic variables and evaluated pain-associated disabilities. The study was carried out in 1964 adults via phone interviews asking about any pain complaint they experienced in the last 6 months, regardless of its intensity and duration. Overall pain prevalence was 78.6%, significantly lower in men, with a trend to decrease with age. Back (50.9%), head (42%) and legs (36.8%) were the most affected locations. Less educated people reported, in general, higher prevalences. Pain described to be most annoying was related to musculoskeletal disease (26.2%) and migraines (16.5%). Pain was either very severe or unbearable in 33% of the sample, with women and older people reporting higher intensities. Personal and social activities were affected in 25.4% of cases and in 10.4% they became virtually impossible. Both the limitation of activity and the need for bed rest, which occurred in 19.6% of those who suffered pain, were more common amongst unemployed people, whereas 10.2% of workers had to take days off work due to pain, and 3.3% were fully incapacitated by it. In conclusion, the prevalence of pain was clearly higher among women, with an inverse relationship to age. Back pain and headaches were most prevalent and pain was rated as very severe to unbearable in one third of the patients. Pain-associated disabilities were a frequent finding. The present survey reports that pain is a substantial problem in the Catalonian population and generally reflects the characteristics of data previously reported in Anglo-saxon and Scandinavian countries.

These data reinforce the need to consider the placebo effect when ascertaining the true therapeutic effect of any drug, as well as to design any clinical trial in the prophylaxis of migraine.

Eleven new 12-amino-6,7,10,11-tetrahydro-7,11-methanocycloocta[b]quinoline derivatives [tacrine (THA)-huperzine A hybrids, rac-21-31] have been synthesized as racemic mixtures and tested as acetylcholinesterase (AChE) inhibitors. For derivatives unsubstituted at the benzene ring, the highest activity was obtained for the 9-ethyl derivative rac-20, previously prepared by our group. More bulky substituents at position 9 led to less active compounds, although some of them [9-isopropyl (rac-22), 9-allyl (rac-23), and 9-phenyl (rac-26)] show activities similar to that of THA. Substitution at position 1 or 3 with methyl or fluorine atoms always led to more active compounds. Among them, the highest activity was observed for the 3-fluoro-9-methyl derivative rac-28 [about 15-fold more active than THA and about 9-fold more active than (-)-huperzine A]. The activity of some THA-huperzine A hybrids (rac-19, rac-20, rac-28, and rac-30), which were separated into their enantiomers by chiral medium-pressure liquid chromatography (chiral MPLC), using microcrystalline cellulose triacetate as the chiral stationary phase, showed the eutomer to be always the levorotatory enantiomer, their activity being roughly double that of the corresponding racemic mixture, the distomer being much less active.

Nerve injuries often lead to neuropathic pain syndrome. The mechanisms contributing to this syndrome involve local inflammatory responses, activation of glia cells, and changes in the plasticity of neuronal nociceptive pathways. Cannabinoid CB 2 receptors contribute to the local containment of neuropathic pain by modulating glial activation in response to nerve injury. Thus, neuropathic pain spreads in mice lacking CB 2 receptors beyond the site of nerve injury. To further investigate the mechanisms leading to the enhanced manifestation of neuropathic pain, we have established expression profiles of spinal cord tissues from wild-type and CB 2 -deficient mice after nerve injury. An enhanced interferon-␥ (IFN-␥) response was revealed in the absence of CB 2 signaling. Immunofluorescence stainings demonstrated an IFN-␥ production by astrocytes and neurons ispilateral to the nerve injury in wild-type animals. In contrast, CB 2 -deficient mice showed neuronal and astrocytic IFN-␥ immunoreactivity also in the contralateral region, thus matching the pattern of nociceptive hypersensitivity in these animals. Experiments in BV-2 microglia cells revealed that transcriptional changes induced by IFN-␥ in two key elements for neuropathic pain development, iNOS (inducible nitric oxide synthase) and CCR2, are modulated by CB 2 receptor signaling. The most direct support for a functional involvement of IFN-␥ as a mediator of CB 2 signaling was obtained with a double knock-out mouse strain deficient in CB 2 receptors and IFN-␥. These animals no longer show the enhanced manifestations of neuropathic pain observed in CB 2 knock-outs. These data clearly demonstrate that the CB 2 receptor-mediated control of neuropathic pain is IFN-␥ dependent.

We have evaluated the possible involvement of delta-opioid receptor (DOR) in the development and expression of neuropathic pain. For this purpose, partial ligation of the sciatic nerve was performed in DOR knockout mice and wild-type littermates. The development of mechanical and thermal allodynia, as well as thermal hyperalgesia was evaluated by using the von Frey filament model, the cold-plate test and the plantar test, respectively. In wild-type and DOR knockout mice, sciatic nerve injury led to a neuropathic pain syndrome revealed in these nociceptive behavioural tests. However, the development of mechanical and thermal allodynia, and thermal hyperalgesia was significantly enhanced in DOR knockout mice. These results reveal the involvement of DOR in the control of neuropathic pain and suggest a new potential therapeutic use of DOR agonists.

Migraine is the most common cause of vascular headache and a highly prevalent illness. In the last 20 years, the discovery of new agents has increased clinical research on migraine. In most of clinical trials that have been conducted, the efficacy was established using a placebo as a control treatment. The objective of the study reported here was to analyse the response rate in patients who received a placebo as well as to determine how a number of the methodological factors may affect the effect of the placebo in clinical trials of acute migraine. Computer-based information searches were conducted on the Medline database. Data analysis included the outcomes 'pain relief', 'pain-free', 'associated symptoms', 'recurrence', 'patients' opinion' about pain relief and 'adverse events'. Administration route, study design and country in which the study was carried out were the methodological factors that were analyzed. Meta-analysis was computed using Mantel-Haenszel, and a total of 98 papers were considered in the final analysis. After 2 h, 28.6% of the patients of the placebo group improved and 8.8% were pain-free. The percentage of pain-free patients was the highest in the placebo and active drug groups in which the placebo or drug had been administered subcutaneously, in parallel design studies (vs. cross-over trials) and in studies performed in Europe (vs. North America). Adverse events in the placebo group were significantly higher in studies performed in North America. These data reinforce the need for knowing the magnitude of the placebo response in each specific situation during the planning of clinical trials on acute migraine.