Pain and pain management in the elderly population is a significant social and medical problem. Pain sensation is a complex phenomenon that typically involves activation of peripheral pain-sensing ...neurons (nociceptors) which send signals to the spinal cord and brain that are interpreted as pain, an unpleasant sensory experience. In this work, young (4–5 months) and aged (26–27 months) Fischer 344 x Brown Norway (F344xBN) rats were examined for nociceptor sensitivity to activation by thermal (cold and heat) and mechanical stimulation following treatment with inflammatory mediators and activators of transient receptor potential (TRP) channels. Unlike other senses that decrease in sensitivity with age, sensitivity of hindpaw nociceptors to thermal and mechanical stimulation was not different between young and aged F344xBN rats. Intraplantar injection of bradykinin (BK) produced greater thermal and mechanical allodynia in aged versus young rats, whereas only mechanical allodynia was greater in aged rats following injection of prostaglandin E2 (PGE2). Intraplantar injection of TRP channel activators, capsaicin (TRPV1), mustard oil (TRPA1) and menthol (TRPM8) each resulted in greater mechanical allodynia in aged versus young rats and capsaicin-induced heat allodynia was also greater in aged rats. A treatment-induced allodynia that was greater in young rats was never observed. The anti-allodynic effects of intraplantar injection of kappa and delta opioid receptor agonists, salvinorin-A and D-Pen2,D-Pen5enkephalin (DPDPE), respectively, were greater in aged than young rats, whereas mu opioid receptor agonists, D-Ala2, N-MePhe4, Gly-ol-enkephalin (DAMGO) and morphine, were not effective in aged rats. Consistent with these observations, in primary cultures of peripheral sensory neurons, inhibition of cAMP signaling in response to delta and kappa receptor agonists was greater in cultures derived from aged rats. By contrast, mu receptor agonists did not inhibit cAMP signaling in aged rats. Thus, age-related changes in nociceptors generally favor increased pain signaling in aged versus young rats, suggesting that changes in nociceptor sensitivity may play a role in the increased incidence of pain in the elderly population. These results also suggest that development of peripherally-restricted kappa or delta opioid receptor agonists may provide safer and effective pain relief for the elderly.
•Nociceptor sensitivity to thermal and mechanical stimulation did not differ between young and aged F344xBNrats.•Inflammatory mediators and TRP channel activators produced greater thermal and mechanical allodynia in aged rats.•Intraplantar injection of kappa and delta opioid receptor agonists produced greater anti-allodynic response in aged rats. whereas mu opioid receptor agonists, DAMGO and morphine, were not effective in aged animals.•In primary cultures of peripheral sensory neurons, inhibition of cAMP signaling in response to delta and kappa opioid receptor agonists was greater in cultures derived from aged rats. By contrast, mu receptor agonists did not inhibit cAMP signaling in cultures from aged rats.•Age-related changes in nociceptors generally favor increased pain signaling in aged rats, suggesting that changes in nociceptor sensitivity may play a major role in the increased incidence of pain in the elderly population.
Insects' thermoregulatory processes depend on thermosensation and further processing of thermal information in the nervous system. It is commonly known that thermosensation involves thermoreceptors, ...including members of the TRP receptor family, but the involvement of neurotransmitters in thermoregulatory pathways remains unstudied. We conducted test to determine whether octopamine, a biogenic amine that acts as a neurotransmitter and neurohormone in insects, is involved in TRP-induced thermoregulatory responses in Periplaneta americana. We used capsaicin, an activator of the heat-sensitive TRP channel, Painless, to induce thermoregulatory response in cockroaches. Then, we evaluated the behavioural (thermal preferences and grooming), physiological (heart rate) and biochemical responses of insects to capsaicin, octopamine and phentolamine - octopaminergic receptor blocker. Capsaicin, similar to octopamine, increased cockroaches' grooming activity and heart rate. Moreover, octopamine level and protein kinase A (PKA) activity significantly increased after capsaicin treatment. Blocking octopaminergic receptors with phentolamine diminished cockroaches' response to capsaicin - thermoregulatory behaviour, grooming and heart rate were abolished. The results indicate that octopamine is a neurotransmitter secreted in insects after the activation of heat receptors.
This study evaluates the pharmacological potential of
-jasmone (CJ) in adult zebrafish (
; aZF). Initially, aZF (n = 6/group) were pretreated (20 µL;
) with CJ (0.1 or 0.3 or 1.0 mg/mL) or vehicle ...(0.5% Tween 80). The animals were submitted to acute toxicity and locomotion tests, pentylenetetrazole-induced seizure, carrageenan-induced abdominal edema, and cinnamaldehyde-, capsaicin-, menthol-, glutamate-, and acid saline-induced orofacial nociception. The possible mechanisms of anticonvulsant, anxiolytic, and antinociceptive action were evaluated. The involvement of central afferent fibers sensitive to cinnamaldehyde and capsaicin and the effect of CJ on the relative gene expression of TRPA1 and TRPV1 in the brain of aZF were also analyzed, in addition to the study of molecular docking between CJ and TRPA1, TRPV1 channels, and GABA
receptors. CJ did not alter the locomotor behavior and showed pharmacological potential in all tested models with no toxicity. The anticonvulsant effect of CJ was prevented by flumazenil (GABAergic antagonist). The anxiolytic-like effect of CJ was prevented by flumazenil and serotonergic antagonists. The antinociceptive effect was prevented by TRPA1 and TRPV1 antagonists. Chemical ablation with capsaicin and cinnamaldehyde prevented the orofacial antinociceptive effect of CJ. Molecular docking studies indicate that CJ interacted with TRPA1, TRPV1, and GABA
receptors. CJ inhibited the relative gene expression of TRPA1 and TRPV1. CJ has pharmacological potential for the treatment of seizures, anxiety, inflammation, and acute orofacial nociception. These effects are obtained by modulating the GABAergic and serotonergic systems, as well as the TRPs and ASIC channels.
A family of endogenous lipids, structurally analogous to the endogenous cannabinoid, N-arachidonoyl ethanolamine (Anandamide), and called N-acyl amides have emerged as a family of biologically active ...compounds at TRP receptors. N-acyl amides are constructed from an acyl group and an amine via an amide bond. This same structure can be modified by changing either the fatty acid or the amide to form potentially hundreds of lipids. More than 70 N-acyl amides have been identified in nature. We have ongoing studies aimed at isolating and characterizing additional members of the family of N-acyl amides in both central and peripheral tissues in mammalian systems. Here, using a unique in-house library of over 70 N-acyl amides we tested the following three hypotheses: (1) Additional N-acyl amides will have activity at TRPV1-4, (2) Acute peripheral injury will drive changes in CNS levels of N-acyl amides, and (3) N-acyl amides will regulate calcium in CNS-derived microglia. Through these studies, we have identified 20 novel N-acyl amides that collectively activate (stimulating or inhibiting) TRPV1-4. Using lipid extraction and HPLC coupled to tandem mass spectrometry we showed that levels of at least 10 of these N-acyl amides that activate TRPVs are regulated in brain after intraplantar carrageenan injection. We then screened the BV2 microglial cell line for activity with this N-acyl amide library and found overlap with TRPV receptor activity as well as additional activators of calcium mobilization from these lipids. Together these data provide new insight into the family of N-acyl amides and their roles as signaling molecules at ion channels, in microglia, and in the brain in the context of inflammation.
Arthritis is a condition characterised by mainly pain, reduced joint movement and signs of inflammation, such as swelling. The disorder has many different types, of which osteoarthritis (a ...degenerative joint disease) and rheumatoid arthritis (a chronic autoimmune disease) are the two most common forms. There are >6 million sufferers in the UK and both conditions have a huge potential to impair capabilities and contribute to social and economic burdens. Whilst there are a wide range of arthritic therapies available, many patients under treatment complain of poor pain relief. Thus there is a need for novel therapeutic approaches, and the transient receptor potential (TRP) family of receptor channels has been investigated. One particular area of recent research has been the ligand-gated transient receptor potential vanilloid 1 (TRPV1) channel. Findings from numerous pre-clinical models and scientific studies have shown that TRPV1 desensitisation, or the use of TRPV1 antagonists alleviates pain and some inflammatory aspects. New findings have started to unveil
the potential of other TRP channels in mediating arthritic pain and inflammation. With the understanding that the currently available treatments for arthritis are limited, researchers have looked into the exciting prospect that TRP receptor antagonists may be developed into effective, specific drugs, which would potentially protect against the complications of arthritis. These antagonists are still under development, although only data from studies from pre-clinical models are currently available. This review acts to summarize knowledge of the potential influence of TRP receptors in arthritis to date.
Capsaicin is known to activate heat receptor TRPV1 and induce changes in thermoregulatory processes of mammals. However, the mechanism by which capsaicin induces thermoregulatory responses in ...invertebrates is unknown. Insect thermoreceptors belong to the TRP receptors family, and are known to be activated not only by temperature, but also by other stimuli. In the following study, we evaluated the effects of different ligands that have been shown to activate (allyl isothiocyanate) or inhibit (camphor) heat receptors, as well as, activate (camphor) or inhibit (menthol and thymol) cold receptors in insects. Moreover, we decided to determine the effect of agonist (capsaicin) and antagonist (capsazepine) of mammalian heat receptor on the American cockroach's thermoregulatory processes. We observed that capsaicin induced the decrease of the head temperature of immobilized cockroaches. Moreover, the examined ligands induced preference for colder environments, when insects were allowed to choose the ambient temperature. Camphor exposure resulted in a preference for warm environments, but the changes in body temperature were not observed. The results suggest that capsaicin acts on the heat receptor in cockroaches and that TRP receptors are involved in cockroaches' thermosensation.
TRPA1 is an ion channel that detects specific chemicals in food and also transduces mechanical, cold and chemical stimulation. Its presence in sensory nerve endings is well known and recent evidence ...indicates that it is expressed by some gastrointestinal enteroendocrine cells (EEC). The purpose of the present work is to identify and quantify EEC that express TRPA1 in the mouse gastrointestinal tract. Combined in situ hybridisation histochemistry for TRPA1 and immunofluorescence for EEC hormones was used. TRPA1 expressing EEC were common in the duodenum and jejunum, were rare in the distal small intestine and were absent from the stomach and large intestine. In the duodenum and jejunum, TRPA1 occurred in EEC that contained both cholecystokinin (CCK) and 5-hydroxytryptamine (5HT) and in a small number of cells expressing 5HT but not CCK. TRPA1 was absent from CCK cells that did not express 5HT and from EEC containing glucagon-like insulinotropic peptide. Thus TRPA1 is contained in very specific EEC populations. It is suggested that foods such as garlic and cinnamon that contain TRPA1 stimulants may aid digestion by facilitating the release of CCK.
Members of TRP receptor family are involved in response to acidification. Here, we determined the effect of capsaicin, one of the TRP receptor activators, on hemolymph acid-base status in the ...American cockroach. Periplaneta americana adult individuals were injected with lactic acid (5% or 10%) and exposed to 100 µM capsaicin solution. Hemolymph pH was measured 15 min, 1, 4, 8 and 24 h after lactic acid and capsaicin application with a glass microelectrode. The results demonstrated that cockroaches recover from acidosis within 4 h from acid injection. Capsaicin impaired the buffering capacity of insects' hemolymph, resulting in significant drop of hemolymph pH observed even 24 h after application. Joint action of capsaicin and acidosis reveals new insight into possible mechanism of capsaicin action on TRP receptors in insects.
Our aim is to describe the physical and physiological effects of local modulated electro-hyperthermia (mEHT). The method concentrates on the energy absorption of cluster rafts of the plasma membrane. ...The targeted cluster contains transmembrane proteins, which can form coherent working voltage-gated ion channels and/or TRP receptors in one domain. This targeting is analogous to nanoparticle heating, except this uses readily available nanoparticles on the cell membrane instead of the artificially placed nano-object to induce selective energy absorption from the outside field. In the discussed non-artificial nanoparticle heating, selectivity is the consequence of the synergy of various interactions embedded into each other in their effective volume in macro-, micro- and nano-ranges. Keywords: Membrane rafts; TRP receptors; Selection; RF current; Cancer; Hyperthermia
PDF
