Serotonin induces peripheral antinociception via the opioidergic system

Exercise as an abortive treatment for cluster headaches: Insights from a large patient registry

OBJECTIVE

This study aimed to evaluate the potential of exercise as an abortive treatment for patients with cluster headache (CH).

METHODS

A cross-sectional survey was conducted among CH patients at a single center in Korea. Demographics and headache characteristics were compared between those who found exercise effective and those who did not. We analyzed the type and intensity of exercise used. Headache improvement was measured as intensity reduction, with ≥50% improvement defined as a reduction in intensity by half or more. Exercise intensity was categorized as moderate ("possible to talk but hard to sing") or high ("difficult to speak without pausing"). Case reports of patients exercising during CH attacks were also reviewed.

RESULTS

Among 167 registered CH patients, 136 patients provided responses about exercise during CH attacks; 39.7% (54/136) attempted exercise as treatment. Improvement was reported by 42.6% (23/54), with ≥50% improvement in 29.6% (16/54). Patients who found exercise effective had lower Headache Impact Test-6 scores. Effective exercises included running (39.1%), squats (30.4%), and stair climbing (21.7%), with high-intensity exercise effective for 52.2% and moderate intensity for 43.5%. Among the 23 patients who benefited from exercise, 18 reported their most effective treatment, which were exercise alone in 50% (9/18), followed by exercise with triptans in 38.9% (7/18), and oxygen with or without triptans in 5.5% (1/18).

INTERPRETATION

About 40% of CH patients attempted exercise for acute CH management, with 30% experiencing over 50% improvement. While evidence is limited, exercise may help alleviate headaches and could be considered an adjunctive treatment for CH attacks.

Participation of the cannabinoid system and the NO/cGMP/KATP pathway in serotonin-induced peripheral antinociception

It has already been shown that serotonin can release endocannabinoids at the spinal cord level, culminating in inhibition of the dorsal horn. At the peripheral level, cannabinoid receptors modulate primary afferent neurons by inhibiting calcium conductance and increasing potassium conductance. Studies have shown that after the activation of opioid receptors and cannabinoids, there is also the activation of the NO/cGMP/KATP pathway, inducing cellular hyperpolarization. In this study, we evaluated the participation of the cannabinoid system with subsequent activation of the NO/cGMP/KATP pathway in the peripheral antinociceptive effect of serotonin. The paw pressure test of mice was used in animals that had their sensitivity to pain increased due to an intraplantar injection of PGE2 (2 μg). Serotonin (250 ng/paw), administered locally in the right hind paw, induced antinociceptive effect. CB1 and CB2 cannabinoid receptors antagonists, AM251 (20, 40 and 80 μg) and AM630 (25, 50 and 100 μg), respectively, reversed the serotonin-induced antinociceptive effect. MAFP (0.5 μg), an inhibitor of the FAAH enzyme that degrades anandamide, and JZL184 (3.75 μg), an inhibitor of the enzyme MAGL that degrades 2-AG, as well as the VDM11 (2.5 μg) inhibitor of anandamide reuptake, potentiated the antinociceptive effect induced by a low dose (62. 5 ng) of serotonin. In the evaluation of the participation of the NO/cGMP/KATP pathway, the antinociceptive effect of serotonin was reversed by the administration of the non-selective inhibitor of NOS isoforms L-NOarg (12.5, 25 and 50 μg) and by the selective inhibitor for the neuronal isoform LNPA (24 μg), as well as by the soluble guanylate cyclase inhibitor ODQ (25, 50 and 100 μg). Among potassium channel blockers, only Glibenclamide (20, 40 and 80 μg), an ATP-sensitive potassium channel blocker, reversed the effect of serotonin. In addition, intraplantar administration of serotonin (250 ng) was shown to induce a significant increase in nitrite levels in the homogenate of the plantar surface of the paw of mice. Taken together, these data suggest that the antinociceptive effect of serotonin occurs by activation of the cannabinoid system with subsequent activation of the NO/cGMP/KATP pathway.

The Foundations for Chronic Low Back Pain Management may Start in Early Life. Exploring the Role of Caregiver Parental Leave on Future Low Back Pain in the Offspring

Chronic low back pain is difficult to treat and despite increased spending on health services, clinical outcomes for people with low back pain have not improved. Innovative, large scale initiatives seem necessary to stem the cost of low back pain. Psychological health contributes to the development and persistence of chronic low back pain and psychological interventions are important in the management of low back pain. Given the contribution of psychological health to low back pain development and management, it raises the question; can we support psychological health in later life by bolstering emotional development in early life, and reduce the burden of this common condition? Positive early life experiences, including those induced by extended paid parental leave, could bolster emotional development and support the psychological health necessary to manage low back pain in later life. We present the current state of evidence demonstrating the potential value of increasing support for parent-child relationships in early life to reduce the burden of low back pain in future generations. The current evidence is limited to cross-sectional associations, but strong preclinical data clearly shows the potential negative impacts of maternal separation on rodent pup health that compels consideration in human populations. PERSPECTIVE: The benefits stemming from enhanced child development include stable emotional foundations, possibly improving psychological health and low back pain management in the future. This perspective raises questions for future studies - within the context of low back pain, what ingredients bolster stable psychological health? And are these ingredients influenced by parental leave?

Integrating LC-MS and HS-GC-MS for the metabolite characterization of the Chinese medicinal plant Platostoma palustre under different processing methods

Platostoma palustre (or Mesona chinensis Benth) is an important medicinal and edible plant in China and Southeast Asian countries. To study the effects of different processing methods on the quality, nutrition, and flavor of P. palustre, we adopted the LC-MS and HS-GC-MS to compare the influences of tedding (S), sweating (M), and drying (H) on the metabolites and volatile substances of P. palustre. Biochemical determinations revealed that the M treatment could promote the accumulation of the contents of total sugar, soluble sugar, and total pectin compared with the H and S treatments but decrease the total flavonoid contents. LC-MS and HS-GC-MS uncovered 98 differential metabolites and 27 differential volatile substances among the three treatments, respectively. Overall, the M treatment facilitated the stabilization and improvement of the quality of polysaccharides and volatile substances, while the H treatment could promote the level of amino acids in P. palustre. The current study provided a theoretical reference for establishing standardized processing methods and sustaining the quality stability of P. palustre in future.

Analgesia and pain: Dual effect of dopamine on the peripheral nociceptive system is dependent on D2-or D1-like receptor activation

In this study, a pharmacological approach, together with the paw pressure test, was used to investigate the role of dopamine and its receptors in the peripheral processing of the nociceptive response in mice. Initially, the administration of dopamine (5, 20, and 80 ng/paw) in the hind paw of male Swiss mice (30-40 g) promoted antinociceptive effects in a dose-dependent manner. This was considered a peripheral effect, as it did not produce changes in the nociceptive threshold of the contralateral paw. The D₂, D₃, and D₄ dopamine receptor antagonists remoxipride (4 μg/paw), U99194 (16 μg/paw), and L-745,870 (16 μg/paw), respectively, reversed the dopamine-mediated antinociception in mice with PGE₂-induced hyperalgesia. The D₁ and D₅ dopamine receptor antagonists SKF 83566 (2 μg/paw) and SCH 23390 (1.6 μg/paw), respectively, did not alter dopamine antinociception. In contrast, dopamine at higher doses (0.1, 1, and 10 μg/paw) caused hyperalgesia in the animals, and the D₁ and D₅ receptor antagonists reversed this pronociceptive effect (10 μg/paw), whereas the D₂ receptor antagonist remoxipride did not. Our data suggest that dopamine has a dual effect that depends on the dose, as it causes peripheral antinociceptive effects at small doses via the activation of D₂-like receptors and nociceptive effects at higher doses via the activation of D₁-like receptors.

Curcumin induces peripheral antinociception by opioidergic and cannabinoidergic mechanism: Pharmacological evidence

BACKGROUND

Curcumin is one of the compounds present in plants of the genus Curcuma sp., being very used not only as condiment but also with medicinal purposes. As an analgesic, papers highlight the efficacy of curcumin in the treatment of various types of pain.

AIMS

In this study we evaluated the peripheral antinociceptive effect of curcumin and by which mechanisms this effect is induced.

MAIN METHODS

The mice paw pressure test was used on animals which had increased pain sensitivity by intraplantar injection of carrageenan. All the drugs were administered in the right hind paw.

KEY FINDINGS

Curcumin was administered to the right hind paw animals induced antinociceptive effect. Non -selective antagonist of opioid receptors naloxone reverted the antinociceptive effect induced by curcumin. Selective antagonists for μ, δ and κ opioid receptors clocinnamox, naltrindole and nor- binaltorphimine, respectively, reverted the antinociceptive effect induced by curcumin. Bestatin, enkephalinases inhibitor that degrade peptides opioids, did not change the nociceptive response. Selective antagonists for CB₁ and CB₂ cannabinoid receptors, AM251 and AM630, respectively, reversed the antinociceptive effect induced by curcumin. The MAFP inhibitor of the enzyme FAAH which breaks down anandamide, JZL184, enzyme inhibitor MAGL which breaks down the 2-AG, as well as the VDM11 anandamide reuptake inhibitor potentiated the antinociceptive effect of curcumin.

SIGNIFICANCE

These results suggest that curcumin possibly peripheral antinociception induced by opioid and cannabinoid systems activation and possibly for endocannabinoids and opioids release.

Daphnetin, a natural coumarin averts reserpine-induced fibromyalgia in mice: modulation of MAO-A

Fibromyalgia is a common, chronic, and generalized pain syndrome that is often associated with comorbid depression. The etiology of fibromyalgia is complex; most researchers have documented that the hallmark symptoms are due to the central nervous system's abnormal functioning. Neurotransmitters such as serotonin, norepinephrine, and glutamate, have been reported to be key regulators of fibromyalgia syndrome. Daphnetin is a 7, 8 dihydroxy coumarin widely distributed in Thymelaeaceae family plants, possessing various activities such as anti-arthritic, anti-tumor, anti-malarial, and anti-parasitic. The present study was designed to explore the potential of daphnetin against reserpine-induced fibromyalgia in mice. In mice, a fibromyalgia-like state was achieved by injecting reserpine (0.5 mg/kg, s.c) continuously for 3 days. All behavioral tests were conducted on the 4th and 6th day of experimentation. Reserpine administration significantly increased the mechanical hypersensitivity in electronic von Frey (eVF) and pressure application measurement (PAM) tests. It also increased the immobility period and time to reach the platform in force swim test (FST) and Morris water maze (MWM) test, respectively. In the biochemical analysis, reserpine treatment upregulated the monoamine oxidase-A (MAO-A) activity and level of glutamate, tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β), and thiobarbituric acid reactive substances (TBARS). Whereas, it decreased the level of glutathione (GSH), dopamine, serotonin, and norepinephrine. Daphnetin pretreatment attenuated the behavioral and biochemical changes induced by reserpine. Thus, the current investigation results delineate that daphnetin might exert its protective effect by inhibiting inflammatory stress and MAO-A-mediated neurotransmitter depletion and oxidative stress.

Abnormal Repetitive Behaviors and Self-Mutilations in Small Mammals

Self-mutilation and abnormal repetitive behaviors in small mammals are challenging conditions for veterinary practitioners. The etiology may be difficult to identify, and the treatment is often unrewarding unless the specific underlying cause can be found. Reinforcement of the abnormal behavior may also complicate the treatment. However, medical causes, including painful conditions, should be investigated thoroughly. Owing to the small blood volume of many small exotic mammals and the associated risk of hypovolemia in case of hemorrhage, an hospitalization with potent multimodal analgesia and physical barriers to prevent self-mutilation is often warranted. Psychogenic drugs may be useful in some cases.

Dexmedetomidine combined with suprascapular nerve block and axillary nerve block has a synergistic effect on relieving postoperative pain after arthroscopic rotator cuff repair

PURPOSE

Suprascapular nerve block (SSNB) is the most commonly used block for the relief of postoperative pain from arthroscopic rotator cuff repair and can be used in combination with axillary nerve block (ANB). Dexmedetomidine (DEX) is a type of alpha agonist that can elongate the duration of regional block. The aim of this study was to compare the effects of the use of dexmedetomidine combined with SSNB and ANB with those of the use of SSNB and ANB alone on postoperative pain, satisfaction, and pain-related cytokines within the first 48 h after arthroscopic rotator cuff repair.

METHODS

Forty patients with rotator cuff tears who had undergone arthroscopic rotator cuff repair were enrolled in this single-center, double-blinded randomized controlled trial study. Twenty patients were randomly allocated to group 1 and received ultrasound-guided SSNB and ANB using a mixture of 0.5 ml (50 μg) of DEX and 9.5 ml of 0.75% ropivacaine preemptively. The other 20 patients were allocated to group 2 and underwent ultrasound-guided SSNB and ANB alone using a mixture of 0.5 ml of normal saline and 9.5 ml of ropivacaine. The visual analog scale (VAS) for pain and patient satisfaction (SAT) scores were postoperatively checked within 48 h. The plasma interleukin (IL)-6, IL-8, IL-1β, cortisol, and serotonin levels were also postoperatively measured within 48 h.

RESULTS

Group 1 showed a significantly lower mean VAS (visual analog scale of pain) score 1, 3, 6, 12, 18 and 24 h after operation, and a significantly higher mean SAT (patient satisfaction) score 1, 3, 6, 12, 18, 24 and 36 h after the operation than group 2. Group 1 showed a significantly lower mean plasma IL-8 level 1 and 48 h after the operation, and a significantly lower mean IL-1β level 48 h after the operation than group 2. Group 1 showed a significantly lower mean plasma serotonin level 12 h after the operation than group 2. The mean timing of rebound pain in group 1 was significantly later than that in group 2 (36 h > 23 h, p = 0.007). Six patients each in groups 1 and 2 showed rebound pain. The others did not show rebound pain.

CONCLUSIONS

Ultrasound-guided SSNA and ANB with DEX during arthroscopic rotator cuff repair resulted in a significantly lower mean VAS score and a significantly higher mean SAT score within 48 h after the operation than SSNB and ANB alone. Additionally, SSNB and ANB with DEX tended to result in a later mean timing of rebound pain accompanied by significant changes in IL-8, IL-1β, and serotonin levels within 48 h after the operation. The present study could provide the basis for selecting objective parameters of postoperative pain in deciding the optimal use of medication for relieving pain.

LEVEL OF EVIDENCE

Level I.

TRIAL REGISTRATION

2015-20, ClinicalTrials.gov Identifier: NCT04398589.

IRB NUMBER

2015-20, Hallym University Chuncheon Sacred Heart Hospital.

Peripherally acting opioid analgesics and peripherally-induced analgesia

The management of pain, particularly chronic pain, is still an area of medical need. In this context, opioids remain a gold standard for the treatment of pain. However, significant side effects, mainly of central origin, limit their clinical use. Here, we review recent progress to improve the therapeutic and safety profiles of opioids for pain management. Characterization of peripheral opioid-mediated pain mechanisms have been a key component of this process. Several studies identified peripheral µ, δ, and κ opioid receptors (MOR, DOR, and KOR, respectively) and nociceptin/orphanin FQ (NOP) receptors as significant players of opioid-mediated antinociception, able to achieve clinically significant effects independently of any central action. Following this, particularly from a medicinal chemistry point of view, main efforts have been directed towards the peripheralization of opioid receptor agonists with the objective of optimizing receptor activity and minimizing central exposure and the associated undesired effects. These activities have allowed the characterization of a great variety of compounds and investigational drugs that show low central nervous system (CNS) penetration (and therefore a reduced side effect profile) yet maintaining the desired opioid-related peripheral antinociceptive activity. These include highly hydrophilic/amphiphilic and massive molecules unable to easily cross lipid membranes, substrates of glycoprotein P (a extrusion pump that avoids CNS penetration), nanocarriers that release the analgesic agent at the site of inflammation and pain, and pH-sensitive opioid agonists that selectively activate at those sites (and represent a new pharmacodynamic paradigm). Hopefully, patients with pain will benefit soon from the incorporation of these new entities.

Endogenous Opiates and Behavior: 2018

This paper is the forty-first consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2018 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (2), the roles of these opioid peptides and receptors in pain and analgesia in animals (3) and humans (4), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (5), opioid peptide and receptor involvement in tolerance and dependence (6), stress and social status (7), learning and memory (8), eating and drinking (9), drug abuse and alcohol (10), sexual activity and hormones, pregnancy, development and endocrinology (11), mental illness and mood (12), seizures and neurologic disorders (13), electrical-related activity and neurophysiology (14), general activity and locomotion (15), gastrointestinal, renal and hepatic functions (16), cardiovascular responses (17), respiration and thermoregulation (18), and immunological responses (19).

Pain pharmacogenetics

Pain is a significant problem in medicine. The use of PGx markers to personalize postoperative analgesia can increase its effectiveness and avoid undesirable reactions. This article describes the mechanisms of nociception and antinociception and shows the pathophysiological mechanisms of pain in the human body. The main subject of this article is pharmacogenetic approach to the selection of anesthetics. Current review presents data for local and general anesthetics, opioids, and non-steroidal anti-inflammatory drugs. None of the anesthetics currently has clinical guidelines for pharmacogenetic testing. This literature review summarizes the results of original research available, to date, and draws attention to this area.

Pathogenesis of Cluster Headache: From Episodic to Chronic Form, the Role of Neurotransmitters and Neuromodulators

OBJECTIVE

To describe the role of biochemical anomalies of tyrosine (TYR), tryptophan (TRP), and arginine (ARG) metabolism in patients suffering from episodic and chronic cluster headache (CCH).

BACKGROUND

The pathogenesis of cluster headache (CH) and the process that transforms the episodic into the chronic form are unknown. However, the accompanying symptoms suggest a dysfunction of the sympathetic system and hypothalamus along with anomalies of metabolism of catecholamines, elusive amines, and nitric oxide (NO) metabolism.

METHODS

We describe the results obtained from the last papers published on this issue. The level of metabolites were analyzed by different high-performance liquid chromatography methods.

RESULTS

In both episodic and CH patients, the levels of dopamine and elusive amines are very elevated. The only biochemical difference found in studies between episodic and chronic cluster was that norepinephrine levels were significantly lower in episodic cluster in comparison to control and chronic subjects. In addition, the levels of ARG, homoarginine, and citrulline, precursors of synthesis of NO, were significantly lower in chronic cluster.

CONCLUSIONS

All these results suggest that TYR, TRP, and ARG metabolism is abnormal and may constitute a biochemical fingerprint of CH patients. The increased levels of norepinephrine in chronic cluster constitute a possible cause of chronicity of this primary headache. The high levels of tryptamine and its activity on the central serotoninergic system may explain why the length of CH is brief in comparison to migraine and tension-type headache. The low levels of ARG, homoarginine, and citrulline may be the consequence of high circulating levels of α₁ -agonists, such as epinephrine and norepinephrine, and their biochemical interaction with endothelial trace amine-associated receptor 1 that induces activation of NO synthase, resulting in NO synthesis in the circulation, NO release, intense vasodilation, and as a result, the cluster attack.

Endogenous Opioids at the Intersection of Opioid Addiction, Pain, and Depression: The Search for a Precision Medicine Approach

Opioid addiction and overdose are at record levels in the United States. This is driven, in part, by their widespread prescription for the treatment of pain, which also increased opportunity for diversion by sensation-seeking users. Despite considerable research on the neurobiology of addiction, treatment options for opioid abuse remain limited. Mood disorders, particularly depression, are often comorbid with both pain disorders and opioid abuse. The endogenous opioid system, a complex neuromodulatory system, sits at the neurobiological convergence point of these three comorbid disease states. We review evidence for dysregulation of the endogenous opioid system as a mechanism for the development of opioid addiction and/or mood disorder. Specifically, individual differences in opioid system function may underlie differences in vulnerability to opioid addiction and mood disorders. We also review novel research, which promises to provide more detailed understanding of individual differences in endogenous opioid neurobiology and its contribution to opioid addiction susceptibility.

The role of neurotransmitters and neuromodulators in the pathogenesis of cluster headache: a review

The pathogenesis underlying cluster headache remains an unresolved issue. Although both the autonomic system and the hypothalamus play a central role, the modality of their involvement remains largely unknown. It is, also, unknown why the duration of the pain attacks is so brief and why their onset and termination are abrupt and extremely painful. This review summarizes the evidence to date accumulated in favor of a possible role of anomalies in the metabolism of tyrosine, tryptophan, and arginine in these unresolved issues.