Low doses of risperidone and morphine interact to produce more analgesia and greater extrapyramidal effects in rats

The effect of risperidone on behavioral reactions and gene expression of pro- and anti-inflammatory cytokines in neuropathic pain model induced by chronic constriction injury of the sciatic nerve in rat

BACKGROUND

Neuropathic pain results from lesions or diseases affecting the somatosensory system. The management of a patient with chronic neuropathic pain remains a challenge several studies report the analgesic effect of serotonin receptor antagonists in different models of experimental pain. The present study was designed to study the effect of systemic administration of risperidone, on behavioral scores of neuropathic pains in chronic constriction (CCI) model in rats.

METHODS

Inducing neuropathic pain with the CCI model which causes heat hyperalgesia, heat, and mechanical allodynia was performed on rats, and then, in two phases, risperidone effect was determined. In the acute phase, risperidone 1, 2, 4 mg was administered for three groups half an hour before behavioral tests on the 7th, 14th, and 21st day after surgery, and in the chronic phase, risperidone 1, 2, and 4 mg was administered for three different groups from the 1st to 14th days after surgery than on 14th-day behavioral scores were performed. For gene expression analysis, samples are taken from spinal cord tissues in lumbar segments.

RESULTS

This study shows chronic administration of risperidone as an antipsychotic drug was effective on heat hyperalgesia and allodynia. However, only the max dosage (4 mg) of risperidone showed meaningful improvement in increasing mechanical allodynia. However, acute administering of risperidone did not show any meaningful changes in behavioral tests on neuropathic pain induced by chronic constriction injury of the sciatic nerve in rats. In addition, gene expression results showed an increase in IL-4 and IL-10 gene expression in the risperidone group compared to the sham group.

CONCLUSION

This study suggests the helpful preventive effects of risperidone in developing and increasing neuropathic pain, but it does not have any instant effect.

Risperidone administered during adolescence induced metabolic, anatomical and inflammatory/oxidative changes in adult brain: A PET and MRI study in the maternal immune stimulation animal model

Inflammation and oxidative stress (IOS) are considered key pathophysiological elements in the development of mental disorders. Recent studies demonstrated that the antipsychotic risperidone elicits an antiinflammatory effect in the brain. We administered risperidone for 2-weeks at adolescence to assess its role in preventing brain-related IOS changes in the maternal immune stimulation (MIS) model at adulthood. We also investigated the development of volumetric and neurotrophic abnormalities in areas related to the HPA-axis. Poly I:C (MIS) or saline (Sal) were injected into pregnant Wistar rats on GD15. Male offspring received risperidone or vehicle daily from PND35-PND49. We studied 4 groups (8-15 animals/group): Sal-vehicle, MIS-vehicle, Sal-risperidone and MIS-risperidone. [¹⁸F]FDG-PET and MRI studies were performed at adulthood and analyzed using SPM12 software. IOS and neurotrophic markers were measured using WB and ELISA assays in brain tissue. Risperidone elicited a protective function of schizophrenia-related IOS deficits. In particular, risperidone elicited the following effects: reduced volume in the ventricles and the pituitary gland; reduced glucose metabolism in the cerebellum, periaqueductal gray matter, and parietal cortex; higher FDG uptake in the cingulate cortex, hippocampus, thalamus, and brainstem; reduced NFκB activity and iNOS expression; and increased enzymatic activity of CAT and SOD in some brain areas. Our study suggests that some schizophrenia-related IOS changes can be prevented in the MIS model. It also stresses the need to search for novel strategies based on anti-inflammatory compounds in risk populations at early stages in order to alter the course of the disease.

Psychiatric agents and implications for perioperative analgesia

The use of antidepressants, anxiolytics, mood stabilizers, anticonvulsants, and major tranquilizers introduces neurochemical, behavioral, cognitive, and emotional factors that increase the complexity of medical and surgical tasks. Increasingly, various classes of psychotropic medications are being prescribed in the perioperative setting for their analgesic properties in patients with or without a psychiatric diagnosis. In many cases, the precise mechanisms of action and dose-response relationships by which these agents mediate analgesia are largely unclear. An appreciation of the side effects and adverse-effect profiles of such medications and familiarity with the clinically relevant drug interactions that may occur in the perioperative setting are imperative to ensure the best possible outcome in dealing with patients on these medications. This review focuses on various classes of psychotropic agents, which are addressed individually, with particular focus on their analgesic properties. The latest published research is summarized, deficiencies in our current collective knowledge are discussed, and evidence-based recommendations are made for clinical practice.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

The role of antipsychotics in the management of fibromyalgia

Fibromyalgia is a syndrome characterized by chronic generalized pain associated with different somatic symptoms, such as sleep disturbances, fatigue, stiffness, balance problems, hypersensitivity to physical and psychological environmental stimuli, depression and anxiety. It has been estimated to affect roughly the 2-4% of the general population in most countries studied, and it has been shown to be much more prevalent in women than in men. Although its pathophysiology is not yet fully understood, it is known that both genetic and environmental factors are involved in its development. Fibromyalgia shares a high degree of co-morbidity with other conditions, including chronic headache, temporomandibular disorder, irritable bowel syndrome, major depression, anxiety disorders and chronic fatigue syndrome. Therefore, this is a syndrome difficult to treat for which multimodal treatments including physical exercise, psychological therapies and pharmacological treatment are recommended. Although different kinds of drugs have been studied for the treatment of fibromyalgia, the most widely used drugs that have the higher degree of evidence for efficacy include the α(2)δ ligands pregabalin and gabapentin, and the tricyclic antidepressants (TCAs) and serotonin noradrenaline (norepinephrine) reuptake inhibitors (SNRIs). However, there is a need to look for newer additional therapeutic pharmacological options for the treatment of this complex and disabling disease. First- and second-generation antipsychotics have shown analgesic properties both in an experimental setting and in humans, although most of the available evidence for the treatment of human pain concerns older antipsychotics and involves clinical trials performed several decades ago. In addition, several second-generation antipsychotics, risperidone, olanzapine and quetiapine, have shown efficacy in the treatment of some anxiety disorders. Some second-generation antipsychotics, mainly quetiapine, aripiprazole and amisulpride, have demonstrated antidepressant activity, with quetiapine approved for the treatment of bipolar depression and refractory major depression, and aripiprazole approved as an adjunctive treatment for major depressive disorder. Finally, several old and new antipsychotics, including promethazine, levopromazine, olanzapine, quetiapine and ziprasidone, have been shown to improve sleep parameters in healthy subjects. Each of these properties suggests that antipsychotics could represent a new potential alternative for the treatment of fibromyalgia syndrome. To date, most of the published studies on the use of antipsychotics in the treatment of fibromyalgia syndrome have been uncontrolled, either case reports or case series, dealing with olanzapine, quetiapine, ziprasidone, levopromazine and amisulpride. The studies on olanzapine and quetiapine have suggested therapeutic efficacy although, in the case of olanzapine, hampered by tolerability problems. A double-blind controlled trial, published in 1980, showed that chlorpromazine increased slow-wave sleep and improved pain and mood disturbances. More recently, four double-blind controlled studies have explored the efficacy of quetiapine, either alone or as an add-on treatment, in fibromyalgia management. None of these trials has yet been published, although two of them have been presented as congress communications, both of them suggesting that quetiapine could be a potential alternative treatment for fibromyalgia. In summary, the current available evidence suggests that at least some antipsychotics, specifically quetiapine, could be useful for the treatment of fibromyalgia and that further studies on the efficacy of these compounds are worth pursuing.