BackgroundE‐52862 (S1RA, 4‐[2‐[[5‐methyl‐1‐(2‐naphthalenyl)‐1H‐pyrazol‐3‐yl]oxy]ethyl]‐morpholine), a novel selective sigma 1 receptor (σ1R) antagonist, has demonstrated efficacy in nociceptive and neuropathic pain models. Our aim was to test if σ1R blockade with E‐52862 may modify the signs of neuropathy in Zucker diabetic fatty (ZDF) rats, a type 2 diabetes model.MethodsMechanical and thermal response thresholds were tested on 7‐, 13‐, 14‐ and 15‐week‐old ZDF rats treated with saline or with E‐52862 acutely administered on week 13, followed by sub‐chronic administration (14 days). Axonal peripheral activity (skin–saphenous nerve preparation) and isolated aorta or mesenteric bed reactivity were analysed in 15‐week‐old ZDF rats treated with saline or E‐52862 and in LEAN rats.ResultsZucker diabetic fatty rats showed significantly decreased thermal withdrawal latency and threshold to mechanical stimulation on week 13 compared to week 7 (prediabetes) and with LEAN animals; single‐dose and sub‐chronic E‐52862 administration restored both parameters to those recorded on week 7. Regarding axonal peripheral activity, E‐52862 treatment increased the mean mechanical threshold (77.3 ± 21 mN vs. 19.6 ± 1.5 mN, saline group) and reduced the response evoked by mechanical increasing stimulation (86.4 ± 36.5 vs. 352.8 ± 41.4 spikes) or by repeated mechanical supra‐threshold steps (39.4 ± 1.4 vs. 83.5 ± 0.9). E‐52862 treatment also restored contractile response to phenylephrine in aorta and mesenteric bed.ConclusionsE‐52862 administration reverses neuropathic (behavioural and electrophysiological) and vascular signs in the ZDF rat.SignificanceBlockade of σ1R avoids the development of diabetic neuropathy in rats, and may represent a potentially useful therapeutic approach to peripheral neuropathies in diabetic patients.What does this study add? This study presents evidences for the potential usefulness of sigma receptor blockade on diabetic neuropathy in rats.The methodology includes behavioural evidences, electrophysiological data and vascular‐isolated models.

Chronic pain remains a major problem worldwide, despite the availability of various non-pharmacological and pharmacological treatment options. Therefore, new analgesics with novel mechanisms of action are needed. Monoclonal antibodies (mAbs) are directed against specific, targeted molecules involved in pain signaling and processing pathways that look to be very effective and promising as a novel therapy in pain management. Thus, there are mAbs against tumor necrosis factor (TNF), nerve growth factor (NGF), calcitonin gene-related peptide (CGRP), or interleukin-6 (IL-6), among others, which are already recommended in the treatment of chronic pain conditions such as osteoarthritis, chronic lower back pain, migraine, or rheumatoid arthritis that are under preclinical research. This narrative review summarizes the preclinical and clinical evidence supporting the use of these agents in the treatment of chronic pain.

Background The antineoplastic drugs cisplatin and vincristine induce peripheral neuropathies. The sigma‐1 receptor (σ1R) is expressed in areas of pain control, and its blockade with the novel selective antagonist MR‐309 has shown efficacy in nociceptive and neuropathic pain models. Our goal was to test whether this compound reduces neuropathic signs provoked by these antitumoural drugs. Methods Rats were treated with cisplatin or vincristine to induce neuropathies. The effects of acute or repeated administration of MR‐309 were tested on mechanical and thermal sensitivity, electrophysiological activity of Aδ‐primary afferents in the rat skin–saphenous nerve preparation, and gastrointestinal or cardiovascular functions. Results Rats treated with antitumourals developed tactile allodynia, while those treated with vincristine also developed mechanical hyperalgesia. These in vivo modifications correlated with electrophysiological hyperactivity (increased spontaneous activity and hyperresponsiveness to innocuous and noxious mechanical stimulation). Animals treated with cisplatin showed gastrointestinal impairment and those receiving vincristine showed cardiovascular toxicity. A single dose of MR‐309 strongly reduced both nociceptive behaviour and electrophysiological changes. Moreover, its concomitant administration with the antitumourals blocked the development of neuropathic symptoms, thus restoring mechanical sensitivity, improving the impairment of feeding behaviour and gastrointestinal transit in the cisplatin‐treated group along with ameliorating the altered vascular reactivity recorded in rats treated with vincristine. Conclusion σ1R antagonist, MR‐309, reduces sensorial and electrophysiological neuropathic signs in rats treated with cisplatin or vincristine and, in addition, reduces gastrointestinal and cardiovascular side effects. Significance σ1R antagonism could be an interesting and new option to palliate antitumoural neuropathies.

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