Alterations in the substance P-induced anti-nociception in the central nervous system of rats after morphine tolerance

Ion Channels Involved in Substance P-Mediated Nociception and Antinociception

Substance P (SP), an 11-amino-acid neuropeptide, has long been considered an effector of pain. However, accumulating studies have proposed a paradoxical role of SP in anti-nociception. Here, we review studies of SP-mediated nociception and anti-nociception in terms of peptide features, SP-modulated ion channels, and differential effector systems underlying neurokinin 1 receptors (NK1Rs) in differential cell types to elucidate the effect of SP and further our understanding of SP in anti-nociception. Most importantly, understanding the anti-nociceptive SP-NK1R pathway would provide new insights for analgesic drug development.

Intravenous Administration of Substance P Attenuates Mechanical Allodynia Following Nerve Injury by Regulating Neuropathic Pain-Related Factors

This study aimed to investigate the analgesic effect of substance P (SP) in an animal model of neuropathic pain. An experimental model of neuropathic pain, the chronic constriction injury (CCI) model, was established using ICR mice. An intravenous (i.v.) injection of SP (1 nmole/kg) was administered to the mice to examine the analgesic effects of systemic SP on neuropathic pain. Behavioral testing and immunostaining was performed following treatment of the CCI model with SP. SP attenuated mechanical allodynia in a time-dependent manner, beginning at 1 h following administration, peaking at 1 day post-injection, and decaying by 3 days post-injection. The second injection of SP also increased the threshold of mechanical allodynia, with the effects peaking on day 1 and decaying by day 3. A reduction in phospho-ERK and glial fibrillary acidic protein (GFAP) accompanied the attenuation of mechanical allodynia. We have shown for the first time that i.v. administration of substance P attenuated mechanical allodynia in the maintenance phase of neuropathic pain using von Frey’s test, and simultaneously reduced levels of phospho-ERK and GFAP, which are representative biochemical markers of neuropathic pain. Importantly, glial cells in the dorsal horn of the spinal cord (L4–L5) of SP-treated CCI mice, expressed the anti-inflammatory cytokine, IL-10, which was not seen in vehicle saline-treated mice. Thus, i.v. administration of substance P may be beneficial for improving the treatment of patients with neuropathic pain, since it decreases the activity of nociceptive factors and increases the expression of anti-nociceptive factors.

Antinociceptive, anti-inflammatory, and antipyretic activity of mangrove plants: a mini review

Mangrove plants are specialised plants that grow in the tidal coasts of tropic and subtropic regions of the world. Their unique ecology and traditional medicinal uses of mangrove plants have attracted the attention of researchers over the years, and as a result, reports on biological activity of mangrove plants have increased significantly in recent years. This review has been set out to compile and appraise the results on antinociceptive, anti-inflammatory, and antipyretic activity of mangrove plants. While the Web of Knowledge, Google Scholar, and PubMed were the starting points to gather information, other pieces of relevant published literature were also adequately explored for this purpose. A total of 29 reports on 17 plant species have been found to report such activities. While 19 reports were on the biological activity of the crude extracts, 10 reports identified the active compound(s) of various chemical classes of natural products including terpenes, steroids, and flavonoids. This review finds that antinociceptive, anti-inflammatory, and antipyretic activity appears to be widespread in mangrove plants.

Substance P N-terminal fragment SP(1-7) attenuates chronic morphine tolerance and affects dynorphin B and nociceptin in rats

The N-terminal substance P fragment SP(1-7) is known to modulate hyperalgesia and opioid withdrawal in animal models. This study examined the effects of intraperitoneal (i.p.) injections of SP(1-7) on chronic morphine tolerance and on the levels of dynorphin B (DYN B) and nociceptin/orphanin FQ (N/OFQ) in various brain areas of male Sprague-Dawley rats. Morphine tolerance was induced by subcutaneous injections of the opioid (10mg/kg) twice daily for 7 days. SP(1-7) injected i.p. (185 nmol/kg) 30 min prior to morphine reduced the development of morphine tolerance. Immunoreactive (ir) DYN B and N/OFQ peptide levels were measured in several areas of the central nervous system. Levels of ir DYN B in rats treated with SP(1-7) and morphine were decreased in the nucleus accumbens, substantia nigra and ventral tegmental area and increased in the frontal cortex. The ir N/OFQ levels were increased in the periaqueductal gray and decreased in the nucleus accumbens. Since the concentration profiles of the two peptides were altered by SP(1-7) in the areas that are implicated in the modulation of opioid tolerance and analgesia, it is suggested that DYN B and N/OFQ systems may be involved in the effects of SP(1-7) on opioid tolerance.

A histologically derived stereotaxic atlas and substance P immunohistochemistry in the brain of the least shrew (Cryptotis parva) support its role as a model organism for behavioral and pharmacological research

Chemotherapy is an effective treatment but difficult to tolerate due to side effects like vomiting. Studies on the etiology of chemotherapy-related emesis have implicated brainstem nuclei and the neurotransmitter substance P, among other substrates. Since rodents do not vomit, other species have been necessary as alternative models of chemotherapy-induced emesis. Of these, the least shrew (Cryptotis parva) has proven valuable due to its small size, hardiness, and close phylogenetic relationship with primates. However, very little neuroanatomical data on C. parva exist. We used histological and immunohistochemical techniques to provide neuroanatomical data to help validate C. parva as a model organism, especially for emesis research. Brains were sectioned and stained for Nissl substance or myelin, or immunofluorescently labeled for substance P. Sections were photographed, traced, and reconstructed with standardized zero points, and these data used to create a stereotaxic atlas. The brain of C. parva was similar to but smaller than other mammalian brains, with the cerebellum and hippocampus demonstrating the biggest differences. Differences appeared to be related to the small size of the brain and the metabolic compromises required of such a small mammal. Substance P-like immunoreactivity (SPL-IR) was semiquantitatively mapped, and correlated very well with SPL-IR observed in other species. Dense SPL-IR areas included the periaqueductal grey, trigeminal nuclei, dorsal raphe, and emesis-related brainstem nuclei including the area postrema and solitary tract nucleus. These data demonstrate that the anatomical differences between C. parva and other mammals will not preclude its use as a model organism.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 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, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).