Differential expression of L- and N-type voltage-sensitive calcium channels in the spinal cord of morphine+nimodipine treated rats

Phα1β, a dual blocker of TRPA1 and Cav2.2, as an adjuvant drug in opioid therapy for postoperative pain

Opioids are the "gold standard" treatment for postoperative pain, but these drugs also have limiting adverse effects. Thus, adjuvant drugs might be useful in opioid therapy for postoperative pain. The aim of the present study was to evaluate the effect of Phα1β, a dual blocker of Cav2 and TRPA1 channels, on antinociceptive and adverse actions of morphine in a model of postoperative pain. Phα1β (100-300 pmol/site) or morphine (3-10 mg/kg), alone, largely reduced postoperative nociception. However, Phα1β (100 pmol/site) or morphine (10 mg/kg) also produced motor impairment. Lower doses of Phα1β (30 pmol/site) or morphine (1 mg/kg), that did not have an effect alone, showed antinociceptive effect when concomitantly administrated. Moreover, co-administration of Phα1β (30 pmol/site) with morphine (1 or 10 mg/kg) was unable to cause motor impairment. Preoperative repeated treatment with morphine increased the expression of Cav2 and TRPA1 channels in spinal cord, and caused tolerance and withdrawal syndrome, which were reversed with a single injection of Phα1β (30 pmol/site). When injected postoperatively, escalating doses of morphine worsened postoperative hyperalgesia, induced tolerance, and withdrawal syndrome. Similarly, Phα1β (30 pmol/site) reversed these adverse effects. Single or repeated morphine caused constipation, which was not altered by Phα1β. Thus, a low dose of Phα1β potentiated the analgesia, and reversed some adverse effects of morphine on operated mice, indicating the potential use of this agent as an adjuvant drug in opioid therapy for postoperative pain.

Fluoxetine increases analgesic effects of morphine, prevents development of morphine tolerance and dependence through the modulation of L-type calcium channels expression in mice

Here, we aimed to investigate the effects of fluoxetine on morphine-induced analgesia, as well as preventive effects of it on morphine induced tolerance and dependence in mice. We also elucidate the involvement of L-type Ca²⁺ channels in these phenomena. To induce morphine tolerance, mice were treated with morphine (50 mg/kg) for 3 consecutive days. To evaluate the involvement of the calcium channel in the effects of fluoxetine (5, 20 mg/kg), combination ineffective doses of the two L-type calcium channel blockers, nimodipine (5 mg/kg) or diltiazem (20 mg/kg) with flouxetine were used with each morphine dose. Nociceptive behavior was evaluated using hot-plate test, while physical dependence assessed by naloxone-precipitated withdrawal on the fourth day of experiment. The expression of Cav1.2 and Cav1.3 subunits of the L-type calcium channels in cortex and mesolimbic tissues were measured using western immunoassay. Results showed that co-administration of fluoxetine (20 mg/kg) with morphine increased its acute analgesia effect and prevented the induction of morphine antinociceptive tolerance and physical dependence in mice. Moreover, these effects was potentiated by pre-treatment with diltiazem or nimodipine. Results also showed up-regulation of the Cav1.3 and Cav1.2 expression in the cerebral cortex and mesolimbic regions through the development of morphine dependence. Moreover, chronic administration of fluoxetine with morphine reduced the observed up-regulation of Cav1.3 and Cav1.2 expression in cortex and mesolimbic tissues. Our data indicated that co-administering of fluoxetine with morphine could potentiate the antinociceptive effect of morphine, prevent morphine analgesia tolerance and attenuated the morphine withdrawal signs during induction phases. Moreover, we also pointed out for the first time the role of L-type Ca²⁺ channel channels in the modulatory effects of fluoxetine on the morphine-related effects.

Effect of Nimodipine on Morphine-related Withdrawal Syndrome in Rat Model: An Observational Study

OBJECTIVE

To observe the effect of L-type calcium channel blocker like nimodipine on morphine's withdrawal when it was administered continuously along with morphine versus a single bolus dose of nimodipine, which was administered at the end of the experiment before the precipitation of withdrawal reaction in morphine-dependent rats.

MATERIALS AND METHODS

Four groups of adult male Wistar rats were rendered morphine dependent by subcutaneous injections of morphine at a dose of 10 mg/kg for 10 days. Nimodipine 10 mg/kg intraperitoneally (ip) administered to one group once daily before morphine administration in the entire experimental period, and another group received nimodipine only once at the end of the experiment as a single bolus dose 2 mg/kg before the administration of naloxone. Naloxone 3 mg/kg was administered ip to all the groups to precipitate withdrawal reactions. The withdrawal reactions were evaluated and scored as per the Gellert and Holtzman global withdrawal rating scale.

RESULTS

Nimodipine when administered as a single bolus dose before naloxone administration in morphine-dependant rats reduced the features of withdrawal reactions more effectively than continuous administration of nimodipine along with morphine throughout the experimental period.

CONCLUSION

We discovered that nimodipine helps in attenuating the severity of morphine withdrawal having potential role encountered during pharmacotherapy with morphine management of opioid dependence, well memory, impairement, cell signaling and phosphorylation of neuron.

N-type voltage-dependent Ca2+ channel in non-excitable microglial cells in mice is involved in the pathophysiology of neuropathic pain

Peripheral nerve injury induces neuropathic pain which is characterized by tactile allodynia and thermal hyperalgesia. N-type voltage-dependent Ca(2+) channel (VDCC) plays pivotal roles in the development of neuropathic pain, since mice lacking Cav2.2, the pore-forming subunit of N-type VDCC, show greatly reduced symptoms of both tactile allodynia and thermal hyperalgesia. Our study on gene expression profiles of the Cav2.2 knockout (KO) spinal cord after spinal nerve ligation (SNL)-injury revealed altered expression of genes known to be expressed in microglia, raising an odd idea that N-type VDCC may function in not only excitable (neurons) but also non-excitable (microglia) cells in neuropathic pain state. In the present study, we have tested this idea by using a transgenic mouse line, in which suppression of Cav2.2 expression can be achieved specifically in microglia/macrophage by the application of tamoxifen. We found SNL-operated transgenic mice exhibited greatly reduced signs of tactile allodynia, whereas the degree of thermal hyperalgesia was almost the same as that of control. Immunohistochemical analysis of the transgenic lumbar spinal cord revealed reduced accumulation of Iba1-positive cells (microglia/macrophage) around the injured neurons, indicating microglial N-type VDCC is important for accumulation of microglia at the lesion sites. Although the mechanism of its activation is not clear at present, activation of N-type VDCC expressed in non-excitable microglial cells contributes to the pathophysiology of neuropathic pain.

Action of Phα1β, a peptide from the venom of the spider Phoneutria nigriventer, on the analgesic and adverse effects caused by morphine in mice

Opioids are standard therapy for the treatment of pain; however, adverse effects limit their use. Voltage-gated calcium channel blockers may be used to increase opioid analgesia, but their effect on opioid-induced side effects is little known. Thus, the goal of this study was to evaluate the action of the peptide Phα1β, a voltage-gated calcium channel blocker, on the antinociceptive and adverse effects produced by morphine in mice. A single administration of morphine (3-10 mg/kg) was able to reduce heat nociception as well as decrease gastrointestinal transit. The antinociception caused by a single injection of morphine was slightly increased by an intrathecal injection of Phα1β (30 pmol/site). Repeated treatment with morphine caused tolerance, hyperalgesia, withdrawal syndrome, and constipation, and the Phα1β (.1-30 pmol/site, intrathecal) was able to reverse these effects. Finally, the effects produced by the native form of Phα1β were fully mimicked by a recombinant version of this peptide. Taken together, these data show that Phα1β was effective in potentiating the analgesia caused by a single dose of morphine as well as in reducing tolerance and the adverse effects induced by repeated administration of morphine, indicating its potential use as an adjuvant drug in combination with opioids.

PERSPECTIVE

This article presents preclinical evidence for a useful adjuvant drug in opioid treatment. Phα1β, a peptide calcium channel blocker, could be used not only to potentiate morphine analgesia but also to reduce the adverse effects caused by repeated administration of morphine.

Calcium-permeable ion channels in pain signaling

The detection and processing of painful stimuli in afferent sensory neurons is critically dependent on a wide range of different types of voltage- and ligand-gated ion channels, including sodium, calcium, and TRP channels, to name a few. The functions of these channels include the detection of mechanical and chemical insults, the generation of action potentials and regulation of neuronal firing patterns, the initiation of neurotransmitter release at dorsal horn synapses, and the ensuing activation of spinal cord neurons that project to pain centers in the brain. Long-term changes in ion channel expression and function are thought to contribute to chronic pain states. Many of the channels involved in the afferent pain pathway are permeable to calcium ions, suggesting a role in cell signaling beyond the mere generation of electrical activity. In this article, we provide a broad overview of different calcium-permeable ion channels in the afferent pain pathway and their role in pain pathophysiology.

Ginger (Zingiber officinale Roscoe) prevents the development of morphine analgesic tolerance and physical dependence in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Ginger (Zingiber officinale Roscoe), a well-known spice plant, has been used traditionally in the treatment of a wide variety of ailments such as opiates withdrawal-induced disorders. However, its influences on opioid tolerance and dependence have not yet been clarified.

MATERIALS AND METHODS

Adult male Wistar rats were rendered tolerant to analgesic effect of morphine by injection of morphine (10 mg/kg, i.p.) twice daily for 8 days. To develop morphine dependence, rats given escalating doses of chronic morphine. To determine the effect of ginger on the development of morphine tolerance and dependence, different doses of ginger were administrated before morphine. The tail-flick and naloxone precipitation tests were used to assess the degree of tolerance and dependence, respectively.

RESULTS

Our results showed that chronic morphine-injected rats displayed tolerance to the analgesic effect of morphine as well as morphine dependence. Ginger (50 and 100 mg/kg) completely prevented the development of morphine tolerance. In addition, concomitant treatment of morphine with 100 and 150 mg/kg attenuated almost all of the naloxone-induced withdrawal sings which include weight lose, abdominal contraction, diarrhea, petosis, teeth chattering, and jumping. In addition, morphine-induced L-type calcium channel over-expression in spinal cord was reversed by 100 mg/kg ginger.

CONCLUSION

The data indicate that ginger extract has a potential anti-tolerant/anti-dependence property against chronic usage of morphine.

Endogenous opiates and behavior: 2009

This paper is the 32nd consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2009 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 and thermoregulation (Section 16); and immunological responses (Section 17).

Does a single dose of intravenous nicardipine or nimodipine affect the bispectral index following rapid sequence intubation?

Background

Theoretically, L-type calcium channel blockers could modulate anesthetic effects. Nicardipine does not affect the bispectral index (BIS), but nimodipine, which can penetrate the blood-brain barrier, has not been studied. The aim of this study was to evaluate whether a single dose of intravenous nicardipine or nimodipine could affect BIS following rapid sequence intubation.

Methods

This study was done in a double-blind, randomized fashion. Anesthesia was induced with fentanyl 2 µg/kg, thiopental sodium 5 mg/kg, and 100% oxygen. After loss of consciousness, patients received rocuronium 1.0 mg/kg and either a bolus of 20 µg/kg nicardipine, nimodipine, or a comparable volume of normal saline (n = 20). Intubation was performed 1 min after study drug administration. BIS, mean blood pressure (MBP), and heart rate (HR) were measured before anesthetic induction, after loss of consciousness, before intubation, during intubation, and 1, 2 and 5 min after intubation.

Results

BIS dropped rapidly after induction but increased to 60 before intubation in all groups irrespective of study drug. In nimodipine, the increase in BIS during intubation was not significant compared to pre-intubation, in contrast to the other two groups, but there was no difference in BIS during intubation. HR significantly increased, but MBP just rose to pre-induction values after intubation in nicardipine and nimodipine groups. BIS, MBP, and HR following intubation increased in control group.

Conclusions

A single dose of intravenous nicardipine or nimodipine could attenuate blood pressure increases but not affect BIS increases in rapid sequence intubation.

Calcium channel functions in pain processing

Voltage-gated calcium channels (VGCC) play obligatory physiological roles, including modulation of neuronal: functions, synaptic plasticity, neurotransmitter release and gene transcription. Dysregulation and maladaptive changes in VGCC expression and activities may occur in the sensory pathway under various pathological conditions that could contribute to the development of pain. In this review, we summarized the most recent findings on the regulation of VGCC expression and physiological functions in the sensory pathway, and in dysregulation and maladaptive changes of VGCC under pain-inducing conditions. The implications of: these changes in understanding the mechanisms of pain transduction and in new drug design are also discussed.