Involvement of the histaminergic system in the nociceptin-induced pain-related behaviors in the mouse spinal cord

Contribution of Histamine to Nociceptive Behaviors Induced by Intrathecally Administered Cholecystokinin-8

The involvement of spinal release of histamine in the nociceptive behaviors induced by cholecystokinin-8 (CCK-8) was investigated in mice. Intrathecal (i.t.) injection of CCK-8 elicited the nociceptive behaviors consisting of biting and licking. The nociceptive behaviors induced by i.t. treatment with CCK-8 showed two bell-shaped patterns. The histamine H₃ receptor antagonist significantly promoted the nociceptive behaviors induced by CCK-8 at doses of 1–100 fmol and 100 pmol. The nociceptive behaviors elicited by CCK-8 was inhibited by i.t. administration of the CCK-B receptor antagonist in a dose-dependent manner, but not by the CCK-A receptor antagonist. The nociceptive behaviors induced by CCK-8 were markedly suppressed by i.t. pretreatment with antiserum against histamine and were abolished in histidine decarboxylase-deleted gene mice. In histamine H₁ receptor-deleted gene mice, the nociceptive behaviors induced at both 10 amol and 10 pmol of CCK-8 were not affected. The tachykinin neurokinin-1 (NK₁) receptor antagonists inhibited CCK-8 (10 pmol)-induced nociceptive behaviors in a dose-dependent manner. CCK-8 (10 amol)-induced nociceptive behaviors was not antagonized by co-administration with the tachykinin NK₁ receptor antagonists. The nociceptive behaviors elicited by CCK-8 were inhibited by i.t. administration of the antagonist for the N-methyl-D-aspartate (NMDA) receptor in a dose-dependent manner. Our results suggest that the nociceptive behaviors induced by i.t. administration of CCK-8 (10 pmol) are mediated through the spinal release of histamine and are elicited via activation of the tachykinin NK₁ and NMDA receptors, whereas the nociceptive behaviors induced by i.t. administration of CCK-8 (10 amol) are mediated through the spinal release of histamine and elicited via NMDA receptor activation.

Involvement of the tuberomammillary nucleus of the hypothalamus in the modulation of nociception and joint edema in a model of monoarthritis

AIMS

Investigate the involvement of the histaminergic projections from tuberomammillary nucleus (TMN) to the spinal cord in the modulation of nociception and peripheral edema in a model of monoarthritis.

MAIN METHODS

Subacute monoarthritis was induced by an intraarticular injection of carrageenan followed by LPS 72 h later. Disability and joint edema were assessed at the 3rd hour after LPS and at every hour up to 6 h.

KEY FINDINGS

Intrathecal administration of histamine potentiated joint incapacitation and edema, while the H1R antagonist cetirizine decreased both. The H3R agonist immepip decreased both incapacitation and edema, while the H3R antagonist thioperamide had the opposite effect. The microinjection of glutamate into the ventral TMN (vTMN) caused an increase of incapacitation and articular edema, whereas the blockade of this nucleus by cobalt chloride inhibited both parameters. Intrathecal administration of cetirizine prevented the increase of incapacitation and joint edema caused by glutamate microinjection into the vTMN. Similarly, an intrathecal injection of the NKCC1 cotransporter inhibitor bumetanide prevented the effects of glutamate microinjection into the vTMN, whereas coadministration of histamine with bumetanide only inhibited the potentiation of joint edema. A microinjection of orexin B into the vTMN potentiated incapacitation and joint edema, while coadministration of the OX1/2 receptor antagonist almorexant with orexin B did not.

SIGNIFICANCE

These data support the notion that TMN participates in the modulation of a peripheral inflammatory process by means of histaminergic projections to the spinal cord, and the hypothalamus may trigger TMN activation by means of glutamate and orexin.

Quantitative Sensory Testing, Antihistamines, and Beta-Blockers for Management of Persistent Breast Pain: A Case Series

BACKGROUND

It is not uncommon for mothers to have persistent pain with breastfeeding beyond the first few weeks after birth. Persistent pain can be multifactorial, with neuropathic pain maintained by central sensitization being one dimension. Our knowledge in delineating categories of persistent pain is simple and not very sophisticated.

METHODS

We have developed and tested a Lactation Quantitative Sensory Test (L-QST) to quantify the neuropathic component of persistent breastfeeding pain. We present three case reports of neuropathic breastfeeding pain and treatment, and we discuss the potential role of histamine and catecholamines in persistent breastfeeding-associated pain.

CONCLUSIONS

The L-QST can be a useful tool to quantify neuropathic pain. Further studies are needed to test inter-observer reliability and reproducibility of this tool. Antihistamines can be considered for treating persistent pain in breastfeeding women with a history of allergy or atopy, and beta-blockers may be helpful in women with multiple pain disorders.

The involvement of spinal release of histamine on nociceptive behaviors induced by intrathecally administered spermine

The involvement of spinal release of histamine on nociceptive behaviors induced by spermine was examined in mice. Intrathecal spermine produced dose-dependent nociceptive behaviors, consisting of scratching, biting and licking. The nociceptive behaviors induced by spermine at 0.02 amol and 10 pmol were markedly suppressed by i.t. pretreatment with antiserum against histamine and were abolished in histidine decarboxylase-deficient mice. In histamine H₁ receptor-deficient mice, the nociceptive behaviors induced by spermine were completely abolished after treatment with 0.02 amol of spermine and significantly suppressed after treatment with 10 pmol of spermine. The i.t. pretreatment with takykinin NK₁ receptor antagonists eliminated the nociceptive behaviors induced by 0.02 amol of spermine, but did not affect the nociceptive behaviors induced by 10 pmol of spermine. On the other hand, the nociceptive behaviors induced by spermine at both 0.02 amol and 10 pmol were suppressed by i.t. pretreatment with antagonists for the NMDA receptor polyamine-binding site. The present results suggest that the nociceptive behaviors induced by i.t. administration of spermine are mediated through the spinal release of histamine and are elicited via activation of NMDA receptors.

Current Knowledge and Perspectives on Histamine H1 and H2 Receptor Pharmacology: Functional Selectivity, Receptor Crosstalk, and Repositioning of Classic Histaminergic Ligands

H₁ and H₂ histamine receptor antagonists, although developed many decades ago, are still effective for the treatment of allergic and gastric acid-related conditions. This article focuses on novel aspects of the pharmacology and molecular mechanisms of histamine receptors that should be contemplated for optimizing current therapies, repositioning histaminergic ligands for new therapeutic uses, or even including agonists of the histaminergic system in the treatment of different pathologies such as leukemia or neurodegenerative disorders. In recent years, new signaling phenomena related to H₁ and H₂ receptors have been described that make them suitable for novel therapeutic approaches. Crosstalk between histamine receptors and other membrane or nuclear receptors can be envisaged as a way to modulate other signaling pathways and to potentiate the efficacy of drugs acting on different receptors. Likewise, biased signaling at histamine receptors seems to be a pharmacological feature that can be exploited to investigate nontraditional therapeutic uses for H₁ and H₂ biased agonists in malignancies such as acute myeloid leukemia and to avoid undesired side effects when used in standard treatments. It is hoped that the molecular mechanisms discussed in this review contribute to a better understanding of the different aspects involved in histamine receptor pharmacology, which in turn will contribute to increased drug efficacy, avoidance of adverse effects, or repositioning of histaminergic ligands.

Role of spinal neurotransmitter receptors in itch: new insights into therapies and drug development

Targets for antipruritic therapies are now expanding from the skin to the central nervous system. Recent studies demonstrate that various neuronal receptors in the spinal cord are involved in pruritus. The spinal opioid receptor is one of the best-known examples. Spinal administration of morphine is frequently accompanied by segmental pruritus. In addition to μ-opioid receptor antagonists, κ-opioid receptor agonists have recently come into usage as novel antipruritic drugs, and are expected to suppress certain subtypes of itch such as hemodialysis- and cholestasis-associated itch that are difficult to treat with antihistamines. The gastrin-releasing peptide receptor in the superficial dorsal horn of the spinal cord has also received recent attention as a novel pathway of itch-selective neural transmission. The NMDA glutamate receptor appears to be another potential target for the treatment of itch, especially in terms of central sensitization. The development of NMDA receptor antagonists with less undesirable side effects on the central nervous system might be beneficial for antipruritic therapies. Drugs suppressing presynaptic glutamate-release such as gabapentin and pregabalin also reportedly inhibit certain subtypes of itch such as brachioradial pruritus. Spinal receptors of other neuromediators such as bradykinin, substance P, serotonin, and histamine may also be potential targets for antipruritic therapies, given that most of these molecules interfere not only with pain, but also with itch transmission or regulation. Thus, the identification of itch-specific receptors and understanding itch-related circuits in the spinal cord may be innovative strategies for the development of novel antipruritic drugs.

Involvement of NMDA receptor in nociceptive effects elicited by intrathecal [Tyr6] gamma2-MSH(6-12), and the interaction with nociceptin/orphanin FQ in pain modulation in mice

The mas-related genes (Mrgs, also known as sensory neuron-specific receptors, SNSRs) are specifically expressed in small diameter sensory neurons in the trigeminal and dorsal root ganglia, suggesting an important role of the receptors in pain transmission. The present study aimed to investigate the underlying mechanism of the nociceptive effects after activation of MrgC, and the interaction between MrgC and N/OFQ-NOP receptor system in modulation of nociception in mice. Intrathecal (i.t.) administration of [Tyr(6)] gamma2-MSH(6-12), the most potent agonist for MrgC receptor, produced a significant hyperalgesic response as assayed by tail withdrawal test and a series of characteristic nociceptive responses, including biting, licking and scratching, in a dose-dependent manner (0.01-10 pmol and 0.01-10 nmol, respectively) in mice. These pronociceptive effects induced by [Tyr(6)] gamma2-MSH(6-12) were inhibited dose-dependently by co-injection of competitive NMDA receptor antagonist D-APV, non-competitive NMDA receptor antagonist MK-801, and nitric oxide (NO) synthase inhibitor L-NAME. However, the tachykinin NK(1) receptor antagonist L-703,606, and tachykinin NK(2) receptor antagonist MEN-10,376, had no influence on pronociceptive effects elicited by [Tyr(6)] gamma2-MSH(6-12). In other groups, [Tyr(6)] gamma2-MSH(6-12)-induced nociceptive responses were bidirectionally regulated by the co-injection of N/OFQ. N/OFQ inhibited nociceptive responses at high doses (0.01-1 nmol), but potentiated the behaviors at low doses (1 fmol-3 pmol). Furthermore, both hyperalgesia and nociceptive responses were enhanced after the co-administration with NOP receptor antagonist [Nphe(1)]N/OFQ(1-13)-NH(2). These results suggest that intrathecal [Tyr(6)] gamma2-MSH(6-12)-induced pronociceptive effects may be mediated through NMDA receptor-NO system in the spinal cord, and demonstrate the interaction between MrgC and N/OFQ-NOP receptor system in pain transmission.

Signal pathways coupled to activation of neuronal nitric oxide synthase in the spinal cord by nociceptin/orphanin FQ

Nociceptin/orphanin FQ (N/OFQ) was earlier shown to be involved in the maintenance of neuropathic pain by activating neuronal nitric oxide synthase (nNOS). We recently established an ex vivo system to elucidate biochemical and molecular mechanisms for nNOS activation by the use of a combination of isolated intact spinal cord preparations and NADPH-diaphorase histochemistry. Here we examined the N/OFQ signal pathways coupled to nNOS activation in the spinal cord by using this ex vivo system. N/OFQ enhanced nNOS activity in the superficial layer of the spinal cord, as assessed by NADPH-diaphorase histochemistry, in a time- and dose-dependent manner. The maximum effect was observed at 3-10 nM. The N/OFQ-stimulated nNOS activity was inhibited by NMDA receptor antagonists MK-801 and D-AP5, but not by the NR2B-selective antagonist CP-101,606; and the stimulated activity was observed in NR2D(-/-) mice, but not in NR2A(-/-) or NR2A(-/-)/NR2D(-/-) mice. N/OFQ receptor antagonists attenuated the nNOS activity stimulated by N/OFQ, but not that by NMDA. Furthermore, the potentiation of nNOS by N/OFQ was inhibited by calphostin C and Ro 31-8220, PP2, and KN-62, but not by H-89. These results suggest that N/OFQ stimulated nNOS activity by a biochemical cascade initiated by activation of NMDA receptors containing NR2A.

Possible involvement of endogenous nociceptin/orphanin FQ in the pain-related behavioral responses induced by its own metabolite, nociceptin/orphanin FQ(14-17)

Nociceptin/orphanin FQ(14-17) (N/OFQ(14-17)) is one of the major fragments that are released from N/OFQ, an endogenous ligand for the opioid receptor like-1 (ORL-1) receptor by endopeptidase 24.11. In the present study, we determined the pharmacological profiles of N/OFQ(14-17) on pain-related behavioral responses in the mouse. Intrathecal (i.t.) administration of N/OFQ(14-17) (5-160 pmol) evoked pain-related behaviors, and these behavioral responses were reduced by i.t. co-administration of an ORL-1 receptor antagonist, [Nphe(1)]N/OFQ(1-13)NH2 (4 pmol). However, in the ligand-binding receptor assay, N/OFQ(14-17) had no affinity for the ORL-1 receptor. Furthermore, i.t. pretreatment with an antiserum against N/OFQ (1:50) diminished the N/OFQ(14-17)-induced pain-related behaviors, suggesting that endogenous N/OFQ is involved in their expression. Therefore, N/OFQ(14-17)-induced pain-related behaviors may be mediated through the release of endogenous N/OFQ in the mouse spinal cord.

Histamine and Schizophrenia

With the availability of an increased number of experimental tools, for example potent and brain-penetrating H1-, H2-, and H3-receptor ligands and mutant mice lacking the histamine synthesis enzyme or the histamine receptors, the functional roles of histaminergic neurons in the brain have been considerably clarified during the recent years, particularly their major role in the control of arousal, cognition, and energy balance. Various approaches tend to establish the implication of histaminergic neurons in schizophrenia. A strong hyperactivity of histamine neurons is induced in rodent brain by administration of methamphetamine or NMDA-receptor antagonists. Histamine neuron activity is modulated by typical and atypical neuroleptics. H3-receptor antagonists/inverse agonists display antipsychotic-like properties in animal models of the disease. Because of the limited predictability value of most animal models and the paucity of drugs affecting histaminergic transmission that were tried so far in human, the evidence remains therefore largely indirect, but supports a role of histamine neurons in schizophrenia.

Enhanced antinociceptive effects of morphine in histamine H2 receptor gene knockout mice

We have previously shown that antinociceptive effects of morphine are enhanced in histamine H1 receptor gene knockout mice. In the present study, involvement of supraspinal histamine H2 receptor in antinociception by morphine was examined using histamine H2 receptor gene knockout (H2KO) mice and histamine H2 receptor antagonists. Antinociception was evaluated by assays for thermal (hot-plate, tail-flick and paw-withdrawal tests), mechanical (tail-pressure test) and chemical (formalin and capsaicin tests) stimuli. Thresholds for pain perception in H2KO mice were higher than wild-type mice. Antinociceptive effects of intracerebroventricularly administered morphine were enhanced in the H2KO mice compared to wild-type mice. Intracerebroventricular co-administration of morphine and cimetidine produced significant antinociceptive effects in the wild-type mice when compared to morphine or cimetidine alone. Furthermore, zolantidine, a selective and hydrophobic H2 receptor antagonist, enhanced the effects of morphine in all nociceptive assays examined. These results suggest that histamine exerts inhibitory effects on morphine-induced antinociception through H2 receptors at the supraspinal level. Our present and previous studies suggest that H1 and H2 receptors cooperatively function to modulate pain perception in the central nervous system.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 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, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Enhanced antinociception by intracerebroventricularly administered orexin A in histamine H1 or H2 receptor gene knockout mice

Orexins are neuropeptides that are mostly expressed in the posterior and lateral hypothalamus, and related to the central control of appetite, arousal, and antinociception. Orexin neurons projected to the tuberomammillary nucleus and orexins may release histamine from the histamine neurons in this nucleus. Histamine is known to cause hypernociception. The roles of histamine H1 and H2 receptors in the orexin A-induced antinociception, however, have not been clarified yet. Here we studied the effects of histamine H1 and H2 receptors on orexin A-produced antinociception using histamine receptor knockout mice in four assays of nociception; the hot-plate, the tail-flick, the tail-pressure and the capsaicin tests. Furthermore we studied effects of histamine H1 and H2 receptor antagonists on orexin A-produced antinociception in C57BL/6 mice. The antinociceptive effects of i.c.v. orexin A were greater in histamine H1 receptor or H2 receptor knockout mice than in the wild-type mice in all four assays of pain. Furthermore, treatment of C57BL/6 mice with a combination of i.c.v. orexin A and d-chlorpheniramine (a histamine H1 receptor antagonist) or cimetidine (a histamine H2 receptor antagonist) showed a greater antinociception than i.c.v. orexin A alone in all four assays. These findings suggest the possibility that orexin A may activate H1 and H2 receptors in the supraspinal levels through the release of histamine from neurons, which might attenuate the antinociceptive effects of orexin A. Thus, the blocking of the histamine H1 or H2 receptor may produce antinociception and enhance the orexin A-induced antinociception.

Neonatal local noxious insult affects gene expression in the spinal dorsal horn of adult rats

Neonatal noxious insult produces a long-term effect on pain processing in adults. Rats subjected to carrageenan (CAR) injection in one hindpaw within the sensitive period develop bilateral hypoalgesia as adults. In the same rats, inflammation of the hindpaw, which was the site of the neonatal injury, induces a localized enhanced hyperalgesia limited to this paw. To gain an insight into the long-term molecular changes involved in the above-described long-term nociceptive effects of neonatal noxious insult at the spinal level, we performed DNA microarray analysis (using microarrays containing oligo-probes for 205 genes encoding receptors and transporters for glutamate, GABA, and amine neurotransmitters, precursors and receptors for neuropeptides, and neurotrophins, cytokines and their receptors) to compare gene expression profiles in the lumbar spinal dorsal horn (LDH) of adult (P60) male rats that received neonatal CAR treatment within (at postnatal day 3; P3) and outside (at postnatal 12; P12) of the sensitive period. The data were obtained both without inflammation (at baseline) and during complete Freund's adjuvant induced inflammation of the neonatally injured paw. The observed changes were verified by real-time RT-PCR. This study revealed significant basal and inflammation-associated aberrations in the expression of multiple genes in the LDH of adult animals receiving CAR injection at P3 as compared to their expression levels in the LDH of animals receiving either no injections or CAR injection at P12. In particular, at baseline, twelve genes (representing GABA, serotonin, adenosine, neuropeptide Y, cholecystokinin, opioid, tachykinin and interleukin systems) were up-regulated in the bilateral LDH of the former animals. The baseline condition in these animals was also characterized by up-regulation of seven genes (encoding members of GABA, cholecystokinin, histamine, serotonin, and neurotensin systems) in the LDH ipsilateral to the neonatally-injured paw. The largest aberration in gene expression, however, was observed during inflammation of the neonatally injured hindpaws in the ipsilateral LDH, which included thirty-six genes (encoding numerous members of glutamate, serotonin, GABA, calcitonin gene-related peptide, neurotrophin, and interleukin systems). These findings suggest that changes in gene expression may be involved in the long-term nociceptive effects of neonatal noxious insult at the spinal level.

Enhanced antinociception by intracerebroventricularly and intrathecally-administered orexin A and B (hypocretin-1 and -2) in mice

Orexins are neuropeptides located exclusively in neurons of the lateral hypothalamic area, which send projections to most monoaminergic nuclei, such as noradrenergic locus coeruleus, dopaminergic ventral tegmental areas, and histaminergic tuberomammillary nuclei. The present work was carried out to examine the role of orexins in nociception in mice. C57BL/6 mice were administered with orexin A and B intracerebroventricularly (i.c.v.), intrathecally (i.t.) and subcutaneously (s.c.) to reveal the sites of action of these peptides and to examine the pain thresholds using four kinds of nociceptive tasks. Orexins showed antinociceptive effects in all four types of assays for thermal (hot-plate, tail-flick, paw-withdrawal), mechanical (tail-pressure), chemical (formalin, capsaicin and abdominal stretch) nociceptions and nociceptin-induced behavioral responses, when administered i.c.v. or i.t., whereas the s.c. administration was ineffective. The antinociceptive effects of orexin A were more remarkable than those of orexin B. The i.c.v. administration of orexin A was as effective as, or more potent than the i.t. administration. The effects of orexin A were completely blocked by adenosine type 1 receptor antagonists, 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) and theophylline, but not by naloxone, suggesting a possible involvement of the adenosine-containing neurons and/or the adenosine pathway in these orexin actions. The i.c.v. administration of nociceptin had no significant effects on orexin expression in the brain and spinal cord. The present findings suggest that orexins have an antinociceptive role in at least four different types of pains, probably acting on both the brain and spinal cord.