Analgesic activity of a synthetic analogue of eel-calcitonin and its effect on the spontaneous activity of brainstem neurons in the rat

Anti-nociceptive effects of elcatonin injection for postmenopausal women with back pain: a randomized controlled trial

BACKGROUND

Eel calcitonin (elcatonin) injection is widely used for elderly patients suffering from somatic pain in Japan. However, there have been few reports on the analgesic effects of elcatonin injection. The purpose of this study was to examine the analgesic effects of elcatonin injection in postmenopausal women with lower back pain.

METHODS

This study was designed as a double-blind, randomized, placebo-controlled study. Thirty-six women aged >/=50 years with acute lower back pain participated in this study. They were randomly divided into two treatment groups according to whether they received a placebo or a weekly trigger point injection of elcatonin (20 units). They were observed for 5 weeks and the extent of pain at motion and at rest according to the visual analog scale (VAS) was evaluated. The mean VAS scores for the elcatonin group were then compared with those of the placebo group.

RESULTS

There were no statistically significant differences in the mean VAS scores for pain at rest between the two groups during the 5-week treatment course. However, the mean VAS scores for motion pain in the elcatonin group were significantly lower than those in the placebo group at the third, fifth and sixth weeks.

CONCLUSIONS

Elcatonin injection (20 units) significantly relieved motion pain in the lower back in postmenopausal women after three weeks of treatment. This analgesic effect continued for the subsequent 3 weeks.

Calcitonin receptor-stimulating peptide: Its evolutionary and functional relationship with calcitonin/calcitonin gene-related peptide based on gene structure

This review focuses on the evolutionary and functional relationship of calcitonin receptor-stimulating peptide (CRSP) with calcitonin (CT)/calcitonin gene-related peptide (CGRP) in mammals. CRSP shows high sequence identity with CGRP, but distinct biological properties. CRSP genes (CRSPs) have been identified in mammals such as pigs and dogs of the Laurasiatheria, but not in primates and rodents of the Euarchontoglires or in non-placental mammals. CRSPs have genomic organizations highly similar to those of CT/CGRP genes (CT/CGRPs), which are located along with CGRPs in a locus between CYP2R1 and INSC, while the other members of the CGRP superfamily, adrenomedullin and amylin, show genomic organizations and locations distinct from CT, CGRP, and CRSP. Thus, we categorized these three peptides into the CT/CGRP/CRSP family. Non-placental mammals having one and placental mammals having multiple CT/CGRP/CRSP family genes suggests that multiplicity of CT/CGRP started at an early stage of mammalian evolution. In the placental mammals, Laurasiatheria generally possesses multiple CRSPs and only one CT/CGRP, while Euarchontoglires possesses CT/CGRP and CGRPbeta but no CRSP, indicating an increase in the diversity and multiplicity of this family of genes in mammalian evolution. Phylogenetic analysis suggests that some CRSPs have been generated very recently in mammalian evolution. Taken together, the increase in the number and complexity of the CT/CGRP/CRSP family genes may have due to evolutionary pressure to facilitate adaptation during mammalian evolution. In this regard, it is important to elucidate the physiological roles of CT, CGRP and CRSP from the viewpoint of the CT/CGRP/CRSP family even in Euarchontoglires.

Localization of calcitonin receptor mRNA in the mouse brain: coexistence with serotonin transporter mRNA

To elucidate the sites of and mechanisms of analgesic effect of centrally injected calcitonin, we examined expression of calcitonin receptor mRNA in the mouse brain by in situ hybridization techniques. Calcitonin receptor mRNA was expressed in various brain regions, including the preoptic area, dorsomedial hypothalamic nucleus, lateral hypothalamic area, periaqueductal gray, dorsal raphe nucleus, locus coeruleus, lateral parabrachial nucleus, gigantocellular reticular nucleus alpha part, lateral paragigantocellular nucleus, raphe magnus nucleus and solitary tract nucleus, which are known to play important roles in pain modulation. In addition, a double in situ hybridization technique demonstrated the intense expression of calcitonin receptor mRNA on serotonergic neurons in some raphe nuclei and the lateral paragigantocellular nucleus, suggesting the involvement of central serotonergic pathways in analgesic effect of calcitonin.

Involvement of brain serotonergic terminals in the antinociceptive action of peripherally applied calcitonin

We investigated the antinociceptive effect of systemic injection of calcitonin and its mechanisms of action in rats. Subcutaneous injection of [Asu(1,7)]eel calcitonin (ECT, 4 U x kg(-1) x day(-1)) daily for 7 days suppressed nociceptive hypersensitivity induced by formalin (and by carrageenan); the effect was gradually increased by the repeated injections and significant effects were observed after administration for more than 4 days. The antinociceptive action of ECT (4 U x kg(-1) x day(-1) for 7 days) was inhibited by intracerebroventricular injection of the serotonergic neurotoxin 5,7-dihydroxytryptamine and serotonin-receptor antagonists methiothepin, cyproheptadine and ketanserin; methysergide showed an inhibitory tendency. Intrathecal injections of 5,7-dihydroxytryptamine, methiothepin, cyproheptadine and ketanserin were without effects on the ECT action. The results suggest the involvement of serotonin in the brain, but not in the spinal cord, in the ECT antinociception. Intracerebroventricular or intrathecal injection of the catecholaminergic neurotoxin 6-hydroxydopamine and intracerebroventricular injection of the alpha-adrenoceptor antagonist phentolamine were also without effects on the ECT action. A subcutaneous infusion of the opioid receptor antagonist naloxone inhibited the antinociceptive action of morphine, but not that of ECT. Thus, adrenergic and opioidergic systems may not play important roles in the ECT antinociception. The present results suggest that repeated systemic injection of ECT produces analgesia and that the brain serotonergic terminals are involved in this action.

Antinociceptive effects of repeated systemic injections of calcitonin in formalin-induced hyperalgesic rats

Calcitonin (CT) produces long-lasting analgesia in patients suffering from painful diseases following repeated systemic injections, but there have been only a few contradictory reports on the antinociceptive action of systemic injections of CTs in animal experiments. This study was conducted to elucidate an antinociceptive action of systemic CT in rats. An injection of dilute formalin induced hyperalgesia for about 2 h. Single topical injections of 0.12 and 1.2 U, but not 0.012 U, of [Asu1.7] eel CT (eCT) into the same site of formalin injection inhibited the hyperalgesia. Repeated systemic injections of eCT (4 and 40, but not 0.4, U kg-1 day-1) for 7 days inhibited the hyperalgesia, while the single injection was without effects at doses tested. Although the highest dose of eCT (40 U kg-1 day-1) inhibited an increase in body weight following repeated injections, lower doses (0.4 and 4 U kg-1 day-1) were without effects. The suppression of hyperalgesia following repeated systemic injections of eCT (4 U kg-1 day-1) lasted for at least 24 h, and subsided by 3 days following the last eCT injection. These results indicate that the repeated systemic injections of eCT produce a long-lasting inhibition of formalin-induced hyperalgesia in rats. This inhibitory effect is similar to CT analgesia in human subjects in terms of a necessity for repeated administration, effective dose and long-lasting effects.

Calcitonin and its antinociceptive activity: animal and human investigations 1975-1992

Calcitonin (CT) is a polypeptide hormone produced in the thyroid gland that regulates, blood calcium levels and bone calcium metabolism. The unexpected finding of binding sites for calcitonin in several areas of the brain oriented attention to activities of CT in the central nervous system and also to its antinociceptive action. The first report of this last effect was in 1975, and the many different experimental and clinical data on this topic reported since then are reviewed here. The heterogenous findings have been organized according to the logical classification of animal and human studies. For each of these headings, subheadings such as acute and chronic pain, different kinds of administration and different procedures used to record the results, are considered. The several proposed mechanisms of action, involving serotoninergic, catecholaminergic, Ca2+ fluxes, protein phosphorylation, beta-endorphin production, cyclooxygenase inhibition and histamine interference are also reviewed. Calcitonin, neurotensin, substance P, VIP and, recently, CGRP are some of the non-opioid peptides that have been reported to interfere with pain and that open up a new, alternative way of investigating antinociceptive drugs different than opioid or opioid-like agents. An examination of the state-of-investigation of calcitonin's antinociceptive activity in the last 17 years shows that many experimental studies indicate the existence of this effect, including studies in humans, and this opens up perspectives for therapy with a new class of antinociceptive agents.

Effects of calcitonin on human auditory and visual evoked brain potentials

Besides its Ca(++)-regulative effects, calcitonin is known to diminish sensitivity to painful stimuli. The present study aimed to clarify whether calcitonin has similar effects on stimulus processing in other modalities. Effects of calcitonin were assessed on brain potentials recorded from the human scalp which were evoked either by auditory clicks or visual checkerboard pattern-reversals. Twelve healthy men were tested in a double-blind intra-subject design receiving either 0.1 IU/kg salmon calcitonin (sCT) or 1.0 IU/kg sCT or saline solution during a 20 min IV infusion. sCT significantly increased latency of wave V of the brainstem auditory evoked potential (BAEP). Effects of BAEP wave V increased in magnitude with increasing dose of sCT and with decreasing intensity of the click stimulus. There was also a slight increase in latency of the N80 of the pattern-reversal visual evoked potential (PR-VEP). Additionally, subjects rated themselves as less activated following the high dose of sCT compared to placebo. The pattern of results is in accord with a slowing or inhibitory influence of calcitonin on auditory and visual sensory processing, thus paralleling findings concerning calcitonin effects on the perception of painful somatosensory stimuli.

Repeated calcitonin treatment reduces the stimulation of inositol phospholipid by norepinephrine and serotonin in rat hippocampus and cerebral cortex

Stimulation of inositol phospholipid hydrolysis by norepinephrine or 5-hydroxytryptamine was reduced in hippocampal or cortical slices from rats repeatedly injected with (Asu1.7)eel-calcitonin (2.5 IU/kg i.p.). This effect was specific, as the basal or carbamylcholine-stimulated inositol phospholipid hydrolysis was unchanged in slices from calcitonin-injected animals. The reduced responsiveness to norepinephrine did not reflect a decreased number or affinity of alpha 1-adrenergic recognition sites, suggesting that calcitonin treatment leads to a reduced coupling between alpha 1-adrenoceptors and phospholipase C.