Medial diencephalic sites involved in calcitonin-induced hyperthermia and analgesia

Central nervous system and other effects

Amylin enhanced the uptake of certain amino acids, crossed the blood-brain barrier, and increased body temperature. The physiological significance of these responses is currently unclear. An effect of peripherally injected amylin to enhance weakly trained memory fitted with similar effects of other gastrointestinal peptide hormones. Centrally administered amylin reduced locomotor and exploratory behavior. Amylin administered alone was analgesic when administered peripherally, via a non-opiate pathway. When administered in combination with opiates, there was an opiate-sparing synergy.

Immunohistochemical mapping of calcitonin receptors in the adult rat brain

Calcitonin receptors (CTR) have previously been identified in specific regions of the rat central nervous system using in situ hybridization or autoradiography with iodinated ligands. In this study, the results of immunohistochemical mapping of CTR in the adult rat brain are reported, using a potent and recently developed antibody that recognizes an intracellular epitope of the rat CTR, and high-resolution immunofluorescence techniques. Abundant expression was found in the brain, with highest densities in the nucleus accumbens, lateral arcuate nucleus, lateral substantia nigra, bed nucleus of the stria terminalis, locus coeruleus, area postrema, nucleus of the solitary tract, and some of the nuclei of the reticular formation. These results are in close correspondence with previous mapping studies. However, we detected CTR immunoreactivity in several additional brain areas, as the ventromedial, lateral and posterior hypothalamus, where CT binding has not yet been described. Our detailed mapping of the CTR in the rat brain has identified CTR-positive cells that will be important for subsequent characterization of behavioral functions associated with the actions of CT-related peptides.

Heroin-induced rhabdomyolysis as a cause of reflex sympathetic dystrophy

Reflex sympathetic dystrophy is an excessive or abnormal response of the sympathetic nervous system in an extremity to an injury or other condition. The authors describe a 37-year-old man who experienced constant pain and vasomotor instability in both feet after nontraumatic rhabdomyolysis secondary to smoking heroin. Three-phase bone scintigraphy was performed and revealed significantly increased blood-flow, blood-pool, and delayed-phase radioactivity. The follow-up three-phase bone scinitigram showed less radiotracer uptake that was consistent with a good response to calcitonin therapy. Heroin-induced rhabdomyolysis should be added to the list of precipitating conditions that can induce this syndrome.

Cold water swim stress increases the expression of neurotensin mRNA in the lateral hypothalamus and medial preoptic regions of the rat brain

Stress-induced analgesia is a well-documented phenomenon that occurs in all mammalian species. Forced cold water swim produces a type of stress-induced analgesia that is independent of mu opioid receptors. The neuropeptide neurotensin (NT) has been implicated in mu opioid-independent analgesia (MOIA), but the circuitry of this system is largely unknown. The medial preoptic area (MPO) and lateral hypothalamus (LH) are two regions that are known to modulate pain processing. These two regions also contain neurotensinergic projections to the periaqueductal gray, a region that has been shown to produce MOIA upon injection of NT. The goal of this study was to determine if cold water swim (CWS) stress, which produces MOIA, activates the NT-ergic systems in these two regions. In situ hybridization results indicate that CWS increases the level of NT mRNA within neurons in the MPO and LH, suggesting that these two regions are activated during this process.

Calcitonin modifies ligand binding to muscarinic receptor in CNS membranes

Calcitonin (CT) is a peptide produced by the thyroid gland, whose best described role is to prevent bone reabsorption, though it also participates in other biological functions through both central and peripheral mechanisms. CT is able to inhibit brain Na(+), K(+)-ATPase activity (Rodríguez de Lores Arnaiz, López Ordieres, Peptides 1997;18:613-5) and a relationship between such enzyme activity and cholinergic function has been suggested. Accordingly, we tested CT effect on [(3)H]-quinuclidinyl benzilate ([(3)H]-QNB) binding to rat CNS membranes to determine whether the peptide is able to modify the cholinergic muscarinic receptor as well. It was found that 1x10(-7)-1x10(-5) M CT decreased 20-70% ligand binding to hippocampal, cerebellar, cortical and striatal membranes. Scatchard analysis of saturation curves showed that 5x10(-6) M CT significantly modified binding kinetic constants, thus it increased roughly 220% K(d) values and decreased 20-36% B(max) values in cerebral cortical and cerebellar membranes. Since the peptide decreases affinity ligand binding and reduces the number of binding sites, CT may well be acting as a cholinergic modulator through a decrease in muscarinic receptor functionality.

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.

Interleukin-1beta and calcitonin, but not corticotropin-releasing factor, alter sleep cycles when injected into the rat hypothalamic lateral paraventricular area

Interleukin-1beta (II-1beta) is a cytokine known to have somnogenic properties. We have previously shown that II-1beta decreases food intake when injected into the lateral part of the paraventricular nucleus of the hypothalamus (PVH), and, because food intake and sleep are closely related behaviors, we tested the hypothesis that II-1beta could alter sleep when injected into the lateral PVH area. We compared the effects of II-1beta with those of two other peptides involved in feeding behavior and known to act in the PVH area, the corticotropin-releasing factor (CRF) and salmon calcitonin (sCT). The EEG of rats was recorded for 48 h after the injection. The results showed that CRF had no effects, II-1beta reduced significantly sleep duration during the first 5 h following the injection, and sCT profoundly affected sleep cycles, producing an almost 30-h long insomnia, with a major reduction of slow wave sleep and a long period of alternation of REM sleep and wakening. It is concluded that (i) the area between the lateral part of the PVH and the fornix is a brain site involved in sleep regulation, (ii) II-1beta, a peptide generally considered as somnogenic, decreases sleep when administered in this area, and (iii) sCT is an extremely potent suppressor of slow wave sleep.

Calcitonin increases 5-HT1A binding site densities in the brain of adrenalectomized rats

Calcitonin is a peptide which acts in the brain to modulate behavior and hormone release, possibly through an interaction with serotonergic systems. We investigated the effects of chronic systemic injections of salmon calcitonin on the [3H]-8-OHDPAT binding to 5-HT1A receptors in the frontal cortex and hippocampus in adrenalectomized and intact (non adrenalectomized) rats. The results show that salmon calcitonin increases the maximal density of 5-HT1A binding sites in both structures in adrenalectomized animals (and decreases the affinity in the frontal cortex only). Calcitonin does not alter this binding in intact rats. These results demonstrate the existence of interactions between calcitonin, serotonin and glucocorticoids, and raise the hypothesis of a neurotrophic effect of calcitonin on serotonergic neurons.

Calcitropic peptides: neural perspectives

In mammals and higher vertebrates, calcitropic peptides are produced by peripheral endocrine glands: the parathyroid gland (PTH), thyroid or ultimobranchial gland (calcitonin) and the anterior pituitary gland (growth hormone and prolactin). These hormones are, however, also found in the neural tissues of lower vertebrates and invertebrates that lack these endocrine organs, suggesting that neural tissue may be an ancestral site of calcitropic peptide synthesis. Indeed, the demonstration of CNS receptors for these calcitropic peptides and their induction of neurological actions suggest that these hormones arose as neuropeptides. Neural and neuroendocrine roles of some of these calcitropic hormones (calcitonin and parathyroid hormone) and related peptides (calcitonin gene related peptide, stanniocalcin and parathyroid hormone related peptide) are thus the focus of this review.

Production of bioactive salmon calcitonin from the nonendocrine cell lines COS-7 and CHO

To produce bioactive salmon calcitonin from the conventional nonendocrine cell lines, COS-7 and CHO, we devised a salmon calcitonin expression vector by combining the amino-terminus of human calcitonin precursor with a salmon calcitonin sequence, inserting the efficient furin-cleavable processing sequence Arg-X-Arg-X-Lys-Arg before salmon calcitonin, and deleting the carboxyl-terminal extension peptide. This chimeric calcitonin precursor terminates at glycine to easily receive an amidation reaction. COS-7 and CHO produced a high level of bioactive calcitonin by the resorption pit formation assay. Although amidating activity is highly expressed in CHO, but only a little in COS-7 cells, both cells produced a similar level of bioactive calcitonin. Thus, the engineered salmon calcitonin expression vector enables nonendocrine cells even with low amidation activity to produce bioactive calcitonin.

A study of calcitonin effect on synaptosomal membrane enzymes

Calcitonin is a hormone peptide produced by the thyroid gland, whose best described role is to prevent bone reabsorption. It also participates in other biological functions, even at central nervous system level. We studied the effect of added calcitonin on ATPase and acetylcholinesterase activities in synaptosomal membranes isolated from rat cerebral cortex. Calcitonin at 10(-7) - 10(-5)M concentration decreased 20-40% Na+, K(+)-ATPase and 15-25% K(+)-p-nitrophenylphosphatase activities, and at 10(-6)-10(-5)M reduced 20-30% Mg(2+)-p-nitrophenylphosphatase activity. However, this peptide failed to modify Mg(2+) - and Ca(2+)-ATPase or acetylcholinesterase activities. Results suggest that the sodium pump may be a target for calcitonin effects at neuronal level. Thus, calcitonin inhibition of sodium/potassium transport through synaptic membranes supports a regulatory role of this peptide on neurotransmission.

Low doses of neurotensin in the preoptic area produce hyperthermia. Comparison with other brain sites and with neurotensin-induced analgesia

High amounts of neurotensin (NT) are found in the preoptic area of the hypothalamus, an area known to be involved in the regulation of body temperature. It is generally believed that NT is a peptide that produces hypothermia, and several sites in the brain have been proposed to mediate NT-induced hypothermia, including the preoptic area. However, the doses of NT used in these experiments were always very high (microgram order) whereas, according to Goedert, the total brain content of NT in the rat does not exceed 10 ng. We therefore reinvestigated the effects of microinjections of NT in the brain, using high (5 micrograms) and low (50 and 5 ng) doses, into the preoptic area and other brain sites (cerebral ventricles, posterior hypothalamus, and nucleus accumbens), and we also studied, as a comparison, the effects of high and low doses of NT on pain sensitivity in the same sites. The results show that the preoptic area has unique properties in the regulation of body temperature: low doses of NT in the preoptic area produce a hyperthermic response, whereas high doses produce hypothermia. In comparison, NT produces hypothermia in the posterior hypothalamus whatever the dose, and NT has analgesic effects in the preoptic area only at high doses. Besides, NT has no thermic effect, but does have an analgesic effect, in the nucleus accumbens. The selectivity of the actions of high doses of NT, as well as the mechanism of action of NT (possibly an endogenous neuroleptic), are discussed.

Hypothalamic and thalamic sites of action of interleukin-1 beta on food intake, body temperature and pain sensitivity in the rat

Interleukin-1beta (IL-1beta ) has anorectic, hyperthermic, and analgesic or hyperalgesic (depending on the studies) effects in the rat. These effects appear to be mediated by the central nervous system; however, the exact localization of action of IL-1beta in the brain has never been delineated with precision. The purpose of this study was to determine precisely where IL- IO acts in the hypothalamus and in the thalamus to modulate food intake, body temperature, and pain sensitivity. Animals were tested after local intracerebral microinjections of 5 ng of IL-1beta dissolved in 0.3 microl of saline, or of 0.3 microl saline alone. The results show that IL-1beta has anorectic effects in 3 diencephalic sites (the perifornical area, an area above the optic chiasma, and an area internal to the mamillo-thalamic tract), and not in 9 other sites tested. IL-1beta has hyperthermic effects in 7 sites (the media] and lateral preoptic area, the hypothalamic periventricular substance, the dorso-medial and arcuate nuclei of the hypothalamus, and the centro-medial and gelatinosus nuclei of the thalamus), and not in 6 other sites. IL-1beta has analgesic effects in the centro-medial and gelatinosus nuclei of the thalamus, and not in 7 other sites. IL-1beta also increases food intake and decreases pain sensation thresholds in the paraventricular nucleus of the hypothalamus. Therefore IL-1beta has very selective anatomical sites of action in the brain, and the paraventricular nucleus of the hypothalamus appears to have special properties regarding the effects of IL-1beta on food intake and pain sensation regulation.

Extensive brain mapping of calcitonin-induced anorexia

The purpose of this study was to compare the localization in the brain of calcitonin-induced anorexia to the distribution of calcitonin binding sites (as described by others). We, thus, performed an extensive mapping of brain structures to determine those involved in calcitonin-induced anorexia. A significant anorexia is found after injection of calcitonin (15 ng in 0.3 microliters) into several brain areas. Forebrain: lateral septum, lateral part of the anterior commissure, and bed nucleus of the stria terminalis; hypothalamus: floor of the anterior part of the hypothalamus, paraventricular nucleus and adjacent perifornical area; thalamus: nucleus reuniens, an area internal to the mamillo-thalamic tract, and medial geniculate body; other areas: amygdala, lateral hippocampus, and central gray. No significant effect is found in the following areas: forebrain: nucleus accumbens, striatum, and medial septum; hypothalamus: lateral, ventro-medial, dorso-medial, and posterior nuclei; thalamus: centro-medial nucleus, lateral part of the zona incerta, and lateral geniculate body; hippocampus: dorsal and ventral parts; midbrain: central tegmentum, ventral tegmental area, and substantia nigra. When these results are compared to the distribution of calcitonin binding sites in the brain, two types of discrepancies are found. The first is the absence of effect in areas containing receptors: these areas may be involved in calcitonin-induced behaviors other than food intake. The second is the occurrence of anorexia in areas where no receptors are found: this finding is not easy to explain and raises some speculative hypotheses. In conclusion, calcitonin is active to decrease food intake in several brain areas, the strongest effect occurring in the paraventricular/perifornical area.(ABSTRACT TRUNCATED AT 250 WORDS)