Antiserotonergic inhibition of calcitonin-induced increase of beta-endorphin, ACTH, and cortisol secretion

Central administration of aminoprocalcitonin inhibits food intake and stimulates the hypothalamic-pituitary-adrenal axis in rats via the corticotrophin-releasing factor system

Aminoprocalcitonin (N-PCT), a neuroendocrine peptide derived from procalcitonin, reduces food intake and body weight when administered centrally in rats. We have recently shown that N-PCT is expressed in brain areas known to be involved in energy homeostasis, including the paraventricular nucleus (PVN) of the hypothalamus, which contains a prominent population of corticotrophin-releasing factor (CRF)-synthesising neurones. CRF plays a pivotal role in the regulation of the hypothalamic-pituitary adrenal (HPA) axis and food intake. However, little is known about functional interactions of N-PCT and CRF. In the present study, we found endogenous N-PCT protein in the rat PVN. We also showed N-PCT immunoreactivity in PVN co-localised with NeuN, a neuronal marker, or glial fibrillary acidic protein, an astrocyte marker. Double staining immunohistochemistry revealed that N-PCT co-localised with CRF in parvocellular neurones of the PVN. Intracerebroventricular N-PCT administration increased CRF mRNA and content in the hypothalamus, suggesting that N-PCT stimulates the HPA axis and suppresses food intake and body weight via CRF-dependent pathways. In keeping with this, i.c.v. co-injection of D-Phe-CRF(12-41), a CRF receptor antagonist, significantly attenuated N-PCT-induced reduction in food intake and body weight in a dose-dependent manner. Furthermore, i.c.v. administration of N-PCT increased plasma adrenocorticotrophic hormone and corticosterone concentrations and induced the expression of Fos protein, a marker of neuronal activity, in parvocellular CRF neurones. These data collectively support the hypothesis that N-PCT inhibits food intake and body weight and stimulates the HPA axis via CRF-mediated pathways.

The effect of calcitonin on β-endorphin levels in postmenopausal osteoporotic patients with back pain

The purpose of this study was to evaluate the efficacy of calcitonin on beta-endorphin levels in female patients experiencing back pain associated with postmenopausal osteoporosis. The secondary purpose was to assess the pain and quality of life in these patients. There were 30 patients with a mean age of 58.2+/-5.4 years in the treatment group and 26 patients with a mean age of 58.8+/-5.2 years in the placebo group in this randomized, placebo-controlled study. The patients subcutaneously received 100 IU salmon calcitonin or placebo injections and 1,000 mg elementary calcium for 2 weeks. Baseline plasma beta-endorphin levels were measured and repeated after 2 weeks. Patients' pain and quality of life (QOL) were evaluated by using the Visual Analogue Scale, Modified Face Scale, Beck Depression Index, and Nottingham Health Profile. Patients' global assessment of disease activity was also performed at baseline and at the end of the first and second week. We found that plasma beta-endorphin levels in the treatment group were significantly higher than the placebo group at the end of the second week (p<0.001). Although pain and QOL scores were improved at the end of the second week in both groups (p<0.05), the improvement in the treatment group was more significant when compared with the placebo group (p<0.05). Therefore, calcitonin is an analgesic agent, as it increases the plasma beta-endorphin levels in patients with postmenopausal osteoporosis, which consequently improves QOL.

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.

Dexamethasone suppression of the calcitonin induced beta-endorphin, ACTH and cortisol secretion

Our previous observations have shown that calcitonin (CT) stimulates beta-endorphin, ACTH, and cortisol secretion. In order to give further information on the supposed hypothalamic pituitary involvement in this effect, we studied the influence of dexamethasone on this stimulative influence of CT. Six healthy women aged 50-65 years were investigated. All the subjects received 100 U CT salmon (Sandoz) i.v. at 0800 (0 time). Plasma beta-endorphin, ACTH, and cortisol were estimated every 30 min from -30 to 120 min by specific radioimmunoassays. The same subjects were evaluated a second time, at the same intervals, when 1 mg dexamethasone was administered per os at 11 PM the previous night and CT i.v. at 0800 the next morning. Beta-endorphin, ACTH, and cortisol levels (mean +/- SEM) rose significantly after 100 U CT from 5.6 +/- 0.17 to 16.75 +/- 1.8 pmol/L (p less than 0.001); from 39.6 +/- 6 to 88.0 +/- 3.1 pg/ml (p less than 0.0001) (from 8.7 +/- 1.3 to 19.4 +/- 0.7 pmol/L); and from 13.1 +/- 1.6 to 23.8 +/- 3.0 micrograms/dl (p less than 0.0001) [374 +/- 45 to 680 +/- 85 nmol/L], respectively. Dexamethasone suppressed almost completely the stimulatory effect of CT beta-endorphin rose from 4.9 +/- 0.12 to 6.3 +/- 1.3 pmol/L (n.s.), ACTH from 38.6 +/- 5.1 to 42.6 +/- 6.2 pg/ml (n.s.) (from 8.5 +/- 1.1 to 9.4 +/- 0.9 pmol/L) and cortisol from 0.88 +/- 0.23 to 0.88 +/- 0.18 microgram/dl (n.s.) (from 25.1 +/- 6.5 to 25.0 +/- 5.1 nmol/L).(ABSTRACT TRUNCATED AT 250 WORDS)

Antagonism of calcitonin-induced anorexia by chronic, but not acute, tricyclic antidepressants in the rat

Intraperitoneal or intracerebral injections of calcitonin in the rat produce several behavioral and hormonal effects which have some analogies with the human depressive syndrome. To determine if calcitonin effects are sensitive to antidepressant drugs, the ability of antidepressants and other psychotropic drugs to interact with calcitonin-induced anorexia was tested. The results show that chronic treatments (21 days) with tricyclic, or with tetracyclic, antidepressants significantly tend to neutralize the anorectic effect of calcitonin. Other antidepressants and other psychotropic drugs had no significant effect. The acute administration (24 h) of clomipramine did not antagonize the effect of calcitonin, and even significantly enhanced it. These results allow the author to propose the effects of calcitonin in the rat as a new animal model of depression, and to raise the hypothesis that a possible mechanism of action of tricyclic antidepressant treatments is to counteract the effects of certain brain peptides.

Salmon calcitonin-induced modulation of free intracellular calcium

Salmon calcitonin (sCT), a hormone shown to modulate calcium in the periphery modulated free, intracellular calcium, ([Ca++]i), in mouse brain synaptosomes as measured by changes in fura-2-mediated fluorescence. A 5-min incubation of synaptosomes with sCT produced an increase in the basal levels of [Ca++]i and an increase in KCl-stimulated levels of [Ca++]i. A 5-min pretreatment of mice with intraventricularly administered sCT antagonized morphine-induced antinociception in the tail-flick test, and facilitated naloxone antagonism of morphine. Conversely, pretreatment of synaptosomes for 1 h with salmon CT produced a decrease in depolarization-stimulated levels of [Ca++]i. The sCT-induced decrease in the stimulated rise in [Ca++]i at 1 h correlated temporally to sCT-induced antinociception in vivo. The effects of sCT in the electrically stimulated guinea pig ileum bioassay appeared to correlate to sCT effects in vivo. The data indicate that calcitonin may function as a neuromodulator via modulation of Ca++ within the central nervous system.

The effects on anterior pituitary hormone secretion of salmon calcitonin in healthy volunteers

The reports of the effect of calcitonin on pituitary function are confusing and often refer to uncontrolled studies. We have now carried out a double-blind placebo-controlled trial of intravenous and subcutaneous salmon calcitonin on anterior pituitary function in 17 healthy volunteers. Visual analogue scores for the nausea and vomiting seen after salmon calcitonin correlated with the rise in ACTH and, secondarily, cortisol. Calcitonin had no effect on growth hormone, prolactin, thyrotrophin, luteinizing hormone or follicle stimulating hormone. It is concluded that the stimulation of ACTH secretion following a single dose of salmon calcitonin is probably the result of the stress of nausea rather than a direct effect on the pituitary.