Sexually dimorphic expression of calcitonin gene-related peptide (CGRP) immunoreactivity by rat mediobasal hypothalamic neurons

Calcitonin gene-related peptide and its receptor plays important role in nociceptive regulation in the arcuate nucleus of hypothalamus of rats with inflammatory pain

The present study has explored the role of calcitonin gene-related peptide (CGRP) and its receptor in inflammatory pain modulation in arcuate nucleus of hypothalamus (ARC). Our study demonstrated that intra-ARC injection of CGRP induced antinociceptive effects to naïve rats and rats with inflammatory pain, the effect could be inhibited by the selective CGRP receptor antagonist CGRP8-37. Interestingly, the CGRP-induced antinociception effect was decreased in rats with inflammatory pain compared to naïve rats. Similarly, we found that calcitonin receptor like receptor (CLR), a main component of CGRP receptor, had a low decreased expression levels in the ARC regions of rats with inflammatory pain. The CGRP-induced antinociceptive effect was significantly impaired after reducing CLR expression by intra-ARC administration of CLR targeted siRNA. These findings demonstrated that CGRP might play a crucial role in nociceptive modulation in the ARC during inflammatory pain, which was mediated by CGRP receptor in the ARC. This study shed light upon CGRP and its receptor interaction might be valuable strategies for the alleviation of inflammatory pain.

CGRP physiology, pharmacology, and therapeutic targets: migraine and beyond

Calcitonin gene-related peptide (CGRP) is a neuropeptide with diverse physiological functions. Its two isoforms (α and β) are widely expressed throughout the body in sensory neurons as well as in other cell types, such as motor neurons and neuroendocrine cells. CGRP acts via at least two G protein-coupled receptors that form unusual complexes with receptor activity-modifying proteins. These are the CGRP receptor and the AMY1 receptor; in rodents, additional receptors come into play. Although CGRP is known to produce many effects, the precise molecular identity of the receptor(s) that mediates CGRP effects is seldom clear. Despite the many enigmas still in CGRP biology, therapeutics that target the CGRP axis to treat or prevent migraine are a bench-to-bedside success story. This review provides a contextual background on the regulation and sites of CGRP expression and CGRP receptor pharmacology. The physiological actions of CGRP in the nervous system are discussed, along with updates on CGRP actions in the cardiovascular, pulmonary, gastrointestinal, immune, hematopoietic, and reproductive systems and metabolic effects of CGRP in muscle and adipose tissues. We cover how CGRP in these systems is associated with disease states, most notably migraine. In this context, we discuss how CGRP actions in both the peripheral and central nervous systems provide a basis for therapeutic targeting of CGRP in migraine. Finally, we highlight potentially fertile ground for the development of additional therapeutics and combinatorial strategies that could be designed to modulate CGRP signaling for migraine and other diseases.

Gestational Exposure to Sodium Valproate Disrupts Fasciculation of the Mesotelencephalic Dopaminergic Tract, With a Selective Reduction of Dopaminergic Output From the Ventral Tegmental Area

Gestational exposure to valproic acid (VPA) is known to cause behavioral deficits of sociability, matching similar alterations in human autism spectrum disorder (ASD). Available data are scarce on the neuromorphological changes in VPA-exposed animals. Here, we focused on alterations of the dopaminergic system, which is implicated in motivation and reward, with relevance to social cohesion. Whole brains from 7-day-old mice born to mothers given a single injection of VPA (400 mg/kg b.wt.) on E13.5 were immunostained against tyrosine hydroxylase (TH). They were scanned using the iDISCO method with a laser light-sheet microscope, and the reconstructed images were analyzed in 3D for quantitative morphometry. A marked reduction of mesotelencephalic (MT) axonal fascicles together with a widening of the MT tract were observed in VPA treated mice, while other major brain tracts appeared anatomically intact. We also found a reduction in the abundance of dopaminergic ventral tegmental (VTA) neurons, accompanied by diminished tissue level of DA in ventrobasal telencephalic regions (including the nucleus accumbens (NAc), olfactory tubercle, BST, substantia innominata). Such a reduction of DA was not observed in the non-limbic caudate-putamen. Conversely, the abundance of TH+ cells in the substantia nigra (SN) was increased, presumably due to a compensatory mechanism or to an altered distribution of TH+ neurons occupying the SN and the VTA. The findings suggest that defasciculation of the MT tract and neuronal loss in VTA, followed by diminished dopaminergic input to the ventrobasal telencephalon at a critical time point of embryonic development (E13-E14) may hinder the patterning of certain brain centers underlying decision making and sociability.

Serum calcitonin gene-related peptide levels in women with polycystic ovary syndrome

PURPOSE

Calcitonin gene-related peptide (CGRP) is an amino acid neuropeptide with widespread expression. It has potent effects on lipid and energy metabolism. It induces insulin resistance. This study was planned to determine CGRP levels in women with polycystic ovary syndrome (PCOS).

METHODS

Forty-seven women with PCOS and 34 healthy controls were evaluated in this controlled clinical study. Serum lipid sub-fractions, postprandial and fasting glucose, insulin and other hormones (gonadotropins, androgens) and CGRP levels were measured. Homeostasis model assessment (HOMA-IR) was used to estimate insulin resistance.

RESULTS

Waist measurements, postprandial and fasting glucose and fasting insulin levels and free androgen index and HOMA-IR were significantly higher in subjects with PCOS. However, the women with PCOS had considerably lower high-density lipoprotein cholesterol levels than healthy subjects. Serum CGRP levels were higher in study subjects than in controls, although it was statistically insignificant.

CONCLUSIONS

Serum CGRP level was not related with insulin resistance, ovarian hyperandrogenism and dyslipidemia in abdominally obese women with PCOS. These outcomes propose that CGRP may not play a pivotal role in the pathogenesis of PCOS.

The control of sexual differentiation of the reproductive system and brain

This review summarizes current knowledge of the genetic and hormonal control of sexual differentiation of the reproductive system, brain and brain function. While the chromosomal regulation of sexual differentiation has been understood for over 60 years, the genes involved and their actions on the reproductive system and brain are still under investigation. In 1990, the predicted testicular determining factor was shown to be theSRYgene. However, this discovery has not been followed up by elucidation of the actions of SRY, which may either stimulate a cascade of downstream genes, or inhibit a suppressor gene. The number of other genes known to be involved in sexual differentiation is increasing and the way in which they may interact is discussed. The hormonal control of sexual differentiation is well-established in rodents, in which prenatal androgens masculinize the reproductive tract and perinatal oestradiol (derived from testosterone) masculinizes the brain. In humans, genetic mutations have revealed that it is probably prenatal testosterone that masculinizes both the reproductive system and the brain. Sexual differentiation of brain structures and the way in which steroids induce this differentiation, is an active research area. The multiplicity of steroid actions, which may be specific to individual cell types, demonstrates how a single hormonal regulator, e.g. oestradiol, can exert different and even opposite actions at different sites. This complexity is enhanced by the involvement of neurotransmitters as mediators of steroid hormone actions. In view of current environmental concerns, a brief summary of the effects of endocrine disruptors on sexual differentiation is presented.

Calcitonin gene-related peptide immunoreactive cells and fibers in forebrain vocal and auditory nuclei of the budgerigar (Melopsittacus undulatus)

The distributions of calcitonin gene-related peptide (CGRP) immunoreactive neurons and fibers were mapped within forebrain vocal control and auditory nuclei of a vocal learning psittacine species, the budgerigar (Melopsittacus undulatus). Immunoreactivity was exhibited by telencephalic nuclei previously associated with vocal control pathways on the basis of both tract tracing studies and gene mapping: the central nucleus of the anterior archistriatum (AAc), central nucleus of the lateral neostriatum (NLc), magnocellular nucleus the lobus parolfactorius (LPOm), the oval nucleus of the ventral hyperstiratum (HVo) and the medial division of the oval nucleus of the anterior neostriatum (NAom). The main body of NAo also contained an exceptionally high density of immunoreactive fibers. In contrast to the condition in oscine songbirds, CGRP-positive neuronal somata were not present in any telencephalic vocal control nucleus. CGRP-positive somata were present, however, in diencephalic cell groups that included the shell region of the nucleus ovoidalis (Ov), the nucleus dorsolateralis posterior (DLP) and a region of the ventral thalamus that was retrogradely labeled by tracer deposits into HVo and AAc. CGRP immunoreactive fibers were observed within auditory areas of the telencephalon including Field L and the neostriatum intermedium pars dorsolateralis. The likely sources of these fibers are CGRP-positive neurons within the Ov shell and DLP.

Projections of the sexually dimorphic calcitonin gene-related peptide neurons of the preoptic area determined by retrograde tracing in the female rat

The medial preoptic area of the rat exhibits morphologic sex differences and is implicated in the control of sexually dimorphic behavior and function. Neurons expressing calcitonin gene-related peptide (CGRP) within the anteroventral periventricular (AVPV) and medial preoptic nucleus (MPN) of the medial preoptic area exhibit female-dominant sex differences in number through organizational and activational effects of gonadal steroids. The present study used retrograde tracing experiments to establish the projections of the AVPV and MPN CGRP neurons in the female rat. After the intraperitoneal administration of Fluoro-Gold to female rats (n = 5), we were unable to detect retrograde tracer in any CGRP-immunoreactive cells of the hypothalamus. Intracerebral injections of 50- to 100-nl volumes of Fluoro-Gold into the mediobasal hypothalamus resulted in up to 70% of CGRP neurons in the AVPV and MPN containing retrograde tracer. Similar large volume tracer depositions in the lateral septum, periaqueductal gray, two likely CGRP projection sites, resulted in no labeling of preoptic CGRP neurons. Experiments using small volume (30-nl) injections of Fluoro-Gold and green fluorescent microspheres at multiple sites in the mediobasal hypothalamus (n = 18) revealed that approximately 60% of AVPV and 30% of MPN neurons expressing CGRP were projecting to the region of the tuberal and ventral premammillary nuclei, with a minor projection to the dorsomedial nucleus. These findings demonstrate a major projection of the preoptic CGRP neurons to the posterior hypothalamus in the female rat and support further a functional role for these neurons in the sexually dimorphic regulation of reproductive functioning.

Arcuate nucleus of the hypothalamus: effects of age and sex

The arcuate nucleus of the hypothalamus (ARN) is involved in a variety of functions known to be sexually dimorphic and altered by aging. Although the effects of sex and age on the synaptic organization and neurochemistry of the ARN have been extensively analyzed, data regarding sex-related differences and age-induced effects on the total number of neurons and volume of the ARN in adult and aged male and female rats are controversial. To address this issue, we have quantitatively analyzed the ARN of male and female Wistar rats aged 6 and 24 months. The optical fractionator, the optical rotator, and the Principle of Cavalieri were used as the estimators of the total number of neurons, mean nuclear volume of ARN neurons, and volume of the ARN, respectively. In addition, a Golgi study was carried out to analyze the dendritic trees of its neurons. We found that in young adult rats, the volume of the ARN is 0.9 mm3 in males and 0.7 mm3 in females, whereas the total number of neurons is 100 x 10(3) in males and 86 x 10(3) in females. ARN neurons of males and females have identical mean nuclear volumes, which we estimated to be 300 microm3. No significant effects of age were found in these parameters, both in males and in females. In adult rats, no sex-related differences were detected in the number of dendritic segments and in the total dendritic length, but the dendritic branching density and the spine density were greater in females than in males. In aged rats there was a significant reduction in the number of dendritic segments, in the total dendritic length, and in the branching and spine densities that, although evident in both sexes, was more marked in females. Our results show that the total number of neurons and the volume of the ARN are sexually dimorphic in adult and aged rats and that neither of these parameters is altered by aging. Conversely, aging induces regressive changes in the dendritic arborizations of ARN neurons of males and females and abolishes the sexual dimorphic pattern of their organization.

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.

CGRP in the trigeminal nucleus, spinal cord and hypothalamus: effect of gonadal steroids

Calcitonin gene-related peptide (CGRP) contents were assayed in cervical spinal cord, trigeminal nucleus and hypothalamus throughout the estrous cycle and in male and ovariectomized rats. In the trigeminal nucleus, neither testosterone nor 17 beta-estradiol seem to affect CGRP accumulation, but progesterone seems to decrease it. In the cervical spinal cord, ovarian steroids seem to decrease CGRP while testosterone does not seem to influence it. In the hypothalamus, CGRP was only detectable in the male rat suggesting a positive effect of testosterone. It had marked circadian rhythm. In conclusion, CGRP content appears to be affected by gonadal steroids in the hypothalamus, the cervical spinal cord and the trigeminal nucleus in the rat.