Arginine-vasopressin and oxytocin response to cholecystokinin-tetrapeptide

Copeptin response to panic provocation with CO2 in healthy adults

Repeated panic attacks are the core symptom of panic disorder and severely stressful for patients. Additional to the psychological response, the physiological symptoms are an important aspect of the experienced panic. However, data on the extent of hypothalamic-pituitary-adrenal (HPA)-axis activation during panic attacks is inconsistent. Therefore, in the present study, we aimed at investigating the stress-axis activity in more detail by including Copeptin (CoP) as a stable surrogate parameter for the vasopressinergic hypothalamic activity during experimentally induced panic attacks in healthy adults (N = 21). During a placebo-controlled panic challenge with 35% CO2 compared to normal air inhalation, we measured CoP and the peripheral effector hormones Adrenocorticotropic Releasing Hormone (ACTH) and cortisol in plasma along with the psychological response to panic anxiety. We analyzed hormonal secretion patterns, their correlations and individual panic ratings over time and explored differences between female and male participants. We found a significant CO2-induced increase of CoP plasma levels and psychological panic symptoms after CO2-administration, while no positive correlations of CoP levels with the peripheral HPA-axis hormones and with panic symptoms were present. No differences between female and male participants concerning their psychological response nor their baseline CoP levels, the release of CoP or its increase during the experiment were found. CoP could be a sensitive indicator for an organism's physiologic acute hypothalamic response during stress and panic attacks.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

Copeptin in CCK-4-induced panic in healthy man: Sexual dimorphisms in secretion pattern and panic response, but no correlation of copeptin with panic symptoms

Copeptin, the C-terminal part of the hypothalamic arginine vaspopressin (AVP) precursor, closely mirrors the production of AVP and was proposed as an easily measured novel marker of the individual stress level in man. First data in male volunteers proposed copeptin as a potential endocrine surrogate marker of cholecystokinin-tetrapeptide (CCK-4)-induced panic. We tried to replicate these pilot data and to extend them to the other sex. 46 healthy human subjects (29 men, 17 women) were given an intravenous bolus of 50 μg CCK-4. Basal and stimulated plasma copeptin was measured and panic symptoms were assessed using the Acute Panic Inventory (API). Basal copeptin was significantly lower in women vs. men, while men showed a significantly higher CCK-4-induced increase of copeptin. In contrast, female subjects displayed a signifcantly higher increase of API ratings by CCK-4. No significant correlations of panic symptoms and copeptin release induced by CCK-4 could be found, neither in man, nor in women, nor in the total sample. A sexual dimorphism in copeptin secretion and in panic response was demonstrated. Prior unexpected findings of copeptin release as an objective read-out of panic could not be replicated. The role of the vasopressinergic system in panic anxiety needs further study in panic patients and in healthy man, using also other panic provocation paradigms.

Menstrual cycle-related fluctuations in oxytocin concentrations: A systematic review and meta-analysis

Oxytocin affects physiological and psychological functions that are often expressed sex-specifically, suggesting interactions between oxytocin and sex hormones. As female sex hormone concentrations change during the menstrual cycle, oxytocin might fluctuate, too. This systematic review and meta-analysis investigated endogenous oxytocin concentrations across menstrual cycle phases in healthy women. Data from 13 studies (120 women) showed a significant increase of oxytocin concentrations from the early follicular phase to ovulation (g = 0.39 [0.25; 0.53], p < .001) and a significant decrease from ovulation to the mid-luteal phase (g = -0.50 [-0.81; -0.18], p < .001). There were no significant differences between the early follicular and mid-luteal phase (g = -0.19 [-0.70; -0.32], p = .471). These findings contribute to a deeper understanding of differences in normal and abnormal psychobiological processes in women. They highlight the necessity to consider the menstrual cycle phase in studies on oxytocin in women.

Copeptin - A potential endocrine surrogate marker of CCK-4-induced panic symptoms?

Intravenous cholecystokinin-tetrapeptide (CCK-4) administration reliably and dose-dependently provokes panic anxiety in man, accompanied by adrenocorticotropic hormone (ACTH) and cortisol release. Preclinical findings suggest that behavioral and endocrine effects of CCK-4 are mediated via corticotropin-releasing hormone (CRH) release. Anxiogenic stimulation of the central CCK-receptors in man was shown to increase as well vasopressin (AVP), which acts synergistically with CRH as pituitary-adrenocortical axis stimulator during stress. Copeptin (CoP), the C-terminal part of pre-pro-AVP, is released in an equimolar ratio to AVP. It is more stable in the circulation and easier to determine than AVP and it was found to closely mirror the production of AVP. So far, CoP secretion has not been characterized during panic provocation. In 30 healthy male human subjects, we repeatedly measured CoP in plasma during a panic challenge and studied its correlation to Acute Panic Inventory (API) ratings and plasma ACTH and cortisol. CoP levels correlated positively with the increase in API ratings (r=0.41, p=0.03), while ACTH or cortisol did not (r=0.08, p=0.68 and r=0.12, p=0.53, respectively). CoP levels correlated also positively with ACTH (r=0.48, p=0.009) and cortisol (r=0.48, p=0.01) concentrations throughout the CCK-4 challenge. As expected, we found a positive correlation between plasma ACTH and cortisol levels (r=0.57, p=0.001). A vasopressinergic activation during CCK-4 induced panic was demonstrated, which was correlated positively to panic symptoms and pituitary-adrenocortical release. Our findings suggest a role of CoP as a potential surrogate marker of CCK-4 panic symptoms. Further studies are needed to replicate our results and to further clarify the role of CoP as a stress-sensitive hormone in different panic paradigms as well as in panic patients.

Oxytocin and Anxiety Disorders

In the present chapter, we review the literature focusing on oxytocin (OT)-centered research in anxiety spectrum conditions, comprising separation anxiety disorder, specific phobias, social anxiety disorder (SAD), panic disorder, generalized anxiety disorder, and anxiety-related endophenotypes (e.g., trust behavior, behavioral inhibition, neuroticism, and state/trait anxiety). OT receptor gene (OXTR) polymorphisms have been implicated in gene-environment interactions with attachment style and childhood maltreatment and to influence clinical outcomes, including SAD intensity and limbic responsiveness. Epigenetic OXTR DNA methylation patterns have emerged as a link between categorical, dimensional, neuroendocrinological, and neuroimaging SAD correlates, highlighting them as potential peripheral surrogates of the central oxytocinergic tone. A pathophysiological framework of OT integrating the dynamic nature of epigenetic biomarkers and the summarized genetic and peripheral evidence is proposed. Finally, we emphasize opportunities and challenges of OT as a key network node of social interaction and fear learning in social contexts. In conjunction with multi-level investigations incorporating a dimensional understanding of social affiliation and avoidance in anxiety spectrum disorders, these concepts will help to promote research for diagnostic, state, and treatment response biomarkers of the OT system, advancing towards indicated preventive interventions and personalized treatment approaches.

Advances in molecular genetics of panic disorder

The molecular genetic research on panic disorder (PD) has grown tremendously in the past decade. Although the data from twin and family studies suggest an involvement of genetic factors in the familial transmission of PD with the heritability estimate near 40%, the genetic substrate underlying panicogenesis is not yet understood. The linkage studies so far have suggested that chromosomal regions 13q, 14q, 22q, 4q31-q34, and probably 9q31 are associated with the transmission of PD phenotypes. To date, more than 350 candidate genes have been examined in association studies of PD, but most of these results remain inconsistent, negative, or not clearly replicated. Only Val158Met polymorphism of the catechol-O-methyltransferase gene has been implicated in susceptibility to PD by several studies in independent samples and confirmed in a recent meta-analysis. However, the specific role of this genetic variation in PD requires additional analysis considering its gender- and ethnicity-dependent effect and putative impact on cognitive functions. The recent advantages in bioinformatics and genotyping technologies, including genome-wide association and gene expression methods, provide the means for far more comprehensive discovery in PD. The progress in clinical and neurobiological concepts of PD may further guide genetic research through the current controversies to more definitive findings.

Cholecystokinin tetrapeptide effects on HPA axis function and elevated plus maze behaviour in maternally separated and handled rats

Deficits in the function of the hypothalamic-pituitary-adrenal (HPA) axis have been suggested to predispose to the development of depression and anxiety disorders. This is mirrored in the animal model "Maternal Separation (MS)" where the stress of repeated separation of rat pups from the dam during early postnatal development results in long lasting alterations in HPA axis function. Cholecystokinin increases serum concentrations of stress axis hormones and might be involved in the dam-pup interaction in rats. Therefore, we hypothesized that adult animals, which had been separated daily (postnatal days (PND) 2-14) for 180 min (MS180) would differ in HPA axis responsiveness to an intravenous challenge dose of cholecystokinin tetrapeptide (CCK-4) compared to handled rats, separated for 15 min daily. The study explored the effects of intravenous CCK-4 on elevated plus maze behaviour and HPA axis hormones. MS180 animals displayed reduced general activity but unaltered levels of open arm activity in the elevated plus maze. CCK-4 administration elevated general activity in the handled rats, while leaving MS180 rats unaffected. MS180 rats had increased baseline CRF mRNA expression in the paraventricular nucleus of the hypothalamus. When CRF mRNA was assessed in chronically catheter implanted and single housed rats, lower levels were found in the paraventricular nucleus of MS180 animals compared to handled animals and this parameter was not affected by CCK-4 treatment. Adrenocorticotropin concentrations in serum were equal in MS180 and handled rats and unaffected by CCK-4. Corticosterone serum concentrations were lower in saline treated MS180 rats compared to saline treated handled rats. CCK-4 injection raised serum corticosterone in MS180 rats to levels equal to the handled rats, while leaving handled rats unaffected. We suggest that the lower levels of hypothalamic CRF mRNA and serum corticosterone concentrations in MS180 rats might be due to the experimental set-up with chronic venous catheter implants and single housing. In conclusion, this study supports the hypothesis of elevated CCK sensitivity in separated rats as measured by corticosterone changes thus adding to the existing literature reporting early life stress having long-term impact on HPA axis function.

Is premenstrual dysphoria a variant of panic disorder? A review

Patients with premenstrual dysphoric disorder (PMDD) and patients with panic disorder (PD) both experience high rates of panic attacks in laboratory panic provocation studies. Recently, this shared elevated rate of challenge-induced panic has received increasing attention. Researchers have suggested that PMDD and panic disorder may share a pathophysiological or psychobiological link. The purpose of this paper is to review the findings from PMDD challenge studies and the theories advanced to connect PMDD to panic disorder. Taken together, the results of the PMDD challenge studies confirm that agents that incite panic in PD patients do so as well in PMDD women. This shared elevated challenge-induced panic cannot be accounted for by explanations such as a history of PD in PMDD women. None of the physiological theories as currently expressed--suffocation false alarm, gamma-aminobutyric acid (GABA), noradrenergic, serotonergic, and cholecystokinin--yet provides a compelling candidate to account for shared elevated challenge-induced panic in PD and PMDD patients. Psychological perspectives on panic emphasize that bodily sensations themselves can cause fear. Researchers have yet to apply several influential psychological approaches--conditioning, catastrophic misinterpretation, and anxiety sensitivity--to PMDD patients. Because psychological factors influence anxious responding in challenge studies, the search for the biological abnormality best accounting for PMDD panic might benefit from a reframing of the question to one that considers the psychological perspective as well.

Differential Effects of Modification of Membrane Cholesterol and Sphingolipids on the Conformation, Function, and Trafficking of the G Protein-coupled Cholecystokinin Receptor

The lipid microenvironment of receptors can influence their conformation, function, and regulation. Cholecystokinin (CCK)-stimulated signaling is abnormal in some forms of hyperlipidemia, suggesting the possibility of unique sensitivity to its lipid environment. Here we examined the influence of cholesterol and sphingolipids on CCK receptors in model Chinese hamster ovary cell systems having lipid levels modified. Cholesterol was modulated chemically or metabolically, and sphingolipids were modulated using a temperature-sensitive cell line (SPB-1). Receptor conformation was probed with a fluorescent full agonist ligand, Alexa 488-conjugated Gly-[Nle(28,31)]CCK-(26-33), shown previously to decrease in anisotropy and lifetime when occupying a receptor in the active conformation (Harikumar, K. G., Pinon, D. L., Wessels, W. S., Prendergast, F. G., and Miller, L. J. (2002) J. Biol. Chem. 277, 18552-18560). Anisotropy and lifetime of this probe were increased and prolonged with cholesterol enrichment, and decreased and shortened with depletion of cholesterol or sphingolipids. The increase in these parameters with cholesterol enrichment may reflect change in CCK receptor conformation toward its inactive, uncoupled state. Indeed, cholesterol enrichment resulted in nonproductive agonist ligand binding, with affinity of binding higher than normal and calcium signaling in response to this reduced. In cholesterol- and sphingolipid-depleted states, the receptor moved into conformations that were less than optimal. With cholesterol depletion, both ligand binding and signaling were decreased, yet internalization and trafficking were unperturbed. With sphingolipid depletion, ligand binding and signaling were normal, but internalization and trafficking were markedly inhibited. Of note, normal transferrin receptor trafficking through the same clathrin-dependent pathway was maintained under these conditions. Thus, lipid microenvironment of the CCK receptor is particularly important, with different lipids having distinct effects.

Effects of peptides, with emphasis on feeding, pain, and behavior A 5-year (1999-2003) review of publications in Peptides

Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure-activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999-2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides.

Central anti-hypertensive effect of tachykinin NK3 receptor antagonists in rat

Tachykinins are involved in the central autonomic control of blood pressure. In the present study, we examined the i.c.v. cardiovascular effects of several tachykinin receptor antagonists in awake spontaneously hypertensive rats (SHR, 15 weeks old). Results showed that two tachykinin NK(3) receptor antagonists (R-820: 3-indolylcarbonyl-Hyp-Phg-N(Me)-Bzl and SB 222200: (S)-(-)-N-(alpha-ethylbenzyl)-3-methyl-2-phenylquinoline-4-carboxamide) caused a sustained and dose-dependent reduction of blood pressure when injected i.c.v. but not i.v. The stereoselective anti-hypertensive effect of SB 222200 peaked at 3 h and faded at 6 h post-injection (if injected at 07:00 h) or had a slower onset and peaked at 8 h post-injection (if injected at 13:00 h). The effect of R-820 was maximal at 24 h and lasted up to 48 h post-injection. Both antagonists failed to alter blood pressure in normotensive Wistar-Kyoto rats (WKY) and heart rate was not affected in both strains. The anti-hypertensive effect of SB 222200 was not associated with changes in plasma levels of catecholamines and vasopressin and it remained unchanged in SHR subjected to acute bilateral nephrectomy. In contrast, blood pressure was not affected by tachykinin NK(1) (RP 67580: (+/-) 7,7-diphenyl-2[1-imino-2(2-methoxy-phenyl)-ethyl]perhydroisoindol-4-one(3aR,7aR)) and NK(2) (SR 48968: (S)-N-methyl-N[4-(4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl)butyl]benzamide) receptor antagonists. Data suggest that brain tachykinin NK(3) receptors are implicated in the maintenance of hypertension in SHR. Hence, these receptors may represent promising therapeutic target in the treatment of arterial hypertension.

IL-1β-mediated neuropeptide and immediate early gene mRNA induction is defective in Lewis hypothalamic cell cultures

We previously found that Lewis (LEW/N) hypothalamic cells respond to interleukin-1beta (IL-1beta) with reduced corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) peptide synthesis and secretion compared to Fischer (F344/N) cells. To investigate whether this peptide hyporesponsiveness in LEW/N cells is secondary to their deficient mRNA expression, temporal mRNA expression patterns of CRH, AVP, and several hypothalamic neuropeptides induced by IL-1beta in LEW/N and F344/N hypothalamic dissociated cell cultures were delineated by quantitative real-time polymerase chain reaction (RT-PCR). To investigate the molecular mechanisms underlying neuropeptide mRNA induction in cells of both strains, temporal mRNA expression patterns of immediate early genes (IEGs) and several signal transduction-associated molecules were also examined. We found that LEW/N hypothalamic cells were hyporesponsive to IL-1beta induction of neuropeptide and IEG mRNA, while LEW/N cells transcribed more IL-1 receptor and inducible nitric oxide synthase (iNOS) compared to F344N/N cells, suggesting that LEW/N and F344/N hypothalamic cells are differentially activated by IL-1beta.