The Melanocortin and Endorphin Neuropeptides in Patients with Restless Legs Syndrome.

OBJECTIVE: Based upon similarities between the urge to move and sensory discomfort of restless legs syndrome (RLS) and properties of melanocortin hormones, including their incitement of movement and hyperalgesia, we assessed plasma and cerebrospinal fluid (CSF) α-melanocyte-stimulating hormone (α-MSH) and ß-endorphin in RLS patients and controls. METHODS: Forty-two untreated moderate-to-severe RLS patients and 44 matched controls underwent venipuncture at 19:00, 20:30, and 22:00; 37 RLS and 36 controls had lumbar puncture at 21:30. CSF and plasma were analyzed for pro-opiomelanocortin (POMC), adrenocorticotropin hormone (ACTH), α-MSH, ß-MSH, and ß-endorphin by immunoassay. RLS severity was assessed by International RLS Study Group Severity Scale. RESULTS: RLS participants were 52.7 ± 12.0 years old, 61.9% were women, 21.4% had painful RLS, and RLS severity was 24.8 ± 9.0. Controls had similar age and sex. Plasma ACTH, α-MSH, and ß-endorphin were similar between groups. Plasma POMC was significantly greater in RLS than controls (17.0 ± 11.5 vs 12.7 ± 6.1fmol/ml, p = 0.048). CSF ACTH was similar between groups. CSF ß-MSH was significantly higher in painful than nonpainful RLS or controls (48.2 ± 24.8 vs 32.1 ± 14.8 vs 32.6 ± 15.2pg/ml, analysis of variance [ANOVA] p = 0.03). CSF α-MSH was higher in RLS than controls (34.2 ± 40.9 vs 20.3 ± 11.0pg/ml, p = 0.062). CSF ß-EDP was lowest in painful RLS, intermediate in nonpainful RLS, and highest in controls (8.0 ± 3.4 vs 10.8 ± 3.1 vs 12.3 ± 5.0pg/ml, ANOVA p = 0.049). The ratio of the sum of CSF α- and ß-MSH to CSF ß-endorphin was highest, intermediate, and lowest in painful RLS, nonpainful RLS, and controls (p = 0.007). INTERPRETATION: CSF ß-MSH is increased and CSF ß-endorphin decreased in RLS patients with painful symptoms. ANN NEUROL 2024;95:688-699.

Elevated Neuropeptides in Dry Eye Disease and Their Clinical Correlations.

PURPOSE: The goal of this study was to assess neuropeptide levels in patients with dry eye disease (DED) and investigate their correlations with clinical characteristics. METHODS: This study included 38 eyes of 38 patients diagnosed with DED (DED group) and 38 eyes of 38 healthy volunteers without DED (control group). Ocular surface evaluation was performed. The severity of dry eye symptoms and signs in the DED group was graded. Neuropeptides [substance P (SP), alpha-melanocyte-stimulating hormone (α-MSH), ß-endorphin, neurotensin, and oxytocin] and inflammatory cytokines levels were measured in basal tears. The link between neuropeptides and clinical parameters was investigated using Spearman rank correlation. RESULTS: Overall, 76.3% of patients in the DED group showed dry eye symptoms and signs that were inconsistent in severity. Compared with the control group, the DED group showed higher levels of SP, α-MSH, and oxytocin in tears (P = 0.012, P = 0.030, and P = 0.006, respectively), but similar levels of ß-endorphin and neurotensin (P = 0.269 and P = 0.052). The levels of SP, α-MSH, and oxytocin were elevated in DED patients with higher grading of symptoms than clinical signs (all P < 0.05). SP, α-MSH, and oxytocin levels in tears were positively correlated with Ocular Surface Disease Index scores, frequency of sensitivity to light, and frequency of blurred vision (all P < 0.05). CONCLUSIONS: The increased tear levels of SP, α-MSH, and oxytocin may be linked to ocular discomfort in DED. Neuropeptides may play a key role in the development of DED, especially in DED patients with more severe symptoms than clinical signs.

[Effect of electroacupuncture on pain threshold and expression of pain-related factors cyclooxygenase-2, prostaglandin E2 and ß-endorphin in rats with chronic pelvic pain syndrome].

OBJECTIVE: To explore the possible mechanism of electroacupuncture (EA) underlying improvement of chronic pelvic pain syndrome (CPPS). METHODS: Fifty SD rats were randomly divided into control, model, sham operation, EA and sham EA groups (n=10 rats in each group). The CPPS model was established by injecting complete Freund's adjuvant (CFA, 50 µL) into the ventral lobes of the prostate. EA (2 Hz/100 Hz) was applied to "Guanyuan"(CV4), "Zhongji"(CV3), "Sanyinjiao" (SP6) and "Huiyang"(BL35) once daily for 40 min, 5 days a week for 4 weeks, while rats in the sham EA group were treated with the same acupoints but without electrical stimulation. Mechanical pain threshold (MPT) and heat pain threshold (HPT) were measured before and after intervention. The body weight and prostate weight were measured and prostate index was calculated. Histopathological changes of prostate tissue were observed by HE staining. The levels of cycloxygenase-2 (COX-2), prostaglandin E2 (PGE2) and ß-endorphin (ß-EP) in prostate tissue were detected by ELISA. RESULTS: Compared with the control and sham operation groups, the MPT and HPT were significantly lower (P<0.01), and the prostate weight, prostate index, the contents of PGE2 and COX-2 were significantly increased (P<0.01), while the content of ß-EP was significantly decreased (P<0.01) in the model group. Compared with the model group, the MPT and HPT were significantly increased (P<0.01) after 3 and 4 courses of treatment, and the prostate weight, prostate index, the contents of PGE2 and COX-2 were significantly decreased (P<0.01), while the content of ß-EP was significantly increased (P<0.01) in the EA group, rather than in the sham EA group (P>0.05). CONCLUSION: EA can effectively relieve pain in CPPS rats, which may be related to its functions in down-regulating COX-2 and PGE2, and up-regulating ß-EP.

µ-opioid receptor, ß-endorphin, and cannabinoid receptor-2 are increased in the colonic mucosa of irritable bowel syndrome patients.

BACKGROUND AND AIMS: The gut immune, cannabinoid, and opioid systems constitute an integrated network contributing to visceral sensation and pain modulation. We aimed to assess the expression of the µ-opioid receptor (MOR), its ligand ß-endorphin (ß-END), and cannabinoid receptor-2 (CB2 ) in patients with irritable bowel syndrome (IBS) and asymptomatic controls (AC) and their correlation with sex and symptom perception. METHODS: Mucosal biopsies were obtained from the left colon of 31 IBS patients (45% women) with predominant constipation (IBS-C, 9) or diarrhea (IBS-D, 10) or with mixed bowel habits (IBS-M, 12) and 32 AC (44% women) and processed for qRT-PCR, Western blotting, and immunohistochemistry. KEY RESULTS: µ-opioid receptor and CB2 mRNA and protein expression and ß-END protein levels were increased in patients with IBS compared to AC (all Ps=0.021). A significant sex by IBS interaction was found in relation to CB2 mRNA expression (P = .003) with women showing a markedly higher expression to men (P = .035). In contrast, in AC, men had higher expression than women (P = .033). ß-END, MOR, and CB2 immunoreactivities (IR) were localized to CD4+T cells including EMR-1+ eosinophils and CD31+ T cells but not to mast cells. CONCLUSIONS: The increased expression of MOR, ß-END, and CB2 in the mucosa of IBS patients, where they are localized to immune cells, suggests that opioid and cannabinoid systems play an immune-related compensatory role in visceral pain in IBS patients. Further work is necessary to support this hypothesis.

Olfactory identification in patients with schizophrenia - the influence of ß-endorphin and calcitonin gene-related peptide concentrations.

BACKGROUND: The relationship between the olfactory system and emotional processing is an area of growing interest in schizophrenia research. Both the orbitofrontal cortex and amygdala are involved in the processing of olfactory information, and olfactory deficits may be also influenced by endogenous opioids and calcitonin gene-related peptide (CGRP), which is probably involved in dopaminergic transmission. However, the relationship between endorphins and dopaminergic transmission has not been fully explored. METHODS: Odor identification performance and valence interaction was evaluated among 50 schizophrenic patients and 50 controls. Schizophrenia symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). All study participants were subjected to the University of Pennsylvania Smell Identification Test (UPSIT), blood ß-endorphin (BE) and CGRP measurement. RESULTS: Insignificantly higher BE concentrations were observed in the patient group, while significantly higher UPSIT scores were seen in controls (mean UPSIT 32.48 vs 26.82). The patients demonstrated significantly more identification errors for pleasant (P=0.000) and neutral (P=0.055) odors than for unpleasant odors. Patients with higher BE concentrations made more identification errors concerning pleasant (Rs=-0.292; P=0.04) and neutral odors (Rs=-0.331; P=0.019). Although the concentration of CGRP was significantly higher in the patient sample (P<0.001), no relationship was observed between concentration and UPSIT performance. A strong negative correlation was observed between PANSS N score and UPSIT total score (Rs=-0.646; P=0.000), between PANSS N score and identification by valence for pleasant and neutral odors (UPSIT n/16: Rs=-0.450, P=0.001; UPSIT n/15: Rs=-0.586, P=0.000), and a weak negative correlation between PANSS N score and identification of unpleasant odors (UPSIT n/9: Rs=-0.325, P=0.021). CONCLUSIONS: Schizophrenic patients present a unique pattern of smell identification characterized by aberrant hedonic ratings for pleasant odors but not unpleasant ones. Individuals with predominant negative symptoms and higher BE concentrations are most able to identify negative odors.

Giant Basal Cell Carcinomas Express Neuroactive Mediators and Show a High Growth Rate: A Case-Control Study and Meta-Analysis of Etiopathogenic and Prognostic Factors.

BACKGROUND: Giant basal cell carcinomas (GBCCs), (BCC ≥ 5 cm), are often painless, destructive tumors resulting from poorly understood patient neglect. OBJECTIVES: To elucidate etiopathogenic factors distinguishing GBCC from basal cell carcinoma (BCC) and identify predictors for disease-specific death (DSD). METHODS: Case-control study examining clinicopathologic and neuroactive factors (ß-endorphin, met-enkephalin, serotonin, adrenocorticotropic hormone, and neurofilament expression) in GBCC and BCC. Systematic literature review to determine DSD predictors. RESULTS: Thirteen GBCCs (11 patients) were compared with 26 BCCs (25 patients). GBCC significantly differed in size, disease duration, and outcomes; patients were significantly more likely to live alone, lack concern, and have alcoholism. GBCC significantly exhibited infiltrative/morpheic phenotypes, perineural invasion, ulceration, and faster growth. All neuromediators were similarly expressed. Adenoid phenotype was significantly more common in GBCC. Adenoid tumors expressed significantly more ß-endorphin (60% vs. 18%, P = 0.01) and serotonin (30% vs. 4%, P = 0.02). In meta-analysis (n ≤ 311: median age 68 years, disease duration 90 months, tumor diameter 8 cm, 18.4% disease-specific mortality), independent DSD predictors included tumor diameter (cm) (hazard ratio (HR): 1.12, P = 0.003), bone invasion (HR: 4.19, P = 0.015), brain invasion (HR: 8.23, P = 0.001), and distant metastases (HR: 14.48, P = 0.000). CONCLUSIONS: GBCC etiopathogenesis is multifactorial (ie, tumor biology, psychosocial factors). BCC production of paracrine neuromediators deserves further study.

[Effect of Electroacupuncture Intervention on ß-endorphin Levels of Hypothalamus and Spinal Cord Tissues in Rats with Pelmatic Incisional Pain].

OBJECTIVE: To observe the effect of electroacupuncture (EA) intervention on pain thresholds (PT) and contents of ß-endorphin (EP) in the hypothalamus and spinal cord, and the expression of 5-HT in the dorsal raphe nucleus(DRN)in rats with pelmatic incisional pain, so as to investigate the underlying mechanisms of acupuncture in reducing post-operative pain. METHODS: Wistar rats were randomized into normal control, model, EA and non-acupoint groups (n=8/group). The pelmatic pain model was induced by making an incision (about 1 cm in length, to the fascia and muscle layers) from the heel towards the toes. EA (2 Hz, 1.5-2 V) was applied to "Zusanli" (ST 36) and "Kunlun" (BL 60) or non-acupoint (about 3 mm beside the ST 36 and BL 60) on the affected side for 20 min, once daily for three days. The thermal PT and mechanical PT were measured before and after operation and after EA. The contents of ß-EP in hypothalamus and L3-S4 spinal cord were detected using enzyme linked immunosorbent assay (ELISA) and the expressions of ß-EP in hypothalamus and 5-HT in DRN were measured with immunohistochemistry. RESULTS: After EA intervention, the markedly decreased mechanical and thermal pain thresholds on day 1 and 3 after paw incision were significantly increased in the EA group (P<0.05), but not in the non-acupoint group (P>0.05). The hypothalamic ß-EP content was significantly higher in the model group than in the normal group (P<0.05), and further up-regulated in the EA group (not the non-acupoint group) than in the model group (P<0.05). In addition, the hypothalamic ß-EP immunoreactive (IR)-positive cell number and 5-HT immunoactivity level in DRN were also considerably up-regulated in the EA group (P<0.05) but not in the non-acupoint group (P>0.05). No significant changes were found in the lumbar spinal ß-EP contents in the model, EA and non-acupoint groups (P>0.05). CONCLUSIONS: EA stimulation of "Zusanli"(ST 36) and "Kunlun" (BL 60) has an analgesic effect in pelmatic incision pain rats, which may be related to its effects in raising the level of hypothalamic ß-EP and the expression of 5-HT in DRN.

Imaging and identification of endogenous peptides from rat pituitary embedded in egg yolk.

RATIONALE: Mass spectrometry imaging (MSI) can provide accurate data containing the spatial distribution of endogenous peptides in tissue sections without previous treatment. One of the key issues in analyzing small samples is establishing a proper technique for mounting and manipulating collected tissue in order to avoid contamination of the sample with optimal cutting temperature (OCT) resin. METHODS: We present a method for embedding rat pituitary tissue in a frozen egg yolk block, which enables its further imaging in experiments on a matrix-assisted laser desorption/ionization (MALDI) mass spectrometer with time-of-flight (TOF) analyzer. Embedding the sample in the egg yolk prevents contamination from the OCT resin, which decreases MALDI signal quality. RESULTS: In the present study we detected numerous m/z peaks related to endogenous peptides. We identified fifteen peptides and their post-translational modifications by tandem mass spectrometry (MS/MS) directly on tissue sections of the hypophysis posterior and intermediate lobes; among these peptides were vasopressin, oxytocin, copeptin, melanocyte-stimulating hormones and beta-endorphin. We also showed that egg yolk itself does not affect localization of peptides in the pituitary. CONCLUSIONS: Egg yolk embedding enables preparation of tissue sections from small tissue fragments to organs such as the pituitary gland, which is suitable for localization and identification of endogenous peptides by the MALDI-MSI and MALDI-MS/MS techniques.

Expression of substance P, calcitonin gene-related peptide, ß-endorphin and methionine-enkephalin in human dental pulp tissue after orthodontic intrusion: a pilot study.

OBJECTIVE: To determine the levels of two sensory neuropeptides (substance P [SP] and calcitonin gene-related peptide [CGRP]) and two endogenous opioids (methionine-enkephalin [Met-Enk] and ß-endorphin [ß-End]) in dental pulp tissue samples subjected to controlled orthodontic intrusive forces. MATERIALS AND METHODS: Sixteen healthy premolars were selected from eight patients who were undergoing extraction for orthodontic purposes. Eight were randomly used as controls, and the other eight were assigned to an experimental group (controlled orthodontic intrusive forces applied for 24 hours). After this period, teeth were extracted, and pulp samples were obtained. All samples were processed to quantify the expression levels of SP, CGRP, Met-Enk, and ß-End using commercial radioimmunoassay kits. RESULTS: All samples exhibited basal levels of both neuropeptides and endogenous opioids. After 24 hours of the intrusive stimulus, all patients reported a tolerable discomfort localized at the involved premolar. Only SP was significantly increased (P<.05). For the other molecules, no statistically significant differences were observed (P>.05); however, they expressed important increasing trends. CONCLUSIONS: The expression levels of SP and CGRP in dental pulp samples from the experimental group support the positive correlation between the symptomatic clinical scenario and increased expression levels of neuropeptides, clarifying the role of neurogenic inflammation in early injury response.

Oxytocin in the periaqueductal gray participates in pain modulation in the rat by influencing endogenous opiate peptides.

Periaqueductal gray (PAG) plays a very important role in pain modulation through endogenous opiate peptides including leucine-enkephalin (L-Ek), methionine-enkephalin (M-Ek), ß-endorphin (ß-Ep) and dynorphin A(1-13) (DynA(1-13)). Our pervious study has demonstrated that intra-PAG injection of oxytocin (OXT) increases the pain threshold, and local administration of OXT receptor antagonist decreases the pain threshold, in which the antinociceptive role of OXT can be reversed by pre-PAG administration of OXT receptor antagonist. The experiment was designed to investigate the effect of OXT on endogenous opiate peptides in the rat PAG during the pain process. The results showed that (1) the concentrations of OXT, L-Ek, M-Ek and ß-Ep, not DynA(1-13) in the PAG perfusion liquid were increased after the pain stimulation; (2) the concentrations of L-Ek, M-Ek and ß-Ep, not DynA(1-13) in the PAG perfusion liquid were decreased by the OXT receptor antagonist; (3) the increased pain threshold induced by the OXT was attenuated by naloxone, an opiate receptor antagonist; and (4) the concentrations of L-Ek, M-Ek and ß-Ep, not DynA(1-13) in the PAG perfusion liquid were increased by exogenous OXT administration. The data suggested that OXT in the PAG could influence the L-Ek, M-Ek and ß-Ep rather than DynA(1-13) to participate in pain modulation, i.e. OXT in the PAG participate in pain modulation by influencing the L-Ek, M-Ek and ß-Ep rather than DynA(1-13).

Fetal stress hormone changes during intrauterine transfusions.

OBJECTIVE: To document fetal stress hormone and Doppler changes after intrauterine transfusions (IUTs) in either the intrahepatic portion of the umbilical vein (IHV) or the placental cord insertion (PCI). METHOD: Pregnant women scheduled for IUT for fetal anemia (N = 25) were included prospectively. Cortisol, ß-endorphin and noradrenalin concentrations in fetal plasma and middle cerebral artery pulsatility index before and after transfusion were compared. Transfusions were performed through the (IHV), thus puncturing the fetus, or at the PCI. RESULTS: There were no measurable differences between the transfusion sites. CONCLUSION: In anemic fetuses undergoing transfusion, Doppler changes and fetal stress hormone changes were unrelated to the site of needle insertion.

Neuronal responses in the brainstem and hypothalamic nuclei following insulin treatment during the late follicular phase in the ewe.

The aim of this study was to determine the neuronal responses following insulin administration during the late follicular phase. Intact ewes were given either saline or insulin (5 IU/kg, i.v.) at 35 h after progesterone withdrawal and killed 3 h later. There was a marked increase in the number of Fos-positive noradrenergic neurones in the caudal brainstem of insulin-treated ewes. In the hypothalamic paraventricular nucleus, insulin treatment increased the presence of Fos-positive corticotrophin-releasing hormone neurones (from 2% to 98%) and Fos-positive arginine vasopressin parvocellular neurones (from 2% to 46%). Interestingly, after insulin treatment, despite a general increase in Fos-positive neurones in the arcuate nucleus (ARC), there was a marked reduction (from 47% to 1%) in Fos-positive ß-endorphin neurones. Similarly, colocalized Fos and oestradiol receptor (ER) α-positive neurones decreased in the ARC after insulin (from 7% to 3%). Conversely, in the ventromedial nucleus, ERα-positive neurones with Fos increased (from 7% to 22%) alongside a general increase in Fos-positive neurones. Overall, a complex system of neurones in brainstem and hypothalamus is activated following insulin administration during the late follicular phase.

Protective effect of electroacupuncture at the Neiguan point in a rabbit model of myocardial ischemia-reperfusion injury.

OBJECTIVES: To investigate possible cardioprotective mechanisms of electroacupuncture (EA) at the Neiguan point and at the Lieque point in the presence of myocardial ischemia-reperfusion injury (MIRI). METHODS: The changes in ventricular tissue Bax and Bcl-2 protein expression, malondialdehyde (MDA) content and glutathione peroxidase (GSH-PX) activity were examined, as well as beta-endorphin (beta-EP) con-tent in a rabbit model of MIRI. Four randomized groups were studied: sham, untreated MIRI, MIRI followed by EA at the Neiguan point, and MIRI followed by EA at the Lieque point. The MIRI model involved ligating the left anterior descending coronary artery for 30 min followed by a 60 min postischemia reperfusion period. RESULTS: EA at the Neiguan point dramatically decreased the number of apoptotic cells and the content of beta-EP and MDA, and inhibited Bax protein expression while enhancing Bcl-2 expression and GSH-PX activity. Furthermore, EA enhanced Bcl-2 expression and GSH-PX activity. Lesser effects were elicited by EA at the Lieque point. CONCLUSIONS: The cardioprotective effects of applying EA at the Neiguan point on MIRI include reducing apoptosis, regulating apoptosis- controlling genes, and decreasing myocardial MDA and beta-EP while enhancing GSH-PX activity.

Human pituitary contains dual cathepsin L and prohormone convertase processing pathway components involved in converting POMC into the peptide hormones ACTH, alpha-MSH, and beta-endorphin.

The production of the peptide hormones ACTH, alpha-MSH, and beta-endorphin requires proteolytic processing of POMC which is hypothesized to utilize dual cysteine- and subtilisin-like protease pathways, consisting of the secretory vesicle cathepsin L pathway and the well-known subtilisin-like prohormone convertase (PC) pathway. To gain knowledge of these protease components in human pituitary where POMC-derived peptide hormones are produced, this study investigated the presence of these protease pathway components in human pituitary. With respect to the cathepsin L pathway, human pituitary contained cathepsin L of 27-29 kDa and aminopeptidase B of approximately 64 kDa, similar to those in secretory vesicles of related neuroendocrine tissues. The serpin inhibitor endopin 2, a selective inhibitor of cathepsin L, was also present. With respect to the PC pathway, human pituitary expresses PC1/3 and PC2 of approximately 60-65 kDa, which represent active PC1/3 and PC2; peptide hormone production then utilizes carboxypeptidase E (CPE) which is present as a protein of approximately 55 kDa. Analyses of POMC products in human pituitary showed that they resemble those in mouse pituitary which utilizes cathepsin L and PC2 for POMC processing. These findings suggest that human pituitary may utilize the cathepsin L and prohormone convertase pathways for producing POMC-derived peptide hormones.

Innervation of gonadotropin-releasing hormone neurons by peptidergic neurons conveying circadian or energy balance information in the mouse.

BACKGROUND: Secretion of gonadotropin-releasing hormone (GnRH) produced in neurons in the basal forebrain is the primary regulator of reproductive maturation and function in mammals. Peptidergic signals relating to circadian timing and energy balance are an important influence on the reproductive axis. The aim of this study was to investigate the innervation of GnRH neurons by peptidergic neurons. METHODOLOGY/PRINCIPAL FINDINGS: Immunohistochemistry and confocal microscopy were used to detect appositions of peptidergic fibers (NPY, beta-endorphin, MCH) associated with energy balance and metabolic status in transgenic mice expressing a green fluorescent protein reporter construct in GnRH neurons. The frequency of these appositions was compared to those of vasoactive intestinal peptide (VIP), a hypothalamic neuropeptide likely to convey circadian timing information to the GnRH secretory system. The majority of GnRH neurons (73-87%) were closely apposed by fibers expressing NPY, beta-endorphin, or MCH, and a significant proportion of GnRH neurons (28%) also had close contacts with VIP-ir fibers. CONCLUSIONS/SIGNIFICANCE: It is concluded that GnRH neurons in the mouse receive a high frequency of direct modulatory inputs from multiple hypothalamic peptide systems known to be important in conveying circadian information and signalling energy balance.

Brain-region responsiveness to DT56a (Femarelle) administration on allopregnanolone and opioid content in ovariectomized rats.

OBJECTIVE: The natural selective estrogen receptor modulator DT56a (Femarelle), derived from soybean, has been shown to relieve menopausal vasomotor symptoms with no effect on sex steroid hormone levels or endometrial thickness.The purpose of the present study was to evaluate the neuroendocrine effect of DT56a administration through the evaluation of brain content of allopregnanolone (AP), an endogenous neurosteroid gamma-aminobutyric acid agonist with anxiolytic properties, and through the assessment of beta-endorphin (beta-END), the endogenous opioid implicated in pain mechanism, emotional state, and autonomic control. METHODS: Five groups of Wistar ovariectomized (OVX) rats received one of the following treatments: oral DT56a administration at doses of 6, 12, 60, and 120 mg kg(-1) day(-1) or estradiol valerate (E2V) at a dose of 0.05 mg kg(-1) day(-1) for 14 days. One group of fertile and one group of OVX rats receiving placebo were used as controls. The concentration of AP was assessed in the frontal and parietal cortex, hippocampus, hypothalamus, anterior pituitary, and serum, whereas the content of beta-END was evaluated in the frontal and parietal cortex, hippocampus, hypothalamus, neurointermediate lobe, anterior pituitary, and plasma. RESULTS: DT56a increased AP levels in all brain areas analyzed and in serum, with a classical dose-related curve in comparison with OVX rats. In some brain areas, such as the frontal cortex, the parietal cortex, and the anterior pituitary, positive results were found even with the administration of a lower DT56a dose of 60 mg kg(-1) day(-1), attaining AP levels in the range of those in animals treated with E2V. Similarly, beta-END levels were enhanced in selected brain areas such as the hippocampus, the hypothalamus, the neurointermediate lobe, and the anterior pituitary in comparison with those in OVX rats, in which the increase of the opioid was dose related and in the range of those in rats treated with E2V. CONCLUSIONS: This study demonstrated that DT56a positively affects brain neurosteroidogenesis and the opiatergic system: DT56a exerts an estrogen-like effect on selective areas related to mood, cognition, and homeostasis control, presenting a specific pattern of interaction with the brain function. These findings may, in part, explain the clinical effect of DT56a on menopausal symptoms.

Practical aspects of in vivo detection of neuropeptides by microdialysis coupled off-line to capillary LC with multistage MS.

A method using capillary liquid chromatography-triple-stage mass spectrometry (LC-MS(3)) to determine endogenous opioid peptides in microdialysis samples collected in vivo was developed, validated, and applied to measurements in the rat striatum. Peptides in dialysate rapidly degraded when stored at room temperature or -80 degrees C. Adding acetic acid to a final concentration of 5% stabilized the peptides for 5 days allowing storage of fractions and off-line measurements which proved more convenient and reliable than previously used on-line methods. Study of the effect of dialysis flow rate from 0.2 to 2 microL/min and column inner diameter (i.d.) from 25 to 75 microm on the relative signal obtained for peptides revealed that lowest flow rates and smallest column i.d. gave the highest relative signal. The method was tested for 10 different neuropeptides and limits of detection (LODs) were from 0.5 to 60 pM (4 microL samples) for most. beta-Endorphin had an LOD of 5 nM when detected directly, but it could be quantitatively determined by detecting a characteristic peptide produced by tryptic digestion with an LOD of 3 pM. This approach may prove useful for other large neuropeptides as well. The method was used to determine met-enkephalin, leu-enkephalin, dynorphin A(1-8), and beta-endorphin in vivo. Endomorphin 1 and 2 were below the detection limit of the method in vivo. Quantitative determination of leu-enkephalin using external calibration was verified by standard addition experiments. The improvements over previous approaches using capillary LC-MS(n) make in vivo neuropeptide monitoring more practical and feasible for a variety of neuropeptides.

Beta-endorphin response to an acute pain stimulus.

The timing of the measurement of biological samples (e.g. biomarkers) is not always standardized. Biomarkers are the focus of many recent studies and treatments. The purpose of this study was to determine the timing of the release of beta-endorphin (BE), a possible biomarker, after exposure to pain and/or handling stress in order to standardize measurements. Mouse plasma was collected for BE analysis following handling i.e. being picked up by the investigator, exposure to a painful (55 degrees C hot-plate), or exposure to a nonpainful stimulus (room temperature hot-plate). The groups exposed to either a painful or nonpainful stimulus released BE in response to the stimulus, but the duration of the response was longer in mice exposed to a painful stimulus than in mice exposed to a nonpainful stimulus. The BE in the mice exposed to a nonpainful stimulus peaked at 1 min and returned to baseline levels by 5 min while the BE response of the mice exposed to a painful stimulus peaked at 10 min and remained elevated for 25 min. The results of this study indicate that BE can be a biomarker for pain and handling stress, however, the timing of the measurement should differ.

[Effects of electroacupuncture on plasma and cerebral somatostatin and beta-EP contents and learning-memory ability in vascular dementia rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on learning-memory ability of vascular dementia (VD) rats, and the simultaneous changes of plasma and cerebral somatostatin (SS) and beta-endorphin (EP) contents. METHODS: Forty-one SD rats were randomly divided into control (n=8), model A (n=8, no treatment) and B (n=8, intragastric perfusion of 15% saline), EA (n=9) and medication (n=8, intragastric perfusion of Nimoldipine, 12 mg/kg) groups. VD model was established by using modified 4-vessels occlusion method. EA (150 Hz, 1-2 mA) was applied to "Baihui" (GV 20), "Dazhui" (DU 14), "Pishu" (BL 20) and "Shenshu" (BL 23) for 20 min, once daily for 15 days. Morris water maze tests were conducted for evaluating the rats' learning-memory ability. The contents of SS and beta-EP in plasma and brain tissue were measured by radioimmunoassay (RIA). RESULTS: In comparison with sham-operation group, the escape latency (EL) prolonged significantly and the target-platform crossing times decreased remarkably (P<0.01) in model group B. In comparison with model group B, EL shortened and target-platform crossing times increased both significantly in EA and medication groups (P<0.01). Plasma and cerebral SS, and cerebral beta-EP contents of model groups A and B were significantly lower than those of sham-operation group(P<0.01), while plasma beta-EP level had no obvious change (P>0.05). Plasma and cerebral SS, and cerebral beta-EP contents in both EA and medication groups were considerably higher than those in model groups A and B (P<0.01). No significant differences were found between EA and medication groups in EL, target-platform crossing times, plasma and cerebral SS and beta-EP levels, and between model group A and model group B in plasma and cerebral SS and beta-EP levels (P>0.05). CONCLUSION: EA can raise plasma and cerebral SS and cerebral beta-EP levels, and improve the learning-memory ability in VD rats.

Ethnicity is associated with alterations in oxytocin relationships to pain sensitivity in women.

UNLABELLED: It is well established that African Americans (AA) experience greater pain associated with a variety of clinical conditions, and greater pain sensitivity to experimental pain tasks relative to non-Hispanic Whites (W). Notably, African Americans do not show the same relationships involving endogenous pain regulatory mechanisms and pain sensitivity documented in Caucasians, including positive associations between blood pressure, norepinephrine, cortisol and greater pain tolerance. OBJECTIVES: The purpose of this study was to examine the relationship between plasma oxytocin (OT) and pain sensitivity and to explore the relation of OT to other factors known to influence pain perception. DESIGN: OT concentration and sensitivity to ischemic, cold pressor, and thermal pain tasks were assessed in African American (n=25) and non-Hispanic White (n=23) pre-menopausal women. RESULTS: African American women demonstrated significantly lower pain tolerance across tasks compared with Whites (F(1,46)=6.31, p=0.0156) and also exhibited lower plasma OT levels (AA: 3.90, W: 7.05 pg/mL; p=0.0014). Greater OT levels were correlated with greater tolerance to ischemic pain (r=0.36, p=0.013) and accounted for a marginally significant portion of the ethnic difference in ischemic pain tolerance (B=+0.29, p=0.06). Greater OT was also correlated with greater tolerance of cold pressor pain (r=0.31, p=0.03); however, this association was no longer seen after the variance due to ethnicity was accounted for. CONCLUSION: These data suggest that reduced oxytocinergic function may be one of multiple biological factors contributing to the greater sensitivity to experimental ischemic pain, and to the greater burden of some types of clinical pain experienced by African Americans compared with Whites.