Release of PACAP-38 in episodic cluster headache patients - an exploratory study.

BACKGROUND: Activation of the trigeminal-autonomic reflex, involving the trigeminal ganglion, the superior salivatory nucleus and the sphenopalatine ganglion (SPG) is crucial in the pathophysiology of cluster headache (CH). Since pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38) is present both in the SPG and the trigeminal ganglion (TG) and its role in migraine has been described, our aim was to determine the plasma PACAP-38 levels in different phases of episodic CH (ECH). Peripheral cubital fossa blood samples were taken during the ictal and inter-bout periods of male ECH patients and from age-matched healthy controls (n = 9). Plasma PACAP-38-like immunoreactivity (LI) was measured with specific and sensitive radioimmunoassay. FINDINGS: Significantly lower plasma PACAP-38-LI was detected in the inter-bout period of ECH patients than in healthy controls. However, PACAP-38 was significantly elevated in the plasma during CH attacks as compared to the inter-bout phase in the same subjects (n = 5). CONCLUSIONS: This exploratory study suggests that PACAP-38 may be released during the attacks of ECH. Further patients and long-term follow-up are necessary to reveal its function.

Alterations in PACAP-38-like immunoreactivity in the plasma during ictal and interictal periods of migraine patients.

BACKGROUND: Recent studies on migraineurs and our own animal experiments have revealed that pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38) has an important role in activation of the trigeminovascular system. The aim of this study was to determine the PACAP-38-like immunoreactivity (LI) in the plasma of healthy subjects, and parallel with the calcitonin gene-related peptide (CGRP)-LI in migraine patients in the ictal and interictal periods. METHODS: A total of 87 migraineurs and 40 healthy control volunteers were enrolled in the examination. Blood samples were collected from the cubital veins in both periods in 21 patients, and in either the ictal or the interictal period in the remaining 66 patients, and were analysed by radioimmunoassay. RESULTS: A significantly lower PACAP-38-LI was measured in the interictal plasma of the migraineurs as compared with the healthy control group ( P < 0.011). In contrast, elevated peptide levels were detected in the ictal period relative to the attack-free period in the 21 migraineurs ( P PACAP-38 < 0.001; P CGRP < 0.035) and PACAP-38-LI in the overall population of migraineurs ( P < 0.009). A negative correlation was observed between the interictal PACAP-38-LI and the disease duration. CONCLUSION: This is the first study that has provided evidence of a clear association between migraine phases (ictal and interictal) and plasma PACAP-38-LI alterations.

Plasma Somatostatin Levels Increase during Scoliosis Surgery, but Not Herniated Disc Operations: Results of a Pilot Study.

Somatostatin (SST) released from capsaicin-sensitive sensory nerves in response to stimulation exerts systemic anti-inflammatory, analgesic actions. Its elevation correlates with the extent of tissue injury. We measured plasma SST alterations during spine operations (scoliosis and herniated disc) to determine whether its release might be a general protective mechanism during painful conditions. Sampling timepoints were baseline (1), after: soft tissue retraction (2), osteotomy (3), skin closure (4), the following morning (5). Plasma SST-like immunoreactivity (SST-LI) determined by radioimmunoassay was correlated with pain intensity and the correction angle (Cobb angle). In scoliosis surgery, postoperative pain intensity (VAS 2.) 1 day after surgery significantly increased (from 1.44 SEM ± 0.68 to 6.77 SEM ± 0.82, p = 0.0028) and positively correlated with the Cobb angle (p = 0.0235). The baseline Cobb degree negatively correlated (p = 0.0459) with the preoperative SST-LI. The plasma SST-LI significantly increased in fraction 3 compared to the baseline (p < 0.05), and significantly decreased thereafter (p < 0.001). In contrast, in herniated disc operations no SST-LI changes were observed in either group. The VAS decreased after surgery both in the traditional (mean 6.83 to 2.29, p = 0.0005) and microdiscectomy groups (mean 7.22 to 2.11, p = 0.0009). More extensive and destructive scoliosis surgery might cause greater tissue damage with greater pain (inflammation), which results in a significant SST release into the plasma from the sensory nerves. SST is suggested to be involved in an endogenous postoperative analgesic (anti-inflammatory) mechanism.

Presence of pituitary adenylate cyclase-activating polypeptide (PACAP) in the plasma and milk of ruminant animals.

Milk contains a variety of proteins and peptides that possess biological activity. Growth factors, such as growth hormone, insulin-like, epidermal and nerve growth factors are important milk components which may regulate growth and differentiation in various neonatal tissues and also those of the mammary gland itself. We have recently shown that pituitary adenylate cyclase-activating polypeptide (PACAP), an important neuropeptide with neurotrophic actions, is present in the human milk in much higher concentration than in the plasma of lactating women. Investigation of growth factors in the milk of domestic animals is of utmost importance for their nutritional values and agricultural significance. Therefore, the aim of the present study was to determine the presence and concentration of PACAP in the plasma and milk of three ruminant animal species. Furthermore, the presence of PACAP and its specific PAC1 receptor were investigated in the mammary glands. Radioimmunoassay measurements revealed that PACAP was present in the plasma and the milk of the sheep, goat and the cow in a similar concentration to that measured previously in humans. PACAP38-like immunoreactivity (PACAP38-LI) was 5-20-fold higher in the milk than in the plasma samples of the respective animals, a similar serum/milk ratio was found in all the three species. The levels did not show significant changes within the examined 3-month-period of lactation after delivery. Similar PACAP38-LI was measured in the homogenates of the sheep mammary gland samples taken 7 and 30 days after delivery. PAC1 receptor expression was detected in these udder biopsies by fluorescent immunohistochemistry suggesting that this peptide might have an effect on the mammary glands themselves. These data show that PACAP is present in the milk of various ruminant domestic animal species at high concentrations, the physiological implications of which awaits further investigation.

Correlation of neurochemical and imaging markers in migraine: PACAP38 and DTI measures.

OBJECTIVE: To examine whether interictal plasma pituitary adenylate cyclase-activating peptide 38-like immunoreactivity (PACAP38-LI) shows correlation with the microstructural integrity of the white matter in migraine. METHODS: Interictal plasma PACAP38-LI was measured by radioimmunoassay in 26 patients with migraine (24 women) who underwent diffusion tensor imaging afterward using a 1.5-tesla magnetic resonance scanner. Data were analyzed using tract-based spatial statistics included in FMRIB's Software Library. RESULTS: Interictal plasma PACAP38-LI showed significant correlation with mean diffusivity (p < 0.0179) mostly in the bilateral occipital white matter spreading into parietal and temporal white matter. Axial and radial diffusivity showed positive correlation with interictal PACAP38-LI (p < 0.0432 and p < 0.0418, respectively) in the left optic radiation and left posterior corpus callosum. Fractional anisotropy did not correlate significantly with PACAP38-LI. With disease duration as a nuisance regressor in the model, PACAP38-LI correlated with axial and mean diffusivity in the left thalamus (p < 0.01). CONCLUSION: We report a link between PACAP38, a pathobiologically important neurochemical biomarker, and imaging markers of the disease that may bolster further research into the role of PACAP38 in migraine.

Kynurenic Acid Inhibits the Electrical Stimulation Induced Elevated Pituitary Adenylate Cyclase-Activating Polypeptide Expression in the TNC.

BACKGROUND: Migraine is a primary headache of imprecisely known mechanism, but activation of the trigeminovascular system (TS) appears to be essential during the attack. Intensive research has recently focused on pituitary adenylate cyclase-activating polypeptide (PACAP) and the kynurenine systems as potential pathogenic factors. AIM: We investigated the link between these important mediators and the effects of kynurenic acid (KYNA) and its synthetic analog (KYNA-a) on PACAP expression in the rat trigeminal nucleus caudalis (TNC) in a TS stimulation model related to migraine mechanisms. METHODS: Adult male Sprague-Dawley rats were pretreated with KYNA, KYNA-a, the NMDA receptor antagonist MK-801, or saline (vehicle). Next, the trigeminal ganglion (TRG) was electrically stimulated, the animals were transcardially perfused following 180 min, and the TNC was removed. In the TNC samples, 38 amino acid form of PACAP (PACAP1-38)-like radioimmunoactivity was measured by radioimmunoassay, the relative optical density of preproPACAP was assessed by Western blot analysis, and PACAP1-38 mRNA was detected by real-time PCR. RESULTS AND CONCLUSION: Electrical TRG stimulation resulted in significant increases of PACAP1-38-LI, preproPACAP, and PACAP1-38 mRNA in the TNC. These increases were prevented by the pretreatments with KYNA, KYNA-a, and MK-801. This is the first study to provide evidence for a direct link between PACAP and the kynurenine system during TS activation.

Evidence for a novel, neurohumoral antinociceptive mechanism mediated by peripheral capsaicin-sensitive nociceptors in conscious rats.

Stimulation of capsaicin-sensitive peripheral sensory nerve terminals induces remote anti-inflammatory effects throughout the body of anesthetized rats and guinea-pigs mediated by somatostatin. As somatostatin has also antinociceptive effects, the study aimed at investigating whether similar remote antinociceptive effects can be demonstrated in awake animals. In conscious rats, nociceptive nerve endings of the right hind paw decentralized by cutting the sciatic and saphenous nerves 18h before were chemically stimulated, and drop of the noxious heat threshold (heat hyperalgesia) induced by prior (18h before) plantar incision was measured on the contralateral, left hind paw using an increasing-temperature water bath. 18h after nerve transection, mustard oil-evoked plasma extravasation was not significantly reduced in the right hind paw as tested by in vivo fluorescence imaging. Applying agonist of either transient receptor potential vanilloid 1 (TRPV1) or transient receptor potential ankyrin 1 (TRPA1) receptor (capsaicin or mustard oil, respectively) to the nerve-transected paw inhibited the plantar incision-induced drop of the noxious heat threshold on the contralateral paw. The onset of these remote antihyperalgesic effects was 10-20min. A similar contralateral inhibitory effect of capsaicin or mustard oil treatment was observed on neuropathic mechanical hyperalgesia evoked by partial sciatic nerve injury 2days before nerve transection and measured by a Randall-Selitto apparatus. The remote thermal antihyperalgesic effect was prevented by chronic (5days) denervation or local capsaicin desensitization of the stimulated paw; reduced by intraperitoneally applied antagonist of somatostatin (cyclosomatostatin) or opioid receptors (naloxone). The response was mimicked by intraperitoneally applied somatostatin and associated with a 72±27% increase in plasma somatostatin-like immunoreactivity that was absent after chronic (5days) denervation. In conclusion, chemical activation of decentralized peripheral capsaicin-sensitive nociceptors evokes remote antihyperalgesic responses initiated outside the central nervous system and mediated by somatostatin and endogenous opioids.

Analgesic topical capsaicinoid therapy increases somatostatin-like immunoreactivity in the human plasma.

The aim of the present study was to evaluate the therapeutic potential of local capsaicinoid (EMSPOMA(®) cream) treatment on chronic low back pain in patients with degenerative spine diseases and to investigate the possible mechanism of action of the therapy. The qualitative and quantitative analyses of capsaicinoids in EMSPOMA(®) cream were performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the clinical study 20 patients with degenerative spine diseases were involved in a self-controlled examination. During the 21 day therapy they received 30 min daily treatment with capsaicinoid (EMSPOMA(®)) cream to the lumbar region of the back. The pain (VASs, Oswestry Disability Index) and the mobility of the lumbar region of the spine (Schober's, Domján's L and R test) were detected at baseline and at the end of the 1st, 2nd and 3rd weeks. The plasma level of somatostatin-like immunoreactivity (SST-LI) was measured by radioimmunoassay (RIA) before and after the treatment on the first and the last day of the therapy. Nonivamide (0.01%) was identified as the only capsaicinoid molecule in the cream. In the clinical study the 21 day local nonivamide treatment reduced the pain sensation. Oswestry Disability Index decreased from 39 ± 3.9% to 32.5 ± 4.4%. VASs showed 37.29%-59.51% improvement. In the plasma level of SST-LI threefold elevation was observed after the first nonivamide treatment. We conclude that nonivamide treatment exerts analgesic action in chronic low back pain and causes the release of the antinociceptive and anti-inflammatory neuropeptide somatostatin which may play pivotal role in the pain-relieving effect.

Changes of PACAP level in cerebrospinal fluid and plasma of patients with severe traumatic brain injury.

PACAP has well-known neuroprotective potential including traumatic brain injury (TBI). Its level is up-regulated following various insults of the CNS in animal models. A few studies have documented alterations of PACAP levels in human serum. The time course of post-ictal PACAP levels, for example, show correlation with migraine severity. Very little is known about the course of PACAP levels following CNS injury in humans and the presence of PACAP has not yet been detected in cerebrospinal fluid (CSF) of subjects with severe TBI (sTBI). The aim of the present study was to determine whether PACAP occurs in the CSF and plasma (Pl) of patients that suffered sTBI and to establish a time course of PACAP levels in the CSF and Pl. Thirty eight subjects with sTBI were enrolled with a Glasgow Coma Scale ≤8 on admission. Samples were taken daily, until the time of death or for maximum 10 days. Our results demonstrated that PACAP was detectable in the CSF, with higher concentrations in patients with TBI. PACAP concentrations markedly increased in both Pl and CSF in the majority of patients 24-48h after the injury stayed high thereafter. In cases of surviving patients, Pl and CSF levels displayed parallel patterns, which may imply the damage of the blood-brain barrier. However, in patients, who died within the first week, Pl levels were markedly higher than CSF levels, possibly indicating the prognostic value of high Pl PACAP levels.

A CRPS-IgG-transfer-trauma model reproducing inflammatory and positive sensory signs associated with complex regional pain syndrome.

The aetiology of complex regional pain syndrome (CRPS), a highly painful, usually post-traumatic condition affecting the limbs, is unknown, but recent results have suggested an autoimmune contribution. To confirm a role for pathogenic autoantibodies, we established a passive-transfer trauma model. Prior to undergoing incision of hind limb plantar skin and muscle, mice were injected either with serum IgG obtained from chronic CRPS patients or matched healthy volunteers, or with saline. Unilateral hind limb plantar skin and muscle incision was performed to induce typical, mild tissue injury. Mechanical hyperalgesia, paw swelling, heat and cold sensitivity, weight-bearing ability, locomotor activity, motor coordination, paw temperature, and body weight were investigated for 8days. After sacrifice, proinflammatory sensory neuropeptides and cytokines were measured in paw tissues. CRPS patient IgG treatment significantly increased hind limb mechanical hyperalgesia and oedema in the incised paw compared with IgG from healthy subjects or saline. Plantar incision induced a remarkable elevation of substance P immunoreactivity on day 8, which was significantly increased by CRPS-IgG. In this IgG-transfer-trauma model for CRPS, serum IgG from chronic CRPS patients induced clinical and laboratory features resembling the human disease. These results support the hypothesis that autoantibodies may contribute to the pathophysiology of CRPS, and that autoantibody-removing therapies may be effective treatments for long-standing CRPS.

Plasma somatostatin-like immunoreactivity increases in the plasma of septic patients and rats with systemic inflammatory reaction: experimental evidence for its sensory origin and protective role.

Alterations of somatostatin-like immunoreactivity (SST-LI) in the plasma of 11 systemic inflammatory response syndrome (SIRS) patients were investigated in correlation with cytokines, adhesion molecules and coagulation markers repeatedly during 4 days. The origin and role of SST were studied in the cecum ligation and puncture (CLP) rat SIRS model. Capsaicin-sensitive peptidergic sensory nerves were defunctionalized by resiniferatoxin (RTX) pretreatment 2 weeks earlier, in a separate group animals were treated with the somatostatin receptor antagonist cyclo-somatostatin (C-SOM). Plasma SST-LI significantly elevated in septic patients compared to healthy volunteers during the whole 4-day period. Significantly decreased Horowitz score showed severe lung injury, increased plasma C-reactive protein and procalcitonin confirmed SIRS. Soluble P-selectin, tissue plasminogen activator and the interleukin 8 and monocyte chemotactic protein-1 significantly increased, interleukin 6 and soluble CD40 ligand did not change, and soluble Vascular Adhesion Molecule-1 decreased. SST-LI significantly increased in rats both in the plasma and the lung 6h after CLP compared to sham-operation. After RTX pretreatment SST-LI was not altered in intact animals, but the SIRS-induced elevation was absent. Lung MPO activity significantly increased 6h following CLP compared to sham operation, which was significantly higher both after RTX-desensitization and C-SOM-treatment. Most non-pretreated operated rats survived the 6h, but 60% of the RTX-pretreated ones died showing a significantly worse survival. This is the first comprehensive study in humans and animal experiments providing evidence that SST is released from the activated peptidergic sensory nerves. It gets into the bloodstream and mediates a potent endogenous protective mechanism.

Lutein inhibits the function of the transient receptor potential A1 ion channel in different in vitro and in vivo models.

Transient receptor potential (TRP) ion channels, such as TRP vanilloid 1 and ankyrin repeat domain 1 (TRPV1 and TRPA1), are expressed on primary sensory neurons. Lutein, a natural tetraterpene carotenoid, can be incorporated into membranes and might modulate TRP channels. Therefore, the effects of the water-soluble randomly methylated-ß-cyclodextrin (RAMEB) complex of lutein were investigated on TRPV1 and TRPA1 activation. RAMEB-lutein (100 µM) significantly diminished Ca(2+) influx to cultured rat trigeminal neurons induced by TRPA1 activation with mustard oil, but not by TRPV1 stimulation with capsaicin, as determined with microfluorimetry. Calcitonin gene-related peptide release from afferents of isolated tracheae evoked by mustard oil, but not by capsaicin, was inhibited by RAMEB-lutein. Mustard oil-induced neurogenic mouse ear swelling was also significantly decreased by 100 µg/ml s.c. RAMEB-lutein pretreatment, while capsaicin-evoked edema was not altered. Myeloperoxidase activity indicating non-neurogenic granulocyte accumulation in the ear was not influenced by RAMEB-lutein in either case. It is concluded that lutein inhibits TRPA1, but not TRPV1 stimulation-induced responses on cell bodies and peripheral terminals of sensory neurons in vitro and in vivo. Based on these distinct actions and the carotenoid structure, the ability of lutein to modulate lipid rafts in the membrane around TRP channels can be suggested.

Comparison of the anti-inflammatory and anti-nociceptive effects of cortistatin-14 and somatostatin-14 in distinct in vitro and in vivo model systems.

We showed that somatostatin (SST) exerts anti-inflammatory and anti-nociceptive effects through somatostatin receptor subtypes 4 and 1 (sst(4)/sst(1)). Since cortistatin (CST) is a structurally similar peptide, we aimed at comparing the sst(1)- and sst(4)-binding and activating abilities, as well as the effects of SST-14 and CST-14 on inflammatory and nociceptive processes. CST-14 concentration-dependently displaced radiolabeled SST-14 binding, induced similar sst(1) and sst(4)-activation with a less potency, and exerted significantly greater inhibitory effect on endotoxin-stimulated interleukin (IL)-1ß production of murine peritoneal macrophages. Capsaicin-induced calcitonin gene-related peptide release from peripheral sensory nerve terminals of isolated rat tracheae was significantly decreased by 2 µM CST and 100 nM SST, but concentration-response correlation was not found. Mustard oil-evoked acute neurogenic plasma protein extravasation in the rat hindpaw skin, carrageenan-induced mouse paw edema, mechanical hyperalgesia, and IL-1ß, tumor necrosis factor-α production, as well as mild heat injury-evoked thermal hyperalgesia were similarly attenuated by both peptides. In the latter case, i.pl. and i.p. injections exerted equal inhibitory actions. CST-14 and SST-14 similarly diminish both acute neurogenic and cellular inflammatory processes, as well as mechanical and heat hyperalgesia, in which their inhibitory effect on sensory nerve endings is likely to be involved. However, CST-14 exerts remarkably greater inhibition on cytokine production.

The role of transient receptor potential ankyrin 1 (TRPA1) receptor activation in hydrogen-sulphide-induced CGRP-release and vasodilation.

Activation of transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) channels on capsaicin-sensitive sensory neurons causes release of inflammatory neuropeptides, including calcitonin gene-related peptide (CGRP). We investigated whether the hydrogen sulphide (H(2)S)-evoked CGRP release from sensory neurons of isolated rat tracheae and H(2)S-induced increases in the microcirculation of the mouse ear were mediated by TRPA1 receptor activation. Allylisothiocyanate (AITC) or the H(2)S donor sodium hydrogen sulphide (NaHS) were used as stimuli and CGRP release of the rat tracheae was measured by radioimmunoassay. AITC or NaHS were applied to the ears of Balb/c, C57BL/6, TRPA1 and TRPV1 receptor gene knockout mice and blood flow was detected by laser Doppler imaging. Both AITC and NaHS increased CGRP release from isolated rat tracheae, and both responses were inhibited by the TRPA1 antagonist, HC-030031, but was not affected by the TRPV1 receptor blocker, BCTC. Application of AITC or NaHS increased the cutaneous blood flow in the mouse ears. Similarly to the effect of AITC, the vasodilatory response to NaHS was reduced by HC-030031 or in TRPA1 deleted mice. In contrast, genetic deletion of TRPV1 did not affect the increase in the ear blood flow evoked by AITC or NaHS. We conclude that H(2)S activates TRPA1 receptors causing CGRP release from sensory nerves of rat tracheae, as well as inducing cutaneous vasodilatation in the mouse ear. TRPV1 receptors were not involved in these processes. Our results highlight that TRPA1 receptor activation should be considered as a potential mechanism of vasoactive effects of H(2)S.

Peripheral and central alterations of pituitary adenylate cyclase activating polypeptide-like immunoreactivity in the rat in response to activation of the trigeminovascular system.

Pituitary adenylate cyclase activating polypeptide (PACAP) is present in the cranial arteries and trigeminal sensory neurons. We therefore examined the alterations in PACAP-like immunoreactivity (PACAP-LI) in a time-dependent manner in two rat models of trigeminovascular system (TS) activation. In one group chemical stimulation (CS) was performed with i.p. nitroglycerol (NTG), and in the other one the trigeminal ganglia (TRG) were subjected to electrical stimulation (ES). The two biologically active forms, PACAP-38 and PACAP-27, were determined by means of radioimmunoassay (RIA) and mass spectrometry (MS) in the plasma, the cerebrospinal fluid (CSF), the trigeminal nucleus caudalis (TNC), the spinal cord (SC) and the TRG. The tissue concentrations of PACAP-27 were 10 times lower than those of PACAP-38 in the TNC and SC, but about half in the TRG. PACAP-38, but not PACAP-27, was present in the plasma. Neither form could be identified in the CSF. PACAP-38-LI in the plasma, SC and TRG remained unchanged after CS, but it was increased significantly in the TNC 90 and 180 min after NTG injection. In response to ES of the TRG, the level of PACAP-38 in the plasma and the TNC was significantly elevated 90 and 180 min later, but not in the SC or the TRG. The alterations in the levels of PACAP-27 in the tissue homogenates in response to both forms of stimulation were identical to those of PACAP-38. The selective increases in both forms of PACAP in the TNC suggest its important role in the central sensitization involved in migraine-like headache.

Surgery and sepsis increase somatostatin-like immunoreactivity in the human plasma.

We have previously shown in animals that somatostatin released from capsaicin-sensitive afferents in response to inflammation and tissue damage exerts systemic anti-nociceptive and anti-inflammatory actions. Since peptidergic sensory innervation of the airways and the joints are particularly dense, we aimed at investigating the alterations of plasma somatostatin-like immunoreactivity (SST-LI) in response to thoracic and orthopedic surgery, as well as sepsis. Thoracotomy, video-assisted thoracoscopy, hip and knee endoprosthesis were performed under general anesthesia. Blood was taken before, during and after the surgical procedures, as well as at admission and every consecutive morning from septic patients receiving exclusively total parenteral nutrition. SST-LI was determined from the plasma with specific and sensitive radioimmunoassay developed in our laboratory. Plasma SST-LI in healthy volunteers and preoperatively was 8-12fmol/ml. Both thoracotomy and thoracoscopy significantly increased SST-LI by 55-60% at the end of the procedures when the thoracic cavity and the skin were closed. Hip endoprosthesis implantation elevated SST-LI by 30% after skin incision, which increased further to 55% by the time the surgery was completed. In contrast, knee operations performed under tourniquet did not alter SST-LI in the systemic circulation. SST-LI was almost 3-fold higher in the plasma of septic patients than in healthy volunteers. This human study revealed that thoracic/hip surgery and sepsis elevate SST-LI in the systemic circulation, presumably by inducing its release from sensory fibres. It is concluded, that the endogenous protective mechanism mediated by neural somatostatin, which has been evidenced in animals, is likely to operate in patients.

Presence of pituitary adenylate cyclase activating polypeptide-38 in human plasma and milk.

OBJECTIVE: Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic and multifunctional neuropeptide widely distributed throughout the body. It is involved in the regulation of various physiological and pathophysiological processes, such as reproduction, thermoregulation, motor activity, brain development, neuronal survival, inflammation and pain. Since little is known about its distribution in humans, our aim was to examine PACAP-38 in human plasma. Furthermore, based on the presence of vasoactive intestinal peptide, structurally the closest to PACAP, in milk and PACAP and its receptors in the mammary gland, our aim was to study PACAP-38 in human milk. DESIGN AND METHODS: The presence of PACAP-38 was determined by mass spectrometry in plasma samples from healthy male and female volunteers (age: 20-40), as well as in plasma and milk samples from lactating women (age: 20-35). PACAP concentration was measured with a specific and sensitive RIA. RESULTS: Our results revealed that PACAP-38 is present in human plasma, its concentration is relatively stable in healthy volunteers and it is not significantly altered by gender, age, food intake or hormonal cycle in females. However, PACAP-38 plasma levels significantly increased in lactating women having 1-6 month-old babies. Moreover, this study is the first which provides evidence for the presence of PACAP-38 in the human milk with levels 5-20-fold greater in the milk whey than in the respective plasma samples. CONCLUSIONS: We found PACAP-38 in human plasma and its increase during the first 6 months of the lactation period. A prominent, nearly 10-fold higher concentration of this peptide was detected in human milk. Based on the literature, several important actions of milk-derived PACAP-38 can be suggested such as mammary gland proliferation, nutrient transfer as well as regulation of growth/differentiation of certain tissues of the neonates. The novelty of the present descriptive data provides a basis for further investigations on the mechanism of PACAP-38 secretion in human milk and its functional significance.