Pituitary adenylate cyclase activating polypeptide plays a role in olfactory memory formation in chicken

Retinoprotective Effects of PACAP Eye Drops in Microbead-Induced Glaucoma Model in Rats

Glaucoma is associated with increased intraocular pressure (IOP), causing the apoptosis of retinal ganglion cells (RGCs) and the loss of their axons leading to blindness. Pituitary adenylate cyclase activating polypeptide (PACAP) is neuroprotective in several neural injuries, including retinopathies. The aim of this study was to investigate the effects of PACAP1-38 eye drops in a model of glaucoma. IOP was elevated bilaterally by injections of microbeads to block the aqueous humor outflow. The control groups received the same volume of saline. Animals were treated with PACAP1-38 (1 µg/drop, 3 × 1 drop/day) or vehicle for 4 weeks starting one day after the injections. Retinal morphology by histology and optical coherence tomography, function by electroretinography, and IOP changes were analyzed. Animals were sacrificed 8 weeks after the injections. Microbeads injections induced a significant increase in the IOP, while PACAP1-38 treatment lowered it to normal levels (~10 mmHg). Significant retinal degeneration and functional impairment were observed in the microbead-injected group without PACAP1-38 treatment. In the microbeads + PACAP1-38 group, the retinal morphology and functionality were close to the normal values. In summary, our results show that PACAP1-38, given in form of eye drops, is neuroprotective in glaucoma, providing the basis for potential future therapeutic administration.

PACAP is Protective Against Cellular Stress in Retinal Pigment Epithelial Cells

The integrity of the innermost, pigment epithelial layer of the retina is crucial for the photoreceptor survival and for maintaining the outer blood–retina barrier. In several ocular degenerations, such as diabetic retinopathy or macular edema, the stress caused by various harmful stimuli (hypoxia, oxidative stress, hyperosmosis) lead to severe molecular biological changes in this layer, promoting neovascularization of the retina. Pituitary adenylate cyclase activating polypeptide (PACAP) occurs throughout the whole body, including the eye. It has numerous functions in the retina, including the previously described anti-apoptotic and anti-angiogenic effects in retinal pigment epithelial cells. The aim of this present study was to investigate the influence of PACAP on different stress factors. In accordance with previous findings, PACAP significantly ameliorated the increased Hif1-α levels in hypoxic conditions. In H2O2-induced oxidative stress PACAP had an anti-apoptotic effect, it could decrease the expression of cytochrome-c and p53, while it upregulated the concentration of three antioxidants, namely SOD2, PON2 and thioredoxin. In conclusion, we provided new information on the molecular biological background of the retinoprotective effect of PACAP.

Alterations of Nigral Dopamine Levels in Parkinson's Disease after Environmental Enrichment and PACAP Treatment in Aging Rats

The neuroprotective effects of environmental enrichment and PACAP (pituitary adenylate cyclase-activating polypeptide) are well-described in Parkinson’s disease. The aim of our study is to investigate the beneficial effects of these factors in aging parkinsonian rats. Newborn Wistar rats were divided into standard and enriched groups according to their environmental conditions. Standard animals were raised under regular conditions. During the first five postnatal weeks, enriched pups were placed in larger cages with different objects. Aging animals received (1) saline, (2) 6-hydroxidopamine (6-OHDA), or (3) 6-OHDA + PACAP injections into the left substantia nigra (s.n.). On the seventh postoperative day, the left and right s.n. were collected. The s.n. of young and aging unoperated animals were also examined in our experiment. We determined the dopamine (DA) levels by the HPLC-MS technique, while the sandwich ELISA method was used to measure the Parkinson disease protein 7 (PARK7) protein levels. In healthy animals, we found an age-related decrease of DA levels. In aging parkinsonian-enriched rats, the operation did not result in a significant DA loss. PACAP treatment could prevent the DA loss in both the standard and enriched groups. All injured PACAP-treated rats showed remarkably higher protective PARK7 levels. The protective effect of PACAP correlated with the increase of the DA and PARK7 levels.

Pituitary adenylate cyclase activating polypeptide acts against neovascularization in retinal pigment epithelial cells

The purpose of this study was to determine whether pituitary adenylate cyclase activating polypeptide (PACAP) could influence the neovascularization processes in hyperosmotic and oxidative stress in retinal pigment epithelial cells. Hyperosmotic conditions and oxidative stress were induced by 200 mM sucrose and 250 µM hydrogen peroxide (H₂ O₂ ), respectively. Morphology and elasticity of adult retinal pigment epithelial (ARPE-19) cells were measured by atomic force microscopy, while the investigation of junctional molecules, such as occludin and ZO-1, was carried out using immunofluorescence. For cell viability measurement, the MTT test was used. The effect of PACAP on the key angiogenic factors, such as vascular endothelial growth factor, angiogenin, and endothelin-1, was measured by an angiogenesis array and flow cytometry. Hyperosmotic stress-induced reorganization of the cytoskeleton and impairment of the junctions decreased cell viability and upregulated several angiogenic factors. In oxidative stress, we found that opening of the junctions decreased viability and upregulated the expression of angiogenic factors. PACAP was shown to be protective in both conditions. Retinal pigment epithelium cells play an important role in several diseases, such as diabetic retinopathy and macular edema. Therefore, protecting retinal pigment epithelial (RPE) cells with PACAP could be a novel and potential treatment in these diseases.

Dysregulation of the SNARE-binding protein Munc18-1 impairs BDNF secretion and synaptic neurotransmission: a novel interventional target to protect the aging brain

Brain-derived neurotrophic factor (BDNF) has a central role in maintaining and strengthening neuronal connections and to stimulate neurogenesis in the adult brain. Decreased levels of BDNF in the aging brain are thought to usher cognitive impairment. BDNF is stored in dense core vesicles and released through exocytosis from the neurites. The exact mechanism for the regulation of BDNF secretion is not well understood. Munc18-1 (STXBP1) was found to be essential for the exocytosis of synaptic vesicles, but its involvement in BDNF secretion is not known. Interestingly, neurons lacking munc18-1 undergo severe degeneration in knock-out mice. Here, we report the effects of BDNF treatment on the presynaptic terminal using munc18-1-deficient neurons. Reduced expression of munc18-1 in heterozygous (+/-) neurons diminishes synaptic transmitter release, as tested here on individual synaptic connections with FM1-43 fluorescence imaging. Transduction of cultured neurons with BDNF markedly increased BDNF secretion in wild-type but was less effective in munc18-1 +/- cells. In turn, BDNF enhanced synaptic functions and restored the severe synaptic dysfunction induced by munc18-1 deficiency. The role of munc18-1 in the synaptic effect of BDNF is highlighted by the finding that BDNF upregulated the expression of munc18-1 in neurons, consistent with enhanced synaptic functions. Accordingly, this is the first evidence showing the functional effect of BDNF in munc18-1 deficient synapses and about the direct role of munc18-1 in the regulation of BDNF secretion. We propose a molecular model of BDNF secretion and discuss its potential as therapeutic target to prevent cognitive decline in the elderly.

VPAC1 receptors play a dominant role in PACAP-induced vasorelaxation in female mice

Background

PACAP and VIP are closely related neuropeptides with wide distribution and potent effect in the vasculature. We previously reported vasomotor activity in peripheral vasculature of male wild type (WT) and PACAP-deficient (KO) mice. However, female vascular responses are still unexplored. We hypothesized that PACAP-like activity is maintained in female PACAP KO mice and the mechanism through which it is regulated differs from that of male PACAP KO animals.

Methods

We investigated the vasomotor effects of VIP and PACAP isoforms and their selective blockers in WT and PACAP KO female mice in carotid and femoral arteries. The expression and level of different PACAP receptors in the vessels were measured by RT-PCR and Western blot.

Results

In both carotid and femoral arteries of WT mice, PACAP1-38, PACAP1-27 or VIP induced relaxation, without pronounced differences between them. Reduced relaxation was recorded only in the carotid arteries of KO mice as compared to their WT controls. The specific VPAC1R antagonist completely blocked the PACAP/VIP-induced relaxation in both arteries of all mice, while PAC1R antagonist affected relaxation only in their femoral arteries.

Conclusion

In female WT mice, VPAC1 receptors appear to play a dominant role in PACAP-induced vasorelaxation both in carotid and in femoral arteries. In the PACAP KO group PAC1R activation exerts vasorelaxation in the femoral arteries but in carotid arteries there is no significant effect of the activation of this receptor. In the background of this regional difference, decreased PAC1R and increased VPAC1R availability in the carotid arteries was found.

Pituitary adenylate cyclase-activating polypeptide (PACAP-38) plays an inhibitory role against inflammation induced by chemical damage to zebrafish hair cells

Pituitary adenylate cyclase-activating polypeptide (PACAP-38) is a common neuropeptide exerting a wide spectrum of functions in many fields, including immunology. In the present study, 5-day post-fertilization (dpf) zebrafish larvae of three diverse genetic lines [transgenic lines Tg(MPX:GFP) with GFP-labelled neutrophils and Tg(pou4f3:GAP-GFP) with GFP-labelled hair cells and the wild-type Tuebingen] were used to investigate an inhibitory role of PACAP-38 in inflammation associated with damaged hair cells of the lateral line. Individuals of each genetic line were assigned to four groups: (1) control, and those consisting of larvae exposed to (2) 10 µM CuSO4, (3) 10 µM CuSO4+100 nM PACAP-38 and (4) 100 nM PACAP-38, respectively. Forty-minute exposure to CuSO4 solution was applied to evoke necrosis of hair cells and consequent inflammation. The inhibitory role of PACAP-38 was investigated in vivo under a confocal microscope by counting neutrophils migrating towards damaged hair cells in Tg(MPX:GFP) larvae. In CuSO4-treated individuals, the number of neutrophils associated with hair cells was dramatically increased, while PACAP-38 co-treatment resulted in its over 2-fold decrease. However, co-treatment with PACAP-38 did not prevent hair cells from extensive necrosis, which was found in Tg(pou4f3:GAP-GFP) individuals. Real-Time PCR analysis performed in wild-type larvae demonstrated differential expression pattern of stress and inflammation inducible markers. The most significant findings showed that CuSO4 exposure up-regulated the expression of IL-8, IL-1β, IL-6 and ATF3, while after PACAP-38 co-treatment expression levels of these genes were significantly decreased. The presence of transcripts for all PACAP receptors in neutrophils was also revealed. Adcyap1r1a and vipr1b appeared to be predominant forms. The present results suggest that PACAP-38 should be considered as a factor playing an important regulatory role in inflammatory response associated with pathological processes affecting zebrafish hair cells and it cannot be excluded that this interesting property has more universal significance.

Aging-Induced Modulation of Pituitary Adenylate Cyclase-Activating Peptide- and Vasoactive Intestinal Peptide-Induced Vasomotor Responses in the Arteries of Mice

Pituitary adenylate cyclase-activating peptide (PACAP; 1-38 and 1-27) and vasoactive intestinal peptide (VIP) are related neuropeptides of the secretin/glucagon family. Overlapping signaling through G-protein-coupled receptors mediates their vasomotor activity. We previously showed that PACAP deficiency (PACAP-KO) shifts the mechanisms of vascular response and maintains arterial relaxation through the VIP backup mechanism and (mainly) its VPAC1R, but their age-dependent modulation is still unknown. We hypothesized that backup mechanisms exist, which maintain the vasomotor activity of these peptides also in older age. Thus, we investigated the effects of exogenous VIP and PACAP peptides in isolated carotid arteries of 2- and 15-month-old wild-type (WT) and PACAP-KO mice. All peptides induced relaxation in the arteries of young WT mice, whereas in young PACAP-KO mice PACAP1-27 and VIP, but not PACAP1-38, induced relaxation. Unlike VIP, PACAP-induced vasomotor responses were reduced in aging WT mice. However, in the arteries of aging PACAP-KO mice, PACAP1-27- and VIP-induced responses were reduced, but PACAP1-38 showed a greater vasomotor response compared to that of young PACAP-KO animals. There were no significant differences between the vasomotor responses of aging WT and PACAP-KO mice. Our data suggest that, in the absence of PACAP both in young and old ages, the vascular response is mediated through backup mechanisms, most likely VIP, maintaining proper vascular relaxation in aging-induced PACAP insufficiency.

Disturbed spermatogenic signaling in pituitary adenylate cyclase activating polypeptide-deficient mice

PACAP is a neuropeptide with diverse functions in various organs, including reproductive system. It is present in the testis in high concentrations, and in addition to the stage-specific expression within the seminiferous tubules, PACAP affects spermatogenesis and the functions of Leydig and Sertoli cells. Mice lacking endogenous PACAP show reduced fertility, but the possibility of abnormalities in spermatogenic signaling has not yet been investigated. Therefore, we performed a detailed morphological analysis of spermatozoa, sperm motility and investigated signaling pathways that play a role during spermatogenesis in knockout mice. No significant alterations were found in testicular morphology or motility of sperm in homozygous and heterozygous PACAP-deficient mice in spite of the moderately increased number of severely damaged sperms. However, we found robust changes in mRNA and/or protein expression of several factors that play an important role in spermatogenesis. Protein kinase A expression was markedly reduced, while downstream phospho-ERK and p38 were elevated in knockout animals. Expression of major transcription factors, such as Sox9 and phospho-Sox9, was decreased, while that of Sox10, as a redundant factor, was increased in PACAP-deficient mice. The reduced phospho-Sox9 expression was partly due to increased expression and activity of phosphatase PP2A in knockout mice. Targets of Sox transcription factors, such as collagen type IV, were reduced in knockout mice. In summary, our results show that lack of PACAP leads to disturbed signaling in spermatogenesis, which could be a factor responsible for reduced fertility in PACAP knockout mice, and further support the role of PACAP in reproduction.

Backup Mechanisms Maintain PACAP/VIP-Induced Arterial Relaxations in Pituitary Adenylate Cyclase-Activating Polypeptide-Deficient Mice

BACKGROUND

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a multifunctional neuropeptide in the VIP/secretin/glucagon peptide superfamily. Two active forms, PACAP1-38 and PACAP1-27, act through G protein-coupled receptors, the PAC1 and VPAC1/2 receptors. Effects of PACAP include potent vasomotor activity. Vasomotor activity and organ-specific vasomotor effects of PACAP-deficient mice have not yet been investigated; thus, the assessment of its physiological importance in vasomotor functions is still missing. We hypothesized that backup mechanisms exist to maintain PACAP pathway activity in PACAP knockout (KO) mice. Thus, we investigated the vasomotor effects of exogenous vasoactive intestinal peptide (VIP) and PACAP polypeptides in PACAP wild-type (WT) and PACAP-deficient (KO) male mice.

METHODS

Carotid and femoral arteries were isolated from 8- to 12-week-old male WT and PACAP-KO mice. Vasomotor responses were measured with isometric myography.

RESULTS

In the arteries of WT mice the peptides induced relaxations, which were significantly greater to PACAP1-38 than to PACAP1-27 and VIP. In KO mice, PACAP1-38 did not elicit relaxation, whereas PACAP1-27 and VIP elicited significantly greater relaxation in KO mice than in WT mice. The specific PAC1R and VPAC1R antagonist completely blocked the PACAP-induced relaxations.

CONCLUSION

Our data suggest that in PACAP deficiency, backup mechanisms maintain arterial relaxations to polypeptides, indicating an important physiological role for the PACAP pathway in the regulation of vascular tone.

Stimulatory effect of pituitary adenylate cyclase-activating polypeptide 6-38, M65 and vasoactive intestinal polypeptide 6-28 on trigeminal sensory neurons

Pituitary adenylate cyclase-activating polypeptide (PACAP) acts on G protein-coupled receptors: the specific PAC1 and VPAC1/VPAC2 receptors. PACAP6-38 was described as a potent PAC1/VPAC2 antagonist in several models, but recent studies reported its agonistic behaviors proposing novel receptorial mechanisms. Since PACAP in migraine is an important research tool, we investigated the effect of PACAP and its peptide fragments on trigeminal primary sensory neurons. Effect of the peptides was studied with ratiometric Ca-imaging technique using the fluorescent indicator fura-2 AM on primary cultures of rat and mouse trigeminal ganglia (TRGs) neurons. Specificity testing was performed on PAC1, VPAC1 and VPAC2 receptor-expressing cell lines with both fluorescent and radioactive Ca-uptake methods. Slowly increasing intracellular free calcium concentration [Ca(2+)]i was detected after PACAP1-38, PACAP1-27, vasoactive intestinal polypeptide (VIP) and the selective PAC1 receptor agonist maxadilan administration on TRG neurons, but interestingly, PACAP6-38, VIP6-28 and the PAC1 receptor antagonist M65 also caused similar activation. The VPAC2 receptor agonist BAY 55-9837 induced similar activation, while the VPAC1 receptor agonist Ala(11,22,28)VIP had no significant effect on [Ca(2+)]i. It was proven that the Ca(2+)-influx originated from intracellular stores using radioactive calcium-45 uptake experiment and Ca-free solution. On the specific receptor-expressing cell lines the antagonists inhibited the stimulating actions of the respective agonists, but had no effects by themselves. PACAP6-38, M65 and VIP6-28, which were described as antagonists in numerous studies in several model systems, act as agonists on TRG primary sensory neurons. Currently unknown receptors or splice variants linked to distinct signal transduction pathways might explain these differences.

Pituitary Adenylate Cyclase Activating Polypeptide (PACAP) Pathway Is Induced by Mechanical Load and Reduces the Activity of Hedgehog Signaling in Chondrogenic Micromass Cell Cultures

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neurohormone exerting protective function during various stress conditions either in mature or developing tissues. Previously we proved the presence of PACAP signaling elements in chicken limb bud-derived chondrogenic cells in micromass cell cultures. Since no data can be found if PACAP signaling is playing any role during mechanical stress in any tissues, we aimed to investigate its contribution in mechanotransduction during chondrogenesis. Expressions of the mRNAs of PACAP and its major receptor, PAC1 increased, while that of other receptors, VPAC1, VPAC2 decreased upon mechanical stimulus. Mechanical load enhanced the expression of collagen type X, a marker of hypertrophic differentiation of chondrocytes and PACAP addition attenuated this elevation. Moreover, exogenous PACAP also prevented the mechanical load evoked activation of hedgehog signaling: protein levels of Sonic and Indian Hedgehogs and Gli1 transcription factor were lowered while expressions of Gli2 and Gli3 were elevated by PACAP application during mechanical load. Our results suggest that mechanical load activates PACAP signaling and exogenous PACAP acts against the hypertrophy inducing effect of mechanical load.

Efferent and afferent connections of the olfactory bulb and prepiriform cortex in the pigeon (Columba livia)

Although olfaction in birds is known to be involved in a variety of behaviors, there is comparatively little detailed information on the olfactory brain. In the pigeon brain, the olfactory bulb (OB) is known to project to the prepiriform cortex (CPP), piriform cortex (CPi), and dorsolateral corticoid area (CDL), which together are called the olfactory pallium, but centrifugal pathways to the OB have not been fully explored. Fiber connections of CPi and CDL have been reported, but those of other olfactory pallial nuclei remain unknown. The present study examines the fiber connections of OB and CPP in pigeons to provide a more detailed picture of their connections using tract-tracing methods. When anterograde and retrograde tracers were injected in OB, projections to a more extensive olfactory pallium were revealed, including the anterior olfactory nucleus, CPP, densocellular part of the hyperpallium, tenia tecta, hippocampal continuation, CPi, and CDL. OB projected commissural fibers to the contralateral OB but did not receive afferents from the contralateral olfactory pallium. When tracers were injected in CPP, reciprocal ipsilateral connections with OB and nuclei of the olfactory pallium were observed, and CPP projected to the caudolateral nidopallium and the limbic system, including the hippocampal formation, septum, lateral hypothalamic nucleus, and lateral mammillary nucleus. These results show that the connections of OB have a wider distribution throughout the olfactory pallium than previously thought and that CPP provides a centrifugal projection to the OB and acts as a relay station to the limbic system.

Pituitary adenylate cyclase-activating polypeptide (PACAP) induces relaxations of peripheral and cerebral arteries, which are differentially impaired by aging

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a well-known neuropeptide, which also has vasomotor effects. However, little is known regarding its age-related and organ-specific vasomotor effects. We hypothesized that the vasomotor effects of PACAP depend on the tissue origin of the vessels and aging substantially modulates its actions. Thus, carotid (CA) and basilar arteries (BA) were isolated from young (2 months old), middle age (12 months old), and old (30 months old) rats. Their vasomotor responses were measured with an isometric myograph (DMT610M) in response to cumulative concentrations of PACAP1-38 (10(-9)-10(-6) M). PACAP1-38 induced (1) significantly greater concentration-dependent relaxations in CA compared to that of BA of young, middle age, and old rats; (2) relaxations of CA significantly decreased, whereas they did not change substantially in BA, as a function of age; (3) sodium nitroprusside (SNP)-induced relaxation did not change after PACAP1-38 administration in any conditions; and (4) inhibition of PAC1 receptors by selective PAC1 receptor blocker (PACAP6-38) completely diminished the responses to PACAP in all age groups of BA and CA. In conclusion, these findings suggest that PACAP1-38 has greater vasomotor effect in CA than that in BA, whereas aging has less effect on PACAP-induced relaxation of cerebral arteries and BA than that in peripheral arteries and CA suggesting that the relaxation to PACAP is maintained in cerebral arteries even in old age.

Reversal of age-related learning deficiency by the vertebrate PACAP and IGF-1 in a novel invertebrate model of aging: the pond snail (Lymnaea stagnalis)

With the increase of life span, nonpathological age-related memory decline is affecting an increasing number of people. However, there is evidence that age-associated memory impairment only suspends, rather than irreversibly extinguishes, the intrinsic capacity of the aging nervous system for plasticity (1). Here, using a molluscan model system, we show that the age-related decline in memory performance can be reversed by administration of the pituitary adenylate cyclase activating polypeptide (PACAP). Our earlier findings showed that a homolog of the vertebrate PACAP38 and its receptors exist in the pond snail (Lymnaea stagnalis) brain (2), and it is both necessary and instructive for memory formation after reward conditioning in young animals (3). Here we show that exogenous PACAP38 boosts memory formation in aged Lymnaea, where endogenous PACAP38 levels are low in the brain. Treatment with insulin-like growth factor-1, which in vertebrates was shown to transactivate PACAP type I (PAC1) receptors (4) also boosts memory formation in aged pond snails. Due to the evolutionarily conserved nature of these polypeptides and their established role in memory and synaptic plasticity, there is a very high probability that they could also act as “memory rejuvenating” agents in humans.

PACAP27 is protective against tat-induced neurotoxicity

Human immunodeficiency virus type-1 (HIV) infection of the central nervous system promotes neuronal injury and apoptosis that culminate in HIV-associated neurocognitive disorders (HAND). Viral proteins, such as transactivator of transcription (Tat), have emerged as leading candidates to explain HIV-mediated neurotoxicity, though the mechanism remains unclear. To determine the effects of Tat, rat cortical neurons were exposed to nanomolar concentrations of Tat for various time points. Within a few hours, Tat induced the production of reactive oxygen species (ROS), and other indices of mitochondrial destabilization. In addition, we observed a significant induction of DNA double-strand breaks (DSBs) by Tat. We next investigated the neuroprotective activity of the pituitary adenylate cyclase-activating polypeptide 27 (PACAP27) against these cardinal features of Tat-induced neurodegeneration. PACAP27 (100 nM) inhibited all Tat-mediated toxic effects including DNA DSBs. Importantly, PACAP27 prevented the induction of neuronal loss induced by Tat. The neuroprotective effect of PACAP27 is correlated with its ability to release the anti-apoptotic chemokine CCL5. Our data support a mechanism of Tat neurotoxicity in which Tat induces mitochondrial destabilization, thus increasing the release of ROS, which causes DNA DSBs leading to cell death. PACAP27, through CCL5, mitigates the effects of Tat-induced neuronal dysfunction, suggesting that PACAP27 could be a new strategy for an adjunct therapy against HIV-associated neurocognitive disorders.

Maternal diet influences offspring feeding behavior and fearfulness in the precocial chicken

Background

In chicken, oils in the maternal diet confer a specific scent to the yolk. Embryos are known to perceive and memorize chemosensory signals of the surrounding environment; however, the potential impact of the maternal diet has not previously been investigated. In the present study, we hypothesized that chicken embryos memorize the chemical signals of the maternal diet and that this perceptual learning may orient subsequent feeding behavior of the hatchlings.

Methodology/Principal Findings

Laying hens were fed standard food enriched with 2% menhaden oil (MH group) or 2% soybean oil (controls). The scent of menhaden was significantly more detected in MH egg yolks than in control yolks by a human panel. We analyzed the development and behavior of offspring towards different types of food, bearing or not bearing the menhaden scent. When chicks were exposed to a 3-min choice test between the familiar food bearing the menhaden scent and the familiar food without menhaden, no effect of treatment was observed. In a 3-min choice test with unfamiliar food (mashed cereals) MH chicks showed a clear positive orientation toward the unfamiliar food bearing the menhaden scent. By contrast, control chicks showed a preference for the non-odorized unfamiliar food. MH chicks expressed higher emotional reactivity level than control chicks as expressed by food neophobia and longer immobility in a restraint test.

Conclusion/Significance

Chicks exposed in ovo to menhaden oil via the maternal diet preferentially oriented their feeding behavior towards food containing menhaden oil, but only when the food was unfamiliar. We propose that oil in the maternal diet engenders maternal effects and contributes to the development of behavioral phenotype in the offspring. In ovo chemosensory learning may have evolved to prepare precocial offspring for their environment. This suggests a common principle of embryonic chemosensory learning across vertebrate taxa.

A homolog of the vertebrate pituitary adenylate cyclase-activating polypeptide is both necessary and instructive for the rapid formation of associative memory in an invertebrate

Similar to other invertebrate and vertebrate animals, cAMP-dependent signaling cascades are key components of long-term memory (LTM) formation in the snail Lymnaea stagnalis, an established experimental model for studying evolutionarily conserved molecular mechanisms of long-term associative memory. Although a great deal is already known about the signaling cascades activated by cAMP, the molecules involved in the learning-induced activation of adenylate cyclase (AC) in Lymnaea remained unknown. Using matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy in combination with biochemical and immunohistochemical methods, recently we have obtained evidence for the existence of a Lymnaea homolog of the vertebrate pituitary adenylate cyclase-activating polypeptide (PACAP) and for the AC-activating effect of PACAP in the Lymnaea nervous system. Here we first tested the hypothesis that PACAP plays an important role in the formation of robust LTM after single-trial classical food-reward conditioning. Application of the PACAP receptor antagonist PACAP6-38 around the time of single-trial training with amyl acetate and sucrose blocked associative LTM, suggesting that in this "strong" food-reward conditioning paradigm the activation of AC by PACAP was necessary for LTM to form. We found that in a "weak" multitrial food-reward conditioning paradigm, lip touch paired with sucrose, memory formation was also dependent on PACAP. Significantly, systemic application of PACAP at the beginning of multitrial tactile conditioning accelerated the formation of transcription-dependent memory. Our findings provide the first evidence to show that in the same nervous system PACAP is both necessary and instructive for fast and robust memory formation after reward classical conditioning.

Stress-related changes in the activity of cocaine- and amphetamine-regulated transcript and nesfatin neurons in the midbrain non-preganglionic Edinger-Westphal nucleus in the rat

Cocaine- and amphetamine-regulated transcript (CART) and nesfatin-1/nucleobindin 2 (NUCB2) are assumed to play a role in feeding and adaptation to stress. Both peptides are highly expressed in the midbrain non-preganglionic Edinger-Westphal nucleus (npEW), a center implicated in the regulation of stress adaptation and in the pathogenesis of stress-induced brain disorders, in a sex-specific manner. The present study was undertaken to test whether CART and nesfatin are involved in these actions of the npEW in the rat. Acute restraint and chronic variable mild stress were used. Following stress, physiological parameters (serum corticosterone levels, body, adrenal and thymus weights) were determined, CART and nesfatin-like immunoreactivity (LI) as well as mRNA expression were analyzed in the npEW nucleus. Our results depict the following changes: (1) Acute stress resulted in an increase in serum corticosterone levels that was higher in females; (2) In males, data on corticosterone and body weight gain and in females, data on body weight gain revealed an effect of chronic stress; (3) Both acute and chronic stress activated npEW neurons expressing CART and nesfatin-LI, as shown by increased cFos immunoreactivity; (4) Chronic, but not acute stress increased the amount of CART and nesfatin-LI in both males and females; (5) Neither acute nor chronic stress had an effect on CART and NUCB2 mRNA contents of npEW neurons in either sex. Taken together, our data suggest that CART and nesfatin are involved in the response of npEW neurons to chronic stress.

Changes in the expression of pituitary adenylate cyclase-activating polypeptide in the human placenta during pregnancy and its effects on the survival of JAR choriocarcinoma cells

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide with survival-promoting actions, has been observed in endocrine organs and is thought to play a role in reproductive functions, including pregnancy. PACAP occurs in two forms, 27 and 38 amino acid residues, with PACAP38 being the predominant form in human tissues. In the present study, we determined the concentrations of PACAP38 and PACAP27 in first-trimester and full-term human placentas using radioimmunoassay. We found high levels of PACAP38 and lower levels of PACAP27 in different parts of the full-term human placenta. PACAP38 content increased in the placenta during pregnancy, both on the maternal side and on the fetal side. The effects of PACAP on the survival of JAR human choriocarcinoma cells were investigated using flow cytometry and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) cell viability assay in cells exposed to the widely used chemotherapeutic agent methotrexate (MTX). It was found that PACAP neither influenced the survival of JAR cytotrophoblast cells nor affected cellular response to the death-inducing effect of the chemotherapeutic agent MTX. The present observations further support the significance of PACAP in the human placenta. The observation that PACAP did not influence the effects of MTX may have future clinical importance, showing that PACAP does not decrease the effects of certain chemotherapeutic agents.

Pituitary adenylate cyclase activating polypeptide (PACAP) and its receptors are present and biochemically active in the central nervous system of the pond snail Lymnaea stagnalis

PACAP is a highly conserved adenylate cyclase (AC) activating polypeptide, which, along with its receptors (PAC1-R, VPAC1, and VPAC2), is expressed in both vertebrate and invertebrate nervous systems. In vertebrates, PACAP has been shown to be involved in associative learning, but it is not known if it plays a similar role in invertebrates. To prepare the way for a detailed investigation into the possible role of PACAP and its receptors in a suitable invertebrate model of learning and memory, here, we undertook a study of their expression and biochemical role in the central nervous system of the pond snail Lymnaea stagnalis. Lymnaea is one of the best established invertebrate model systems to study the molecular mechanisms of learning and memory, including the role of cyclic AMP-activated signaling mechanisms, which crucially depend on the learning-induced activation of AC. However, there was no information available on the expression of PACAP and its receptors in sensory structures and central ganglia of the Lymnaea nervous system known to be involved in associative learning or whether or not PACAP can actually activate AC in these ganglia. Here, using matrix-assisted laser desorption ionization time of flight (MALDI-TOF) and immunohistochemistry, we established the presence of PACAP-like peptides in the cerebral ganglia and the lip region of Lymnaea. The MALDI-TOF data indicated an identity with mammalian PACAP-27 and the presence of a squid-like PACAP-38 highly homologous to vertebrate PACAP-38. We also showed that PACAP, VIP, and maxadilan stimulated the synthesis of cAMP in Lymnaea cerebral ganglion homogenates and that this effect was blocked by the appropriate general and selective PACAP receptor antagonists.

PACAP has anti-apoptotic effect in the salivary gland of an invertebrate species, Helix pomatia

Pituitary adenylate cyclase activating polypeptide (PACAP) shows a remarkable sequence similarity among species and several studies provide evidence that the functions of PACAP have also been conserved among vertebrate species. Relatively little is known about its presence and functions in invertebrates. The aim of the present study was to investigate whether the well-known anti-apoptotic effect of PACAP can also be demonstrated in invertebrates. This effect was studied in the salivary gland of a molluscan species, Helix pomatia. In this work, we first showed the presence of PACAP-like immunoreactivity in the Helix salivary gland by means of immunohistochemistry. Radioimmunoassay measurements showed that PACAP38-like immunoreactivity dominated in the salivary gland of both active and inactive snails and its concentration was higher in active than in inactive animals in contrast to PACAP27-like immunoreactivity, which did not show activity-dependent changes. PACAP induced a significant elevation of cAMP level in salivary gland extracts. Application of apoptosis-inducing agents, dopamine and colchicine, led to a marked increase in the number of terminal uridine deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic cells in the salivary gland, which was significantly attenuated by PACAP treatment. In a similar manner, the number of caspase-positive cells was reduced after co-application of dopamine and PACAP. Taken together, the data indicate that PACAP activates cAMP in a molluscan species and we show, for the first time, that PACAP is anti-apoptotic in the invertebrate Helix pomatia.

Protective effects of pituitary adenylate cyclase activating polypeptide in endothelial cells against oxidative stress-induced apoptosis

Pituitary adenylate cyclase activating polypeptide (PACAP) is a widely distributed neuropeptide that has various different functions in the nervous system and in non-neural tissues. Little is known about the effects of PACAP in endothelial cells. The aim of the present study was to investigate the effects of PACAP on endothelial cell survival and apoptotic signaling pathways under oxidative stress. Mouse hemangioendothelioma (EOMA) cells were exposed to 0.5mM H(2)O(2) which resulted in a marked reduction of cell viability and a parallel increase of apoptotic cells assessed by MTT test and flow cytometry. Co-incubation with 20nM PACAP1-38 increased cell viability and reduced the percentage of apoptotic cells. Flow cytometry analysis showed that oxidative stress reduced the phosphorylation of the anti-apoptotic ERK and increased the phosphorylation of the pro-apoptotic JNK and p38 MAP kinases. PACAP1-38 treatment ameliorated these changes: levels of phospho-ERK were elevated and those of phospho-JNK and p38 were decreased. All these effects were abolished by simultaneous treatment with the PACAP antagonist PACAP6-38. In summary, our results show that PACAP effectively protects endothelial cells against the apoptosis-inducing effects of oxidative stress.

Development of the rhythmic melatonin secretion in the embryonic chicken pineal gland

In order to elucidate details on the development of the circadian clock, the effects of light on the in vitro melatonin (MT) release and the presence of mRNAs of several clock genes in the embryonic chicken pineal gland were investigated. Chicken embryos of various developmental stages were exposed to stimuli of light in vitro in dynamic, four day long bioassay (perifusion). MT secretion and mRNA levels of Cry1, Cry2, Clock and Bmal2 clock genes were determined. Our conclusions: (1) environmental illumination modified MT secretion from explanted embryonic pineal glands as early as on the 13th embryonic day, (2) daily rhythm of MT release develops between embryonic days 16 and 18 under periodic environmental illumination. (3) Chicken Cry1, Cry2, Clock and Bmal2 clock gene mRNAs were also detected in glands of animals of 15th embryonic day. Although both MT secretion and clock genes have been developed by then, the circadian MT rhythm appears first on the 17th embryonic day. Either the mechanisms coupling the clock with the melatonin output or the synchronization of the individual pinealocytes develop around this age. Rhythmic MT release in the embryonic chicken pineal gland evolves only if the egg is exposed to rhythmic environmental stimuli.

Pituitary adenylate cyclase activating polypeptide protects cardiomyocytes against oxidative stress-induced apoptosis

Pituitary adenylate cyclase activating polypeptide (PACAP) has well-known neuroprotective effects, and one of the main factors leading to neuroprotection seems to be its anti-apoptotic effects. The peptide and its receptors are present also in the heart, but whether PACAP can be protective in cardiomyocytes, is not known. Therefore, the aim of the present study was to investigate the effects of PACAP on oxidative stress-induced apoptosis in cardiomyocytes. Our results show that PACAP increased cell viability by attenuating H2O2-induced apoptosis in a cardiac myocyte culture. PACAP also decreased caspase-3 activity and increased the expression of the anti-apoptotic markers Bcl-2 and phospho-Bad. These effects of PACAP were counteracted by the PACAP antagonist PACAP6-38. In summary, our results show that PACAP is able to attenuate oxidative stress-induced cardiomyocyte apoptosis.