Regensburg, Univ., Diss., 2008

Alcohol Use Disorders (AUDs) have devastating economic, mortality, and public health implications on society. Repeated cycles of alcohol intoxication and abstinence are known to induce neuroplastic alterations in specific brain regions, alterations which in turn trigger and sustain excessive alcohol drinking. The Bed Nucleus of the Stria Terminalis (BNST) has been proposed as a critical brain site for neuroadaptations induced by chronic alcohol. The Pituitary Adenylate-Cyclase Activating Polypeptide (PACAP) system highly expressed in the BNST, has been proposed to be a master regulator of the stress response. These experiments aimed to investigate the role of the PACAP system of the BNST in alcohol drinking. Using a two-bottle choice chronic intermittent ethanol paradigm, we demonstrated that excessive intermittent alcohol consumption causes a marked increase in PACAP immunoreactivity in the BNST of mice. In addition, we observed a significant higher PACAP expression in the BNST of female, compared to male mice. These data lay the foundation for more extensive studies which may lead to the identification of a neuropeptide system with a critical role in heavy alcohol drinking. A deeper understanding of the specific neuroadaptations produced by chronic alcohol will be essential for the discovery of novel therapeutic agents to alleviate alcoholism. / 2019-07-11T00:00:00Z

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Endogenous peptides modulate a wide range of physiological conditions in the central and peripheral nervous systems, but have not been harnessed to perform similar functions in pharmaceutical roles due to their ease of degradation and difficulty in introducing into the neurovascular unit. We report herein advances that evidence the wide applicability that glycosylation provides as a pathway for improving the drug-like properties of peptides. This is demonstrated by utilizing novel sugar-amino acids to modify the potent mu opioid receptor agonist DAMGO to provide antinociception, and serine glycosides to modify secretin family peptides for neuroprotection and angiotensin-(1-7) to both reduce cognitive impedance following myocardial infarction and as a treatment for peripheral neuropathy. Evidence is presented via a series of in vitro and in vivo models and assays, and demonstrates the advantageous effects of glycosylation through increased persistence in serum, greatly improved blood-brain barrier penetration, and the tolerance of receptor interactions to the addition of a carbohydrate.

Pituitary adenylate cyclase activating polypeptide (PACAP) is associated with Alzheimer's disease (AD), but its age-related effects are unknown. We chose the rhesus macaque due to its closeness to human anatomy and physiology. We examined four variables: aging, cognitive performance, amyloid plaques and PACAP. Delayed nonmatching-to-sample recognition memory scores declined with age and correlated with PACAP levels in the striatum, parietal and temporal lobes. Because amyloid plaques were the only AD pathology in the old rhesus macaque, we further studied human amyloid precursor protein (hAPP) transgenic mice. Aging was associated with decreased performance in the Morris Water Maze (MWM). In wild type (WT) C57BL/ 6 mice, the performance was decreased at age 24-26 month whereas in hAPP transgenic mice, it was decreased as early as 9-12 month. Neuritic plaques in adult hAPP mice clustered in hippocampus and adjacent cortical regions, but did not propagate further into the frontal cortex. Cerebral PACAP protein levels were reduced in hAPP mice compared to age-matched WT mice, but the genetic predisposition dominated cognitive decline. Taken together, these data suggest an association among PACAP levels, aging, cognitive function and amyloid load in nonhuman primates, with both similarities and differences from human AD brains. Our results suggest caution in choosing animal models and in extrapolating data to human AD studies.

Stress is one of the leading predisposing factors for the onset of anxiety and depression. The mechanisms underlying stress vulnerability remain not fully understood and this gap significantly delays the advancement of the biomedical field. Pituitary adenylate cyclase-activating polypeptide (PACAP), a 38-amino acid peptide, has been proposed to regulate the stress response by acting at multiple levels. The central hypothesis of this work was that the PACAP system of the extended amygdala, a basal forebrain structure that includes the central nucleus of the amygdala (CeA) and the bed nucleus of the stria terminalis (BNST), plays a critical role in the physiological and pathological behavioral response to stress. I found that central (intracerebroventricular) administration of PACAP in rats is able to produce a depressive-like endophenotype, as measured by increased current threshold for intracranial self-stimulation (ICSS), reduced preference for a sweet solution, and reduced time spent interacting with a novel animal in a social interaction test. I then went on investigating the brain structures and mechanisms contributing to PACAP-induced behavioral effects. I found that microinfusion of PACAP, but not VIP, into the CeA and BNST caused a dose-dependent increase in acoustic startle response (ASR), a rapid defensive reflex that is an index of stress. In addition, PACAP(6-38) infusions into either of these structures was instead able to prevent the sensitization of ASR induced by footshock stress, in line with the observation that the acute exposure to footshock stress induced a significant increase in PACAP, but not VIP, levels in both the CeA and the BNST. Finally, I found that the continuous recruitment of the PACAP system of the CeA was essential to the emergence of the negative outcomes of chronic stress. Indeed, chronic social defeat stress significantly increased PACAP levels in the CeA, but not the BNST; furthermore, viral vector-mediated knockdown of the PACAP receptor PAC1R in the CeA significantly attenuated decreased body weight gain, decreased saccharin consumption, and heightened anxiety-like behavior induced by chronic social defeat and also prevented the increase in CeA corticotropin-releasing factor (CRF) levels. The results obtained provide novel insights into the neurobiological mechanisms underlying the psychopathological consequences of stress. / 2020-06-12T00:00:00Z

The neuropeptide PACAP is found in neurons of the prefrontal cortex, hippocampus, thalamus, hypothalamus, and brainstem. PACAP-38 and the truncated PACAP-27 are produced via cleavage of the 176 amino acid precursor (prepro-PACAP). These peptides act at class B G protein-coupled receptors (GPCRs); PAC1 receptor (PAC1R) is the PACAP selective receptor, binding PACAP with an affinity 1000-fold greater compared to the vasoactive intestinal peptide (VIP). PACAP neurons send widespread projections to regions of the brain that regulate arousal and behavioral states, including the nucleus accumbens and the extended amygdala. The PACAP system is recognized as a key master regulator of the stress response as it regulates the autonomic, endocrine, as well as behavioral response to stress. Notably, the brain PACAP system, recruited after exposure to stress, stays active when the stressor persists, and mediates the detrimental effects of chronic stress. Evidence indicates that the PACAP system is dysregulation in specific neural circuits in several stress-related and trauma-related disorders, but also in addiction. Here, we will review evidence that PACAP is implicated in the pathophysiology of several psychiatric disorders by reviewing current preclinical and clinical evidence, with a focus on the brain regions and circuits where the dysregulated PACAP signaling may mediate the abnormal behaviors. The data available suggest that blocking PAC1R would have beneficial effects and warrant the further investigation of the topic, with the ultimate goal of developing small molecule antagonists for PAC1R for the treatment of stress-related disorders, PTSD, and addiction. / 2025-02-01T00:00:00Z

Le PACAP38 est un polypeptide endogène secrété par le thalamus exerçant différents rôles physiologiques tels que vasodilatateur, immunomodulateur ou encore, analgésique. Selon certaines études, il aurait, également, un impact sur les processus cognitifs au niveau de l’hippocampe. Cependant, son mécanisme d’action est assez peu connu. Son analogue, récemment synthétisé, a, quant à lui, été très peu étudié. Il s'agit d'une version beaucoup plus stable et avec une meilleure affinité aux récepteurs au PACAP que le peptide natif.Le travail effectué et présenté dans ce mémoire a permis de comparer les effets du PACAP38 et de son analogue sur le processus de mémorisation chez des rats ayant subit des expériences de navigation spatiale hippocampo-dépendante.Lors du test de l'objet déplacé (OLT), nous avons montré qu'une dose de 30 µg/kg de PACAP38 injecté en intraveineuse améliore la consolidation de la mémoire chez des rats souffrant de troubles cognitifs induits par une injection en intrapéritonéale de lipopolysaccharides ou d'ifenprodil. L'analogue n'a, quant à lui, pas permis de réduire ces troubles.Lors du test de la piscine de Morris, le PACAP38 a exercé un effet promnésique mais pas l'analogue.Il s'est avéré que le PACAP38 contribue à l'amélioration des processus cognitifs par son activité antioxydante, en régulant les taux de cytokines pro et anti-inflammatoires et les taux de BDNF centraux d'une manière plus efficace que celle de l'analogue. / PACAP38 is an endogenous polypeptide secreted by the thalamus. It is exerting different physiological roles such as vasodilator, immunomodulator or analgesic. According to some studies, it would also have an impact on cognitive processes in the hippocampus. However, its action mechanism is relatively unknown. Its analog, recently synthesized, has, for its part, been studied very little. It is a much more stable version with better affinity to PACAP receptors than the native peptide.The work performed compares the effects of PACAP38 and its analog on memory process in rats that had undergone hippocampo-dependent spatial navigation experiments.In the object location test (OLT), we have shown that a 30 µg/kg dose of PACAP38 injected intravenously improves memory consolidation in rats with cognitive impairment induced by intraperitoneal injection of lipopolysaccharides or ifenprodil. The analog was not able to reduce these disorders.In the Morris water maze test, PACAP38 exerted a promnesic effect but not the analog.It has been found that PACAP38 contributes to the improvement of cognitive processes by its antioxidant activity, by regulating pro and anti-inflammatory cytokine levels and central BDNF levels in a more efficient manner than the analog. .

Chronic pain alters sensory responses and carries a strong emotional component. Persistent pain can heighten pain experiences, resulting in hyperalgesia and allodynia. Further, patients suffering from chronic pain are more prone to experience a range of affective disorders including depression, sleep dysregulation, panic disorders, anxiety abnormalities and stress-related disorders including post-traumatic stress disorder (PTSD). Hence while pain serves a protective function to prevent additional physiological harm by driving behavioral and cognitive responses, chronic or persistent pain can lead to maladaptive nociceptive responses and exacerbate psychopathologies. Among brain regions, the amygdala is centrally situated to integrate the many descending and ascending signals to modulate the sensory and emotional components of pain. The amygdala is well studied for its role in fear and stress-related behavioral processes. The central nucleus of the amygdala (CeA), and in particular the lateral capsular subdivision of the CeA (CeLC), receives prominent ascending pain neurotransmission via the spino- parabrachioamygdaloid tract. In this pathway, peripheral nociceptive signals carried via primary sensory Aδ- and C-fibers terminate in the dorsal horn where second order neurons send projections via the spino-parabrachial pathway to the lateral parabrachial nucleus (LPBn). Thus, the LPBn collects cutaneous (mechanical and thermal), deep (muscular and articular) and visceral nociceptive signals and relays the information in a highly organized manner principally to the CeLC for nociceptive processing. In pain, the CeA and the LPBn-CeLC projections have been shown to undergo plasticity in the forms of enhanced synaptic transmission and alterations in neurotransmitter and receptor expression. Accordingly, the neurocircuit intersections in the CeA can modulate the sensory and emotional responses to pain. Yet despite these associations, the mediators and mechanisms underlying the emotional consequences of pain are poorly understood. Pituitary adenylate cyclase activating polypeptide (PACAP) is a neural and endocrine pleiotropic peptide important in the development and homeostatic regulation of many physiological systems. Recently, the expression of PACAP and its cognate PAC1 receptor has been shown to be upregulated in specific limbic regions by chronic stress. PACAP infusions into several limbic regions is anxiogenic, and altered blood PACAP levels and PAC1 receptor polymorphism have been associated with PTSD and other stress-related disorders. Here, we establish that CeLC PACAP originates from the LPBn as part of the spino-parabrachoamygdaloid pathway. Chronic pain enhanced PACAP expression along LPBn-CeLC projections, indicating it may be a component of pain- related plasticity. CeA PACAP signaling was sufficient to induce nociceptive hypersensitivity and anxiety-like behaviors. In a chronic neuropathic pain model, CeA PACAP signaling was found to contribute to heightened anxiety-like behaviors and nociceptive responses. Further, we characterized one prominent intracellular signaling mechanism through which CeA PACAP signaling influences these behaviors. In these experiments we provide evidence that CeA PACAP signaling plays an important role in the emotional components of pain and that alterations in CeA PACAP signaling are part of pain-related plasticity. This work establishes novel molecular mechanisms that underlie the emotional component of pain and may contribute to the development of chronic pain and associated affective disorders.

The abuse of and addiction to drugs of abuse, such as tobacco, alcohol, opioids, and illicit drugs, are growing global problems that affect the welfare of individuals and societies worldwide. The National Institute of Drug Abuse estimates the annual cost of substance abuse to be over $740 billion in costs related to drug intoxication, withdrawal and relapse. A primary challenge in the treatment of substance abuse is the tendency of users to relapse following acute or extended periods of abstinence; on average over 60% of substance abusers will return to drug use within a year of receiving treatment, many relapsing following stressful life events. Central to the successful treatment of drug addiction is understanding the cellular mechanisms by which relapse episodes occur. Current data suggest that the activation of pituitary adenylate cyclase activating peptide (PACAP) systems in the bed nucleus of the stria terminalis (BNST) is an important event underlying stress-induced reinstatement to drug-seeking in a rodent model of stress-induced relapse. In conjunction with immunohistochemistry and pharmacological treatments, we used this behavioral model of stress-induced relapse to evaluate PACAP and PACAP type-1 receptor (PAC1-R) signaling in stress-induced reinstatement to cocaine seeking. Activation of the PAC1 receptor appears to be critical to stress-induced reinstatement, as the selective PAC1-R agonist, maxadilan, produced reinstatement behaviors in the absence of stress. Moreover, BNST pretreatment with either mitogen activated protein kinase-ERK (MEK) or endocytosis inhibitors to block extracellular signal-related kinase (ERK) signaling attenuated stress-induced reinstatement. Furthermore, BNST phosphorylated ERK (pERK) expression, mediated by PAC1-R activation, is substantially potentiated in cocaine-experienced animals after stressor exposure, in a manner that is dependent on endosomal signaling and MEK activity. These data suggest that the activation of a PAC1 signaling cascade is a key event underlying stress-induced reinstatement. Furthermore, this data may suggest a permanent change in the BNST PACAP system (sensitization) following cocaine exposure.