Acetylcholine Engages Distinct Amygdala Microcircuits to Gate Internal Theta Rhythm.

Acetylcholine (ACh) is released from basal forebrain cholinergic neurons in response to salient stimuli and engages brain states supporting attention and memory. These high ACh states are associated with theta oscillations, which synchronize neuronal ensembles. Theta oscillations in the basolateral amygdala (BLA) in both humans and rodents have been shown to underlie emotional memory, yet their mechanism remains unclear. Here, using brain slice electrophysiology in male and female mice, we show large ACh stimuli evoke prolonged theta oscillations in BLA local field potentials that depend upon M3 muscarinic receptor activation of cholecystokinin (CCK) interneurons (INs) without the need for external glutamate signaling. Somatostatin (SOM) INs inhibit CCK INs and are themselves inhibited by ACh, providing a functional SOM→CCK IN circuit connection gating BLA theta. Parvalbumin (PV) INs, which can drive BLA oscillations in baseline states, are not involved in the generation of ACh-induced theta, highlighting that ACh induces a cellular switch in the control of BLA oscillatory activity and establishes an internally BLA-driven theta oscillation through CCK INs. Theta activity is more readily evoked in BLA over the cortex or hippocampus, suggesting preferential activation of the BLA during high ACh states. These data reveal a SOM→CCK IN circuit in the BLA that gates internal theta oscillations and suggest a mechanism by which salient stimuli acting through ACh switch the BLA into a network state enabling emotional memory.

A Cholecystokinin Analogue Ameliorates Cognitive Deficits and Regulates Mitochondrial Dynamics via the AMPK/Drp1 Pathway in APP/PS1 Mice.

BACKGROUND: There are no drugs on the market that can reverse or slow Alzheimer's disease (AD) progression. A protease-resistant Cholecystokinin (CCK) analogue used in this study is based on the basic structure of CCK, which further increases the stability of the peptide fragment and prolongs its half-life in vivo. We observed a neuroprotective effect of CCK-8L in APPswe/PS1dE9 (APP/PS1) AD mice. However, its corresponding mechanisms still need to be elucidated. OBJECTIVE: This study examined CCK-8L's neuroprotective effects in enhancing cognitive impairment by regulating mitochondrial dynamics through AMPK/Drp1 pathway in the APP/PS1 AD mice. METHODS: Behavioural tests are applied to assess competence in cognitive functions. Transmission electron microscopy (TEM) was performed to observe the ultrastructure of mitochondria of hippocampal neurons, Immunofluorescent staining was employed to assay for Aß1-42, APP, Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and dynamin-related protein1 (Drp1). CRISPR/Cas9 was utilized for targeted knockout of the CCKB receptor (CCKBR) in the mouse APP/PS1 hippocampal CA1 region. A model of lentiviral vector-mediated overexpression of APP in N2a cells was constructed. RESULTS: In vivo, experiments revealed that CCK analogue and liraglutide significantly alleviated cognitive deficits in APP/PS1 mice, reduced Aß1-42 expression, and ameliorated l damage, which is associated with CCKBR activation in the hippocampal CA1 region of mice. In vitro tests showed that CCK inhibited mitochondrial fission and promoted fusion through AMPK/Drp1 pathway. CONCLUSIONS: CCK analogue ameliorates cognitive deficits and regulates mitochondrial dynamics by activating the CCKB receptor and the AMPK/Drp1 pathway in AD mice.

A new experimental rat model of nocebo-related nausea involving double mechanisms of observational learning and conditioning.

AIM: The nocebo effect, such as nausea and vomiting, is one of the major reasons patients discontinue therapy. The underlying mechanisms remain unknown due to a lack of reliable experimental models. The goal of this study was to develop a new animal model of nocebo-related nausea by combining observational learning and Pavlovian conditioning paradigms. METHODS: Male Sprague-Dawley rats with nitroglycerin-induced migraine were given 0.9% saline (a placebo) or LiCl (a nausea inducer) following headache relief, according to different paradigms. RESULTS: Both strategies provoked nocebo nausea responses, with the conditioning paradigm having a greater induction impact. The superposition of two mechanisms led to a further increase in nausea responses. A preliminary investigation of the underlying mechanism revealed clearly raised peripheral and central cholecystokinin (CCK) levels, as well as specific changes in the 5-hydroxytryptamine and cannabinoid systems. Brain networks related to emotion, cognition, and visceral sense expressed higher c-Fos-positive neurons, including the anterior cingulate cortex (ACC), insula, basolateral amygdala (BLA), thalamic paraventricular nucleus (PVT), hypothalamic paraventricular nucleus (PVN), nucleus tractus solitarius (NTS), periaqueductal gray (PAG), and dorsal raphe nucleus-dorsal part (DRD). We also found that nausea expectances in the model could last for at least 12 days. CONCLUSION: The present study provides a useful experimental model of nocebo nausea that might be used to develop potential molecular pathways and therapeutic strategies for nocebo.

TRPV1 enhances cholecystokinin signaling in primary vagal afferent neurons and mediates the central effects on spontaneous glutamate release in the NTS.

The gut peptide cholecystokinin (CCK) is released during feeding and promotes satiation by increasing excitation of vagal afferent neurons that innervate the upper gastrointestinal tract. Vagal afferent neurons express CCK1 receptors (CCK1Rs) in the periphery and at central terminals in the nucleus of the solitary tract (NTS). While the effects of CCK have been studied for decades, CCK receptor signaling and coupling to membrane ion channels are not entirely understood. Previous findings have implicated L-type voltage-gated calcium channels as well as transient receptor potential (TRP) channels in mediating the effects of CCK, but the lack of selective pharmacology has made determining the contributions of these putative mediators difficult. The nonselective ion channel transient receptor potential vanilloid subtype 1 (TRPV1) is expressed throughout vagal afferent neurons and controls many forms of signaling, including spontaneous glutamate release onto NTS neurons. Here we tested the hypothesis that CCK1Rs couple directly to TRPV1 to mediate vagal signaling using fluorescent calcium imaging and brainstem electrophysiology. We found that CCK signaling at high concentrations (low-affinity binding) was potentiated in TRPV1-containing afferents and that TRPV1 itself mediated the enhanced CCK1R signaling. While competitive antagonism of TRPV1 failed to alter CCK1R signaling, TRPV1 pore blockade or genetic deletion (TRPV1 KO) significantly reduced the CCK response in cultured vagal afferents and eliminated its ability to increase spontaneous glutamate release in the NTS. Together, these results establish that TRPV1 mediates the low-affinity effects of CCK on vagal afferent activation and control of synaptic transmission in the brainstem.NEW & NOTEWORTHY Cholecystokinin (CCK) signaling via the vagus nerve reduces food intake and produces satiation, yet the signaling cascades mediating these effects remain unknown. Here we report that the capsaicin receptor transient receptor potential vanilloid subtype 1 (TRPV1) potentiates CCK signaling in the vagus and mediates the ability of CCK to control excitatory synaptic transmission in the nucleus of the solitary tract. These results may prove useful in the future development of CCK/TRPV1-based therapeutic interventions.

Central effects of the serotoninergic, GABAergic, and cholecystokinin systems on neuropeptide VF (NPVF)-induced hypophagia and feeding behavior in neonatal broiler chicken.

The study was performed to evaluate the role of central serotoninergic, GABAergic, and cholecystokinin systems in neuropeptide VF (NPVF)-induced hypophagia in broiler chickens. In this study, 9 experiments were designed, each with one control and three treatment groups (n = 44 in each experiment). Control chicks of all groups were subjected to normal saline + Evans blue 0.1 % Intracerebroventricular (ICV) injection. In the first experiment, 3 groups of chicks received NPVF (4, 8, and 16 nmol). In experiment 2-9, one group of chicks received NPVF (16 nmol), another received 10 µg fluoxetine (serotonin reuptake inhibitor) (experiment 2), 1.25 µg PCPA (serotonin synthesis inhibitor) (experiment 3), 1.5 µg SB-242,084 (5-HT2C receptor antagonist) (experiment 4), 15.25 nmol 8-OH-DPAT (5-HT1A receptor antagonist) (experiment 5), 0.5 µg picrotoxin (GABAA receptor antagonist) (experiment 6), 20 ng CGP54626 (GABAB receptor antagonist) (experiment 7), 1 nmol devazepide (CCKA receptor antagonist) (experiment 8), and 1 nmol/L-365(-|-),260 (CCKB receptor antagonist) (experiment 9), and another final group received combination of specific neurotransmitter + NPVF Then, the cumulative food intake was measured until 120 min post-injection. ICV injection of NPVF (8 and 16 nmol) significantly decreased food intake (P < 0.05). Simultaneous injection of fluoxetine + NPVF and also picrotoxin + NPVF significantly increased hypophagia caused by NPVF (P < 0.05). However, co-administration of PCPA + NPVF and also SB242084 + NPVF significantly decreased NPVF-induced hypophagia (P < 0.05). Finally, 8-OH-DPAT, CGP54626, devazepide, and L-365,260 had no effect on the hypophagia brought on by NPVF (P > 0.05). Count-type behaviors were dose-dependent and decreased in groups that received NPVF compared to the control group (P < 0.05). Our finding recommended an interconnection between central NPVF and serotoninergic, GABAergic, and cholecystokinin systems in neonatal chickens.

Effect of cholecystokinin on small intestinal motility in suncus murinus.

In a fasting gastrointestinal tract, a characteristic cyclical rhythmic migrating motor complex (MMC) occur that comprises of three phases: I, II, and III. Among these, phase III contractions propagate from the stomach to the lower intestine in mammals, including humans, dogs, and Suncus murinus (suncus). Apart from the phase III of MMC propagating from the stomach, during the gastric phase II, small intestine-originated strong contractions propagate to the lower small intestine; however, the mechanism of contractions originating in the small intestine has not been clarified. In this study, we aimed to elucidate the role of cholecystokinin (CCK) in small intestinal motility. Administration of sulfated CCK-8 in phase I induced phase II-like contractions in the small intestine, which lasted for approximately 10-20 min and then returned to the baseline, while no change was observed in the stomach. Contractions of small intestine induced by CCK-8 were abolished by lorglumide, a CCK1 receptor antagonist. Gastrin, a ligand for the CCK2 receptor, evoked strong contractions in the stomach, but did not induce contractions in the small intestine. To examine the effect of endogenous CCK on contractions of small intestinal origin, lorglumide was administered during phase II. However, there was no change in the duodenal motility pattern, and strong contractions of small intestinal origin were not abolished by treatment with lorglumide. These results suggest that exogenous CCK stimulates contractions of small intestine via CCK1 receptors, whereas endogenous CCK is not involved in the strong contractions of small intestinal origin.

Boar sperm motility is modulated by CCK at a low concentration of bicarbonate under capacitation conditions.

In a previous study, our group detected the cholecystokinin (CCK) protein in the porcine oviduct. This fact, together with the involvement of CCK in the regulation of sperm protein tyrosine phosphorylation by the modulation of HCO3 - uptake (in mice and humans) suggests a role for CCK during sperm capacitation. Therefore, on the one hand, the expression of CCK receptors (CCK1R and CCK2R) on boar testes has been investigated and probed; on the other hand, boar spermatozoa (from seminal doses of 1-day and 5-day storage) were exposed to different concentrations of CCK (0-control, 25 or 50 µM) in a medium supporting capacitation supplemented with 0, 5 or 25 mmol/L of HCO3 - for 1 h at 38.5°C. Sperm motion (total and progressive motility), kinetic parameters, viability, acrosome status, and mitochondrial activity were determined. No differences between groups (0, 25 or 50 µM of CCK) were observed when HCO3 - was absent in the media (p > .05). However, the results showed that when the media was supplemented with 5 mmol/L HCO3 - in 1-day seminal dose storage, the linearity index (LIN, %), straightness index (STR, %) and oscillation index (WOB, %) (sperm kinetics parameters) increased in the presence of CCK regardless the concentration (p < .05). Nevertheless, CCK in sperm from 5-day storage only increased the WOB parameter in comparison to the control (p < .05). Furthermore, the average amplitude of the lateral displacement of the sperm head (ALH, µm) and curvilinear velocity (VCL, µm/s) decreased when CCK was present, depending on its concentration and sperm aging (1-day vs. 5-days) (p < .05). In the case of the media supporting capacitation supplemented with 25 mmol/L HCO3 - , any differences were observed except for sperm viability in the 5-day seminal doses, which increased in the 50 µM-CCK group compared to the control (p < .05). In conclusion, these data suggest an implication of CCK protein during sperm capacitation under low bicarbonate concentration increasing the sperm linear trajectory.

Cultured Vagal Afferent Neurons as Sensors for Intestinal Effector Molecules.

The gut-brain axis embodies the bi-directional communication between the gastrointestinal tract and the central nervous system (CNS), where vagal afferent neurons (VANs) serve as sensors for a variety of gut-derived signals. The gut is colonized by a large and diverse population of microorganisms that communicate via small (effector) molecules, which also act on the VAN terminals situated in the gut viscera and consequently influence many CNS processes. However, the convoluted in vivo environment makes it difficult to study the causative impact of the effector molecules on VAN activation or desensitization. Here, we report on a VAN culture and its proof-of-principle demonstration as a cell-based sensor to monitor the influence of gastrointestinal effector molecules on neuronal behavior. We initially compared the effect of surface coatings (poly-L-lysine vs. Matrigel) and culture media composition (serum vs. growth factor supplement) on neurite growth as a surrogate of VAN regeneration following tissue harvesting, where the Matrigel coating, but not the media composition, played a significant role in the increased neurite growth. We then used both live-cell calcium imaging and extracellular electrophysiological recordings to show that the VANs responded to classical effector molecules of endogenous and exogenous origin (cholecystokinin serotonin and capsaicin) in a complex fashion. We expect this study to enable platforms for screening various effector molecules and their influence on VAN activity, assessed by their information-rich electrophysiological fingerprints.

Cholecystokinin B receptor antagonists for the treatment of depression via blocking long-term potentiation in the basolateral amygdala.

Depression is a common and severe mental disorder. Evidence suggested a substantial causal relationship between stressful life events and the onset of episodes of major depression. However, the stress-induced pathogenesis of depression and the related neural circuitry is poorly understood. Here, we investigated how cholecystokinin (CCK) and CCKBR in the basolateral amygdala (BLA) are implicated in stress-mediated depressive-like behavior. The BLA mediates emotional memories, and long-term potentiation (LTP) is widely considered a trace of memory. We identified that the cholecystokinin knockout (CCK-KO) mice impaired LTP in the BLA, while the application of CCK4 induced LTP after low-frequency stimulation (LFS). The entorhinal cortex (EC) CCK neurons project to the BLA and optogenetic activation of EC CCK afferents to BLA-promoted stress susceptibility through the release of CCK. We demonstrated that EC CCK neurons innervate CCKBR cells in the BLA and CCK-B receptor knockout (CCKBR-KO) mice impaired LTP in the BLA. Moreover, the CCKBR antagonists also blocked high-frequency stimulation (HFS) induced LTP formation in the BLA. Notably, CCKBR antagonists infusion into the BLA displayed an antidepressant-like effect in the chronic social defeat stress model. Together, these results indicate that CCKBR could be a potential target to treat depression.

Anatomical basis of gastrin- and CCK-secreting cells and their functions. A review.

Gastrin and CCK (cholecystokinin), gut hormones first secreted after postprandial stages, share the C-terminal amino acids and some types of receptors to be stimulated. Both types of hormone-secreting cells are typical open-type cells which detect foods and their digested elements in the lumen and regulate the secretion of gastric acid and digestive enzymes, gut motility, and satiety. Gastrin cell granules are characterized by their heterogenous ultrastructure within the cell, while CCK cell granules show a uniform ultrastructural figure. Gastrin cells are equipped with peptone receptor GPR92, amino acid receptor GPRC6A, and a Ca-sensing receptor. In addition to nutrient receptors, the release of CCK is regulated by a unique negative feedback mechanism. Development of an antibody for CCK-specific receptor (CCK-1R) has revealed its exact localization throughout the body, but specific antibodies against CCK-2R remain unavailable. Gastrin affects differentiation and proliferation-including cancer cells, while CCK possesses trophic effects to target tissues. CCK is a peripheral satiety signal and acts either via the vagus or directly on the dorsal medulla via CCK-1R. In this review, endocrine cells secreting these unique and so-called old gut hormones are described on a morphological basis.

Cholecystokinin Signaling can Rescue Cognition and Synaptic Plasticity in the APP/PS1 Mouse Model of Alzheimer's Disease.

Synaptic impairment and loss are an important pathological feature of Alzheimer's disease (AD). Memory is stored in neural networks through changes in synaptic activity, and synaptic dysfunction can cause cognitive dysfunction and memory loss. Cholecystokinin (CCK) is one of the major neuropeptides in the brain, and plays a role as a neurotransmitter and growth factor. The level of CCK in the cerebrospinal fluid is decreased in AD patients. In this study, a novel CCK analogue was synthesized on the basis of preserving the minimum bioactive fragment of endogenous CCK to investigate whether the novel CCK analogue could improve synaptic plasticity in the hippocampus of the APP/PS1 transgenic mouse model of AD and its possible molecular biological mechanism. Our study found that the CCK analogue could effectively improve spatial learning and memory, enhance synaptic plasticity in the hippocampus, normalize synapse numbers and morphology and the levels of key synaptic proteins, up-regulate the PI3K/Akt signaling pathway and normalize PKA, CREB, BDNF and TrkB receptor levels in APP/PS1 mice. The amyloid plaque load in the brain was reduced by CCK, too. The use of a CCKB receptor antagonist and targeted knockdown of the CCKB receptor (CCKBR) attenuated the neuroprotective effect of the CCK analogue. These results demonstrate that the neuroprotective effect of CCK analogue is achieved by activating the PI3K/Akt as well as the PKA/CREB-BDNF/TrkB signaling pathway that leads to protection of synapses and cognition.

The administration of Exendin-4 and CCK affects food intake differentially in female and male rats tested on an alternate day fasting paradigm.

Alternate day fasting (ADF) which involves the repetition of a 2-day cycle of a day of free access to food followed by a day of limited or no access to food, is an effective dietary intervention for weight loss in both humans and rats. We have previously reported that when presented with a high energy (HE) and standard chow diet, rats maintained on an ADF schedule displayed decreased HE diet preference compared to controls. Both male and female ADF rats increased overall intake of chow. However, this increase was driven by both meal size and meal number for males and only number of meals for females. Administration of cholecystokinin (CCK) or the glucagon-like peptide 1 (GLP-1) receptor agonist Exendin-4 (Ex-4) reduces food intake. It appears that CCK decreases food intake primarily through satiety signals whereas GLP-1 signaling may reduce intake by satiety and reward cues. Here, female and male rats were administered (i.p.) saline, 3.0 µg/kg Ex-4 (3 h before test), 3.0 µg/kg CCK (15 min before test) or a combination of both. Next, all rats were presented 23-h access to both HE diet and chow following food-restriction (ADF) or free access to chow (CON). Compared to saline-control sessions, administration of the combination of Ex-4 and CCK, but not Ex-4 or CCK alone, resulted in a decrease in both HE and chow intake early in the session for male ADF rats but the combination primarily decreased chow diet intake early in the session for female ADF rats. Thus, it appears that under these energy homeostatic conditions, administration of Ex-4 or CCK alone does not affect intake in ADF rats, but the combination produces decreases in feeding that are more than the sum of their individual effects. These findings support a role for the combination of GLP-1 and CCK signaling in the changes in diet preference induced by an alternate day fasting paradigm differentially in female and male rats.

Ca2+ signals in pancreatic acinar cells in response to physiological stimulation in vivo.

The exocrine pancreas secretes fluid and digestive enzymes in response to parasympathetic release of acetylcholine (ACh) via the vagus nerve and the gut hormone cholecystokinin (CCK). Both secretion of fluid and exocytosis of secretory granules containing enzymes and zymogens are dependent on an increase in the cytosolic [Ca2+ ] in acinar cells. It is thought that the specific spatiotemporal characteristics of the Ca2+ signals are fundamental for appropriate secretion and that these properties are disrupted in disease states in the pancreas. While extensive research has been performed to characterize Ca2+ signalling in acinar cells, this has exclusively been achieved in ex vivo preparations of exocrine cells, where it is difficult to mimic physiological conditions. Here we have developed a method to optically observe pancreatic acinar Ca2+ signals in vivo using a genetically expressed Ca2+ indicator and imaged with multi-photon microscopy in live animals. In vivo, acinar cells exhibited baseline activity in fasted animals, which was dependent on CCK1 receptors (CCK1Rs). Both stimulation of intrinsic nervous input and administration of systemic CCK induced oscillatory activity in a proportion of the cells, but the maximum frequencies were vastly different. Upon feeding, oscillatory activity was also observed, which was dependent on CCK1Rs. No evidence of a vago-vagal reflex mediating the effects of CCK was observed. Our in vivo method revealed the spatial and temporal profile of physiologically evoked Ca2+ signals, which will provide new insights into future studies of the mechanisms underlying exocrine physiology and that are disrupted in pathological conditions. KEY POINTS: In the exocrine pancreas, the spatiotemporal properties of Ca2+ signals are fundamentally important for the appropriate stimulation of secretion by the neurotransmitter acetylcholine and gut hormone cholecystokinin. These characteristics were previously defined in ex vivo studies. Here we report the spatiotemporal characteristics of Ca2+ signals in vivo in response to physiological stimulation in a mouse engineered to express a Ca2+ indicator in acinar cells. Specific Ca2+ 'signatures' probably important for stimulating secretion are evoked in vivo in fasted animals, by feeding, neural stimulation and cholecystokinin administration. The Ca2+ signals are probably the result of the direct action of ACh and CCK on acinar cells and not indirectly through a vago-vagal reflex.

Hindbrain ghrelin and liver-expressed antimicrobial peptide 2, ligands for growth hormone secretagogue receptor, bidirectionally control food intake.

Hindbrain growth hormone secretagogue receptor (GHSR) agonism increases food intake, yet the underlying neural mechanisms remain unclear. The functional effects of hindbrain GHSR antagonism by its endogenous antagonist liver-expressed antimicrobial peptide 2 (LEAP2) are also yet unexplored. To test the hypothesis that hindbrain GHSR agonism attenuates the food intake inhibitory effect of gastrointestinal (GI) satiation signals, ghrelin (at a feeding subthreshold dose) was administered to the fourth ventricle (4V) or directly to the nucleus tractus solitarius (NTS) before systemic delivery of the GI satiation signal cholecystokinin (CCK). Also examined, was whether hindbrain GHSR agonism attenuated CCK-induced NTS neural activation (c-Fos immunofluorescence). To investigate an alternate hypothesis that hindbrain GHSR agonism enhances feeding motivation and food seeking, intake stimulatory ghrelin doses were administered to the 4V and fixed ratio 5 (FR-5), progressive ratio (PR), and operant reinstatement paradigms for palatable food responding were evaluated. Also assessed were 4V LEAP2 delivery on food intake and body weight (BW) and on ghrelin-stimulated feeding. Both 4V and NTS ghrelin blocked the intake inhibitory effect of CCK and 4V ghrelin blocked CCK-induced NTS neural activation. Although 4V ghrelin increased low-demand FR-5 responding, it did not increase high-demand PR or reinstatement of operant responding. Fourth ventricle LEAP2 reduced chow intake and BW and blocked hindbrain ghrelin-stimulated feeding. Data support a role for hindbrain GHSR in bidirectional control of food intake through mechanisms that include interacting with the NTS neural processing of GI satiation signals but not food motivation and food seeking.

Neonatal overnutrition, but not neonatal undernutrition, disrupts CCK-induced hypophagia and neuron activation of the nucleus of the solitary tract and paraventricular nucleus of hypothalamus of male Wistar rats.

Metabolic programming may be induced by reduction or enhancement of litter size, which lead to neonatal over or undernutrition, respectively. Changes in neonatal nutrition can challenge some regulatory processes in adulthood, such as the hypophagic effect of cholecystokinin (CCK). In order to investigate the effects of nutritional programming on the anorexigenic function of CCK in adulthood, pups were raised in small (SL, 3 pups per dam), normal (NL, 10 pups per dam), or large litters (LL, 16 pups per dam), and on postnatal day 60, male rats were treated with vehicle or CCK (10 µg/Kg) for the evaluation of food intake and c-Fos expression in the area postrema (AP), nucleus of solitary tract (NTS), and paraventricular (PVN), arcuate (ARC), ventromedial (VMH), and dorsomedial (DMH) nuclei of the hypothalamus. Overnourished rats showed increased body weight gain that was inversely correlated with neuronal activation of PaPo, VMH, and DMH neurons, whereas undernourished rats had lower body weight gain, inversely correlated with increased neuronal activation of PaPo only. SL rats showed no anorexigenic response and lower neuron activation in the NTS and PVN induced by CCK. LL exhibited preserved hypophagia and neuron activation in the AP, NTS, and PVN in response to CCK. CCK showed no effect in c-Fos immunoreactivity in the ARC, VMH, and DMH in any litter. These results indicate that anorexigenic actions, associated with neuron activation in the NTS and PVN, induced by CCK were impaired by neonatal overnutrition. However, these responses were not disrupted by neonatal undernutrition. Thus, data suggest that an excess or poor supply of nutrients during lactation display divergent effects on programming CCK satiation signaling in male adult rats.

Altered neurotransmission in stress-induced depressive disorders: The underlying role of the amygdala in depression.

Depression is the second leading cause of disability in the world population, for which currently available pharmacological therapies either have poor efficacy or have some adverse effects. Accumulating evidence from clinical and preclinical studies demonstrates that the amygdala is critically implicated in depressive disorders, though the underlying pathogenesis mechanism needs further investigation. In this literature review, we overviewed depression and the key role of Gamma-aminobutyric acid (GABA) and Glutamate neurotransmission in depression. Notably, we discussed a new cholecystokinin-dependent plastic changes mechanism under stress and a possible antidepressant response of cholecystokinin B receptor (CCKBR) antagonist. Moreover, we discussed the fundamental role of the amygdala in depression, to discuss and understand the pathophysiology of depression and the inclusive role of the amygdala in this devastating disorder.

Cholecystokinin Activation of Cholecystokinin 1 Receptors: a Purkinje Cell Neuroprotective Pathway.

This is a summary of the virtual presentation given at the 2021 meeting of the Society for Research on the Cerebellum and Ataxias, https://www.meetings.be/SRCA2021/ , where the therapeutic potential of the CCK-CCK1R pathway for treating diseases involving Purkinje cell degeneration was presented. Spinocerebellar ataxia type 1 (SCA1) is one of a group of almost 50 genetic diseases characterized by the degeneration of cerebellar Purkinje cells. The SCA1 Pcp2-ATXN1[30Q]D776 mouse model displays ataxia, i.e. Purkinje cell dysfunction, but lacks progressive Purkinje cell degeneration. RNA-seq revealed increased expression of cholecystokinin (CCK) in cerebella of Pcp2-ATXN1[30Q]D776 mice. Importantly, the absence of Cck1 receptor (CCK1R) in Pcp2-ATXN1[30Q]D776 mice conferred a progressive degenerative disease with Purkinje cell loss. Administration of a CCK1R agonist to Pcp2-AXTN1[82Q] mice reduced Purkinje cell pathology and associated deficits in motor performance. In addition, administration of the CCK1R agonist improved motor performance of Pcp2-ATXN2[127Q] SCA2 mice. Furthermore, CCK1R activation corrected mTORC1 signaling and improved the expression of calbindin in the cerebella of AXTN1[82Q] and ATXN2[127Q] mice. These results support the Cck-Cck1R pathway is a potential therapeutic target for the treatment of diseases involving Purkinje neuron degeneration.

Somatodendritic Release of Cholecystokinin Potentiates GABAergic Synapses Onto Ventral Tegmental Area Dopamine Cells.

BACKGROUND: Neuropeptides are contained in nearly every neuron in the central nervous system and can be released not only from nerve terminals but also from somatodendritic sites. Cholecystokinin (CCK), among the most abundant neuropeptides in the brain, is expressed in the majority of midbrain dopamine neurons. Despite this high expression, CCK function within the ventral tegmental area (VTA) is not well understood. METHODS: We confirmed CCK expression in VTA dopamine neurons through immunohistochemistry and in situ hybridization and detected optogenetically induced CCK release using an enzyme-linked immunosorbent assay. To investigate whether CCK modulates VTA circuit activity, we used whole-cell patch clamp recordings in mouse brain slices. We infused CCK locally in vivo and tested food intake and locomotion in fasted mice. We also used in vivo fiber photometry to measure Ca2+ transients in dopamine neurons during feeding. RESULTS: Here we report that VTA dopamine neurons release CCK from somatodendritic regions, where it triggers long-term potentiation of GABAergic (gamma-aminobutyric acidergic) synapses. The somatodendritic release occurs during trains of optogenetic stimuli or prolonged but modest depolarization and is dependent on synaptotagmin-7 and T-type Ca2+ channels. Depolarization-induced long-term potentiation is blocked by a CCK2 receptor antagonist and mimicked by exogenous CCK. Local infusion of CCK in vivo inhibits food consumption and decreases distance traveled in an open field test. Furthermore, intra-VTA-infused CCK reduced dopamine cell Ca2+ signals during food consumption after an overnight fast and was correlated with reduced food intake. CONCLUSIONS: Our experiments introduce somatodendritic neuropeptide release as a previously unknown feedback regulator of VTA dopamine cell excitability and dopamine-related behaviors.

Food peptides as inducers of CCK and GLP-1 secretion and GPCRs involved in enteroendocrine cell signalling.

The strong effect of protein digestion products on gastrointestinal-released hormones is recognised. However, little is known about the specific peptide sequences able to induce gastrointestinal hormone secretion and the receptors involved. Our objective was to identify peptides able to induce the secretion of cholecystokinin (CCK) and glucagon like peptide-1 (GLP-1) in the enteroendocrine cell line STC-1, and to evaluate the involvement of the calcium-sensing receptor and G-protein coupled receptor-93 in this cell signalling. The key role of the amino acidic sequence on CCK and GLP-1 secretion is demonstrated. Removing Ser from the N-terminus of κ-casein 33SRYPS37, or the N-terminal Trp-Ile in lysozyme 123WIRGCRL129 decreased the secretion of both hormones. However, substituting Tyr by Ala in peptide αs1-CN 90RYLG93 enhanced the CCK secretion levels but not the GLP-1 ones. In addition, the involvement of CaSR and GPR93 was evidenced, but our results pointed to the contribution of additional receptors or transporters.

Interactions of Cholecystokinin and Glutamatergic Systems in Feeding Behavior of Neonatal Chickens.

This study aimed to assess the possible feeding behavior alterations by central interactions of cholecystokinin (CCK) and glutamatergic systems in neonatal chickens. In experiment 1, chickens received intracerebroventricular (ICV) administration of saline and CCK (CCK4; 0.25, 0.5, and 1 nmol). In experiment 2, birds were ICV injected with saline, CCK8s (0.25, 0.5, and 1 nmol). In experiment 3, chickens received the ICV injection of saline, CCK8s (1 nmol), MK-801 (15 nmol), and co-injection of the CCk8s+MK-801. Experiments 4-7 were performed similar to experiment 3, except for chickens that were injected with CNQX (390 nmol), AIDA (2 nmol), LY341495 (150 nmol), and UBP1112 (2 nmol) instead of MK-801. Subsequently, the total amount of the consumed food was determined. According to the results, the ICV administration of CCK4 (0.25, 0.5, and 1 nmol) could not affect the food intake in chickens (P>0.05). The ICV injection of the CCK8s (0.25, 0.5, and 1 nmol) led to a dose-dependent hypophagia (P<0.05). Moreover, hypophagia induced by CCK8s decreased by the co-injection of the CCK8s+MK-801 (P<0.05). These results showed that the hypophagic effects of the CCK on food intake can be mediated by NMDA glutamate receptors in layer-type chickens.