ABSTRACT
Contrasting to the established role of the hypothalamic agouti-related protein (AgRP) neurons in feeding regulation, the neural circuit and signaling mechanisms by which they control energy expenditure remains unclear. Here, we report that energy expenditure is regulated by a subgroup of AgRP neurons that send non-collateral projections to neurons within the dorsal lateral part of dorsal raphe nucleus (dlDRN) expressing the melanocortin 4 receptor (MC4R), which in turn innervate nearby serotonergic (5-HT) neurons. Genetic manipulations reveal a bi-directional control of energy expenditure by this circuit without affecting food intake. Fiber photometry and electrophysiological results indicate that the thermo-sensing MC4RdlDRN neurons integrate pre-synaptic AgRP signaling, thereby modulating the post-synaptic serotonergic pathway. Specifically, the MC4RdlDRN signaling elicits profound, bi-directional, regulation of body weight mainly through sympathetic outflow that reprograms mitochondrial bioenergetics within brown and beige fat while feeding remains intact. Together, we suggest that this AgRP neural circuit plays a unique role in persistent control of energy expenditure and body weight, hinting next-generation therapeutic approaches for obesity and metabolic disorders.
Subject(s)
Agouti-Related Protein/metabolism , Energy Metabolism/physiology , Hypothalamus/metabolism , Neural Conduction/physiology , Serotonergic Neurons/physiology , Adipose Tissue, Beige/metabolism , Adipose Tissue, Brown/metabolism , Animals , Body Weight , Chromatography, Liquid , Eating/physiology , Energy Metabolism/genetics , Male , Mice , Neural Conduction/drug effects , Neural Conduction/radiation effects , Obesity/metabolism , Optogenetics , Receptor, Melanocortin, Type 4/genetics , Receptor, Melanocortin, Type 4/metabolism , Serotonergic Neurons/drug effects , Serotonergic Neurons/radiation effects , Serotonin/metabolism , Serotonin/physiology , Signal Transduction/genetics , Signal Transduction/physiology , Tandem Mass Spectrometry , TemperatureABSTRACT
ETHNOPHARMACOLOGICAL RELEVANCE: The aerial parts of Tilia americana var. mexicana (Malvaceae, formerly Tiliaceae) or "sirimo" are used in Mexican traditional medicine for the relief of mild symptoms of mental stress, commonly referred to as "nerve diseases". Individuals use this plant to fall asleep, to calm states of nervous excitement, headaches, mood disorders, and general discomfort. Recent studies indicated that fractions standardized in their flavonoid content possess antidepressant activity in behavioral assays in mice. The present study aims to focus on the evaluation of the antidepressant effect of the mixture of two flavonoids (FMix), and its interaction with serotonergic drugs. Also, the pharmacological effect of the products of the metabolism of aglycone, quercetin, was evaluated in mice subjected to forced swimming test (FST) and open field test (OFT). MATERIALS AND METHODS: A methanol-soluble extract obtained from leaves of Tilia americana was fractionated in an open column chromatographic separation. One of the fractions contained FMix wich is constituted of the mixture of quercetin 4'-O-rhamnoside (1, 47%) y isoquercitrin (2, 53%). The mice were divided into the several following groups: FMix (0.01, 0.1, 0.5, 1.0, and 2 mg/kg); FMix (1.0 mg/kg) and agonist DOI (2.0 mg/kg); FMix (1.0 mg/kg) and antagonist ketanserin (KET, 0.03 mg/kg) of 5-HT2A receptors; FMix (1.0 mg/kg) and selective agonist 8-OH-DPAT (8-OH, 0.01 mg/kg); FMix (1.0 mg/kg) and antagonist WAY100635 (WAY, 0.5 mg/kg) of 5HT1 receptors; Phloroglucinol (PHL); 3,4-dihydroxy-phenyl acid (DOPAC); p-hydroxyphenyl acetic acid (p-HPAA); and m-hydroxyphenyl acetic acid (m-HPAA) were tested in FST or OFT. RESULTS: FMix induced dependent-dose antidepressant activity and, at the highest dose administered, a sedative effect was also observed. The 8-OH-DPAT, or the DOI, or the KET combination with FMix (1.0 mg/kg) induced a higher antidepressant effect than compounds alone; there was no effect exerted with WAY. The activity on OFT increased only with the FMix and KET combination. At the same time, the products of the aglycone metabolism of quercetin, that is, DOPAC and p-HPAA, decreased the immobility time of the mice in FST at 1.0 mg/kg, and a dose-curve was formed for these. CONCLUSION: The antidepressant effect of FMix could depend, at least in part, on the degradation products of quercetin and with a possible action mode through interaction with the serotoninergic system.
Subject(s)
Antidepressive Agents/pharmacology , Behavior, Animal/drug effects , Brain/drug effects , Depression/prevention & control , Plant Extracts/pharmacology , Quercetin/analogs & derivatives , Serotonergic Neurons/drug effects , Tilia , Animals , Antidepressive Agents/isolation & purification , Antidepressive Agents/metabolism , Biotransformation , Brain/metabolism , Brain/physiopathology , Depression/metabolism , Depression/physiopathology , Depression/psychology , Disease Models, Animal , Exploratory Behavior/drug effects , Male , Mice, Inbred ICR , Motor Activity/drug effects , Plant Extracts/isolation & purification , Quercetin/isolation & purification , Quercetin/metabolism , Quercetin/pharmacology , Receptor, Serotonin, 5-HT1A/metabolism , Receptor, Serotonin, 5-HT2A/metabolism , Serotonergic Neurons/metabolism , Serotonin/metabolism , Tilia/chemistryABSTRACT
We tested whether Sake Lees (SL) had inhibitory effects on hyperalgesia in the hindpaw under psychophysical stress conditions. Male rats were subjected to repeated forced swim stress treatments (FST) from Day -3 to Day -1. Intraperiotoneal administration of SL which contained low concentration of ethanol (SLX) was conducted after each FST. On Day 0, formalin-evoked licking behaviors and Fos responses in the lumbar spinal cord (DH) and several areas within the rostral ventromedial medulla (RVM) were quantified as nociceptive responses. FST-induced hyperalgesia in the hindpaw was prevented by repeated SL and SLX treatments. Fos expression was significantly increased in DH and some areas within the RVM under FST, which was prevented by repeated SL or SLX. These findings indicated that daily administration of SL had the potential to alleviate stress-induced hyperalgesia.
Subject(s)
Fermentation , Hindlimb/metabolism , Hyperalgesia/drug therapy , Oryza/chemistry , Plant Extracts/pharmacology , Proto-Oncogene Proteins c-fos/metabolism , Spinal Cord Dorsal Horn/metabolism , Stress, Physiological/physiology , Animals , Behavior, Animal/drug effects , Ethanol/chemistry , Formaldehyde/administration & dosage , Formaldehyde/pharmacology , Hyperalgesia/etiology , Immunohistochemistry , Male , Pain Management , Pain Measurement , Plant Extracts/administration & dosage , Proto-Oncogene Proteins c-fos/immunology , Rats , Rats, Sprague-Dawley , Serotonergic Neurons/drug effects , Serotonergic Neurons/metabolism , Serotonin/immunology , Serotonin/metabolism , Swimming/physiology , Tissue DistributionABSTRACT
Dysfunctions in dopamine (DA) and serotonin (5HT) metabolism have been widely implicated in Tourette syndrome (TS); however, the exact nature of these dysfunctions remains unclear. The objective of the present study was to investigate the variation in DA and 5HT metabolism in a rat model of TS, and to evaluate the therapeutic effect of Ningdong granule (NDG), a traditional Chinese medicine (TCM) preparation used specifically for the treatment of TS. Rats were treated with 3,3'iminodipropionitrile for 7 days to induce the model of TS, and were then intragastrically administered NDG each day. After 8 weeks of treatment, micropositron emission tomography was used to measure the binding of DA D2 receptors (D2Rs), DA transporters (DATs), 5HT2A receptors (5HT2ARs) and 5HT transporters (SERTs) in brain regions of interest. The results indicated that NDG could significantly reduce the typical characteristics of TS in the rat model. Decreased D2R binding and increased DAT binding were detected in the striatum compared with the binding activities in untreated rats. The density of 5HT2AR was also significantly increased in the striatum following NDG treatment; however, SERT levels were decreased in certain brain regions, including the striatum, cortex, nucleus accumbens and amygdala. Taken together, the current results demonstrated that NDG may be effective in treating patients with TS.
Subject(s)
Dopaminergic Neurons/metabolism , Drugs, Chinese Herbal/pharmacology , Serotonergic Neurons/metabolism , Tourette Syndrome/drug therapy , Animals , Corpus Striatum/metabolism , Corpus Striatum/physiology , Disease Models, Animal , Dopamine/genetics , Dopamine Plasma Membrane Transport Proteins/genetics , Dopaminergic Neurons/drug effects , Dopaminergic Neurons/pathology , Humans , Medicine, Chinese Traditional , Nitriles/toxicity , Rats , Receptor, Serotonin, 5-HT2A/genetics , Receptors, Dopamine D2/genetics , Serotonergic Neurons/drug effects , Serotonergic Neurons/pathology , Serotonin/genetics , Serotonin Plasma Membrane Transport Proteins/genetics , Synaptic Transmission/drug effects , Synaptic Transmission/genetics , Tourette Syndrome/chemically induced , Tourette Syndrome/genetics , Tourette Syndrome/pathologyABSTRACT
Annona vepretorum is an endemic species of the Caatinga biome, known in Northeastern Brazil as "araticum" and/or "pinha da Caatinga". In the present study it was evaluated the neuropharmacological potential of the essential oil obtained from the leaves of Annona vepretorum, as well as of the inclusion complexes of oil obtained with cyclodextrin. Thus, were used neuropharmacological tests already consolidated in the literature like open-field, elevated plus maze, rota-rod, tail suspension test, thiopental-induced sleep test, among others. The acute treatment of essential oil (EO) has anxiolytic, sedative, antiepileptic and antidepressant effects. The anxiolytic and anticonvulsant effects seems to be related to the GABAergic system, probably in the receptor subtypes that mediate the effects of the benzodiazepines, to generate anxiolytic activity. The sedative effect seems to be involved with other signaling pathways. The antidepressant effect of EO seems to be related to its action on serotonergic receptors. It was verified that some behavioral parameters were improved with the oil complexed with ß-cyclodextrin, but this effect was not uniform for all the doses and tests used. Further studies are needed in order to use other options for drug delivery systems. Thus, the essential oil of Annona vepretorum is a promising agent with neurobiological activity and a potential target for drug discovery, since the natural products such as medicinal plants have been a source of new therapeutic proposals.
Subject(s)
Annona/chemistry , Anti-Anxiety Agents/pharmacology , Anticonvulsants/pharmacology , Antidepressive Agents/pharmacology , GABAergic Neurons/drug effects , Hypnotics and Sedatives/pharmacology , Oils, Volatile/pharmacology , Serotonergic Neurons/drug effects , Animals , Anxiety/drug therapy , Behavior, Animal/drug effects , Male , Mice , Plant Extracts/pharmacology , Plant Leaves/chemistry , Plants, Medicinal/chemistry , Signal Transduction/drug effectsABSTRACT
The present study was conducted to investigate the sedative and hypnotic activities of Vaccinium bracteatum Thunb. fruit (VBFW) in an animal model and to identify the underlying mechanisms of its action. VBFW exhibited sedative effects through a reduction in the locomotor activity in the open field test (OFT). In addition, VBFW significantly reduced the sleep latency and increased total sleep duration in pentobarbital-induced sleeping behaviors in mice. The effects of 4-Chloro-DL-phenylalanine methyl ester hydrochloride (PCPA) were studied in normal and serotonin-depleted mice. Additionally, the changes in the related serum corticosterone (CORT) and neurotransmitter levels were evaluated. Pretreatment with VBFW (50, and 100 mg/kg) produced a significant decrease in the immobility time in the forced swim test (FST), while VBFW 100 plus PCPA treatment attenuated the change in immobility time observed following administration of VBFW alone. However, VBFW plus PCPA treatments did not significantly influence the changes in the locomotor activity that were induced by VBFW alone. The results suggest that VBFW leads to a decrease in the levels of serum CORT and norepinephrine in the hippocampus (HC) region (P < 0.01). Furthermore, PCPA treatment alone decreased serotonin (5-HT) levels in the HC (P < 0.05) and the prefrontal cortex (PFC; P < 0.05), while VBFW plus PCPA significantly increased the 5-HT levels in both the HC and the PFC (P < 0.05). In addition, we also found that VBFW showed a strong agonistic effect at the 5-HT1A receptor by activating 5-HT1A receptor-mediated intracellular Ca2+ and ERK1/2 phosphorylation. Similarly, VBFW (30 and 100 µg/mL) significantly increased the intracellular Cl- influx through its effects on the γ-aminobutyric acid type A receptor (GABAA receptor) subunits (α5, ß1, and ß2) in primary rat cerebellar granule cells. Moreover, the glutamate decarboxylase (GAD)65/67 protein was upregulated following VBFW treatment (30 and 100 µg/mL). The results of our study indicate that VBFW induces sedative and hypnotic effects by regulating the serotonergic and GABAA-ergic systems, which is possibly associated with 5-HT1A receptor agonistic activity. Additionally, this data suggests that VBFW up-regulates intracellular Cl- and GABAA receptor subunits as well as GAD65/67 protein levels.
Subject(s)
GABAergic Neurons/drug effects , Hypnotics and Sedatives/pharmacology , Plant Extracts/pharmacology , Serotonergic Neurons/drug effects , Serotonin 5-HT1 Receptor Agonists/pharmacology , Vaccinium myrtillus , Animals , CHO Cells , Cells, Cultured , Cricetinae , Cricetulus , Dose-Response Relationship, Drug , GABAergic Neurons/physiology , Humans , Locomotion/drug effects , Locomotion/physiology , Male , Mice , Mice, Inbred ICR , Plant Extracts/isolation & purification , Receptor, Serotonin, 5-HT1A/physiology , Serotonergic Neurons/physiology , Serotonin 5-HT1 Receptor Agonists/isolation & purificationABSTRACT
The present study evaluated the possible antiallodynic effect induced by [6]-gingerol in rats with L5-L6 spinal nerve ligation (SNL). Moreover, we determined the possible mechanism underlying the antiallodynic effect induced by [6]-gingerol in neuropathic rats. The animals underwent L5-L6 SNL for the purpose of developing tactile allodynia. Tactile allodynia was measured with von Frey filaments. Intrathecal administration of [6]-gingerol reversed SNL-induced tactile allodynia. The [6]-gingerol-induced antiallodynic effect was prevented by the intrathecal administration of methiothepin (30 µg per rat; nonselective 5-hydroxytryptamine [5-HT] antagonist), WAY-100635 (6 µg per rat; selective 5-HT1A receptor antagonist), SB-224289 (5 µg per rat; selective 5-HT1B receptor antagonist), BRL-15572 (4 µg per rat; selective 5-HT1D receptor antagonist), and SB-659551 (6 µg per rat; selective 5-HT5A receptor antagonist), but naloxone (50 µg per rat; nonselective opioid receptor antagonist) did not prevent the [6]-gingerol-induced antiallodynic effect. Moreover, intrathecal administration of Nω-nitro-l-arginine methyl ester (100 µg per rat; nonselective nitric oxide [NO] synthase inhibitor), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 µg per rat; inhibitor of guanylate cyclase), and glibenclamide (50 µg per rat; channel blocker of adenosine triphosphate [ATP]-sensitive K+ channels) prevented the [6]-gingerol-induced antiallodynic effect. These data suggest that the antiallodynic effect induced by [6]-gingerol is mediated by the serotoninergic system involving the activation of 5-HT1A/1B/1D/5A receptors, as well as the NO-cyclic guanosine monophosphate-ATP-sensitive K+ channel pathway but not by the opioidergic system.
Subject(s)
Analgesics/pharmacology , Catechols/pharmacology , Fatty Alcohols/pharmacology , Hyperalgesia/drug therapy , Neuralgia/drug therapy , Adenosine Triphosphate/metabolism , Animals , Biphenyl Compounds/pharmacology , Cyclic GMP/metabolism , Female , Guanosine Monophosphate/metabolism , Hyperalgesia/metabolism , Hyperalgesia/pathology , Male , Neuralgia/metabolism , Neuralgia/pathology , Nitric Oxide/metabolism , Piperazines/pharmacology , Piperidones/pharmacology , Pyridines/pharmacology , Rats , Rats, Wistar , Receptors, Serotonin/metabolism , Serotonergic Neurons/drug effects , Serotonergic Neurons/physiology , Spiro Compounds/pharmacologyABSTRACT
Our previous studies found that n-3 polyunsaturated fatty acids (PUFAs) and estrogen had synergistic antidepressant-like effects. The purpose of the present study was to investigate the hypothesis that three major n-3 PUFAs, α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), individually had antidepressant effects combined with 17ß-estradiol-3-benzoate (E) through a neurobiological pathway in ovariectomized rats. Rats were fed a modified American Institute of Nutrition-93G diet with 0% n-3 PUFAs and 1% ALA, EPA and DHA relative to total energy intake for 12 weeks and were injected with corn oil or E every 4 days during the last 3 weeks. Supplementation of EPA, DHA and E increased serum concentrations of serotonin and climbing behavior, and decreased immobility during a forced swimming test. Supplementation with EPA, DHA and E also decreased hippocampal expressions of interleukin-6 and tumor necrosis factor-α, and increased cAMP response element binding protein, brain-derived neurotrophic factor (BDNF) and estrogen receptor-α. Immunofluorescence staining consistently showed elevated expressions of BDNF. Magnetic resonance spectroscopy showed that E increased glucose and decreased glutamate, glutamine and myo-inositol concentrations regardless of n-3 PUFA supplementation. In addition, supplementation with EPA, DHA and E decreased levels of nitrite and nitrate. However, ALA had no antidepressant effect. The present study suggested that the antidepressant-like effects of EPA and DHA supplementation and E injection could be due to the regulation of serotonergic neurotransmission and inflammatory cytokines rather than due to the antioxidative system. Supplementation with n-3 PUFA and E had the additional function of modulating neurometabolites in the hippocampus.
Subject(s)
Antidepressive Agents/therapeutic use , Depression/prevention & control , Dietary Supplements , Disease Models, Animal , Docosahexaenoic Acids/therapeutic use , Eicosapentaenoic Acid/therapeutic use , Estradiol/therapeutic use , Animals , Behavior, Animal/drug effects , Brain Chemistry/drug effects , Depression/immunology , Depression/metabolism , Depression/pathology , Estradiol/administration & dosage , Estradiol/analogs & derivatives , Female , Hippocampus/drug effects , Hippocampus/immunology , Hippocampus/metabolism , Hippocampus/pathology , Hormone Replacement Therapy , Injections, Subcutaneous , Nerve Tissue Proteins/metabolism , Ovariectomy/adverse effects , Random Allocation , Rats, Wistar , Serotonergic Neurons/drug effects , Serotonergic Neurons/immunology , Serotonergic Neurons/metabolism , Serotonergic Neurons/pathology , Serotonin/blood , alpha-Linolenic Acid/therapeutic useABSTRACT
Pain is fundamentally unpleasant and induces a negative affective state. The affective component of pain is mediated by circuits that are distinct from those mediating the sensory-discriminative component. Here, we have investigated the role of prostaglandins in the affective dimension of pain using a rodent pain assay based on conditioned place aversion to formalin injection, an inflammatory noxious stimulus. We found that place aversion induced by inflammatory pain depends on prostaglandin E2 that is synthesized by cyclooxygenase 2 in neural cells. Further, mice lacking the prostaglandin E2 receptor EP3 selectively on serotonergic cells or selectively in the area of the dorsal raphe nucleus failed to form an aversion to formalin-induced pain, as did mice lacking the serotonin transporter. Chemogenetic manipulations revealed that EP3 receptor activation elicited conditioned place aversion to pain via inhibition of serotonergic neurons. In contrast to their role in inflammatory pain aversion, EP3 receptors on serotonergic cells were dispensable for acute nociceptive behaviors and for aversion induced by thermal pain or a κ opioid receptor agonist. Collectively, our findings show that prostaglandin-mediated modulation of serotonergic transmission controls the affective component of inflammatory pain.
Subject(s)
Dinoprostone/physiology , Pain Perception , Pain/psychology , Serotonergic Neurons/metabolism , Serotonin/physiology , Affect , Animals , Cyclooxygenase 2/metabolism , Cyclooxygenase Inhibitors/pharmacology , Drug Evaluation, Preclinical , Inflammation/pathology , Inflammation/psychology , Mice, Knockout , Pyrazoles/pharmacology , Receptors, Prostaglandin E, EP3 Subtype/metabolism , Serotonergic Neurons/drug effects , Signal TransductionABSTRACT
The neurochemical serotonin (5-hydroxytryptamine, 5-HT) is involved in a variety of behavioral functions including arousal, reward, and attention, and has a role in several complex disorders of the brain. In the auditory system, 5-HT fibers innervate a number of subcortical nuclei, yet the modulatory role of 5-HT in nearly all of these areas remains poorly understood. In this study, we examined spiking activity of neurons in the dorsal cochlear nucleus (DCN) following iontophoretic application of 5-HT. The DCN is an early site in the auditory pathway that receives dense 5-HT fiber input from the raphe nuclei and has been implicated in the generation of auditory disorders marked by neuronal hyperexcitability. Recordings from the DCN in awake mice demonstrated that iontophoretic application of 5-HT had heterogeneous effects on spiking rate, spike timing, and evoked spiking threshold. We found that 56% of neurons exhibited increases in spiking rate during 5-HT delivery, while 22% had decreases in rate and the remaining neurons had no change. These changes were similar for spontaneous and evoked spiking and were typically accompanied by changes in spike timing. Spiking increases were associated with lower first spike latencies and jitter, while decreases in spiking generally had opposing effects on spike timing. Cases in which 5-HT application resulted in increased spiking also exhibited lower thresholds compared to the control condition, while cases of decreased spiking had no threshold change. We also found that the 5-HT2 receptor subtype likely has a role in mediating increased excitability. Our results demonstrate that 5-HT can modulate activity in the DCN of awake animals and that it primarily acts to increase neuronal excitability, in contrast to other auditory regions where it largely has a suppressive role. Modulation of DCN function by 5-HT has implications for auditory processing in both normal hearing and disordered states.
Subject(s)
Auditory Perception/drug effects , Behavior, Animal/drug effects , Cochlear Nucleus/drug effects , Receptors, Serotonin, 5-HT2/drug effects , Serotonergic Neurons/drug effects , Serotonin 5-HT2 Receptor Agonists/administration & dosage , Serotonin/administration & dosage , Acoustic Stimulation , Animals , Cochlear Nucleus/metabolism , Electroencephalography , Evoked Potentials, Auditory, Brain Stem/drug effects , Female , Iontophoresis , Male , Mice, Inbred CBA , Reaction Time/drug effects , Receptors, Serotonin, 5-HT2/metabolism , Serotonergic Neurons/metabolism , Serotonin/metabolism , Time FactorsABSTRACT
Task-specific rehabilitation has been shown to promote functional recovery after acute spinal cord injury (SCI). Recently, the omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), has been shown to promote neuroplasticity after SCI. Here, we investigated whether the combination of a single bolus of DHA with rehabilitation can enhance the effect of DHA or rehabilitation therapy in adult injured spinal cord. We found enhanced functional improvement with DHA in combination with rehabilitation compared with either treatment alone in a rat cervical lateral hemisection SCI model. This behavioral improvement correlated with a significant sprouting of uninjured corticospinal and serotonergic fibers. We also observed that the greatest increase in the synaptic vesicle protein, synaptophysin, and the synaptic active zone protein, Bassoon, occurred in animals that received both DHA and rehabilitation. In summary, the functional, anatomical, and synaptic plasticity induced by task-specific rehabilitation can be further enhanced by DHA treatment. This study shows the potential beneficial effects of DHA combined with rehabilitation for the treatment of patients with SCI.
Subject(s)
Docosahexaenoic Acids/therapeutic use , Neuroprotective Agents/therapeutic use , Recovery of Function/drug effects , Spinal Cord Injuries/drug therapy , Spinal Cord Injuries/rehabilitation , Animals , Cervical Vertebrae/injuries , Docosahexaenoic Acids/administration & dosage , Fatty Acids, Omega-3/therapeutic use , Female , Immunohistochemistry , Locomotion , Motor Skills , Nerve Regeneration/drug effects , Nerve Tissue Proteins/biosynthesis , Nerve Tissue Proteins/genetics , Neuronal Plasticity/drug effects , Neuroprotective Agents/administration & dosage , Pyramidal Tracts/cytology , Pyramidal Tracts/drug effects , Pyramidal Tracts/growth & development , Rats , Rats, Sprague-Dawley , Serotonergic Neurons/drug effects , Synaptophysin/biosynthesis , Synaptophysin/geneticsABSTRACT
Inter-individual behavioral variation is thought to increase fitness and aid adaptation to environmental change, but the underlying mechanisms are poorly understood. We find that variation between individuals in neuromodulatory input contributes to individuality in short-term habituation of the zebrafish (Danio Rerio) acoustic startle response (ASR). ASR habituation varies greatly between individuals, but differences are stable over days and are heritable. Acoustic stimuli that activate ASR-command Mauthner cells also activate dorsal raphe nucleus (DRN) serotonergic neurons, which project to the vicinity of the Mauthner cells and their inputs. DRN neuron activity decreases during habituation in proportion to habituation and a genetic manipulation that reduces serotonin content in DRN neurons increases habituation, whereas serotonergic agonism or DRN activation with ChR2 reduces habituation. Finally, level of rundown of DRN activity co-segregates with extent of behavioral habituation across generations. Thus, variation between individuals in neuromodulatory input contributes to individuality in a core adaptive behavior. VIDEO ABSTRACT.
Subject(s)
Dorsal Raphe Nucleus/cytology , Dorsal Raphe Nucleus/physiology , Habituation, Psychophysiologic/physiology , Individuality , Reflex, Startle/physiology , Serotonergic Neurons/physiology , Zebrafish/physiology , Acoustic Stimulation , Animals , Animals, Genetically Modified , Apomorphine/pharmacology , Dorsal Raphe Nucleus/drug effects , Dorsal Raphe Nucleus/metabolism , Habituation, Psychophysiologic/drug effects , Quipazine/pharmacology , Reflex, Startle/drug effects , Rhodopsin/biosynthesis , Rhodopsin/genetics , Serotonergic Neurons/drug effects , Serotonergic Neurons/metabolism , Serotonin/metabolismABSTRACT
5-hydroxytryptamine (5-HT) is a key regulator of muscle contraction in parasitic flatworms. In Schistosoma mansoni, the myoexcitatory action of 5-HT is effected through activation of a serotonergic GPCR (Sm.5HTRL), prioritizing pharmacological characterization of this target for anthelmintic drug discovery. Here, we have examined the effects of several aporphine alkaloids on the signaling activity of a heterologously expressed Sm.5HTRL construct using a cAMP biosensor assay. Four structurally related natural products - nuciferine, D-glaucine, boldine and bulbocapnine - were demonstrated to block Sm.5HTRL evoked cAMP generation with the potency of GPCR blockade correlating well with the ability of each drug to inhibit contractility of schistosomule larvae. Nuciferine was also effective at inhibiting both basal and 5-HT evoked motility of adult schistosomes. These data advance our understanding of structure-affinity relationships at Sm.5HTRL, and demonstrate the effectiveness of Sm.5HTRL antagonists as hypomotility-evoking drugs across different parasite life cycle stages.
Subject(s)
Anthelmintics/pharmacology , Aporphines/pharmacology , Receptors, G-Protein-Coupled/antagonists & inhibitors , Schistosoma mansoni/drug effects , Schistosoma mansoni/enzymology , Serotonergic Neurons/drug effects , Serotonin Antagonists/pharmacology , Animals , Drug Evaluation, Preclinical/methods , Locomotion/drug effectsABSTRACT
The diversity and uniqueness of flatworm G protein coupled receptors (GPCRs) provides impetus for identifying ligands useful as tools for studying flatworm biology, or as therapeutics for treating diseases caused by parasitic flatworm infections. To catalyse this discovery process, technologies optimized for mammalian GPCR high throughput screening need be transposed for screening flatworm GPCRs. Here, we demonstrate the utility of a genetically encoded cAMP biosensor for resolving the properties of an abundantly expressed planarian serotonergic GPCR (S7.1R). Application of this methodology resolved the real time kinetics of GPCR modulation by ligands and demonstrated a marked difference in the kinetic action of antagonists at S7.1R. Notably, bromocriptine caused a protracted inhibition of S7.1R activity in vitro and a protracted paralysis of planarian movement, replicating the effect of S7.1R in vivo RNAi. The lengthy inhibition of function caused by bromocriptine at this abundantly expressed GPCR provides a useful tool to ablate serotonergic signaling in vivo, and is a noteworthy feature for exploitation as an anthelmintic vulnerability.
Subject(s)
Anthelmintics/pharmacology , Bromocriptine/pharmacology , Planarians/drug effects , Planarians/enzymology , Receptors, G-Protein-Coupled/antagonists & inhibitors , Serotonergic Neurons/drug effects , Serotonin Antagonists/pharmacology , Animals , Drug Evaluation, Preclinical/methods , Kinetics , Locomotion/drug effectsABSTRACT
BACKGROUND: Pain is the most common cause of patients seeking medical advice as a result of its association with different pathologies. This study evaluated the antinociceptive property of Haematostaphis barteri as well as the possible mechanism(s) associated with its antinociceptive property. METHODS: Mice were administered H. barteri (30-300 mg kg-1; p.o.), followed by intraplantar injection of 10 µL of 5% formalin into the hind paws. The pain score was determined for 1 h in the formalin test. The possible nociceptive pathways involved in the antinociceptive action of H. barteri were determined by pre-treating mice with theophylline (5 mg kg-1, a non-selective adenosine receptor antagonist), naloxone (2 mg kg-1, a non-selective opioid receptor antagonist), glibenclamide (8 mg kg-1; an ATP-sensitive K+ channel inhibitor), and atropine (3 mg kg-1; non-selective muscarinic antagonist). RESULTS: H. barteri (30-300 mg kg-1) significantly and dose dependently precluded both first and second phases of nociception. Pre-treatment with naloxone had no effect on the analgesic activities of H. barteri in the first phase. Again, pre-treatment with atropine and glibenclamide did not significantly reverse the neurogenic antinociception of the extract in phase 1. However, theophylline reversed the analgesic effect of the extract in the first phase. In phase 2, theophylline had no effect on the analgesic activities of the extract. Naloxone, atropine, and glibenclamide significantly blocked the antinociception of H. barteri in the inflammatory phase of the formalin test. CONCLUSIONS: H. barteri possesses antinociceptive property mediated via the opioidergic, adrenergic, muscarinic, ATP-sensitive K+ channels, and adenosinergic nociceptive pathways.
Subject(s)
Anacardiaceae , Analgesics/pharmacology , KATP Channels/antagonists & inhibitors , Pain Measurement/drug effects , Plant Extracts/pharmacology , Plant Leaves , Adrenergic Neurons/drug effects , Adrenergic Neurons/physiology , Analgesics/isolation & purification , Animals , Female , KATP Channels/physiology , Male , Mice , Mice, Inbred ICR , Pain Measurement/methods , Plant Extracts/isolation & purification , Receptors, Muscarinic/physiology , Receptors, Opioid/physiology , Receptors, Purinergic P1/physiology , Serotonergic Neurons/drug effects , Serotonergic Neurons/physiologyABSTRACT
Depression continues to be a major global health problem. Although antidepressants are used for its treatment, efficacy is often inconsistent. Thus, the search for alternative therapeutic medicines for its treatment is still important. In this study, the antidepressant-like effect of Pseudospondias microcarpa extract (30-300 mg kg(-1), p.o.) was investigated in two predictive models of depression--forced swimming test and tail suspension test in mice. Additionally, the mechanism(s) of action involved were assessed. Acute treatment with the extract dose dependently reduced immobility of mice in both models. The antidepressant-like effect of the extract (100 mg kg(-1), p.o.) was blocked by p-chlorophenylalanine and cyproheptadine but not prazosin, propranolol, or yohimbine. Concomitant administration of D-cycloserine and the extract potentiated the anti-immobility effect. In contrast, D-serine, a full agonist of glycine/NMDA receptors, abolished the effects. Anti-immobility effects of PME were prevented by pretreatment of mice with L-arginine (750 mg kg(-1), i.p.) and sildenafil (5 mg kg(-1), i.p.). On the contrary, pretreatment of mice with L-NAME (30 mg kg(-1), i.p.) or methylene blue (10 mg kg(-1), i.p.) potentiated its effects. The extract produces an antidepressant-like effect in the FST and TST that is dependent on the serotoninergic system, NMDA receptor complex, and the nitric oxide pathway.
Subject(s)
Antidepressive Agents/administration & dosage , Depression/drug therapy , Plant Extracts/administration & dosage , Serotonergic Neurons/drug effects , Anacardiaceae/chemistry , Animals , Antidepressive Agents/chemistry , Cycloserine/administration & dosage , Depression/metabolism , Depression/pathology , Humans , Mice , Nitric Oxide/metabolism , Plant Extracts/chemistry , Plant Leaves/chemistry , Receptors, N-Methyl-D-Aspartate/metabolism , Signal Transduction/drug effectsABSTRACT
BACKGROUND: Whereas some studies have demonstrated the essential role of 5-hydroxytryptamine (5-HT) in tramadol and acetaminophen analgesia, other research has presented conflicting results. To dispel doubts, some aspects of the involvement of 5-HT in the antinociceptive properties of these drugs remain to be clarified. OBJECTIVES: The aim of this study was to determine whether the serotoninergic system dysfunction produced by neonatal 5-HT lesion in rats may affect the antinociceptive effects of tramadol and acetaminophen administered in adulthood. MATERIAL AND METHODS: Three days after birth, the control rats were pretreated with desipramine HCl (20 mg/kg i.p.) 30 min before intraventricular saline--vehicle injection. A separate group received 5.7-DHT; 2×35 µg in each lateral ventricle. At the age of 8 weeks, 5-HT and 5-hydroxyidoleaceticacid (5-HIAA) concentrations were determined in the thalamus and spinal cord by an HPLC/ED method. The antinociceptive effects of tramadol (20 mg/kg i.p.) or acetaminophen (100 mg/kg i.p.) were evaluated by a battery of tests. RESULTS: 5.7-DHT lesioning was associated with a reduction in 5-HT and 5-HIAA content of the thalamus (>85% and >90%) and spinal cord (>58% and 70%). Neonatal 5.7-DHT treatment produced a significant reduction in the antinociceptive effect of tramadol in the hot plate, tail-immersion, paw withdrawal and writhing tests. In the formalin hind paw test, the results were ambiguous. 5-HT lesion was also associated with a decrease in the analgesic effect of acetaminophen in the hot plate and writhing tests. A similar relationship wasn't found in the other assessments conducted with the use of acetaminophen. CONCLUSIONS: The present study provides evidence that (1) an intact serotoninergic system is required for the adequate antinociceptive action of tramadol, and (2) the serotoninergic system exerts a negligible influence on acetaminophen-induced analgesia in rats. We hypothesize that similar abnormalities in nociception may occur in patients with 5-HT dysfunction (e.g. depression), so these results should be complied in analgesic dosage adjustment.
Subject(s)
5,7-Dihydroxytryptamine/toxicity , Acetaminophen/pharmacology , Analgesics, Non-Narcotic/pharmacology , Analgesics, Opioid/pharmacology , Pain Perception/drug effects , Pain/prevention & control , Spinal Cord/drug effects , Thalamus/drug effects , Tramadol/pharmacology , Age Factors , Animals , Animals, Newborn , Disease Models, Animal , Hydroxyindoleacetic Acid/metabolism , Male , Pain/etiology , Pain/metabolism , Pain/physiopathology , Pain/psychology , Pain Measurement , Rats, Wistar , Serotonergic Neurons/drug effects , Serotonergic Neurons/metabolism , Serotonin/metabolism , Spinal Cord/metabolism , Spinal Cord/physiopathology , Thalamus/metabolism , Thalamus/physiopathology , Time FactorsABSTRACT
OBJECTIVES: We attempted to ascertain if bisbenzylisoquinoline alkaloids, liensinine and isoliensinine from Nelumbo nuciferaâ Gaertner have antidepressant-like effects and compare the effects with those previously obtained by their analogue neferine. METHODS: Using mice, the forced swimming test (FST) was carried out after treatment with liensinine, isoliensinine and neferine. KEY FINDINGS: Liensinine and isoliensinine elicited antidepressant-like effects in mice after the FST. Anti-immobility effects of liensinine and isoliensinine were antagonized by the 5-hydroxytryptamine1 A (5-HT1 A ) receptor antagonist WAY 100635, but not by the α1 -adrenoceptor antagonist prazosin. The anti-immobility effects of liensinine, isoliensinine and neferine were blocked by pretreatment with p-chlorophenylalanine (PCPA), which depletes serotonin (5-HT). CONCLUSIONS: These data suggest that liensinine and isoliensinine from Nelumbo nuciferaâ Gaertner have antidepressant-like effects and that antidepressant-like effects of liensinine and its analogues are closely related to serotonergic mechanisms.
Subject(s)
Antidepressive Agents/pharmacology , Behavior, Animal/drug effects , Benzylisoquinolines/pharmacology , Isoquinolines/pharmacology , Nelumbo/chemistry , Phenols/pharmacology , Plant Extracts/pharmacology , Serotonin Agents/pharmacology , Stress, Psychological/drug therapy , Animals , Antidepressive Agents/isolation & purification , Benzylisoquinolines/isolation & purification , Disease Models, Animal , Dose-Response Relationship, Drug , Isoquinolines/isolation & purification , Male , Mice, Inbred ICR , Motor Activity/drug effects , Nelumbo/embryology , Phenols/isolation & purification , Phytotherapy , Plant Extracts/isolation & purification , Plants, Medicinal , Seeds , Serotonergic Neurons/drug effects , Serotonergic Neurons/metabolism , Serotonin Agents/isolation & purification , Stress, Psychological/metabolism , Stress, Psychological/psychology , SwimmingABSTRACT
A number of behavioral, neurochemical and electrophysiological studies have emphasized the importance of the serotonergic neurons in the pathophysiology of psychiatric disorders and the therapeutic actions of psychotropics. However, no in vitro serotonergic culture systems have successfully analyzed the long-term effects of psychotropics or the neural interaction between serotonergic and excitatory/inhibitory neurons. Recently, we have established rat organotypic raphe slice cultures, which have functional serotonergic neurons with the ability to release 5-HT in response to stimulation and to reuptake 5-HT through serotonin transporter and retain neural and synaptic functions. Here, we show the following results in the raphe slice cultures: 1) acute and sustained treatments with 3,4-methylenedioxymethamphetamine induce the 5-HT efflux via serotonin transporter and AMPA receptor-mediated exocytotic 5-HT release, respectively; 2) sustained treatment with antidepressants enhances the exocytotic 5-HT release, which is dependent on AMPA receptor stimulation, but not on desensitization of 5-HT(1A/1B) autoreceptors; 3) the augmentation therapy of an atypical antipsychotic, olanzapine, with antidepressants is caused by the decrease in the raphe inhibitory GABAergic tone through 5-HT6 receptor antagonism. Our findings suggest that the raphe slice cultures are suitable for analyzing the neural and molecular mechanisms underlying the efficacy of psychotropics in vitro.
Subject(s)
Psychotropic Drugs/pharmacology , Serotonergic Neurons/drug effects , Animals , Drug Evaluation, Preclinical , Humans , Serotonergic Neurons/metabolism , Serotonin/metabolism , Synaptic Transmission , Tissue Culture TechniquesABSTRACT
Previous studies have suggested that estrogen and n-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have antidepressant-like effects. The purpose of the present study was to determine the interaction between n-3 PUFAs and estrogen, and their neurotrophic mechanism in rats after the forced swimming test (FST). Rats were fed a modified American Institute of Nutrition 93G diet with 0%, 1% or 2% EPA+DHA relative to the total energy intake during 12 weeks. At 8 weeks, rats were ovariectomized and injected with either 17ß-estradiol-3-benzoate (E2) or corn oil during the last 3 weeks. Both n-3 PUFA supplementation and E2 injection increased climbing and decreased immobility during the FST. Serum serotonin concentration was also increased by both n-3 PUFA and E2. N-3 PUFA and E2 decreased hippocampal expressions of interleukin (IL)-6 and tumor necrosis factor-α, and increased cAMP response element binding protein (CREB), phosphorylated CREB and brain-derived neurotrophic factor (BDNF). N-3 PUFA supplementation decreased hippocampal expression of IL-1ß only in rats injected with E2. Both n-3 PUFA supplementation and E2 injection increased estrogen receptor (ER)-α in the hippocampus, but ER-ß was increased only by E2 injection. Additionally, there was a significant interaction between n-3 PUFA supplementation and E2 injection on the hippocampal expression of pCREB, suggesting membrane-mediated interaction of n-3 PUFAs and E2. In conclusion, both n-3 PUFA and E2 had antidepressant-like effects by regulating serotonergic neurotransmission through BDNF and inflammatory cytokines.