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1.
FASEB J ; 38(1): e23380, 2024 01.
Artigo em Inglês | MEDLINE | ID: mdl-38102980

RESUMO

The urinary bladder is supplied by a rich network of sensory and autonomic axons, commonly visualized by immunolabeling for neural markers. This approach demonstrates overall network patterning but is less suited to understanding the structure of individual motor and sensory terminals within these complex plexuses. There is a further limitation visualizing the lightly myelinated (A-delta) class of sensory axons that provides the primary mechanosensory drive for initiation of voiding. Whereas most unmyelinated sensory axons can be revealed by immunolabeling for specific neuropeptides, to date no unique neural marker has been identified to immunohistochemically label myelinated visceral afferents. We aimed to establish a non-surgical method to visualize and map myelinated afferents in the bladder in rats. We found that in rats, the adeno-associated virus (AAV), AAV-PHP.S, which shows a high tropism for the peripheral nervous system, primarily transduced myelinated dorsal root ganglion neurons, enabling us to identify the structure and regional distribution of myelinated (mechanosensory) axon endings within the muscle and lamina propria of the bladder. We further identified the projection of myelinated afferents within the pelvic nerve and lumbosacral spinal cord. A minority of noradrenergic and cholinergic neurons in pelvic ganglia were transduced, enabling visualization and regional mapping of both autonomic and sensory axon endings within the bladder. Our study identified a sparse labeling approach for investigating myelinated sensory and autonomic axon endings within the bladder and provides new insights into the nerve-bladder interface.


Assuntos
Dependovirus , Bexiga Urinária , Ratos , Animais , Dependovirus/genética , Neurônios , Axônios , Medula Espinal/fisiologia , Gânglios Espinais , Neurônios Aferentes
2.
APL Bioeng ; 7(4): 046110, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37928642

RESUMO

Real-time closed-loop control of neuromodulation devices requires long-term monitoring of neural activity in the peripheral nervous system. Although many signal extraction methods exist, few are both clinically viable and designed for extracting small signals from fragile peripheral visceral nerves. Here, we report that our minimally invasive recording and analysis technology extracts low to negative signal to noise ratio (SNR) neural activity from a visceral nerve with a high degree of specificity for fiber type and class. Complex activity was recorded from the rat pelvic nerve that was physiologically evoked during controlled bladder filling and voiding, in an extensively characterized in vivo model that provided an excellent test bed to validate our technology. Urethane-anesthetized male rats (n = 12) were implanted with a four-electrode planar array and the bladder instrumented for continuous-flow cystometry, which measures urodynamic function by recording bladder pressure changes during constant infusion of saline. We demonstrated that differential bipolar recordings and cross-correlation analyses extracts afferent and efferent activity, and discriminated between subpopulations of fibers based on conduction velocity. Integrated Aδ afferent fiber activity correlated with bladder pressure during voiding (r2: 0.66 ± 0.06) and was not affected by activating nociceptive afferents with intravesical capsaicin (r2: 0.59 ± 0.14, P = 0.54, and n = 3). Collectively, these results demonstrate our minimally invasive recording and analysis technology is selective in extracting mixed neural activity with low/negative SNR. Furthermore, integrated afferent activity reliably correlates with bladder pressure and is a promising first step in developing closed-loop technology for bladder control.

3.
Neuron ; 110(14): 2242-2257.e6, 2022 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-35643078

RESUMO

Gene therapy offers great promise in addressing neuropathologies associated with the central and peripheral nervous systems (CNS and PNS). However, genetic access remains difficult, reflecting the critical need for the development of effective and non-invasive gene delivery vectors across species. To that end, we evolved adeno-associated virus serotype 9 (AAV9) capsid in mice and validated two capsids, AAV-MaCPNS1 and AAV-MaCPNS2, across rodent species (mice and rats) and non-human primate (NHP) species (marmosets and rhesus macaques). Intravenous administration of either AAV efficiently transduced the PNS in rodents and both the PNS and CNS in NHPs. Furthermore, we used AAV-MaCPNS1 in mice to systemically deliver the following: (1) the neuronal sensor jGCaMP8s to record calcium signal dynamics in nodose ganglia and (2) the neuronal actuator DREADD to dorsal root ganglia to mediate pain. This conclusively demonstrates the translatability of these two systemic AAVs across four species and their functional utility through proof-of-concept studies in mice.


Assuntos
Vetores Genéticos , Roedores , Animais , Sistema Nervoso Central , Dependovirus/genética , Técnicas de Transferência de Genes , Terapia Genética , Macaca mulatta/genética , Camundongos , Ratos , Roedores/genética , Transdução Genética
4.
J Comp Neurol ; 529(2): 311-326, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-32415681

RESUMO

Storage and voiding of urine from the lower urinary tract (LUT) must be timed precisely to occur in appropriate behavioral contexts. A major part of the CNS circuit that coordinates this activity is found in the lumbosacral spinal cord. Immediate early gene (IEG) activity mapping has been widely used to investigate the lumbosacral LUT-related circuit, but most reports focus on the effects of noxious stimulation in anesthetized female rats. Here we use c-Fos and EGR-1 (Zif268) activity mapping of lumbosacral spinal cord to investigate cystometry-induced micturition in awake female and male rats. In females, after cystometry c-Fos neurons in spinal cord segments L5-S2 were concentrated in the sacral parasympathetic nucleus (SPN), dorsal horn laminae II-IV, and dorsal commissural nucleus (SDCom). Comparisons of cystometry and control groups in male and female revealed sex differences. Activity mapping suggested dorsal horn laminae II-IV was activated in females but showed net inhibition in males. However, inhibition in male rats was not detected by EGR-1 activity mapping, which showed low coexpression with c-Fos. A class of catecholamine neurons in SPN and SDCom neurons were also more strongly activated by micturition in females. In both sexes, most c-Fos neurons were identified as excitatory by their absence of Pax2 expression. In conclusion, IEG mapping in awake male and female rats has extended our understanding of the functional molecular anatomy of the LUT-related circuit in spinal cord. Using this approach, we have identified sex differences that were not detected by previous studies in anesthetized rats.


Assuntos
Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Caracteres Sexuais , Medula Espinal/metabolismo , Micção/fisiologia , Animais , Proteína 1 de Resposta de Crescimento Precoce/análise , Feminino , Masculino , Proteínas Proto-Oncogênicas c-fos/análise , Ratos , Ratos Sprague-Dawley , Sacro/inervação , Sacro/metabolismo , Medula Espinal/química , Bexiga Urinária/química , Bexiga Urinária/inervação , Bexiga Urinária/metabolismo
5.
Front Neurosci ; 14: 619275, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33390899

RESUMO

Bioelectronic medical devices are well established and widely used in the treatment of urological dysfunction. Approved targets include the sacral S3 spinal root and posterior tibial nerve, but an alternate target is the group of pelvic splanchnic nerves, as these contain sacral visceral sensory and autonomic motor pathways that coordinate storage and voiding functions of the bladder. Here, we developed a device suitable for long-term use in an awake rat model to study electrical neuromodulation of the pelvic nerve (homolog of the human pelvic splanchnic nerves). In male Sprague-Dawley rats, custom planar four-electrode arrays were implanted over the distal end of the pelvic nerve, close to the major pelvic ganglion. Electrically evoked compound action potentials (ECAPs) were reliably detected under anesthesia and in chronically implanted, awake rats up to 8 weeks post-surgery. ECAP waveforms showed three peaks, with latencies that suggested electrical stimulation activated several subpopulations of myelinated A-fiber and unmyelinated C-fiber axons. Chronic implantation of the array did not impact on voiding evoked in awake rats by continuous cystometry, where void parameters were comparable to those published in naïve rats. Electrical stimulation with chronically implanted arrays also induced two classes of bladder pressure responses detected by continuous flow cystometry in awake rats: voiding contractions and non-voiding contractions. No evidence of tissue pathology produced by chronically implanted arrays was detected by immunohistochemical visualization of markers for neuronal injury or noxious spinal cord activation. These results demonstrate a rat pelvic nerve electrode array that can be used for preclinical development of closed loop neuromodulation devices targeting the pelvic nerve as a therapy for neuro-urological dysfunction.

6.
Mol Cell Neurosci ; 65: 125-34, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25752731

RESUMO

Neurotrophic factors have been intensively studied as potential therapeutic agents for promoting neural regeneration and functional recovery after nerve injury. Artemin is a member of the glial cell line-derived neurotrophic factor (GDNF) family of ligands (GFLs) that forms a signalling complex with GFRα3 and the tyrosine kinase Ret. Systemic administration of artemin in rodents is reported to facilitate regeneration of primary sensory neurons following axotomy, improve recovery of sensory function, and reduce sensory hypersensitivity that is a cause of pain. However, the biological mechanisms that underlie these effects are mostly unknown. This study has investigated the biological significance of the colocalisation of GFRα3 with TrkA (neurotrophin receptor for nerve growth factor [NGF]) in the peptidergic type of unmyelinated (C-fibre) sensory neurons in rat dorsal root ganglia (DRG). In vitro neurite outgrowth assays were used to study the effects of artemin and NGF by comparing DRG neurons that were previously uninjured, or were axotomised in vivo by transecting a visceral or somatic peripheral nerve. We found that artemin could facilitate neurite initiation but in comparison to NGF had low efficacy for facilitating neurite elongation and branching. This low efficacy was not increased when a preconditioning in vivo nerve injury was used to induce a pro-regenerative state. Neurite initiation was unaffected by artemin when PI3 kinase and Src family kinase signalling were blocked, but NGF had a reduced effect.


Assuntos
Fator de Crescimento Neural/farmacologia , Proteínas do Tecido Nervoso/farmacologia , Neuritos/efeitos dos fármacos , Traumatismos dos Nervos Periféricos/metabolismo , Células Receptoras Sensoriais/metabolismo , Animais , Células Cultivadas , Feminino , Gânglios Espinais/citologia , Receptores de Fator Neurotrófico Derivado de Linhagem de Célula Glial/metabolismo , Humanos , Masculino , Regeneração Nervosa , Neuritos/metabolismo , Ratos , Ratos Sprague-Dawley , Receptor trkA/metabolismo , Células Receptoras Sensoriais/efeitos dos fármacos , Células Receptoras Sensoriais/fisiologia
7.
Front Neurosci ; 7: 206, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24223534

RESUMO

Bladder sensation is mediated by lumbosacral dorsal root ganglion neurons and is essential for normal voiding and nociception. Numerous electrophysiological, structural, and molecular changes occur in these neurons following inflammation. Defining which neurons undergo these changes is critical for understanding the mechanism underlying bladder pain and dysfunction. Our first aim was to define the chemical classes of bladder sensory neurons that express receptors for the endogenous modulators of nociceptor sensitivity, glial cell line-derived neurotrophic factor (GDNF), the related neurotrophic factor, artemin, and estrogens. Bladder sensory neurons of adult female Sprague-Dawley rats were identified with retrograde tracer. Diverse groups of neurons express these receptors, and some neurons express receptors for both neurotrophic factors and estrogens. Lumbar and sacral sensory neurons showed some distinct differences in their expression profile. We also distinguished the chemical profile of myelinated and unmyelinated bladder sensory neurons. Our second aim was to identify bladder sensory neurons likely to be undergoing structural remodeling during inflammation. Following systemic administration of cyclophosphamide (CYP), its renal metabolite acrolein causes transient urothelial loss, exposing local afferent terminals to a toxic environment. CYP induced expression of the injury-related immediate-early gene product, activating transcription factor-3 (ATF-3), in a small population of sacral nitrergic bladder sensory neurons. In conclusion, we have defined the bladder sensory neurons that express receptors for GDNF, artemin and estrogens. Our study has also identified a sub-population of sacral sensory neurons that are likely to be undergoing structural remodeling during acute inflammation of the bladder. Together these results contribute to increased understanding of the neurons that are known to be involved in pain modulation and hyperreflexia during inflammation.

8.
J Urol ; 190(2): 737-45, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23353045

RESUMO

PURPOSE: Recent evidence suggests that the urothelium functions as a sensory transducer of chemical, mechanical or thermal stimuli and signals to nerve terminals and other cells in the bladder wall. The cellular and molecular basis of neuro-urothelial communication is not easily studied in the intact bladder. This led us to establish a method of co-culturing dorsal root ganglion sensory neurons and bladder urothelial cells. MATERIALS AND METHODS: Sensory neurons and urothelial cells obtained from dorsal root ganglia and bladders dissected from adult female Sprague-Dawley® rats were isolated by enzyme treatment and mechanical dissociation. They were plated together or separately on collagen coated substrate and cultured in keratinocyte medium for 48 to 72 hours. Retrograde tracer labeling was performed to identify bladder afferents used for functional testing. RESULTS: Neurite growth and complexity in neurons co-cultured with urothelial cells was increased relative to that in neuronal monocultures. The growth promoting effect of urothelial cells was reduced by the tyrosine kinase inhibitor K252a but upstream inhibition of nerve growth factor signaling with TrkA-Fc had no effect. Fura-2 calcium imaging of urothelial cells showed responses to adenosine triphosphate (100 µM) and activation of TRPV4 (4α-PDD, 10 µM) but not TRPV1 (capsaicin, 1 µM), TRPV3 (farnesyl pyrophosphate, 1 µM) or TRPA1 (mustard oil, 100 µM). In contrast, co-cultured neurons were activated by all agonists except farnesyl pyrophosphate. CONCLUSIONS: Co-culturing provides a new methodology for investigating neuro-urothelial interactions in animal models of urological conditions. Results suggest that neuronal properties are maintained in the presence of urothelium and neurite growth is potentiated by a nerve growth factor independent mechanism.


Assuntos
Gânglios Espinais/metabolismo , Células Receptoras Sensoriais/metabolismo , Urotélio/citologia , Trifosfato de Adenosina/farmacologia , Análise de Variância , Animais , Capsaicina/farmacologia , Carbazóis/farmacologia , Técnicas de Cocultura , Dronabinol/farmacologia , Feminino , Fura-2/farmacologia , Imuno-Histoquímica , Alcaloides Indólicos/farmacologia , Indóis/farmacologia , Mentol/farmacologia , Modelos Animais , Fator de Crescimento Neural/farmacologia , Faloidina/farmacologia , Fosfatos de Poli-Isoprenil/farmacologia , Ratos , Ratos Sprague-Dawley , Sesquiterpenos/farmacologia , Canais de Cátion TRPV/biossíntese
9.
Pain ; 151(1): 184-193, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20675054

RESUMO

Spinal cord injury (SCI) is a major cause of persistent neuropathic pain of central origin. Recent evidence suggests neuropathic pain in clinically complete SCI patients correlates with limited sensory function below the lesion (sensory discomplete). On this basis we examined if the onset of mechanical hyperalgesia was different in rodents after a severe incomplete clip-compression SCI versus a complete spinal cord transection at thoracic segment T13. Above-level withdrawal behaviors evoked by forepaw stimulation provided evidence of mechanical hyperalgesia after incomplete but not complete SCI, whereas below-level responses evoked by hindpaw stimulation revealed hypersensitivity after both injuries. The latency of the above-level response was 4-5 wks but was longer after a moderate clip-compression injury. Mechanical hyperalgesia was fully reversed by three analgesic drugs used in treating neuropathic SCI pain, but their duration of action differed significantly, showing a rank order of amitriptyline (24-48 h)≫morphine (6 h)>gabapentin (2 h). Evidence of central sensitization in cervical spinal cord segments that receive sensory projections from the forelimbs was provided by immunohistochemistry for Zif268, a functional marker of neuroplasticity. Zif268-immunoreactive neurons in laminae I/II increased in response to repetitive noxious forepaw stimulation in the incomplete SCI group, and this response was reduced in the complete transection and sham-operated groups. These data are consistent with the hypothesis that neuropathic pain of cord origin is more likely to develop after SCI when there is an incomplete loss of axons traversing the lesion.


Assuntos
Analgésicos/uso terapêutico , Hiperalgesia/tratamento farmacológico , Hiperalgesia/etiologia , Limiar da Dor/efeitos dos fármacos , Traumatismos da Medula Espinal/complicações , Aminas/uso terapêutico , Amitriptilina/uso terapêutico , Animais , Contagem de Células , Estudos Cross-Over , Ácidos Cicloexanocarboxílicos/uso terapêutico , Modelos Animais de Doenças , Método Duplo-Cego , Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Lateralidade Funcional , Gabapentina , Regulação da Expressão Gênica/efeitos dos fármacos , Masculino , Morfina/uso terapêutico , Fosfopiruvato Hidratase/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Sprague-Dawley , Medula Espinal/efeitos dos fármacos , Medula Espinal/metabolismo , Traumatismos da Medula Espinal/classificação , Ácido gama-Aminobutírico/uso terapêutico
10.
Neuropharmacology ; 56(4): 798-807, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19705550

RESUMO

A history of intermittent exposures to drugs of abuse can cause long-term changes in acute behavioural responses to a subsequent drug exposure. In drug-naive rats, morphine can elicit intermittent cataleptic postures followed by sustained increases in locomotor activity. Chronic intermittent morphine treatment can reduce catalepsy and increase locomotor behaviour and stereotypy induced by morphine, even after prolonged periods of abstinence. The nucleus accumbens and limbic basal ganglia circuitry are implicated in the expression of various morphine-induced motor behaviours and catalepsy. We examined the effect of intermittent morphine exposure on the distribution of Fos proteins in the basal ganglia following a subsequent morphine challenge administered after a period of drug abstinence. We found that such exposures increased c-Fos induced by a morphine challenge in accumbens core regions that were immunoreactive for the micro-opioid receptor, and this correlated with the frequency of stereotypic behaviours displayed by the rats. We also found that a history of morphine exposures increased c-Fos in the ventrolateral striatum in response to a morphine challenge following 14 d but not 24 h of drug abstinence. In contrast, such a history induced acute Fras in the nucleus accumbens in response to a morphine challenge following 24 h but not 14 d of morphine abstinence. These data provide further confirmation that psychomotor sensitisation induced by repetitive morphine exposure involves long-term neuroadaptations in basal ganglia circuitry particularly at the level of the nucleus accumbens.


Assuntos
Analgésicos Opioides/farmacologia , Catalepsia/induzido quimicamente , Morfina/farmacologia , Neostriado/metabolismo , Núcleo Accumbens/metabolismo , Proteínas Oncogênicas v-fos/biossíntese , Comportamento Estereotipado/efeitos dos fármacos , Analgésicos Opioides/administração & dosagem , Animais , Catalepsia/psicologia , Contagem de Células , Imuno-Histoquímica , Masculino , Morfina/administração & dosagem , Neurônios/efeitos dos fármacos , Ratos , Síndrome de Abstinência a Substâncias/psicologia
11.
Neuroreport ; 19(18): 1793-6, 2008 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-18955903

RESUMO

Opioid efficacy on mu-receptor may be influenced by various Gi/o-G-protein subunits interacting with intracellular face of receptor. Pertussis toxin-insensitive Galphai1 and Galphai2 subunits tethered with mu-receptor were stably transfected into AtT20 cells to (i) determine coupling of different alpha-subunits on opioid efficacy, and (ii) determine coupling to downstream effectors, for example, calcium and potassium channels. After pertussis toxin, stimulation of [35S]GTP-gamma-S incorporation persisted. Both constructs were able to couple to native calcium and potassium channels, with endomorphins 1 and 2 equally effective. However, pertussis toxin abolished opioid actions on calcium and potassium channels suggesting strong coupling to endogenous G-proteins, and that differences in coupling efficacy to Galphai1 and Galphai2 previously observed are restricted to initial step of signaling cascade.


Assuntos
Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/metabolismo , Toxina Pertussis/farmacologia , Receptores Opioides mu/metabolismo , Analgésicos Opioides/farmacologia , Animais , Canais de Cálcio/metabolismo , Linhagem Celular Tumoral , Colo/metabolismo , Diprenorfina/farmacologia , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/genética , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Humanos , Camundongos , Neuroblastoma/genética , Neuroblastoma/metabolismo , Neuroblastoma/patologia , Oligopeptídeos/farmacologia , Canais de Potássio/metabolismo , Ligação Proteica/efeitos dos fármacos , Receptores Opioides mu/genética , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Transfecção/métodos
12.
Endocrinology ; 149(11): 5540-8, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18617618

RESUMO

There is mounting evidence that estrogens act directly on the nervous system to affect the severity of pain. Estrogen receptors (ERs) are expressed by sensory neurons, and in trigeminal ganglia, 17beta-estradiol can indirectly enhance nociception by stimulating expression and release of prolactin, which increases phosphorylation of the nociceptor transducer transient receptor potential vanilloid receptor 1 (TRPV1). Here, we show that 17beta-estradiol acts directly on dorsal root ganglion (DRG) sensory neurons to reduce TRPV1 activation by capsaicin. Capsaicin-induced cobalt uptake and the maximum TRPV1 current induced by capsaicin were inhibited when isolated cultured DRGs neurons from adult female rats were exposed to 17beta-estradiol (10-100 nm) overnight. There was no effect of 17beta-estradiol on capsaicin potency, TRPV1 activation by protons (pH 6-4), and P2X currents induced by alpha,beta-methylene-ATP. Diarylpropionitrile (ERbeta agonist) also inhibited capsaicin-induced TRPV1 currents, whereas propylpyrazole triol (ERalpha agonist) and 17alpha-estradiol (inactive analog) were inactive, and 17beta-estradiol conjugated to BSA (membrane-impermeable agonist) caused a small increase. TRPV1 inhibition was antagonized by tamoxifen (1 microm), but ICI182870 (10 microm) was a potent agonist and mimicked 17beta-estradiol. We conclude that TRPV1 in DRG sensory neurons can be inhibited by a nonclassical estrogen-signalling pathway that is downstream of intracellular ERbeta. This affects the vanilloid binding site targeted by capsaicin but not the TRPV1 activation site targeted by protons. These actions could curtail the nociceptive transducer functions of TRPV1 and limit chemically induced nociceptor sensitization during inflammation. They are consistent with clinical reports that female pelvic pain can increase after reductions in circulating estrogens.


Assuntos
Capsaicina/antagonistas & inibidores , Estradiol/farmacologia , Receptor beta de Estrogênio/metabolismo , Neurônios Aferentes/efeitos dos fármacos , Canais de Cátion TRPV/antagonistas & inibidores , Animais , Cobalto/metabolismo , Feminino , Gânglios Espinais/efeitos dos fármacos , Gânglios Espinais/metabolismo , Neurônios Aferentes/metabolismo , Nociceptores/efeitos dos fármacos , Nociceptores/metabolismo , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos , Potenciais Sinápticos/efeitos dos fármacos , Canais de Cátion TRPV/metabolismo , Canais de Cátion TRPV/fisiologia
13.
Neuropharmacology ; 53(2): 330-43, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17631915

RESUMO

Opioid-induced analgesia can be followed by spontaneous pain in humans, and hyperalgesia in rodents. In this study, opioid-induced hyperalgesia was measured by the tail-flick test when acute abstinence was precipitated by administering naloxone to drug naive rats that had experienced morphine analgesia for only 30 min. In a further experiment, the drug treatment that previously caused opioid-induced hyperalgesia was found to increase neurons expressing nuclear c-Fos or zif268 proteins in extended amygdalar regions targeted by projections of the ascending spino-parabrachio-amygdaloid nociceptive pathway. Transcription factor induction, however, was not detected in multiple brain regions known to respond in parallel with the same extended amygdalar structures when (1) rats are exposed to interoceptive/physical stressors, or (2) naloxone is used to precipitate abstinence in opioid dependent rats. Surprisingly, in many regions c-Fos induction by morphine was reduced or blocked by naloxone, even though these subjects had also experienced the effects of morphine for 30 min prior to antagonist administration. It is suggested transcription factor induction during opioid hyperalgesia in non-dependent rats could support the induction or consolidation of neural plasticity in nociceptive amygdaloid circuitry previously suggested to function in bi-directional control of pain and expression of pain-related behaviors.


Assuntos
Tonsila do Cerebelo/metabolismo , Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Hiperalgesia/metabolismo , Morfina/administração & dosagem , Entorpecentes/administração & dosagem , Proteínas Proto-Oncogênicas c-fos/metabolismo , Tonsila do Cerebelo/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Peptídeo Relacionado com Gene de Calcitonina/metabolismo , Contagem de Células , Relação Dose-Resposta a Droga , Esquema de Medicação , Interações Medicamentosas , Interações Alimento-Droga/efeitos da radiação , Hiperalgesia/induzido quimicamente , Masculino , Naloxona , Medição da Dor , Ratos , Ratos Wistar , Tempo de Reação/efeitos dos fármacos , Tirosina 3-Mono-Oxigenase/metabolismo
14.
J Biol Chem ; 278(21): 18776-84, 2003 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-12642578

RESUMO

The differential ability of various mu-opioid receptor (MOP) agonists to induce rapid receptor desensitization and endocytosis of MOP could arise simply from differences in their efficacy to activate G proteins or, alternatively, be due to differential capacity for activation of other signaling processes. We used AtT20 cells stably expressing a low density of FLAG-tagged MOP to compare the efficacies of a range of agonists to 1) activate G proteins using inhibition of calcium channel currents (ICa) as a reporter before and after inactivation of a fraction of receptors by beta-chlornaltrexamine, 2) produce rapid, homologous desensitization of ICa inhibition, and 3) internalize receptors. Relative efficacies determined for G protein coupling were [Tyr-D-Ala-Gly-MePhe-Glyol]enkephalin (DAMGO) (1) > or = methadone (0.98) > morphine (0.58) > pentazocine (0.15). The same rank order of efficacies for rapid desensitization of MOP was observed, but greater concentrations of agonist were required than for G protein activation. By contrast, relative efficacies for promoting endocytosis of MOP were DAMGO (1) > methadone (0.59) >> morphine (0.07) > or = pentazocine (0.03). These results indicate that the efficacy of opioids to produce activation of G proteins and rapid desensitization is distinct from their capacity to internalize mu-opioid receptors but that, contrary to some previous reports, morphine can produce rapid, homologous desensitization of MOP.


Assuntos
Proteínas de Ligação ao GTP/fisiologia , Naltrexona/análogos & derivados , Entorpecentes/farmacologia , Receptores Opioides mu/efeitos dos fármacos , Receptores Opioides mu/metabolismo , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/efeitos dos fármacos , Canais de Cálcio/fisiologia , Condutividade Elétrica , Endocitose/efeitos dos fármacos , Ala(2)-MePhe(4)-Gly(5)-Encefalina/farmacologia , Metadona/farmacologia , Camundongos , Morfina/farmacologia , Naltrexona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Neuroblastoma , Pentazocina/farmacologia , Neoplasias Hipofisárias , Receptores Opioides mu/genética , Transfecção , Células Tumorais Cultivadas
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