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1.
Nat Neurosci ; 24(10): 1441-1451, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34545249

RESUMO

Associative memories are stored in distributed networks extending across multiple brain regions. However, it is unclear to what extent sensory cortical areas are part of these networks. Using a paradigm for visual category learning in mice, we investigated whether perceptual and semantic features of learned category associations are already represented at the first stages of visual information processing in the neocortex. Mice learned categorizing visual stimuli, discriminating between categories and generalizing within categories. Inactivation experiments showed that categorization performance was contingent on neuronal activity in the visual cortex. Long-term calcium imaging in nine areas of the visual cortex identified changes in feature tuning and category tuning that occurred during this learning process, most prominently in the postrhinal area (POR). These results provide evidence for the view that associative memories form a brain-wide distributed network, with learning in early stages shaping perceptual representations and supporting semantic content downstream.


Assuntos
Aprendizagem/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Animais , Mapeamento Encefálico , Sinalização do Cálcio/fisiologia , Condicionamento Operante , Discriminação Psicológica , Agonistas GABAérgicos/farmacologia , Generalização Psicológica , Masculino , Memória , Camundongos , Camundongos Endogâmicos C57BL , Muscimol/farmacologia , Neocórtex/fisiologia , Plasticidade Neuronal/fisiologia , Estimulação Luminosa , Recrutamento Neurofisiológico
2.
Int J Mol Sci ; 22(17)2021 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-34502229

RESUMO

The two-pore domain K+ (K2P) channel, which is involved in setting the resting membrane potential in neurons, is an essential target for receptor agonists. Activation of the γ-aminobutyric acid (GABA) receptors (GABAAR and GABABR) reduces cellular excitability through Cl- influx and K+ efflux in neurons. Relatively little is known about the link between GABAAR and the K+ channel. The present study was performed to identify the effect of GABAR agonists on K2P channel expression and activity in the neuroblastic B35 cells that maintain glutamic acid decarboxylase (GAD) activity and express GABA. TASK and TREK/TRAAK mRNA were expressed in B35 cells with a high level of TREK-2 and TRAAK. In addition, TREK/TRAAK proteins were detected in the GABAergic neurons obtained from GABA transgenic mice. Furthermore, TREK-2 mRNA and protein expression levels were markedly upregulated in B35 cells by GABAAR and GABABR agonists. In particular, muscimol, a GABAAR agonist, significantly increased TREK-2 expression and activity, but the effect was reduced in the presence of the GABAAR antagonist bicuculine or TREK-2 inhibitor norfluoxetine. In the whole-cell and single-channel patch configurations, muscimol increased TREK-2 activity, but the muscimol effect disappeared in the N-terminal deletion mutant. These results indicate that muscimol directly induces TREK-2 activation through the N-terminus and suggest that muscimol can reduce cellular excitability by activating the TREK-2 channel and by inducing Cl- influx in GABAergic neurons.


Assuntos
Agonistas de Receptores de GABA-A/farmacologia , Neurônios GABAérgicos/metabolismo , Potenciais da Membrana , Muscimol/farmacologia , Canais de Potássio de Domínios Poros em Tandem/metabolismo , Receptores de GABA/química , Animais , Células Cultivadas , Neurônios GABAérgicos/efeitos dos fármacos , Células HEK293 , Humanos , Masculino , Camundongos , Canais de Potássio de Domínios Poros em Tandem/genética , Ratos
3.
Nat Neurosci ; 24(10): 1392-1401, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34400844

RESUMO

Compromised placental function or premature loss has been linked to diverse neurodevelopmental disorders. Here we show that placenta allopregnanolone (ALLO), a progesterone-derived GABA-A receptor (GABAAR) modulator, reduction alters neurodevelopment in a sex-linked manner. A new conditional mouse model, in which the gene encoding ALLO's synthetic enzyme (akr1c14) is specifically deleted in trophoblasts, directly demonstrated that placental ALLO insufficiency led to cerebellar white matter abnormalities that correlated with autistic-like behavior only in male offspring. A single injection of ALLO or muscimol, a GABAAR agonist, during late gestation abolished these alterations. Comparison of male and female human preterm infant cerebellum also showed sex-linked myelination marker alteration, suggesting similarities between mouse placental ALLO insufficiency and human preterm brain development. This study reveals a new role for a placental hormone in shaping brain regions and behaviors in a sex-linked manner. Placental hormone replacement might offer novel therapeutic opportunities to prevent later neurobehavioral disorders.


Assuntos
Cerebelo/crescimento & desenvolvimento , Glândulas Endócrinas/fisiologia , Placenta/fisiologia , Pregnanolona/deficiência , Pregnanolona/fisiologia , Comportamento Social , Aldeído Redutase/genética , Animais , Transtorno do Espectro Autista/etiologia , Cerebelo/fisiologia , Feminino , Agonistas GABAérgicos/farmacologia , Moduladores GABAérgicos , Deleção de Genes , Humanos , Lactente , Recém-Nascido , Masculino , Camundongos , Muscimol/farmacologia , Gravidez , Receptores de GABA-A/fisiologia , Caracteres Sexuais , Trofoblastos/metabolismo , Substância Branca/patologia
4.
Am J Physiol Heart Circ Physiol ; 321(3): H580-H591, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34355986

RESUMO

Tumor necrosis factor-α (TNFα) in the hypothalamic paraventricular nucleus (PVN) contributes to increased sympathetic nerve activity (SNA) in cardiovascular disease models, but mechanisms are incompletely understood. As previously reported, bilateral PVN TNFα (0.6 pmol, 50 nL) induced acute ramping of splanchnic SNA (SSNA) that averaged +64 ± 7% after 60 min and +109 ± 17% after 120 min (P < 0.0001, n = 10). Given that TNFα can rapidly strengthen glutamatergic transmission, we hypothesized that progressive activation of ionotropic glutamate receptors is critically involved. When compared with that of vehicle (n = 5), prior blockade of PVN AMPA or NMDA receptors in anesthetized (urethane/α-chloralose) adult male Sprague-Dawley rats dose-dependently (ED50: 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), 2.48 nmol; D-(-)-2-amino-5-phosphonopentanoic acid (APV), 12.33 nmol), but incompletely (Emax: NBQX, 64%; APV, 41%), attenuated TNFα-induced SSNA ramping (n = 5/dose). By contrast, combined receptor blockade prevented ramping (1.3 ± 2.1%, P < 0.0001, n = 5). Whereas separate blockade of PVN AMPA or NMDA receptors (n = 5/group) had little effect on continued SSNA ramping when performed 60 min after TNFα injection, combined blockade (n = 5) or PVN inhibition with the GABA-A receptor agonist muscimol (n = 5) effectively stalled, without reversing, the SSNA ramp. Notably, PVN TNFα increased local TNFα immunofluorescence after 120, but not 60 min. Findings indicate that AMPA and NMDA receptors each contribute to SSNA ramping to PVN TNFα, and that their collective availability and ongoing activity are required to initiate and sustain the ramping response. We conclude that acute sympathetic activation by PVN TNFα involves progressive local glutamatergic excitation that recruits downstream neurons capable of maintaining heightened SSNA, but incapable of sustaining SSNA ramping.NEW & NOTEWORTHY The proinflammatory cytokine TNFα contributes to heightened SNA in cardiovascular disease models, but mechanisms remain obscure. Here, we demonstrate that TNFα injection into the hypothalamic PVN triggers SNA ramping by mechanisms dependent on local ionotropic glutamate receptor availability, but largely independent of TNFα autoinduction. Continued SNA ramping depends on ionotropic glutamate receptor and neuronal activity in PVN, indicating that strengthening and/or increased efficacy of glutamatergic transmission is necessary for acute sympathoexcitation by PVN TNFα.


Assuntos
Núcleo Hipotalâmico Paraventricular/metabolismo , Receptores de AMPA/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Nervos Esplâncnicos/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , 2-Amino-5-fosfonovalerato/farmacologia , Animais , Antagonistas de Aminoácidos Excitatórios/farmacologia , Agonistas de Receptores de GABA-A/farmacologia , Masculino , Muscimol/farmacologia , Núcleo Hipotalâmico Paraventricular/fisiologia , Quinoxalinas/farmacologia , Ratos , Ratos Sprague-Dawley , Receptores de GABA-A/metabolismo , Nervos Esplâncnicos/efeitos dos fármacos , Nervos Esplâncnicos/fisiologia
5.
Exp Neurol ; 343: 113775, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34081986

RESUMO

After incomplete spinal cord injury (SCI), cortical plasticity is involved in hindlimb locomotor recovery. Nevertheless, whether cortical activity is required for motor map plasticity and recovery remains unresolved. Here, we combined a unilateral thoracic spinal cord injury (SCI) with a cortical inactivation protocol that uncovered a functional role of contralesional cortical activity in hindlimb recovery and ipsilesional map plasticity. In adult rats, left hindlimb paralysis was induced by sectioning half of the spinal cord at the thoracic level (hemisection) and we used a continuous infusion of muscimol (GABAA agonist, 10 mM, 0.11 µl/h) delivered via implanted osmotic pump (n = 9) to chronically inactivate the contralesional hindlimb motor cortex. Hemisected rats with saline infusion served as a SCI control group (n = 8), and intact rats with muscimol infusion served as an inactivation control group (n = 6). Locomotion was assessed in an open field, on a horizontal ladder, and on a treadmill prior to and for three weeks after hemisection. Cortical inactivation after hemisection significantly impeded hindlimb locomotor recovery in all tasks and specifically disrupted the ability of rats to generate proper flexion of the affected hindlimb during stepping compared to SCI controls, with no significant effect of inactivation in intact rats. Chronic and acute (n = 4) cortical inactivation after hemisection also significantly reduced the representation of the affected hindlimb in the ipsilesional motor cortex derived with intracortical microsimulation (ICMS). Our results provide evidence that residual activity in the contralesional hindlimb motor cortex after thoracic hemisection contributes to spontaneous locomotor recovery and map plasticity.


Assuntos
Membro Posterior/fisiopatologia , Locomoção/fisiologia , Córtex Motor/fisiopatologia , Recuperação de Função Fisiológica/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Vértebras Torácicas/lesões , Animais , Feminino , Agonistas de Receptores de GABA-A/toxicidade , Membro Posterior/efeitos dos fármacos , Membro Posterior/inervação , Locomoção/efeitos dos fármacos , Córtex Motor/efeitos dos fármacos , Muscimol/toxicidade , Ratos , Ratos Long-Evans , Recuperação de Função Fisiológica/efeitos dos fármacos
6.
Eur J Neurosci ; 54(2): 4595-4608, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34043849

RESUMO

Interval timing-the perception of durations mainly in seconds or minutes-is a ubiquitous behavior in organisms. Animal studies have suggested that the hippocampus plays an essential role in duration memory; however, the memory processes involved are unclear. To clarify the role of the dorsal hippocampus in the acquisition of long-term duration memories, we adapted the "time-shift paradigm" to a peak-interval procedure. After a sufficient number of training with an initial target duration (20 s), the rats underwent "shift sessions" with a new target duration (40 s) under a muscimol (0.5 µg per side) infusion into the bilateral dorsal hippocampus. The memory of the new target duration was then tested in drug-free "probe sessions," including trials in which no lever presses were reinforced. In the probe sessions, the mean response rate distribution of the muscimol group was located leftward to the control group, but these two response rate distributions were superimposed on the standardized time axis, suggesting a scalar property. In the session-by-session analysis, the mean peak time (an index of timing accuracy) of the muscimol group was lower than that of the control group in the probe sessions, but not in the shift sessions. These findings suggest that the dorsal hippocampus is required for the formation of long-term duration memories within the range of interval timing.


Assuntos
Hipocampo , Memória de Longo Prazo , Animais , Memória , Muscimol/farmacologia , Ratos
7.
Psychopharmacology (Berl) ; 238(6): 1657-1669, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33715044

RESUMO

RATIONALE: Nucleus cuneiformis (NC), a reticular nucleus of the midbrain, is a part of the descending pain modulatory system and therefore has an important role in pain perception. OBJECTIVES: Considering the abundance of GABAA and cannabinoid receptors in the NC and also the bidirectional roles for GABA in controlling nociception, the present study examined the effects of bilateral intra-NC microinjection of different doses of the GABAA receptor agonist, muscimol, and the GABAA receptor antagonist, bicuculline, on pain modulation using formalin test. We also assessed interaction between canabinergic and GABAergic systems in the NC during this test. METHODS: Rats were exposed to intra-NC microinjection of bicuculline (50,100, and 200 ng/side) or muscimol (60, 120, and 240 ng/side) and then subjected to the formalin test. In another set of experiments, the effects of muscimol (60 ng/side) or bicuculline (50 ng/side) administration 5 min before a cannabinoid receptor agonist WIN 55,212-2 (5, 10, and 20 µg/side) microinjection into NC on the formalin test were evaluated. RESULTS: Microinjection of bicuculline and muscimol into the NC decreased and increased pain responses, respectively, in a dose-dependent manner during both phases of the test. Microinjection of WIN 55,212-2 into the NC significantly reduced pain responses in a dose-dependent manner. Microinjection of bicuculline or muscimol in combination with WIN 55,212-2 into the NC respectively potentiated and attenuated WIN 55,212-2-induced antinociception in the formalin test. CONCLUSIONS: This study shows that GABA in the NC is involved in pain modulation and suggests the existence of a GABAA-mediated inhibitory system in the NC on pain control. Furthermore, it seems that the antinociceptive effect of WIN 55,212-2 in the formalin test is mediated partly by the activity of local GABAA receptors in the NC.


Assuntos
Benzoxazinas/farmacologia , Bicuculina/farmacologia , Agonistas de Receptores de GABA-A/farmacologia , Morfolinas/farmacologia , Muscimol/farmacologia , Naftalenos/farmacologia , Animais , Bicuculina/administração & dosagem , Canabinoides/farmacologia , Antagonistas de Receptores de GABA-A/farmacologia , Masculino , Nociceptividade/efeitos dos fármacos , Dor/tratamento farmacológico , Medição da Dor , Ratos , Ratos Wistar , Receptores de GABA-A/efeitos dos fármacos , Ácido gama-Aminobutírico/metabolismo
8.
Behav Neurosci ; 135(3): 343-346, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33630616

RESUMO

Previous studies found that inactivation of the central amygdala (CeA) severely impaired acquisition of cerebellum-dependent delay eye-blink conditioning (EBC) in male rats and rabbits. Sex differences in EBC and the effects of stress on EBC have been reported and might be related to sex differences in amygdala modulation of cerebellar learning. The current study examined the effects of CeA inactivation with muscimol on acquisition and retention of EBC in female rats. Like male rats, CeA inactivation in female rats severely impaired EBC acquisition and retention. Comparison of the female data with previously published data from males indicates no substantive sex differences in the effects of CeA inactivation on acquisition or retention of EBC. The results indicate that amygdala modulation of cerebellar learning is not sex-specific. (PsycInfo Database Record (c) 2021 APA, all rights reserved).


Assuntos
Núcleo Central da Amígdala , Condicionamento Palpebral , Animais , Cerebelo , Feminino , Masculino , Muscimol/farmacologia , Coelhos , Ratos , Ratos Long-Evans
9.
Laryngoscope ; 131(10): 2187-2198, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-33146426

RESUMO

OBJECTIVES: We aimed to examine the effect of unilateral inhibition of the medullary dorsal swallowing networks on the activities of swallowing-related cranial motor nerves and swallowing interneurons. METHODS: In 25 juvenile rats, we recorded bilateral vagal nerve activity (VNA) as well as unilateral phrenic and hypoglossal activity (HNA) during fictive swallowing elicited by electrical stimulation of the superior laryngeal nerve during control and following microinjection of the GABA agonist muscimol into the caudal dorsal medulla oblongata in a perfused brainstem preparation. In 20 animals, swallowing interneurons contralateral to the muscimol injection side were simultaneously recorded extracellularly and their firing rates were analyzed during swallowing. RESULTS: Integrated VNA and HNA to the injection side decreased to 49.0 ± 16.6% and 32.3 ± 17.9%, respectively. However, the VNA on the uninjected side showed little change after muscimol injection. Following local inhibition, 11 out of 20 contralateral swallowing interneurons showed either increased or decreased of their respective firing discharge during evoked-swallowing, while no significant changes in activity were observed in the remaining nine neurons. CONCLUSION: The neuronal networks underlying the swallowing pattern generation in the dorsal medulla mediate the ipsilateral motor outputs and modulate the contralateral activity of swallowing interneurons, suggesting that the bilateral coordination of the swallowing central pattern generator regulates the spatiotemporal organization of pharyngeal swallowing movements. LEVEL OF EVIDENCE: NA Laryngoscope, 131:2187-2198, 2021.


Assuntos
Deglutição/fisiologia , Agonistas de Receptores de GABA-A/administração & dosagem , Bulbo/fisiologia , Faringe/fisiologia , Nervo Vago/fisiologia , Animais , Deglutição/efeitos dos fármacos , Estimulação Elétrica , Nervo Hipoglosso/efeitos dos fármacos , Nervo Hipoglosso/fisiologia , Masculino , Bulbo/efeitos dos fármacos , Microinjeções , Modelos Animais , Muscimol/administração & dosagem , Rede Nervosa/efeitos dos fármacos , Rede Nervosa/fisiologia , Neurônios/fisiologia , Faringe/inervação , Ratos , Análise Espaço-Temporal , Nervo Vago/efeitos dos fármacos
10.
Behav Brain Res ; 398: 112967, 2021 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-33075397

RESUMO

The postpartum period is commonly accompanied by emotional changes, which for many new mothers includes a reduction in anxiety. Previous research in rodents has shown that the postpartum attenuation in anxiety is dependent on offspring contact and has further implicated enhanced GABAergic neurotransmission as an underlying mechanism. However, the specific brain regions where GABA acts to regulate the offspring-induced reduction in postpartum anxiety requires further investigation. Here, we test the hypothesis that offspring interactions suppress anxiety-like behavior in postpartum female rats via GABA signaling in the medial prefrontal cortex (mPFC). Our results show a postpartum reduction in anxiety-like behavior, an effect which was abolished by localized infusion of the GABAA receptor antagonist bicuculline in the mPFC. We also show that activation of GABAA receptors in the mPFC by the agonist muscimol was effective in restoring anxiolyisis in mothers separated from their pups. Lastly, we show that heightened anxiety-like behavior in pup-separated mothers was accompanied by a lower number and percentage of activated GABAergic neurons within the mPFC. Together, these results suggest that mother-offspring interactions reduce anxiety-like behavior in postpartum females via GABAA neurotransmission in the mPFC and in doing so provide insight into mechanisms that may become dysfunctional in mothers who experience high postpartum anxiety.


Assuntos
Ansiedade/metabolismo , Agonistas de Receptores de GABA-A/farmacologia , Antagonistas de Receptores de GABA-A/farmacologia , Neurônios GABAérgicos/fisiologia , Privação Materna , Córtex Pré-Frontal/fisiologia , Transtornos Puerperais/metabolismo , Ácido gama-Aminobutírico/fisiologia , Animais , Ansiedade/tratamento farmacológico , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Bicuculina/farmacologia , Modelos Animais de Doenças , Feminino , Agonistas de Receptores de GABA-A/administração & dosagem , Antagonistas de Receptores de GABA-A/administração & dosagem , Humanos , Masculino , Muscimol/farmacologia , Córtex Pré-Frontal/metabolismo , Transtornos Puerperais/tratamento farmacológico , Ratos Sprague-Dawley
11.
Behav Brain Res ; 401: 113077, 2021 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-33345825

RESUMO

Food neophobia is a behavior observed in rodents involving reduced consumption of a novel food or drink. In the absence of negative post-ingestive consequences, consumption increases with exposure (attenuation of neophobia), which is seen as an associative safe memory. Olfaction and gustation are sensory modalities essential for the development of a food preference. However, little is known about the neural mechanisms underlying neophobia to a food-related odor stimulus. In the present study, we examined the effect of pharmacological inactivation of the ventral hippocampus (vHPC) on neophobia to orally consumed solutions in rats using muscimol, a gamma aminobutyric acid type A receptor agonist. Two different types of solutions, almond odor (benzaldehyde) and sweet taste (saccharin), were prepared. In the results, microinjections of muscimol into the bilateral vHPC before the first odor and taste exposures did not alter the neophobic reactions of the rats to each stimulus. However, in the second odor, but not taste, exposure, the muscimol-injected rats showed higher consumption in comparison to that observed in the control rats, suggesting that the vHPC inactivation facilitates the attenuation of odor neophobia. On the other hand, intra-vHPC muscimol microinjections after the first odor and taste exposures did not facilitate consumption at the second exposures. These results indicate that neural activations within vHPC during orally consuming a novel odor, but not taste, solution play an inhibitory role in the subsequent attenuation of neophobia.


Assuntos
Comportamento Animal/fisiologia , Preferências Alimentares/fisiologia , Agonistas de Receptores de GABA-A/farmacologia , Hipocampo/efeitos dos fármacos , Muscimol/farmacologia , Percepção Olfatória/fisiologia , Percepção Gustatória/fisiologia , Animais , Comportamento Animal/efeitos dos fármacos , Preferências Alimentares/efeitos dos fármacos , Agonistas de Receptores de GABA-A/administração & dosagem , Masculino , Muscimol/administração & dosagem , Percepção Olfatória/efeitos dos fármacos , Ratos , Ratos Wistar , Percepção Gustatória/efeitos dos fármacos
12.
Nat Commun ; 11(1): 6050, 2020 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-33247191

RESUMO

The cerebellum is crucial for various associative sensorimotor behaviors. Delay eyeblink conditioning (DEC) depends on the simplex lobule-interposed nucleus (IN) pathway, yet it is unclear how other cerebellar modules cooperate during this task. Here, we demonstrate the contribution of the vermis-fastigial nucleus (FN) pathway in controlling DEC. We found that task-related modulations in vermal Purkinje cells and FN neurons predict conditioned responses (CRs). Coactivation of the FN and the IN allows for the generation of proper motor commands for CRs, but only FN output fine-tunes unconditioned responses. The vermis-FN pathway launches its signal via the contralateral ventral medullary reticular nucleus, which converges with the command from the simplex-IN pathway onto facial motor neurons. We propose that the IN pathway specifically drives CRs, whereas the FN pathway modulates the amplitudes of eyelid closure during DEC. Thus, associative sensorimotor task optimization requires synergistic modulation of different olivocerebellar modules each provide unique contributions.


Assuntos
Comportamento Animal/fisiologia , Núcleos Cerebelares/fisiologia , Cerebelo/fisiologia , Potenciais de Ação/efeitos dos fármacos , Animais , Comportamento Animal/efeitos dos fármacos , Piscadela/efeitos dos fármacos , Núcleos Cerebelares/efeitos dos fármacos , Cerebelo/efeitos dos fármacos , Condicionamento Clássico/efeitos dos fármacos , Glutamatos/metabolismo , Integrases/metabolismo , Camundongos Endogâmicos C57BL , Neurônios Motores/efeitos dos fármacos , Neurônios Motores/fisiologia , Movimento/efeitos dos fármacos , Muscimol/farmacologia , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Optogenética , Células de Purkinje/efeitos dos fármacos , Células de Purkinje/fisiologia , Análise e Desempenho de Tarefas
13.
Nat Commun ; 11(1): 4929, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33004789

RESUMO

Non-invasive, molecularly-specific, focal modulation of brain circuits with low off-target effects can lead to breakthroughs in treatments of brain disorders. We systemically inject engineered ultrasound-controllable drug carriers and subsequently apply a novel two-component Aggregation and Uncaging Focused Ultrasound Sequence (AU-FUS) at the desired targets inside the brain. The first sequence aggregates drug carriers with millimeter-precision by orders of magnitude. The second sequence uncages the carrier's cargo locally to achieve high target specificity without compromising the blood-brain barrier (BBB). Upon release from the carriers, drugs locally cross the intact BBB. We show circuit-specific manipulation of sensory signaling in motor cortex in rats by locally concentrating and releasing a GABAA receptor agonist from ultrasound-controlled carriers. Our approach uses orders of magnitude (1300x) less drug than is otherwise required by systemic injection and requires very low ultrasound pressures (20-fold below FDA safety limits for diagnostic imaging). We show that the BBB remains intact using passive cavitation detection (PCD), MRI-contrast agents and, importantly, also by sensitive fluorescent dye extravasation and immunohistochemistry.


Assuntos
Barreira Hematoencefálica/metabolismo , Encefalopatias/tratamento farmacológico , Portadores de Fármacos/efeitos da radiação , Agonistas de Receptores de GABA-A/administração & dosagem , Ultrassonografia de Intervenção/métodos , Animais , Barreira Hematoencefálica/diagnóstico por imagem , Barreira Hematoencefálica/efeitos da radiação , Relação Dose-Resposta à Radiação , Portadores de Fármacos/química , Portadores de Fármacos/farmacocinética , Feminino , Agonistas de Receptores de GABA-A/farmacocinética , Humanos , Imageamento por Ressonância Magnética , Modelos Animais , Muscimol/administração & dosagem , Muscimol/farmacocinética , Ratos , Técnicas Estereotáxicas , Ondas Ultrassônicas
14.
Pharmacol Biochem Behav ; 198: 173034, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32910929

RESUMO

In the spinal cord, γ-aminobutyric acid (GABA) interneurons play an essential role in antinociception. However, not all actions of GABA favor antinociception at the supraspinal level. We previously reported that gabaculine, which increases endogenous GABA in the synaptic clefts, induces loss of the righting reflex (LORR) that is one indicator of hypnosis, but not immobility in response to noxious stimulus. A slow pain is transmitted to the spinal cord via C fibers and evokes substance P (SP) release from their terminals. However, the antinociceptive effects of gabaculine are still unknown. Our study examined whether the analgesic effects of the opioid morphine or the α2-adrenoceptor agonist dexmedetomidine, whose actions are mediated through facilitation of the descending analgesic pathway, are affected by gabaculine-induced LORR. We also explored the effects of GABA receptor agonists on SP release from cultured dorsal root ganglion (DRG) neurons. All drugs were administered systemically to mice. To assess antinociception, loss of nociceptive response (analgesia) and immobility were evaluated. DRG cells were dissected from rats. Gabaculine produced no analgesia. Either morphine or dexmedetomidine in combination with gabaculine induced immobility; however, the doses of each drug required to induce immobility were much higher than those required to induce analgesia. Capsaicin significantly increased SP release from DRG cells, but a high concentration (1 mM) of the GABA receptor agonist muscimol, propofol, gaboxadol, or baclofen did not inhibit the capsaicin-induced SP release, suggesting that their antinociceptive effects were not through this mechanism. Thus, the gabaculine-induced LORR may inhibit the descending analgesic pathway.


Assuntos
Analgésicos/farmacologia , Ácidos Cicloexanocarboxílicos/farmacologia , Dexmedetomidina/farmacologia , Morfina/farmacologia , Reflexo de Endireitamento/efeitos dos fármacos , Agonistas de Receptores Adrenérgicos alfa 2/farmacologia , Analgésicos/metabolismo , Animais , Baclofeno/farmacologia , Agonistas GABAérgicos/farmacologia , Gânglios Espinais/efeitos dos fármacos , Masculino , Camundongos , Muscimol/farmacologia , Vias Neurais/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Medição da Dor/efeitos dos fármacos , Ratos , Transdução de Sinais/efeitos dos fármacos , Medula Espinal/efeitos dos fármacos , Substância P/efeitos dos fármacos , Substância P/metabolismo
15.
Pflugers Arch ; 472(11): 1563-1576, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32914212

RESUMO

Active expiration represents an important mechanism to improve ventilation in conditions of augmented ventilatory demand, such as hypercapnia. While a rostral ventromedullary region, the parafacial respiratory group (pFRG), has been identified as a conditional expiratory oscillator, little is known about how central chemosensitive sites contribute to modulate active expiration under hypercapnia. In this study, we investigated the influence of the medullary raphe in the emergence of phasic expiratory abdominal activity during hypercapnia in unanesthetized adult male rats, in a state-dependent manner. To do so, reverse microdialysis of muscimol (GABAA receptor agonist, 1 mM) or 8-OH-DPAT (5-HT1A agonist, 1 mM) was applied in the MR during sleep and wakefulness periods, both in normocapnic (room air) and hypercapnic conditions (7% CO2). Electromyography (EMG) of diaphragm and abdominal muscles was performed to measure inspiratory and expiratory motor outputs. We found that active expiration did not occur in room air exposure during wakefulness or sleep. However, hypercapnia did recruit active expiration, and differential effects were observed with the drug dialyses in the medullary raphe. Muscimol increased the diaphragm inspiratory motor output and also increased the amplitude and frequency of abdominal expiratory rhythmic activity during hypercapnia in wakefulness periods. On the other hand, the microdialysis of 8-OH-DPAT attenuated hypercapnia-induced active expiration in a state-dependent manner. Our data suggest that the medullary raphe can either inhibit or potentiate respiratory motor activity during hypercapnia, and the balance of these inhibitory or excitatory outputs may determine the expression of active expiration.


Assuntos
Diafragma/fisiopatologia , Expiração , Hipercapnia/fisiopatologia , Núcleos da Rafe/fisiopatologia , 8-Hidroxi-2-(di-n-propilamino)tetralina/farmacologia , Músculos Abdominais/inervação , Músculos Abdominais/fisiopatologia , Animais , Diafragma/inervação , Agonistas de Receptores de GABA-A/farmacologia , Masculino , Muscimol/farmacologia , Contração Muscular , Núcleos da Rafe/efeitos dos fármacos , Ratos , Ratos Wistar , Agonistas do Receptor de Serotonina/farmacologia , Sono , Vigília
16.
Neurobiol Learn Mem ; 175: 107313, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32956808

RESUMO

The neural circuit supporting aversive memory destabilization after retrieval includes the hippocampus, amygdala, and medial prefrontal cortex. The nucleus reuniens (NR) contributes to the functional interaction of these brain regions relevant to cognitive processing. However, the direct participation of this thalamic subregion in memory destabilization is yet to be investigated. The present study addressed this question in contextually fear-conditioned rats. Pre-reactivation infusion of the GABAA receptor agonist muscimol, the protein degradation inhibitor clasto-lactacystin ß-lactone (ß-lac), or the glutamate N2B-containing NMDA receptors antagonist ifenprodil into the NR prevented the post-reactivation amnestic effects of both locally infused anisomycin and systemically administered clonidine. In either case, the results suggest a significant disruption in memory destabilization. It is noteworthy that these pharmacological interventions induced no changes in expression or contextual specificity of the memory. Moreover, omitting memory reactivation precluded the muscimol, ß-lac, and ifenprodil effects on destabilization and the anisomycin and clonidine effects on reconsolidation. We also quantified the Egr1/Zif268-expressing neurons to investigate the effects of muscimol-induced NR inactivation on the activity-related plasticity locally, and in other brain regions supporting fear memory destabilization-reconsolidation. Relative to controls, there were reduced values in the NR, the dorsal CA1 hippocampus, the prelimbic cortex, and the infralimbic cortex. In contrast, increases happened in the ventral CA1 hippocampus and the basolateral amygdala. These results suggest that NR has a circuit-level influence on this process. Together, present findings demonstrate how the NR can regulate contextual fear memory destabilization upon retrieval.


Assuntos
Tonsila do Cerebelo/fisiologia , Região CA1 Hipocampal/fisiologia , Medo , Memória/fisiologia , Núcleos da Linha Média do Tálamo/fisiologia , Neurônios/fisiologia , Córtex Pré-Frontal/fisiologia , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/metabolismo , Animais , Anisomicina/farmacologia , Região CA1 Hipocampal/efeitos dos fármacos , Região CA1 Hipocampal/metabolismo , Clonidina/farmacologia , Cognição , Inibidores de Cisteína Proteinase/farmacologia , Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Antagonistas de Aminoácidos Excitatórios/farmacologia , Agonistas de Receptores de GABA-A/farmacologia , Lactonas/farmacologia , Memória/efeitos dos fármacos , Núcleos da Linha Média do Tálamo/efeitos dos fármacos , Núcleos da Linha Média do Tálamo/metabolismo , Muscimol/farmacologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Piperidinas/farmacologia , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Ratos , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores
17.
Sci Rep ; 10(1): 15827, 2020 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-32985565

RESUMO

Lesioning or inactivating the infralimbic (IL) subregion of the medial prefrontal cortex before acquisition produces more generalized and extinction-resistant fear memories. However, whether and how it modulates memory specificity and extinction susceptibility while consolidation takes place is still unknown. The present study aims to investigate these questions using muscimol-induced temporary inactivation and anisomycin-induced protein synthesis inhibition in the rat IL following contextual fear conditioning. Results indicate that the IL activity immediately after acquisition, but not six hours later, controls memory generalization over a week, regardless of its strength. Such IL function depends on the context-shock pairing since muscimol induced no changes in animals exposed to immediate shocks or the conditioning context only. Animals in which the IL was inactivated during consolidation extinguished similarly to controls within the session but were unable to recall the extinction memory the following day. Noteworthy, these post-acquisition IL inactivation-induced effects were not associated with changes in anxiety, as assessed in the elevated plus-maze test. Anisomycin results indicate that the IL protein synthesis during consolidation contributes more to producing extinction-sensitive fear memories than memory specificity. Collectively, present results provide evidence for the IL's role in controlling generalization and susceptibility to extinction during fear memory consolidation.


Assuntos
Extinção Psicológica/fisiologia , Medo/fisiologia , Generalização Psicológica/fisiologia , Lobo Límbico/fisiologia , Consolidação da Memória/fisiologia , Animais , Anisomicina/farmacologia , Condicionamento Clássico , Eletrodos Implantados , Generalização Psicológica/efeitos dos fármacos , Lobo Límbico/efeitos dos fármacos , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Aprendizagem em Labirinto/fisiologia , Memória/fisiologia , Muscimol/farmacologia , Ratos , Ratos Wistar
18.
Mol Pharmacol ; 98(4): 303-313, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32873746

RESUMO

Muscimol is a psychoactive isoxazole derived from the mushroom Amanita muscaria and a potent orthosteric agonist of the GABAA receptor. The binding of [3H]muscimol has been used to evaluate the distribution of GABAA receptors in the brain, and studies of modulation of [3H]muscimol binding by allosteric GABAergic modulators such as barbiturates and steroid anesthetics have provided insight into the modes of action of these drugs on the GABAA receptor. It has, however, not been feasible to directly apply interaction parameters derived from functional studies to describe the binding of muscimol to the receptor. Here, we employed the Monod-Wyman-Changeux concerted transition model to analyze muscimol binding isotherms. We show that the binding isotherms from recombinant α1ß3 GABAA receptors can be qualitatively predicted using electrophysiological data pertaining to properties of receptor activation and desensitization in the presence of muscimol. The model predicts enhancement of [3H]muscimol binding in the presence of the steroids allopregnanolone and pregnenolone sulfate, although the steroids interact with distinct sites and either enhance (allopregnanolone) or reduce (pregnenolone sulfate) receptor function. We infer that the concerted transition model can be used to link radioligand binding and electrophysiological data. SIGNIFICANCE STATEMENT: The study employs a three-state resting-active-desensitized model to link radioligand binding and electrophysiological data. We show that the binding isotherms can be qualitatively predicted using parameters estimated in electrophysiological experiments and that the model accurately predicts the enhancement of [3H]muscimol binding in the presence of the potentiating steroid allopregnanolone and the inhibitory steroid pregnenolone sulfate.


Assuntos
Agonistas de Receptores de GABA-A/farmacologia , Muscimol/farmacologia , Receptores de GABA-A/metabolismo , Esteroides/farmacologia , Regulação Alostérica/efeitos dos fármacos , Sítios de Ligação , Células HEK293 , Humanos , Complexos Multiproteicos/química , Complexos Multiproteicos/genética , Muscimol/química , Pregnanolona/farmacologia , Pregnenolona/farmacologia , Receptores de GABA-A/química , Receptores de GABA-A/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Trítio/química
19.
Psychopharmacology (Berl) ; 237(12): 3759-3771, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32875348

RESUMO

RATIONALE: Compulsive cocaine use, defined as the continued use despite the dire consequences, is a hallmark of cocaine addiction. Thus, understanding the brain mechanism regulating the compulsive cocaine-seeking and cocaine-taking behaviors is essential to understand cocaine addiction and the key to identification of the molecular targets for the development of medications against this condition. OBJECTIVE: This study aimed to determine how the GABAa and GABAb receptors of the central nucleus of the amygdala (CeA) regulate the compulsive cocaine-seeking behavior. METHODS: Male Wistar outbred rats were trained to self-administer intravenous cocaine (0.4 mg/kg/infusion) under a chained schedule. The compulsive cocaine-seeking behavior was measured as the cocaine-seeking behavior in the face of footshock punishment. The role of the GABA receptors of CeA in the regulation of such behavior was determined by measuring the dose-dependent effects of the GABAa agonist muscimol or the GABAb agonist baclofen bilaterally microinjected into the CeA on the punished cocaine-seeking behavior. RESULTS: The cocaine-seeking behavior was inhibited by footshock punishment in an intensity-dependent manner. Both muscimol and baclofen dose-dependently increased the punished cocaine-seeking behavior. However, the potency of muscimol but not baclofen was negatively correlated with the effects of punishment. CONCLUSION: These data indicate that the CeA GABAa receptors play a key role in the regulation of the compulsive cocaine-seeking behavior and suggest that an increase in the function of the GABAa receptors possibly induced by cocaine or genetic factors may be an important mechanism involved in the development of or vulnerability to the compulsive cocaine use and addiction.


Assuntos
Comportamento Aditivo/psicologia , Núcleo Central da Amígdala/fisiologia , Cocaína/administração & dosagem , Comportamento Compulsivo/psicologia , Receptores de GABA-A/fisiologia , Receptores de GABA-B/fisiologia , Animais , Baclofeno/administração & dosagem , Comportamento Aditivo/tratamento farmacológico , Núcleo Central da Amígdala/efeitos dos fármacos , Transtornos Relacionados ao Uso de Cocaína/tratamento farmacológico , Transtornos Relacionados ao Uso de Cocaína/psicologia , Comportamento Compulsivo/tratamento farmacológico , Agonistas de Receptores de GABA-A/administração & dosagem , Agonistas dos Receptores de GABA-B/administração & dosagem , Masculino , Microinjeções , Muscimol/administração & dosagem , Ratos , Ratos Wistar , Autoadministração
20.
Mol Brain ; 13(1): 112, 2020 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-32799906

RESUMO

A unique feature of fear memory is its persistence that is highly relevant to fear and anxiety-related mental disorders. Recurrent reactivation of neural representations acquired from a traumatic event is thought to contribute to the indelibility of fear memory. Given a well-established role of hippocampus for memory reactivation, hippocampus is likely involved in consolidation process of fear memory. However, evidence suggests that formation of fear memory to a discrete sensory cue is hippocampus-independent. Here, using a pharmacological reversible inactivation of dorsal hippocampus in auditory cued fear conditioning by local infusion of muscimol, we demonstrate in mice that hippocampus is critical for remote memory formation of learned fear to the discrete sensory cue. Muscimol infusion before conditioning did not affect formation of recent auditory fear memory as previously reported. Same muscimol infusion, however, impaired remote auditory fear memory. Muscimol infusion before remote test of auditory fear memory did not affect memory retrieval, indicating hippocampus is not a brain site for storage of remote cued fear memory. Moreover, memory reactivation enforced by re-exposure to the conditioned tone could compensate for hippocampal inactivation, as memory-reactivated mice showed normal remote auditory fear memory despite hippocampal inactivation. Our findings support that hippocampus may have a general role for consolidation of remote associative memory through reactivation of memory trace, giving an insight into how learned fear persists over time.


Assuntos
Sinais (Psicologia) , Medo/fisiologia , Hipocampo/fisiopatologia , Memória de Longo Prazo/fisiologia , Estimulação Acústica , Animais , Condicionamento Clássico/efeitos dos fármacos , Medo/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Masculino , Transtornos da Memória/fisiopatologia , Memória de Longo Prazo/efeitos dos fármacos , Rememoração Mental/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Muscimol/farmacologia
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