RESUMEN
Systemic administration of dopamine (DA) receptor agonists leads to falls in body temperature. However, the central thermoregulatory pathways modulated by DA have not been fully elucidated. Here we identified a source and site of action contributing to DA's hypothermic action by inhibition of brown adipose tissue (BAT) thermogenesis. Nanoinjection of the type 2 and type 3 DA receptor (D2R/D3R) agonist, 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT), in the rostral raphe pallidus area (rRPa) inhibits the sympathetic activation of BAT evoked by cold exposure or by direct activation of N-methyl-d-aspartate (NMDA) receptors in the rRPa. Blockade of D2R/D3R in the rRPa with nanoinjection of SB-277011A increases BAT thermogenesis, consistent with a tonic release of DA in the rRPa contributing to inhibition of BAT thermogenesis. Accordingly, D2Rs are expressed in cold-activated and serotonergic neurons in the rRPa, and anatomical tracing studies revealed that neurons in the posterior hypothalamus (PH) are a source of dopaminergic input to the rRPa. Disinhibitory activation of PH neurons with nanoinjection of gabazine inhibits BAT thermogenesis, which is reduced by pretreatment of the rRPa with SB-277011A. In conclusion, the rRPa, the site of sympathetic premotor neurons for BAT, receives a tonically active, dopaminergic input from the PH that suppresses BAT thermogenesis.
Asunto(s)
Tejido Adiposo Pardo/inervación , Dopamina/metabolismo , Neuronas Dopaminérgicas/metabolismo , Hipotálamo Posterior/metabolismo , Inhibición Neural , Núcleo Pálido del Rafe/metabolismo , Termogénesis , Animales , Agonistas de Dopamina/administración & dosificación , Neuronas Dopaminérgicas/efectos de los fármacos , Antagonistas del GABA/administración & dosificación , Hipotálamo Posterior/efectos de los fármacos , Inyecciones , Masculino , Vías Nerviosas/metabolismo , Núcleo Pálido del Rafe/efectos de los fármacos , Ratas Sprague-Dawley , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D3/metabolismo , Receptores de GABA-A/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Termogénesis/efectos de los fármacosRESUMEN
Dopamine receptors (DRs) are generally considered as mediators of vasomotor functions. However, when used in pharmacological studies, dopamine and/or DR agonists may not discriminate among different DR subtypes and may even stimulate alpha1 and beta-adrenoceptors. Here, we tested the hypothesis that D2R and/or D3R may specifically induce vasoconstriction in isolated mouse aorta. Aorta, isolated from wild-type (WT) and D3R-/- mice, was mounted in a wire myograph and challenged with cumulative concentrations of phenylephrine (PE), acetylcholine (ACh), and the D3R agonist 7-hydrxy-N,N-dipropyl-2-aminotetralin (7-OH-DPAT), with or without the D2R antagonist L741,626 and the D3R antagonist SB-277011-A. The vasoconstriction to PE and the vasodilatation to ACh were not different in WT and D3R-/-; in contrast, the contractile responses to 7-OH-DPAT were significantly weaker in D3R-/-, though not abolished. L741,626 did not change the contractile response induced by 7-OH-DPAT in WT or in D3R-/-, whereas SB-277011-A significantly reduced it in WT but did not in D3R-/-. D3R mRNA (assessed by qPCR) was about 5-fold more abundant than D2R mRNA in aorta from WT and undetectable in aorta from D3R-/-. Following transduction with lentivirus (72-h incubation) delivering synthetic microRNAs to specifically inactivate D2R (LV-miR-D2) or D3R (LV-miR-D3), the contractile response to 7-OH-DPAT was unaffected by LV-miR-D2, while it was significantly reduced by LV-miR-D3. These data indicate that, at least in mouse aorta, D3R stimulation induces vasoconstriction, while D2R stimulation does not. This is consistent with the higher expression level of D3R. The residual vasoconstriction elicited by high concentration D3R agonist in D3R-/- and/or in the presence of D3R antagonist is likely to be unrelated to DRs.
Asunto(s)
Aorta/fisiología , Receptores de Dopamina D3/metabolismo , Vasoconstricción/genética , Animales , Aorta/efectos de los fármacos , Indoles/farmacología , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Nitrilos/farmacología , Piperidinas/farmacología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Receptores de Dopamina D2/genética , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D3/agonistas , Receptores de Dopamina D3/antagonistas & inhibidores , Receptores de Dopamina D3/genética , Tetrahidroisoquinolinas/farmacología , Tetrahidronaftalenos/farmacología , Vasoconstricción/efectos de los fármacosRESUMEN
The sensory nervous system controls cardiovascular homeostasis via capsaicin-sensitive neurons that release calcitonin gene-related peptide (CGRP), which subsequently activates CGRP receptors. How this perivascular CGRPergic discharge is modulated, nevertheless, remains unclear. In pithed rats, systemic vasodilation induced by CGRPergic discharge stimulation results in diastolic blood pressure (BP) decrements that are inhibited by the dopamine D2-like receptor agonist quinpirole. Since this inhibition is mediated by raclopride- or haloperidol-sensitive D2-like receptors (comprising the D2, D3, and D4 subtypes), the present study pharmacologically investigated the specific contribution of these subtypes to the modulation of the systemic CGRPergic vasodilation, using highly specific antagonists. To that end, 55 male Wistar rats were pithed for thoracic (T9-T12) spinal stimulation of the perivascular CGRPergic discharge. The resulting frequency-dependent decrements in diastolic BP were inhibited by quinpirole, and this sensory-inhibition was (a) unchanged after i.v. injections of the antagonists L-741,626 (D2) or L-745,870 (D4) and (b) completely blocked by SB-277011-A (D3). Accordingly, we suggest the main role of the D3 receptor subtypes in the inhibition by quinpirole of the neurogenic CGRPergic systemic vasodilation. These findings contribute to a better understanding of the dopaminergic modulation of the rat perivascular CGRPergic discharge producing systemic vasodilation.
Asunto(s)
Presión Sanguínea/efectos de los fármacos , Péptido Relacionado con Gen de Calcitonina/metabolismo , Agonistas de Dopamina/farmacología , Frecuencia Cardíaca/fisiología , Receptores de Dopamina D3/antagonistas & inhibidores , Vasodilatación/efectos de los fármacos , Animales , Estimulación Eléctrica , Frecuencia Cardíaca/efectos de los fármacos , Masculino , Quinpirol/farmacología , Racloprida/farmacología , Ratas , Ratas WistarRESUMEN
The dopamine D3 receptor (D3R), in the nucleus accumbens (NAc), plays an important role in alcohol reward mechanisms. The major neuronal type within the NAc is the GABAergic medium spiny neuron (MSN), whose activity is regulated by dopaminergic inputs. We previously reported that genetic deletion or pharmacological blockade of D3R increases GABAA α6 subunit in the ventral striatum. Here we tested the hypothesis that D3R-dependent changes in GABAA α6 subunit in the NAc affect voluntary alcohol intake, by influencing the inhibitory transmission of MSNs. We performed in vivo and ex vivo experiments in D3R knockout (D3R -/-) mice and wild type littermates (D3R +/+). Ro 15-4513, a high affinity α6-GABAA ligand was used to study α6 activity. At baseline, NAc α6 expression was negligible in D3R+/+, whereas it was robust in D3R-/-; other relevant GABAA subunits were not changed. In situ hybridization and qPCR confirmed α6 subunit mRNA expression especially in the NAc. In the drinking-in-the-dark paradigm, systemic administration of Ro 15-4513 inhibited alcohol intake in D3R+/+, but increased it in D3R-/-; this was confirmed by intra-NAc administration of Ro 15-4513 and furosemide, a selective α6-GABAA antagonist. Whole-cell patch-clamp showed peak amplitudes of miniature inhibitory postsynaptic currents in NAc medium spiny neurons higher in D3R-/- compared to D3R+/+; Ro 15-4513 reduced the peak amplitude in the NAc of D3R-/-, but not in D3R+/+. We conclude that D3R-dependent enhanced expression of α6 GABAA subunit inhibits voluntary alcohol intake by increasing GABA inhibition in the NAc.
Asunto(s)
Consumo Excesivo de Bebidas Alcohólicas/genética , Neuronas GABAérgicas/patología , Receptores de Dopamina D3/genética , Receptores de GABA-A/genética , Animales , Consumo Excesivo de Bebidas Alcohólicas/patología , Neuronas GABAérgicas/metabolismo , Regulación de la Expresión Génica , Masculino , Ratones , Ratones Noqueados , Núcleo Accumbens/metabolismo , Núcleo Accumbens/patología , Subunidades de Proteína/genética , ARN Mensajero/genéticaRESUMEN
Post-traumatic stress disorder (PTSD) is a debilitating psychiatric syndrome that occurs in individuals exposed to extremely threatening or traumatic events. In both animals and humans, dopamine (DA) function appears to be dysregulated in brain areas involved in the conditioned fear response(s) that underlie PTSD. In this study, we determined the effect of the selective DA D3 receptor antagonists YQA14A (6.25, 12.5 and 25 mg/kg i.p.) and SB-277011A (6 mg/kg i.p.) on tone-induced fear (assessed by measuring freeze time) in a modified version of the single-prolonged stress (SPS) model of PTSD in adult male Sprague-Dawley rats. Rats pretreated with vehicle and then subjected to restraint stress, forced swim and random foot shock (SPS) in the presence of a distinctive tone, displayed a significantly increased tone-induced contextual freeze time and fecal pellet mass following re-exposure to the tone. Rats pretreated with a single i.p. injection of 6.25 or 12.5 mg/kg of YQA14 or 6 mg/kg of SB-277011A showed significantly attenuated contextual freeze time in the presence of the tone when tested 14 days after exposure to SPS. Overall, our results indicate that selectively antagonizing DA D3 receptors significantly decreases freezing time caused by an environment previously associated with stress. If our findings can be extrapolated to humans with PTSD, they suggest that DA D3 receptors may play a role in the pathophysiology of PTSD, and may have therapeutic utility for the clinical management of PTSD.
Asunto(s)
Benzoxazoles/farmacología , Nitrilos/farmacología , Piperazinas/farmacología , Psicotrópicos/farmacología , Receptores de Dopamina D3/antagonistas & inhibidores , Trastornos por Estrés Postraumático/tratamiento farmacológico , Tetrahidroisoquinolinas/farmacología , Animales , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Heces , Reacción Cataléptica de Congelación/efectos de los fármacos , Reacción Cataléptica de Congelación/fisiología , Masculino , Actividad Motora/efectos de los fármacos , Actividad Motora/fisiología , Distribución Aleatoria , Ratas Sprague-Dawley , Receptores de Dopamina D3/metabolismo , Trastornos por Estrés Postraumático/metabolismo , Estrés Psicológico/tratamiento farmacológico , Estrés Psicológico/metabolismoRESUMEN
The ATP - binding cassette (ABC) family G2 (ABCG2) transporters are known to produce multidrug resistance (MDR) in cancer, thereby limiting the clinical response to chemotherapy. Molecular modeling data indicated that certain dopamine (DA) D3 receptor antagonists had a significant binding affinity for ABCG2 transporter. Therefore, in this in vitro study, we determined the effect of the D3 receptor antagonists PG01037, NGB2904, SB277011A, and U99194 on MDR resulting from the overexpression of ABCG2 transporters. The D3 receptor antagonists, at concentrations >100 µM, did not significantly affect the viability of H460-MX20, S1M1-80, A549-MX10 or wild type ABCG2 overexpressing (HEK293-R2) cells. However, at concentrations ranging from 0.01 to 10 µM, the D3 receptor antagonists PG01037, NGB2904, SB-277011A, and U99194 significantly increased the efficacy of the anticancer drugs mitoxantrone and doxorubicin in ABCG2-overexpressing MDR cells. Efflux studies indicated that both PG01037 and NGB2904, at a concentration of 5 µM, significantly decreased the efflux of rhodamine 123 from H460-MX20 cells. Interestingly, 5 µM of PG01037 or NGB2904 significantly decreased the expression levels of the ABCG2 protein, suggesting that these compounds inhibit both the function and expression of ABCG2 transporters at non-toxic concentrations.
Asunto(s)
Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2/antagonistas & inhibidores , Proteínas de Neoplasias/antagonistas & inhibidores , Receptores de Dopamina D3/antagonistas & inhibidores , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2/biosíntesis , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2/metabolismo , Benzamidas/farmacología , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Línea Celular Tumoral , Neoplasias del Colon/tratamiento farmacológico , Neoplasias del Colon/metabolismo , Regulación hacia Abajo/efectos de los fármacos , Doxorrubicina/farmacología , Resistencia a Múltiples Medicamentos , Resistencia a Antineoplásicos , Sinergismo Farmacológico , Fluorenos/farmacología , Células HEK293 , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/metabolismo , Mitoxantrona/farmacología , Proteínas de Neoplasias/biosíntesis , Proteínas de Neoplasias/metabolismo , Nitrilos/farmacología , Piperazinas/farmacología , Piridinas/farmacología , Tetrahidroisoquinolinas/farmacologíaRESUMEN
Despite the existence of several treatment options for smoking cessation, the rate of relapse after treatment is very high. We and others have proposed that targeting the dopamine D3 receptor (DRD3) may be a good strategy for treatment of nicotine dependence. In human participants, reintroduction to an environment previously associated with drug-taking may induce relapse. In animals, such phenomenon can be studied using the context-induced reinstatement paradigm. As the role of DRD3 in context-induced reinstatement of nicotine-seeking has not yet been explored, we investigated the effects of different doses of the selective DRD3 antagonist SB-277011-A on this reinstatement. Sprague-Dawley adult rats were first trained to self-administer nicotine and subsequently underwent extinction in a second context for 5-7 days. We evaluated the effect of 1, 3 or 10mg/kg of SB-277011-A administered prior to the reintroduction to the training context. We used two different designs: 1) a between-subjects design with a unique reinstatement test; and 2) a counterbalanced within-subjects design, with 4 reinstatement tests. Our findings indicate that, in the within-subjects design, the magnitude of responding induced by the context-induced reinstatement of nicotine seeking was robust during the first reinstatement test, but significantly decreased with repeated testing. SB-277011-A (10mg/kg) blocked context-induced reinstatement of nicotine-seeking at first exposure to the context (between-subjects design), but not after repeated context exposure which produced weaker reinstatement over days. Our results support a role for DRD3 mediating context-induced reinstatement of nicotine seeking, but these effects may not be sustained over time. Further studies should explore this in human participants for validation.
Asunto(s)
Antagonistas de Dopamina/farmacología , Comportamiento de Búsqueda de Drogas/efectos de los fármacos , Nitrilos/farmacología , Receptores de Dopamina D3/antagonistas & inhibidores , Tetrahidroisoquinolinas/farmacología , Tabaquismo/tratamiento farmacológico , Animales , Condicionamiento Operante/efectos de los fármacos , Condicionamiento Operante/fisiología , Relación Dosis-Respuesta a Droga , Comportamiento de Búsqueda de Drogas/fisiología , Extinción Psicológica/efectos de los fármacos , Extinción Psicológica/fisiología , Alimentos , Nicotina/administración & dosificación , Agonistas Nicotínicos/administración & dosificación , Ratas Sprague-Dawley , Receptores de Dopamina D3/metabolismo , Recompensa , Autoadministración , Conducta Espacial/efectos de los fármacos , Conducta Espacial/fisiología , Tabaquismo/metabolismoRESUMEN
We determined the effect of the selective dopamine D3 receptor antagonist SB-277011A on reactivation of conditioned place preference (CPP) to cocaine elicited by priming injections of cocaine or exposure to food deprivation stress (21 h) in male Sprague-Dawley rats. Animals paired with the cocaine-associated chamber displayed a robust and consistent CPP response. This CPP was extinguished after repeated pairings of the conditioned stimuli (cocaine-paired chamber contextual cues) in the absence of the unconditioned stimulus (cocaine). Twenty-four hours later, the administration of 5 mg kg(-1) i.p. of cocaine (immediately before the test) or exposure to 21 h of food deprivation reactivated the expression of the cocaine-induced CPP. In contrast, administration of 1 ml kg(-1) i.p. of vehicle did not reactivate the CPP response. Administration of the selective dopamine D3 receptor antagonist SB-277011A (3-24 mg kg(-1) i.p.) 30 min before cocaine administration on the test day produced a significant attenuation of CPP reactivation. Reactivation of the CPP response produced by food deprivation was also significantly attenuated by SB-277011A (6 or 12 mg kg(-1) i.p.) given 30 min before the test session. SB-277011A (12 or 24 mg kg(-1) i.p.) did not itself produce reactivation of the CPP response. Overall, these results suggest that the reactivation of the incentive value of drug-associated cues by cocaine or food deprivation is attenuated by selective antagonism of D3 receptors.
Asunto(s)
Cocaína/farmacología , Condicionamiento Psicológico/efectos de los fármacos , Antagonistas de Dopamina/farmacología , Inhibidores de Captación de Dopamina/farmacología , Nitrilos/farmacología , Conducta Espacial/efectos de los fármacos , Tetrahidroisoquinolinas/farmacología , Animales , Condicionamiento Psicológico/fisiología , Extinción Psicológica/efectos de los fármacos , Extinción Psicológica/fisiología , Privación de Alimentos/fisiología , Masculino , Distribución Aleatoria , Ratas Sprague-Dawley , Receptores de Dopamina D3/antagonistas & inhibidores , Receptores de Dopamina D3/metabolismo , Conducta Espacial/fisiologíaRESUMEN
BACKGROUND AND PURPOSE: Quinpirole (a dopamine D2-like receptor agonist) inhibits the cardioaccelerator sympathetic outflow in pithed rats by sympathoinhibitory D2-like receptors. The present study was designed to identify pharmacologically the specific D2-like receptor subtypes (i.e. D2 , D3 and D4) involved in this sympathoinhibition by quinpirole. EXPERIMENTAL APPROACH: One hundred fourteen male Wistar rats were pithed, artificially ventilated with room air and prepared for either preganglionic spinal (C7-T1) stimulation of the cardioaccelerator sympathetic outflow (n = 102) or i.v. bolus injections of exogenous noradrenaline (n = 12). This approach resulted in frequency-dependent and dose-dependent tachycardic responses, respectively, as previously reported by our group. KEY RESULTS: I.v. continuous infusions of quinpirole (0.1-10 µg kg(-1) min(-1)), but not of saline (0.02 mL min(-1)), dose-dependently inhibited the sympathetically induced tachycardic responses. Moreover, the cardiac sympathoinhibition induced by 3 µg kg(-1) min(-1) quinpirole (which failed to affect the tachycardic responses to i.v. noradrenaline) was: (i) unchanged after i.v. injections of the antagonists SB-277011-A (D3 ; 100-300 µg kg(-1)) or L-745,870 (D4 ; 30-100 µg kg(-1)); and (ii) markedly blocked and abolished by, respectively, 100 and 300 µg kg(-1) of the D2 preferring receptor subtype antagonist L-741,626. These doses of antagonists, which did not affect per se the sympathetically induced tachycardic responses, were high enough to completely block their respective receptors. CONCLUSIONS AND IMPLICATIONS: The cardiac sympathoinhibition induced by 3 µg kg(-1) min(-1) quinpirole involves the dopamine D2 receptor subtype, with no evidence for the involvement of the D3 or D4 subtypes. This provides new evidence for understanding the modulation of the cardioaccelerator sympathetic outflow.