RESUMEN

Striatal projection neurons (SPNs) process motor and cognitive information. Their activity is affected by Parkinson's disease, in which dopamine concentration is decreased and acetylcholine concentration is increased. Acetylcholine activates muscarinic receptors in SPNs. Its main source is the cholinergic interneuron that responds with a briefer latency than SPNs during a cortical command. Therefore, an important question is whether muscarinic G-protein coupled receptors and their signaling cascades are fast enough to intervene during synaptic responses to regulate synaptic integration and firing. One of the most known voltage dependent channels regulated by muscarinic receptors is the KV7/KCNQ channel. It is not known whether these channels regulate the integration of suprathreshold corticostriatal responses. Here, we study the impact of cholinergic muscarinic modulation on the synaptic response of SPNs by regulating KV7 channels. We found that KV7 channels regulate corticostriatal synaptic integration and that this modulation occurs in the dendritic/spines compartment. In contrast, it is negligible in the somatic compartment. This modulation occurs on sub- and suprathreshold responses and lasts during the whole duration of the responses, hundreds of milliseconds, greatly altering SPNs firing properties. This modulation affected the behavior of the striatal microcircuit.

Asunto(s)

Potenciales de Acción , Neuronas GABAérgicas/fisiología , Canales de Potasio KCNQ/fisiología , Neostriado/fisiología , Sinapsis/fisiología , Potenciales de Acción/efectos de los fármacos , Animales , Corteza Cerebral/fisiología , Neuronas Colinérgicas/fisiología , Estimulación Eléctrica , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Neuronas GABAérgicas/citología , Neuronas GABAérgicas/metabolismo , Péptidos y Proteínas de Señalización Intercelular , Ratones Transgénicos , Muscarina/farmacología , Agonistas Muscarínicos/farmacología , Neostriado/citología , Neostriado/metabolismo , Péptidos/farmacología , Receptor Muscarínico M1/agonistas , Receptor Muscarínico M1/antagonistas & inhibidores , Receptores de Dopamina D1/metabolismo , Receptores de Dopamina D2/metabolismo

RESUMEN

The external globus pallidus (GPe) is central for basal ganglia processing. It expresses muscarinic cholinergic receptors and receives cholinergic afferents from the pedunculopontine nuclei (PPN) and other regions. The role of these receptors and afferents is unknown. Muscarinic M1-type receptors are expressed by synapses from striatal projection neurons (SPNs). Because axons from SPNs project to the GPe, one hypothesis is that striatopallidal GABAergic terminals may be modulated by M1 receptors. Alternatively, some M1 receptors may be postsynaptic in some pallidal neurons. Evidence of muscarinic modulation in any of these elements would suggest that cholinergic afferents from the PPN, or other sources, could modulate the function of the GPe. In this study, we show this evidence using striatopallidal slice preparations: after field stimulation in the striatum, the cholinergic muscarinic receptor agonist muscarine significantly reduced the amplitude of inhibitory postsynaptic currents (IPSCs) from synapses that exhibited short-term synaptic facilitation. This inhibition was associated with significant increases in paired-pulse facilitation, and quantal content was proportional to IPSC amplitude. These actions were blocked by atropine, pirenzepine, and mamba toxin-7, suggesting that receptors involved were M1. In addition, we found that some pallidal neurons have functional postsynaptic M1 receptors. Moreover, some evoked IPSCs exhibited short-term depression and a different kind of modulation: they were indirectly modulated by muscarine via the activation of presynaptic cannabinoid CB1 receptors. Thus pallidal synapses presenting distinct forms of short-term plasticity were modulated differently.

Asunto(s)

Globo Pálido/fisiología , Potenciales Postsinápticos Inhibidores , Receptor Muscarínico M1/metabolismo , Sinapsis/metabolismo , Animales , Atropina/farmacología , Neuronas Colinérgicas/efectos de los fármacos , Neuronas Colinérgicas/metabolismo , Neuronas Colinérgicas/fisiología , Globo Pálido/citología , Péptidos y Proteínas de Señalización Intercelular , Muscarina/farmacología , Agonistas Muscarínicos/farmacología , Antagonistas Muscarínicos/farmacología , Péptidos/farmacología , Pirenzepina/farmacología , Ratas , Ratas Wistar , Receptor Cannabinoide CB1/metabolismo , Receptor Muscarínico M1/agonistas , Receptor Muscarínico M1/antagonistas & inhibidores , Sinapsis/efectos de los fármacos , Sinapsis/fisiología

RESUMEN

We have studied the cardiac chronotropic responses to the Valsalva maneuver and to dynamic exercise of twenty chronic chagasic patients with normal left ventricular function and no segmental wall abnormalities by two-dimensional echocardiogram. The absolute increase in heart rate of the patients (Δ = 21.5 ± 10 bpm, M±SD) during the maneuver was significantly diminished when compared to controls (Δ = 31.30 ± 70, M±SD, p = 0.03). The minimum heart rate (58.24 ± 8.90 vs. 62.80 ± 10, p = 0.68) and the absolute decrease in heart rate at the end of the maneuver (Δ = 38.30 ± 13 vs. Δ = 31.47 ± 17, p = 0.10) were not different from controls. The initial heart rate acceleration during dynamic exercise (Δ = 12 ± 7.55 vs. Δ = 19 ± 7.27, M±SD, p = 0.01) was also diminished, but the heart rate recovery during the first ten seconds was more prominent in the sero-positive patients (Median: 14, Interquartile range: (9.75-17.50 vs. 5(0-8.75, p = 0.001). The serum levels of muscarinic cardiac auto-antibodies were significantly higher in the chagasic patients (Median: 34.58, Interquartile Range: 17-46.5, Optical Density) than in controls (Median: 0, Interquartile Range: 0-22.25, p = 0.001) and correlated significantly and directly (r = 0.68, p = 0.002) with early heart rate recovery during dynamic exercise. The results of this investigation indirectly suggest that, the cardiac muscarinic auto-antibodies may have positive agonist effects on parasympathetic heart rate control of chagasic patients.

---

Foram estudadas as respostas cronotrópicas cardíacas à manobra de Valsalva e ao exercício dinâmico de vinte pacientes chagásicos com função ventricular esquerda normal e sem alterações da contractilidade segmentar por ecocardiografia bidimensional. O aumento absoluto da frequência cardíaca dos pacientes (Δ = 21,5 ± 10 bpm, M ± DP) durante a manobra de Valsalva foi significativamente menor quando se comparava ao grupo controle (Δ = 31,30 ± 70, p = 0,03). A frequência cardíaca mínima (58,24 ± 8,90 vs 62,80 ± 10, p = 0,68) e a diminuição da frequência cardíaca absoluta no final da manobra (Δ = 38,30 ± 13 vs Δ = 31,47 ± 17, p = 0,10) não foram diferentes em comparação com o grupo controle. A aceleração inicial da frequência cardíaca durante o exercício dinâmico (Δ = 12 ± 7,55 vs Δ = 19 ± 7,27, p = 0,01) também foi menor, mas a recuperação da frequência cardíaca, durante os primeiros dez segundos, foi maior no grupo sero-positivos [mediana:14 (intervalo interquartil: 9,75-17,50) vs 5 (0 - 8,75), p = 0,001]. Os níveis séricos de auto-anticorpos muscarínicos cardíacos foram significativamente maiores nos pacientes chagásicos do que no grupo controle [(mediana: 34,58 densidade óptica (intervalo interquartil 17 - 46,5) vs (mediana: 0, intervalo interquartil 0 - 22,25) p = 0,001] e a correlação é significativa e direta (r = 0,68, p = 0,002) com o início da recuperação da frequência cardíaca durante o exercício dinâmico. Os resultados desta investigação sugerem que indiretamente, os auto-anticorpos muscarínicos cardíacos, podem ter ação agonista positiva sobre o controle parassimpático da frequência cardíaca dos pacientes chagásicos.

Asunto(s)

Adulto , Femenino , Humanos , Masculino , Persona de Mediana Edad , Autoanticuerpos/sangre , Cardiomiopatía Chagásica/fisiopatología , Ejercicio Físico/fisiología , Frecuencia Cardíaca/fisiología , Muscarina/inmunología , Sistema Nervioso Parasimpático/fisiopatología , Maniobra de Valsalva/fisiología , Estudios de Casos y Controles , Cardiomiopatía Chagásica/sangre , Ecocardiografía , Ensayo de Inmunoadsorción Enzimática , Muscarina/sangre

RESUMEN

We have studied the cardiac chronotropic responses to the Valsalva maneuver and to dynamic exercise of twenty chronic chagasic patients with normal left ventricular function and no segmental wall abnormalities by two-dimensional echocardiogram. The absolute increase in heart rate of the patients (Δ = 21.5 ± 10 bpm, M±SD) during the maneuver was significantly diminished when compared to controls (Δ = 31.30 ± 70, M±SD, p = 0.03). The minimum heart rate (58.24 ± 8.90 vs. 62.80 ± 10, p = 0.68) and the absolute decrease in heart rate at the end of the maneuver (Δ = 38.30 ± 13 vs. Δ = 31.47 ± 17, p = 0.10) were not different from controls. The initial heart rate acceleration during dynamic exercise (Δ = 12 ± 7.55 vs. Δ = 19 ± 7.27, M±SD, p = 0.01) was also diminished, but the heart rate recovery during the first ten seconds was more prominent in the sero-positive patients (Median: 14, Interquartile range: (9.75-17.50 vs. 5(0-8.75, p = 0.001). The serum levels of muscarinic cardiac auto-antibodies were significantly higher in the chagasic patients (Median: 34.58, Interquartile Range: 17-46.5, Optical Density) than in controls (Median: 0, Interquartile Range: 0-22.25, p = 0.001) and correlated significantly and directly (r = 0.68, p = 0.002) with early heart rate recovery during dynamic exercise. The results of this investigation indirectly suggest that, the cardiac muscarinic auto-antibodies may have positive agonist effects on parasympathetic heart rate control of chagasic patients.

Asunto(s)

Autoanticuerpos/sangre , Cardiomiopatía Chagásica/fisiopatología , Ejercicio Físico/fisiología , Frecuencia Cardíaca/fisiología , Muscarina/inmunología , Sistema Nervioso Parasimpático/fisiopatología , Maniobra de Valsalva/fisiología , Adulto , Estudios de Casos y Controles , Cardiomiopatía Chagásica/sangre , Ecocardiografía , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , Masculino , Persona de Mediana Edad , Muscarina/sangre

RESUMEN

The role of calcium and its relevance have been deeply revised with respect to trypanosomatids, as the mechanism by which calcium enters trypanosomes was, until now, not well understood. There is evidence supporting the presence of a nAChR in another member of the trypanosomatidae family, Trypanosoma cruzi, these receptors being one entry path to calcium ions. The aims of this work were to determine if there was a nicotinic acetylcholine receptor (nAChR) in Trypanosoma evansi, and to subsequently perform a partial pharmacological characterization of this receptor. After being loaded with FURA-2AM, individual cells of T. evansi, were exposed to cholinergic compounds, and the cells displayed a dose-dependent response to carbachol. This observation indicated that a cholinergic receptor may be present in T. evansi. Although a dose-dependent response to muscarine could not be demonstrated, nicotine could promote an incremental dose-dependent response. The relative potency of this specific agonist of nAChR is in agreement with previous reports. The estimated affinity values were a Kd1 value of 29.6+/-5.72 nM and a Kd2 value of 315.9+/-26.6 nM, which is similar to the Kd value reported for the alpha4 nicotinic receptor. The Hill coefficients were determined to be an n1 of 1.2+/-0.3 and an n2 of 4.2+/-1.3. Finally, our calculations indicated that there are about 1020 receptors in each T. evansi parasite, which is approximately 15-fold lower than the number reported in Torpedo californica electric cells. These results suggest the presence of a nAChR in T. evansi, which is able to bind nicotinic ligands and induce calcium signals.

Asunto(s)

Calcio/metabolismo , Nicotina/farmacología , Agonistas Nicotínicos/farmacología , Receptores Nicotínicos/metabolismo , Trypanosoma/metabolismo , Animales , Bungarotoxinas/metabolismo , Relación Dosis-Respuesta a Droga , Masculino , Muscarina/farmacología , Agonistas Muscarínicos/farmacología , Antagonistas Nicotínicos/farmacología , Distribución Normal , Ratas , Ratas Sprague-Dawley , Receptores Nicotínicos/efectos de los fármacos , Trypanosoma/efectos de los fármacos

RESUMEN

Endothelial cells are directly involved in many functions of the cardiovascular system by regulating blood flow and blood pressure through Ca(2+) dependent exocitosis of vasoactive compounds. Using the Ca(2+) indicator Fluo-3 and the patch-clamp technique, we show that bovine adrenal medulla capillary endothelial cells (B AMCECs) respond to acetylcholine (ACh) with a cytosolic Ca(2+) increase and depolarization of the membrane potential (20.3+/-0.9 mV; n=23). The increase in cytosolic Ca(2+) induced by 10microM ACh was mimicked by the same concentration of nicotine but not by muscarine and was blocked by 100 microM of hexamethonium. On the other hand, the increase in cytosolic Ca(2+) could be depressed by nifedipine (0.01 -100 microM) or withdrawal of extracellular Ca(2+). Taken together, these results give evidence for functional nicotinic receptors (nAChRs) in capillary endothelial cells of the adrenal medulla. It suggests that nAChRs in B AMCECs may be involved in the regulation of the adrenal gland's microcirculation by depolarizing the membrane potential, leading to the opening of voltage-activated Ca(2+) channels, influx of external Ca(2+) and liberation of vasoactive compounds.

Asunto(s)

Médula Suprarrenal/efectos de los fármacos , Canales de Calcio/efectos de los fármacos , Citosol/efectos de los fármacos , Células Endoteliales/efectos de los fármacos , Nicotina/farmacología , Receptores Nicotínicos/efectos de los fármacos , Acetilcolina/farmacología , Médula Suprarrenal/irrigación sanguínea , Médula Suprarrenal/citología , Animales , Canales de Calcio/metabolismo , Capilares/citología , Capilares/efectos de los fármacos , Bovinos , Citosol/metabolismo , Potenciales Evocados/efectos de los fármacos , Hexametonio/farmacología , Potenciales de la Membrana/efectos de los fármacos , Muscarina/farmacología , Receptores Nicotínicos/metabolismo

RESUMEN

Endothelial cells are directly involved in many functions of the cardiovascular system by regulating blood flow and blood pressure through Ca2+ dependent exocitosis of vasoactive compounds. Using the Ca2+ indicator Fluo-3 and the patch-clamp technique, we show that bovine adrenal medulla capillary endothelial cells (B AMCECs) respond to acetylcholine (ACh) with a cytosolic Ca2+ increase and depolarization of the membrane potential (20.3±0.9 mV; n=23). The increase in cytosolic Ca2+ induced by 10µM ACh was mimicked by the same concentration of nicotine but not by muscarine and was blocked by 100 µM of hexamethonium. On the other hand, the increase in cytosolic Ca2+ could be depressed by nifedipine (0.01 -100 µM) or withdrawal of extracellular Ca2+. Taken together, these results give evidence for functional nicotinic receptors (nAChRs) in capillary endothelial cells of the adrenal medulla. It suggests that nAChRs in B AMCECs may be involved in the regulation of the adrenal gland's microcirculation by depolarizing the membrane potential, leading to the opening of voltage-activated Ca2+ channels, influx of external Ca2+ and liberation of vasoactive compounds.

Asunto(s)

Animales , Bovinos , Médula Suprarrenal/efectos de los fármacos , Canales de Calcio/efectos de los fármacos , Citosol/efectos de los fármacos , Células Endoteliales/efectos de los fármacos , Nicotina/farmacología , Receptores Nicotínicos/efectos de los fármacos , Acetilcolina/farmacología , Médula Suprarrenal/irrigación sanguínea , Médula Suprarrenal/citología , Canales de Calcio/metabolismo , Capilares/citología , Capilares/efectos de los fármacos , Citosol/metabolismo , Potenciales Evocados/efectos de los fármacos , Hexametonio/farmacología , Potenciales de la Membrana/efectos de los fármacos , Muscarina/farmacología , Receptores Nicotínicos/metabolismo

RESUMEN

Coordinated proliferation and differentiation of progenitor cells is the base for production of appropriate numbers of neurons and glia during neuronal development in order to establish normal brain functions. We have used murine embryonal carcinoma P19 cells as an in vitro model for early differentiation to study participation of nicotinic (nAChR) and muscarinic acetylcholine (mAChR) receptors in the proliferation of neural progenitor cells and their differentiation to neurons. We have previously shown that functional nicotinic acetylcholine receptors (nAChRs) already expressed in embryonic cells mediate elevations in cytosolic free calcium concentration ([Ca2+]i) via calcium influx through nAChR channels whereas intracellular stores contribute to nAChR- and mAChR-mediated calcium fluxes in differentiated cells [Resende et al., Cell Calcium 43 (2008) 107-121]. In the present study, we have demonstrated that nicotine provoked inhibition of proliferation in embryonic cells as determined by BrdU labeling. However, in neural progenitor cells nicotine stimulated proliferation which was reversed in the presence of inhibitors of calcium mobilization from intracellular stores, indicating that liberation of intracellular calcium contributed to this proliferation induction. Muscarine induced proliferation stimulation in progenitor cells by activation of Galphaq/11-coupled M1, M3 and M5 receptors and intracellular calcium stores, whereas Galphai/o-protein coupled M2 receptor activity mediated neuronal differentiation.

Asunto(s)

Diferenciación Celular , Células Madre de Carcinoma Embrionario/patología , Receptores Colinérgicos/metabolismo , Animales , Bromodesoxiuridina/metabolismo , Señalización del Calcio/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Agonistas Colinérgicos/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Proteínas de Filamentos Intermediarios/genética , Proteínas de Filamentos Intermediarios/metabolismo , Espacio Intracelular/efectos de los fármacos , Espacio Intracelular/metabolismo , Ratones , Muscarina/farmacología , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Nestina , Neuronas/citología , Neuronas/efectos de los fármacos , Nicotina/farmacología , Receptores Muscarínicos/metabolismo , Receptores Nicotínicos/metabolismo , Células Madre/citología , Células Madre/efectos de los fármacos , Fosfolipasas de Tipo C/metabolismo

RESUMEN

Besides a reduction of L-type Ca2+-currents (Ca(V)1), muscarine and the peptidic M1-selective agonist, MT-1, reduced currents through Ca(V)2.1 (P/Q) and Ca(V)2.2 (N) Ca2+ channel types. This modulation was strongly blocked by the peptide MT-7, a specific muscarinic M1-type receptor antagonist but not significantly reduced by the peptide MT-3, a specific muscarinic M4-type receptor antagonist. Accordingly, MT-7, but not MT-3, blocked a muscarinic reduction of the afterhyperpolarizing potential (AHP) and decreased the GABAergic inhibitory postsynaptic currents (IPSCs) produced by axon collaterals that interconnect spiny neurons. Both these functions are known to be dependent on P/Q and N types Ca2+ channels. The action on the AHP had an important effect in increasing firing frequency. The action on the IPSCs was shown to be caused presynaptically as it coursed with an increase in the paired-pulse ratio. These results show: first, that muscarinic M1-type receptor activation is the main cholinergic mechanism that modulates Ca2+ entry through voltage-dependent Ca2+ channels in spiny neurons. Second, this muscarinic modulation produces a postsynaptic facilitation of discharge together with a presynaptic inhibition of the GABAergic control mediated by axon collaterals. Together, both effects would tend to recruit more spiny neurons for the same task.

Asunto(s)

Acetilcolina/metabolismo , Caveolinas/fisiología , Neostriado/citología , Neuronas/fisiología , Transmisión Sináptica/fisiología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Bloqueadores de los Canales de Calcio/farmacología , Caveolina 2 , Caveolinas/clasificación , Caveolinas/efectos de los fármacos , Células Cultivadas , Interacciones Farmacológicas , Estimulación Eléctrica/métodos , Técnicas In Vitro , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Potenciales de la Membrana/efectos de la radiación , Muscarina/farmacología , Agonistas Muscarínicos/clasificación , Agonistas Muscarínicos/farmacología , Inhibición Neural/efectos de los fármacos , Inhibición Neural/fisiología , Neuronas/efectos de los fármacos , Técnicas de Placa-Clamp/métodos , Ratas , Ratas Wistar , Receptores Muscarínicos/clasificación , Receptores Muscarínicos/efectos de los fármacos , Transmisión Sináptica/efectos de los fármacos

RESUMEN

Penile reflexes (PRs) were monitored in chronic spinal cord-transected rats by identifying them visually, and at the same time they were recorded as the electromyographic activity of bulbospongiosus muscles. Intraperitoneal injection of the agonist muscarine (10 microg) produced a facilitation of PRs. A decrease in the latency, an increase in the number of clusters and often an increase in the duration of cups were found after muscarine. In addition, 66% (six out of nine) of the animals ejaculated after muscarine. These results suggest that cholinergic receptor stimulation may be involved in erectile and ejaculatory mechanisms mediated by the spinal cord.

Asunto(s)

Eyaculación/efectos de los fármacos , Disfunción Eréctil/tratamiento farmacológico , Muscarina/farmacología , Agonistas Muscarínicos/farmacología , Erección Peniana/efectos de los fármacos , Traumatismos de la Médula Espinal/complicaciones , Animales , Eyaculación/fisiología , Electromiografía , Disfunción Eréctil/etiología , Disfunción Eréctil/fisiopatología , Masculino , Erección Peniana/fisiología , Ratas , Ratas Wistar , Receptores Muscarínicos/fisiología , Reflejo/efectos de los fármacos , Traumatismos de la Médula Espinal/fisiopatología

RESUMEN

The effects of muscarinic receptor stimulation were tested on the urethro genital reflex (UGR) in anesthetized and spinal cord-transected rats. Drugs were applied directly to the spinal cord. The electromyographic activity (EMG) of the bulbospongiosus (BS) muscle was used for recording UGR. In six animals BS as well as soleus, posterior biceps or peroneus tertius muscle EMG was recorded simultaneously. Muscarine (5, 10, 20, 50 and 100 microg) was applied in 22 animals after cutting L6-S1 dorsal roots. Some observations were made on another six animals, to which an extensive bilateral dorsal rhizotomy (L3-S2) was performed. Rhythmic bursts of similar frequency and size to those seen during UGR were found in BS muscle a few minutes after muscarine application. No rhythmic bursting was found on the hindlimb muscles, but exclusively on BS muscles. The effects of homatropine (25, 50, 100 and 200 microg), an acetylcholine muscarinic receptor antagonist, were tested in 21 rats after UGR was elicited three times at low stimulation intensity (7 mm Hg). Homatropine produced two effects: (i) A significant increase in the latency of UGR. (ii) A facilitation of UGR inhibition. In view of these results it can be speculated that muscarinic receptor stimulation is involved in the elicitation of UGR.

Asunto(s)

Genitales Masculinos/fisiología , Receptores Muscarínicos/fisiología , Médula Espinal/cirugía , Animales , Relación Dosis-Respuesta a Droga , Genitales Masculinos/efectos de los fármacos , Genitales Masculinos/inervación , Masculino , Muscarina/farmacología , Agonistas Muscarínicos/farmacología , Parasimpatolíticos/farmacología , Erección Peniana/efectos de los fármacos , Ratas , Ratas Wistar , Receptores Muscarínicos/efectos de los fármacos , Reflejo/efectos de los fármacos , Rizotomía , Tropanos/farmacología

RESUMEN

Behavioral experiments were conducted to examine the role of the cholinergic receptor-agonist muscarine or its antagonist homatropine on the mating behavior of sexually experienced male rats. Male copulatory behavior was recorded after intrathecally administered saline, muscarine (7.5 microg), or homatropine (25 microg). Changes in copulatory behavior were assessed by the following parameters: intromission latency, intromission frequency, intercopulatory interval, ejaculation latency, and postejaculatory interval. Intromission frequency, intercopulatory interval, and ejaculation latency were decreased significantly by muscarine. Intrathecal homatropine decreased the number of copulating animals (five out of 13). In the five animals that were able to ejaculate after homatropine, intromission latency, intercopulatory interval, and ejaculation latency increased significantly. The effects of both drugs on locomotion were also tested. Muscarine induced no significant changes in locomotion compared with saline. A significant increase in locomotion was found after homatropine treatment. These results suggest that acetylcholine, acting at spinal-cord muscarinic receptors, may be involved in ejaculation.

Asunto(s)

Copulación/efectos de los fármacos , Actividad Motora/efectos de los fármacos , Muscarina/farmacología , Animales , Copulación/fisiología , Eyaculación/efectos de los fármacos , Eyaculación/fisiología , Inyecciones Espinales , Masculino , Actividad Motora/fisiología , Muscarina/administración & dosificación , Parasimpatolíticos/administración & dosificación , Parasimpatolíticos/farmacología , Ratas , Ratas Wistar , Tiempo de Reacción , Médula Espinal/efectos de los fármacos , Médula Espinal/fisiología , Tropanos/administración & dosificación , Tropanos/farmacología

RESUMEN

It is demonstrated that acetylcholine released from cholinergic interneurons modulates the excitability of neostriatal projection neurons. Physostigmine and neostigmine increase input resistance (RN) and enhance evoked discharge of spiny projection neurons in a manner similar to muscarine. Muscarinic RN increase occurs in the whole subthreshold voltage range (-100 to -45 mV), remains in the presence of TTX and Cd2+, and can be blocked by the relatively selective M1,4 muscarinic receptor antagonist pirenzepine but not by M2 or M3 selective antagonists. Cs+ occludes muscarinic effects at potentials more negative than -80 mV. A Na+ reduction in the bath occludes muscarinic effects at potentials more positive than -70 mV. Thus, muscarinic effects involve different ionic conductances: inward rectifying and cationic. The relatively selective M2 receptor antagonist AF-DX 116 does not block muscarinic effects on the projection neuron but, surprisingly, has the ability to mimic agonistic actions increasing RN and firing. Both effects are blocked by pirenzepine. HPLC measurements of acetylcholine demonstrate that AF-DX 116 but not pirenzepine greatly increases endogenous acetylcholine release in brain slices. Therefore, the effects of the M2 antagonist on the projection neurons were attributable to autoreceptor block on cholinergic interneurons. These experiments show distinct opposite functions of muscarinic M1- and M2-type receptors in neostriatal output, i.e., the firing of projection neurons. The results suggest that the use of more selective antimuscarinics may be more profitable for the treatment of motor deficits.

Asunto(s)

Acetilcolina/fisiología , Agonistas Muscarínicos/farmacología , Antagonistas Muscarínicos/farmacología , Neostriado/fisiología , Neuronas/fisiología , Receptores Muscarínicos/fisiología , Animales , Cloruro de Cadmio/farmacología , Cesio/farmacología , Cloruros/farmacología , Estimulación Eléctrica , Técnicas In Vitro , Potenciales de la Membrana/efectos de los fármacos , Muscarina/farmacología , Neuronas/efectos de los fármacos , Fisostigmina/farmacología , Pirenzepina/análogos & derivados , Pirenzepina/farmacología , Ratas , Receptor Muscarínico M1 , Receptor Muscarínico M2 , Receptor Muscarínico M3 , Receptor Muscarínico M4 , Tetrodotoxina/farmacología

RESUMEN

We studied the influence of muscarinic and nicotinic stimulation on both phosphoinositide metabolism and intracellular calcium levels in rat skeletal muscle primary cultures. Both nicotine and muscarine induced an increase in cytosolic calcium measured by fluo 3 fluorescence in confocal microscopy. The mass of inositol (1,4,5)trisphosphate measured by radioreceptor assay rose 2- to 3.5-fold upon carbachol, nicotine, or muscarine stimulation. The muscarine effect was mimicked by oxotremorine-M; pirenzepine prevented the muscarine-induced inositol (1,4,5)trisphosphate increase, whereas 4-diphenylacetoxy-N-methyl piperidine methiodide was ineffective. A relatively small (40 fmol/mg protein) high-affinity 3-quinuclidinylbenzilate binding to rat myotube microsomes was consistent with the muscarinic effect found. On the other hand, the effect of nicotine on the mass of inositol (1,4,5)trisphosphate was totally suppressed in sodium-free medium. Expression of Ml muscarinic receptors coupled to phospholipase C and to internal calcium stores in cultured skeletal muscle is proposed; nicotinic receptors could be acting via ion fluxes and membrane depolarization.

Asunto(s)

Músculo Esquelético/metabolismo , Receptores Muscarínicos/metabolismo , Animales , Animales Recién Nacidos , Calcio/metabolismo , Carbacol/farmacología , Células Cultivadas , Inositol 1,4,5-Trifosfato/metabolismo , Microscopía Confocal , Microscopía Fluorescente , Muscarina/farmacología , Agonistas Muscarínicos/farmacología , Antagonistas Muscarínicos/farmacología , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/ultraestructura , Nicotina/farmacología , Fosfatidilinositoles/metabolismo , Quinuclidinil Bencilato/metabolismo , Ensayo de Unión Radioligante , Ratas

RESUMEN

3,4-dihydroxyphenylacetic acid (DOPAC) was measured by differential pulse voltammetry in the neostriatum of anesthetized rats. DL-Muscarine (2.9 nmol) applied into the substantia nigra pars compacta, increased DOPAC concentration in the ipsilateral neostriatum. This effect was blocked by pirenzepine (2.8 nmol), and potentiated by AF-DX 116 (2.8 nmol). These results indicate the existence of two types of muscarinic receptors on dopaminergic neurons, whose activation produces opposing effects on dopamine metabolism in neostriatum.

Asunto(s)

Ácido 3,4-Dihidroxifenilacético/metabolismo , Cuerpo Estriado/metabolismo , Muscarina/farmacología , Pirenzepina/farmacología , Receptores Muscarínicos/fisiología , Sustancia Negra/fisiología , Animales , Cuerpo Estriado/efectos de los fármacos , Electroquímica/métodos , Lateralidad Funcional , Masculino , Muscarina/administración & dosificación , Parasimpatolíticos/farmacología , Pirenzepina/análogos & derivados , Ratas , Ratas Endogámicas , Receptores Muscarínicos/efectos de los fármacos , Técnicas Estereotáxicas , Sustancia Negra/efectos de los fármacos

RESUMEN

To determine the effects of parasympathetic blockade and beta-blockade on the elastic response of aortic stiffness to vasopressive interventions, we studied 5 unanesthetised adult mongrel dogs by means of a pressure microtransducer and two ultrasonic crystals positioned at opposing sites in the proximal descending thoracic aorta which were used for diameter measurements. Systolic and diastolic changes in pressure and diameter were used to calculate Peterson and incremental elastic moduli. Acute hypertension was induced using infusions of epinephrine during the control period and later propranolol (1.5 mg/kg) plus atropine (0.2 mg/kg). Percent variations of mean aortic diameter were correlated to percent variations in mean aortic pressure in the control period and after autonomic blockade (P less than .001). The slopes of these correlations in the control group were higher than after autonomic blockade (P less than .05). Correlations were also found between Peterson and incremental elastic moduli and mean pressure in the control group and after autonomic blockade (P less than .001). The slopes of the correlations of incremental elastic modulus and Peterson's modulus versus mean aortic pressure were lower in the control group than after blockade (P less than .001). We conclude that in conscious dogs, autonomic blockade with propranolol and atropine decreased the distension and increased the stiffness of the aortic wall in response to acute hypertension mediated by epinephrine.

Asunto(s)

Antagonistas Adrenérgicos beta/farmacología , Aorta/efectos de los fármacos , Epinefrina/farmacología , Hipertensión/fisiopatología , Muscarina/antagonistas & inhibidores , Enfermedad Aguda , Animales , Aorta/fisiología , Atropina/farmacología , Presión Sanguínea/efectos de los fármacos , Perros , Relación Dosis-Respuesta a Droga , Elasticidad , Frecuencia Cardíaca/efectos de los fármacos , Hipertensión/inducido químicamente , Propranolol/farmacología , Vasodilatación/efectos de los fármacos

RESUMEN

Denervation procedures that affect the sympathetic system of the kidney, as demonstrated by norepinephrine depletion of renal tissue, increased urine volume, fractional sodium excretion, and free water clearance in anesthetized water-loaded dogs. These increases were reduced by atropine, which also blocked the increase above those basal functional levels produced by acetylcholine in both innervated and denervated kidneys. An in vitro tubular cell preparation of innervated kidneys corresponding to the outer cortex showed [3H]quinuclidinyl benzilate (QNB) binding parameters characteristic of muscarinic receptors. Denervation did not change either [3H]QNB binding parameters or the ability of inner and outer cortex cells to perform the hemicholinium-3-inhibitable, sodium-dependent choline uptake and conversion of [3H]choline to [3H]acetylcholine. This cell membrane behavior is similar to that observed in tissues where cholinergic neuronal structures are present, suggesting the existence of a cholinergic innervation of the kidney, independent of the integrity of vessel-traveling nerves. Similarly, the finding of choline acetyltransferase in renal tissue, unaffected by sympathetic denervation, seems to confirm the presence of cholinergic nerve terminals. The cholinergic system may thus contribute to the regulation of tubular reabsorption of sodium and water in some conditions.

Asunto(s)

Riñón/inervación , Sistema Nervioso Parasimpático/fisiología , Acetilcolina/biosíntesis , Acetilcolina/farmacología , Animales , Atropina/farmacología , Colina/metabolismo , Colina O-Acetiltransferasa/metabolismo , Desnervación , Perros , Riñón/efectos de los fármacos , Riñón/metabolismo , Masculino , Muscarina/metabolismo

RESUMEN

The effect of superior cervical ganglionectomy (SCGx) on basal and glucose-stimulated insulin release in vitro was examined in pancreas slices of BALB/c mice subjected to surgery 14-96 h earlier. Fourteen or 20 h after SCGx a significant increase of insulin response to 11 mM glucose was detectable, while 96 h after SCGx a depression in response was found. Perifused pancreas slices obtained from mice subjected to SCGx 7 days earlier showed a decreased in vitro insulin response to glucose during both phases of insulin secretion. In sham-operated mice, injection of the beta-adrenoceptor blocker propranolol or of the cholinergic muscarinic antagonist atropine decreased basal and glucose-stimulated insulin release, while the alpha-adrenoceptor blocker phenoxybenzamine did not affect it significantly. In mice subjected to SCGx 14 h earlier, propranolol treatment decreased basal insulin release and impaired the release elicited by glucose to values similar to those found in controls, phenoxybenzamine injection increased the basal and amplified the enhanced glucose-stimulated insulin release, and atropine injection, although unable to affect basal insulin release, impaired partially the amplification of response detectable after surgery. Our results support the existence of significant effects of SCG neurons on insulin release in mice.

Asunto(s)

Ganglios Simpáticos/fisiología , Insulina/metabolismo , Páncreas/metabolismo , Animales , Técnicas In Vitro , Masculino , Ratones , Ratones Endogámicos BALB C , Muscarina/antagonistas & inhibidores , Simpatectomía , Simpaticolíticos/farmacología