[The effects of lesions in the compact part of the substantia nigra on glutamate and GABA release in the pedunculopontine nucleus]. / Efecto de la lesión de la sustancia negra pars compacta sobre la liberación de glutamato y GABA en el núcleo pedunculopontino.

INTRODUCTION: The pedunculopontine nucleus (PPN), co-localized with the mesencephalic locomotor region, has been proposed as a key structure in the physiopathology of Parkinson's disease. OBJECTIVES: The goal of the present study was to assess if the aminoacid neurotransmitter release in the PPN is modified by the degeneration of dopaminergic cells, from substantia nigra pars compacta in 6-hydroxidopamine (6-OHDA)-lesioned rats. In addition, it was studied the aminoacid neurotransmitter release in the PPN of rats with lesion of the subthalamic nucleus by quinolinic acid (QUIN) (100 nmol) intracerebral injection. MATERIALS AND METHODS: Rats were assigned to five groups: untreated rats (I) (n = 13), 6-OHDA lesion (II) (n = 11), 6-OHDA + QUIN lesion (III) (n = 9), sham-operated (IV) (n = 10), QUIN, STN (V) lesioned (n = 9). The extracellular concentrations of glutamic acid (GLU) and gamma-aminobutyric acid (GABA) were determined by brain microdialysis and high performance liquid chromatography (HPLC). RESULTS. GLU released in PPN from 6-OHDA lesioned rats (group II), was significantly increased in comparison with the others groups (F(4, 47) = 18.21, p < 0.001). GABA released shows significant differences between experimental groups (F(4, 45) = 12.75, p < 0.001). It was detected a higher valour (p < 0.05) in-group II. The groups III and IV exhibited intermeddle valour (p < 0.001) and groups I and IV (p < 0.001) showed the lower GABA extracellular concentrations. The infusion of artificial cerebrospinal fluid with higher potassium (100 mmol) induced an increase in the GLU and GABA released in all groups, which confirm the neuronal origin of the extracellular content. CONCLUSION: These results are in agreement with the current model of basal ganglia functioning and suggest the role of STN-PPN projection in the physiopathology of Parkinson's disease.

Efecto de la lesión de la sustancia negra parte compacta sobre la liberación de glutamato y GABA en el núcleo pedunculopontino / The effects of lesions in the compact part of the substantia nigra on glutamate and GABA release in the pedunculopontine nucleus

The pedunculopontine nucleus (PPN), co-localized with the mesencephalic locomotor region, has been proposed as a key structure in the physiopathology of Parkinson's disease. OBJECTIVES: The goal of the present study was to assess if the aminoacid neurotransmitter release in the PPN is modified by the degeneration of dopaminergic cells, from substantia nigra pars compacta in 6-hydroxidopamine (6-OHDA)-lesioned rats. In addition, it was studied the aminoacid neurotransmitter release in the PPN of rats with lesion of the subthalamic nucleus by quinolinic acid (QUIN) (100 nmol) intracerebral injection...(AU)

Efecto de la lesión de la sustancia negra pars compacta sobre la liberación de glutamato y GABA en el núcleo pedunculopontino / The effects of lesions in the compact part of the substantia nigra on glutamate and gaba release in the pedunculopontine nucleus

Introducción. El núcleo pedunculopontino (NPP), colocalizado con el área locomotora mesencefálica, se ha señalado como una estructura clave en la fisiopatología de la enfermedad de Parkinson. Objetivos. 1. Estudiar el efecto de la lesión de la sustancia negra pars compacta -por inyección de 6-hidroxidopamina (6-OHDA)- sobre la liberación de aminoácidos neurotransmisores en el NPP. 2. Estudiar el efecto de la lesión del núcleo subtalámico (NST), por inyección intracerebral de 100 nmol de ácido quinolínico (QUIN), sobre la liberación de aminoácidos neurotransmisores en el NPP. Materiales y métodos. Se organizaron cinco grupos experimentales: ratas sanas (I; n = 13), lesión con 6-OHDA (II; n = 11), lesión simultánea de 6-OHDA + QUIN (III; n = 9), falsa lesión de 6-OHDA (IV; n = 10), y lesión del NST con QUIN (V; n = 9). Las concentraciones extracelulares de ácido glutámico (GLU) y GABA se determinaron por medio de cromatografía líquida de alta resolución (HPLC) con detección fluorimétrica. Resultados. Se detectaron diferencias significativas en la liberación de GLU entre todos los grupos experimentales (F(4, 47) = 18,21, p < 0,001), con un aumento significativo de esta variable en el grupo II. La liberación de GABA en el NPP mostró diferencias significativas entre los grupos en estudio (F(4, 45) = 12,75, p < 0,001). Para esta variable se produjo una separación entre los grupos, con un aumento significativo (p < 0,05) en el grupo II, valores intermedios y significativamente diferentes para los grupos III y V (p < 0,001) y valores menores para los grupos I y IV. La infusión de una solución de líquido cefalorraquídeo artificial con mayor concentración de potasio (100 mmol) produjo un incremento en la liberación de los aminoácidos neurotransmisores en todos los grupos experimentales, lo cual confirma el origen neuronal del contenido extracelular estudiado. Conclusiones. Estos resultados concuerdan con el ‘modelo’ actual de funcionamiento de los ganglios basales y sugieren un papel importante a la proyección STN-NPP en la fisiopatología de la enfermedad de Parkinson

Introduction. The pedunculopontine nucleus (PPN), co-localized with the mesencephalic locomotor region, has been proposed as a key structure in the physiopathology of Parkinson’s disease. Objectives. The goal of the present study was to assess if the aminoacid neurotransmitter release in the PPN is modified by the degeneration of dopaminergic cells, from substantia nigra pars compacta in 6-hydroxidopamine (6-OHDA)-lesioned rats. In addition, it was studied the aminoacid neurotransmitter release in the PPN of rats with lesion of the subthalamic nucleus by quinolinic acid (QUIN) (100 nmol) intracerebral injection. Materials and methods. Rats were assigned to five groups: untreated rats (I) (n = 13), 6-OHDA lesion (II) (n = 11), 6-OHDA + QUIN lesion (III) (n = 9), sham-operated (IV) (n = 10), QUIN, STN (V) lesioned (n = 9). The extracellular concentrations of glutamic acid (GLU) and gamma-aminobutyric acid (GABA) were determined by brain microdialysis and high performance liquid chromatography (HPLC). Results. GLU released in PPN from 6-OHDA lesioned rats (group II), was significantly increased in comparison with the others groups (F(4, 47) = 18.21, p < 0.001). GABA released shows significant differences between experimental groups (F(4, 45) = 12.75, p < 0.001). It was detected a higher valour (p < 0.05) in-group II. The groups III and IV exhibited intermeddle valour (p < 0.001) and groups I and IV (p < 0.001) showed the lower GABA extracellular concentrations. The infusion of artificial cerebrospinal fluid with higher potassium (100 mmol) induced an increase in the GLU and GABA released in all groups, which confirm the neuronal origin of the extracellular content. Conclusion. These results are in agreement with the current model of basal ganglia functioning and suggest the role of STN-PPN projection in the physiopathology of Parkinson’s disease

[Lesions in the pars compacta substantiae nigra and the subthalamic nucleus modify the density of muscarinic receptors in different nuclei of the basal ganglia]. / La lesión de la sustancia negra pars compacta y del núcleo subtalámico modifica la densidad de receptores muscarínicos en distintos núcleos de los ganglios basales.

INTRODUCTION: Several studies that has focused to the dopaminergic transmission in the basal ganglia in parkinsonian condition, but only a few article has taking into account the imbalance between dopaminergic and cholinergic transmission. OBJECTIVE: To evaluate the muscarinic cholinergic receptors density in SNc and PPN in the 6-OHDA model. MATERIALS AND METHODS: Were organized five experimental groups in correspondence to the place of the lesion: I. Non treated rats, II. 6-OHDA lesion in SNc, III. 6-OHDA lesion in SNc + quinolinic acid lesion in NST, IV. Sham operated rats, V. Quinolinic acid in STN. Were obtained coronal sections of 20 microm thickness of SNc and PPN from rats and in these sections was evaluated the muscarinic receptors density through autoradiographic technique with [3H]quinuclidinylbenzilate (QNB) (1.23 nM). The muscarinic antagonist atropine (1 microM) was utilized as non-specific union. The density was evaluated in both hemispheres and the density optical was converted in fentomolas/mg of tissue with base to values obtained from tritium standards. RESULTS: Significant diminution of the muscarinic receptors density was found in the SNc ipsilateral to the 6-OHDA lesion from experimental groups II (t=2.76; p<0.05) and III (t=4.06; p<0.05). In the group V, was seen a significant increase of muscarinic receptor density in the SNc ipsilateral to the 6-OHDA lesion. The comparison between experimental groups evidenced significant differences among them (F=13.13; p<0.001) with a significant decrease in the density from SNc of groups II and III and significant increase in the density from SNc of group V in comparison of the others groups. In relation to PPN, muscarinic receptors density from right PPN ipsilateral to the 6-OHDA lesion, shown significant differences (F=3.93; p<0.01) between the experimental groups with a significant increase of this variable in the group II. CONCLUSIONS: These results signal a modification of cholinergic activity after 6-OHDA lesion. The changes in the muscarinic receptors populations located in SNc and PPN could be part of different compensatory mechanisms to attempt ameliorate the imbalance between dopaminergic and cholinergic transmission that it was installed after denervation of nigrostriatal forebrain bundle. The excitotoxic lesion of STN impose a new adjust mechanism for cell from PPN, which could be expressed in the changes of muscarinic cholinergic receptors population at the level of SNc.

La lesión de la sustancia negra pars compacta y del núcleo subtalámico modifica la densidad de receptores muscarínicos en distintos núcleos de los ganglios basales / Lesions in the pars compacta substantiae nigrae and the subthalamic nucleus modify the density of muscarinic receptors in different nuclei of the basal ganglia

Introducción. Numerosos estudios han abordado el papel de la neurotransmisión dopaminérgica en los ganglios basales en condiciones de parkinsonismo, pero pocos se han encaminado hacia el desequilibrio entre la trasmisión dopaminérgica y colinérgica. Objetivo. Evaluar la densidad de receptores colinérgicos muscarínicos en sustancia negra pars compacta (SNc) y núcleo pedunculopontino (NPP) en el modelo de 6-OHDA. Materiales y métodos. Se organizaron cinco grupos experimentales según la lesión de SNcyNST: 1. Animales sanos; 2. Ratas lesionadas con 6-OHDA; 3. Ratas con lesión simultánea de SNcyNST; 4. Ratas Sham del modelo de 6-OHDA; 5. Ratas con lesión de NST. Se obtuvieron cortes de 20 µm de grosor de SNc y NPP de ratas, en los cuales se evaluó la densidad de receptores colinérgicos muscarínicos por autorradiografía con [3H]quinuclidinilbencilato (QNB) (1,23 nM). Como unión no específica se usó el antagonista muscarínico atropina (1 µM). Se realizaron lecturas en los dos hemisferios y la densidad óptica se convirtió en fentomolas por mg de tejido con base en los valores obtenidos de los estándares de tritio. Resultados. En los grupos 2 (t = 2,76; p < 0,05) y 3 (t = 4,06; p < 0,05) se evidenció una disminución significativa de la densidad de receptores muscarínicos en la SNc ipsilateral a la lesión de 6-OHDA. El grupo 5 mostró un aumento significativo de la densidad de receptores muscarínicos en la SNc lesionada con 6-OHDA (t = 2,69; p < 0,05). La comparación entre grupos experimentales arrojó diferencias significativas entre éstos (F=13,13;p<0,001), con una disminución en los grupos 2 y 3 y un aumento significativo en el grupo 5, en relación con los restantes grupos. La densidad de receptores muscarínicos para el NPP derecho ipsilateral a la lesión de SNc mostró diferencias significativas entre los grupos experimentales (F=3,93;p<0,01), con un aumento significativo de esta variable en el grupo 2. Conclusiones. Estos resultados apuntan hacia una modificación de la actividad colinérgica posterior a la denervación de la SNc por inyección de 6-OHDA. Los cambios en las poblaciones de receptores muscarínicos distribuidos en SNc y NPP pueden ser parte de distintos mecanismos compensatorios que intentan atenuar el desequilibrio entre las transmisiones dopaminérgica y colinérgica, que se instala después de la degeneración de la vía negroestriatal. La lesión excitotóxica de lNST impone un nuevo mecanismo de ajuste a las células del NPP, que pudiera expresarse en los cambios en las poblaciones de receptores colinérgicos de la SNc (AU)

Introduction. Several studies that has focused to the dopaminergic transmission in the basal ganglia in parkinsonian condition, but only a few article has taking into account the imbalance between dopaminergic and cholinergic transmission. Objective. To evaluate the muscarinic cholinergic receptors density in SNc and PPN in the 6-OHDA model. Materials and methods. Were organized five experimental groups in correspondence to the place of the lesion: I. Non treated rats, II. 6-OHDA lesion in SNc, III. 6-OHDA lesion in SNc + quinolinic acid lesion in NST, IV. Sham operated rats, V. Quinolinic acid in STN. Were obtained coronal sections of 20 µm thickness of SNc and PPN from rats and in these sections was evaluated the muscarinic receptors density through autoradiographic technique with [3H]quinuclidinylbenzilate (QNB) (1.23 nM). The muscarinic antagonist atropine (1 µM) was utilized as non-specific union. The density was evaluated in both hemispheres and the density optical was converted in fentomolas/mg of tissue with base to values obtained from tritium standards. Results. Significant diminution of the muscarinic receptors density was found in the SNc ipsilateral to the 6-OHDA lesion from experimental groups II (t = 2.76; p < 0.05) and III (t = 4.06; p < 0.05). In the group V, was seen a significant increase of muscarinic receptor density in the SNc ipsilateral to the 6-OHDA lesion. The comparison between experimental groups evidenced significant differences among them (F = 13.13; p < 0.001) with a significant decrease in the density from SNc of groups II and III and significant increase in the density from SNc of group V in comparison of the others groups. In relation to PPN, muscarinic receptors density from right PPN ipsilateral to the 6-OHDA lesion, shown significant differences (F = 3.93; p < 0.01) between the experimental groups with a significant increase of this variable in the group II. Conclusions. These results signal a modification of cholinergic activity after 6-OHDA lesion. The changes in the muscarinic receptors populations located in SNc and PPN could be part of different compensatory mechanisms to attempt ameliorate the imbalance between dopaminergic and cholinergic transmission that it was installed after denervation of nigrostriatal forebrain bundle. The excitotoxic lesion of STN impose a new adjust mechanism for cell from PPN, which could be expressed in the changes of muscarinic cholinergic receptors population at the level of SNc (AU)