GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects

The activation of pituitary GABAB receptors by the specific agonist baclofen inhibits pituitary hormone secretion in vitro. Here we studied the mechanism of action of GABAB receptors in rat adenohypophysis. Anterior pituitary cells were obtained by trypsinization and were either plated for hormonal...

Descripción completa

Guardado en:

Detalles Bibliográficos
Publicado:	2001
Materias:	Calcium Cyclic AMP G proteins GABAB receptors Gamma-aminobutyric acid Gamma-aminobutyric acid receptors Gonadotropin-releasing hormone Gonadotropins Prolactin Thyrotropin-releasing hormone 2 hydroxysaclofen 4 aminobutyric acid B receptor 4 aminobutyric acid B receptor blocking agent baclofen barium calcium channel calcium ion cyclic AMP dopamine forskolin fura 2 acetoxymethyl ester gonadorelin guanine nucleotide binding protein hypophysis hormone luteinizing hormone nifedipine pertussis toxin potassium channel blocking agent prolactin protirelin tetrylammonium trypsin verapamil adenohypophysis animal cell animal tissue article calcium cell level controlled study female hypophysis cell luteinizing hormone release nonhuman presynaptic nerve priority journal proestrus prolactin release rat receptor binding Animals Baclofen Barium Compounds Calcium Channel Blockers Cells, Cultured Chlorides Dopamine Female Forskolin Luteinizing Hormone Pertussis Toxin Pituitary Gland, Anterior Potassium Channel Blockers Potassium Chloride Proestrus Rats Receptors, GABA-B Tetraethylammonium Thyrotropin-Releasing Hormone Virulence Factors, Bordetella
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00283835_v73_n5_p334_LuxLantos http://hdl.handle.net/20.500.12110/paper_00283835_v73_n5_p334_LuxLantos
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paper:paper_00283835_v73_n5_p334_LuxLantos
record_format	dspace
spelling	paper:paper_00283835_v73_n5_p334_LuxLantos2023-06-08T14:55:04Z GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects Calcium Cyclic AMP G proteins GABAB receptors Gamma-aminobutyric acid Gamma-aminobutyric acid receptors Gonadotropin-releasing hormone Gonadotropins Prolactin Thyrotropin-releasing hormone 2 hydroxysaclofen 4 aminobutyric acid B receptor 4 aminobutyric acid B receptor blocking agent baclofen barium calcium channel calcium ion cyclic AMP dopamine forskolin fura 2 acetoxymethyl ester gonadorelin guanine nucleotide binding protein hypophysis hormone luteinizing hormone nifedipine pertussis toxin potassium channel blocking agent prolactin protirelin tetrylammonium trypsin verapamil adenohypophysis animal cell animal tissue article calcium cell level controlled study female hypophysis cell luteinizing hormone release nonhuman presynaptic nerve priority journal proestrus prolactin release rat receptor binding Animals Baclofen Barium Compounds Calcium Calcium Channel Blockers Cells, Cultured Chlorides Cyclic AMP Dopamine Female Forskolin Luteinizing Hormone Pertussis Toxin Pituitary Gland, Anterior Potassium Channel Blockers Potassium Chloride Proestrus Prolactin Rats Receptors, GABA-B Tetraethylammonium Thyrotropin-Releasing Hormone Virulence Factors, Bordetella The activation of pituitary GABAB receptors by the specific agonist baclofen inhibits pituitary hormone secretion in vitro. Here we studied the mechanism of action of GABAB receptors in rat adenohypophysis. Anterior pituitary cells were obtained by trypsinization and were either plated for hormonal studies and cAMP determination or incubated in FURA 2AM for calcium measurements. Baclofen (BACL: 1·10-5 M) significantly inhibited basal and thyrotropic releasing hormone (TRH)-stimulated (1·10-7 M) PRL secretion in anterior pituitary cells from proestrous rats. In the presence of pertussis toxin (PTX: 150 ng/ml, 20 h), which leads to the uncoupling of the Gi/o-protein from the receptor, both effects of BACL were abolished while the effect of dopamine (DA: 1·10-8 M), used as an inhibitory control, was reduced from 70 to 25%. PTX also reversed BACL-induced inhibition of gonadotropin-releasing hormone (GnRH)-elicited luteinizing hormone (LH) secretion in anterior pituitary cells from 15-day-old female rats. In addition, though working in a pituitary mixed cell population, in which only some cell types possess GABAB receptors, BACL (1·10-5 M) attenuated the forskolin-induced (0.5 μM) increase in cAMP. This effect was prevented by co-incubation with the antagonist 2 hydroxysaclofen and by preincubation with PTX. BACL (5·10-5 M) and DA (5·10-7 M) inhibited basal intracellular calcium concentrations ([Ca2+]i) in pituitary cells and the effect of the latter was significantly stronger. The effect of BACL on [Ca2+]i was abolished after preincubation with PTX. In the presence of the potassium channel blocking agents barium (200 μM and 1 mM) and tetraethylammonium (10 mM), BACL was still able to inhibit [Ca2+]i. Blockade of voltage-sensitive calcium channels (VSCC) with either verapamil (5·10-6 M) or nifedipine (1·10-6 M) completely abolished the effect of BACL on [Ca2+]i. In the presence of 12.5 mM potassium concentration baclofen significantly inhibited [Ca2+]i. In conclusion, our results describe the negative coupling of adenohypophyseal GABAB receptors to VSCC through PTX-sensitive G-proteins. These characteristics suggest a resemblance of these receptors to the typical presynaptic GABAB sites described in the central nervous system. Copyright © 2001 S. Karger AG, Basel. 2001 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00283835_v73_n5_p334_LuxLantos http://hdl.handle.net/20.500.12110/paper_00283835_v73_n5_p334_LuxLantos
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Calcium Cyclic AMP G proteins GABAB receptors Gamma-aminobutyric acid Gamma-aminobutyric acid receptors Gonadotropin-releasing hormone Gonadotropins Prolactin Thyrotropin-releasing hormone 2 hydroxysaclofen 4 aminobutyric acid B receptor 4 aminobutyric acid B receptor blocking agent baclofen barium calcium channel calcium ion cyclic AMP dopamine forskolin fura 2 acetoxymethyl ester gonadorelin guanine nucleotide binding protein hypophysis hormone luteinizing hormone nifedipine pertussis toxin potassium channel blocking agent prolactin protirelin tetrylammonium trypsin verapamil adenohypophysis animal cell animal tissue article calcium cell level controlled study female hypophysis cell luteinizing hormone release nonhuman presynaptic nerve priority journal proestrus prolactin release rat receptor binding Animals Baclofen Barium Compounds Calcium Calcium Channel Blockers Cells, Cultured Chlorides Cyclic AMP Dopamine Female Forskolin Luteinizing Hormone Pertussis Toxin Pituitary Gland, Anterior Potassium Channel Blockers Potassium Chloride Proestrus Prolactin Rats Receptors, GABA-B Tetraethylammonium Thyrotropin-Releasing Hormone Virulence Factors, Bordetella
spellingShingle	Calcium Cyclic AMP G proteins GABAB receptors Gamma-aminobutyric acid Gamma-aminobutyric acid receptors Gonadotropin-releasing hormone Gonadotropins Prolactin Thyrotropin-releasing hormone 2 hydroxysaclofen 4 aminobutyric acid B receptor 4 aminobutyric acid B receptor blocking agent baclofen barium calcium channel calcium ion cyclic AMP dopamine forskolin fura 2 acetoxymethyl ester gonadorelin guanine nucleotide binding protein hypophysis hormone luteinizing hormone nifedipine pertussis toxin potassium channel blocking agent prolactin protirelin tetrylammonium trypsin verapamil adenohypophysis animal cell animal tissue article calcium cell level controlled study female hypophysis cell luteinizing hormone release nonhuman presynaptic nerve priority journal proestrus prolactin release rat receptor binding Animals Baclofen Barium Compounds Calcium Calcium Channel Blockers Cells, Cultured Chlorides Cyclic AMP Dopamine Female Forskolin Luteinizing Hormone Pertussis Toxin Pituitary Gland, Anterior Potassium Channel Blockers Potassium Chloride Proestrus Prolactin Rats Receptors, GABA-B Tetraethylammonium Thyrotropin-Releasing Hormone Virulence Factors, Bordetella GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects
topic_facet	Calcium Cyclic AMP G proteins GABAB receptors Gamma-aminobutyric acid Gamma-aminobutyric acid receptors Gonadotropin-releasing hormone Gonadotropins Prolactin Thyrotropin-releasing hormone 2 hydroxysaclofen 4 aminobutyric acid B receptor 4 aminobutyric acid B receptor blocking agent baclofen barium calcium channel calcium ion cyclic AMP dopamine forskolin fura 2 acetoxymethyl ester gonadorelin guanine nucleotide binding protein hypophysis hormone luteinizing hormone nifedipine pertussis toxin potassium channel blocking agent prolactin protirelin tetrylammonium trypsin verapamil adenohypophysis animal cell animal tissue article calcium cell level controlled study female hypophysis cell luteinizing hormone release nonhuman presynaptic nerve priority journal proestrus prolactin release rat receptor binding Animals Baclofen Barium Compounds Calcium Calcium Channel Blockers Cells, Cultured Chlorides Cyclic AMP Dopamine Female Forskolin Luteinizing Hormone Pertussis Toxin Pituitary Gland, Anterior Potassium Channel Blockers Potassium Chloride Proestrus Prolactin Rats Receptors, GABA-B Tetraethylammonium Thyrotropin-Releasing Hormone Virulence Factors, Bordetella
description	The activation of pituitary GABAB receptors by the specific agonist baclofen inhibits pituitary hormone secretion in vitro. Here we studied the mechanism of action of GABAB receptors in rat adenohypophysis. Anterior pituitary cells were obtained by trypsinization and were either plated for hormonal studies and cAMP determination or incubated in FURA 2AM for calcium measurements. Baclofen (BACL: 1·10-5 M) significantly inhibited basal and thyrotropic releasing hormone (TRH)-stimulated (1·10-7 M) PRL secretion in anterior pituitary cells from proestrous rats. In the presence of pertussis toxin (PTX: 150 ng/ml, 20 h), which leads to the uncoupling of the Gi/o-protein from the receptor, both effects of BACL were abolished while the effect of dopamine (DA: 1·10-8 M), used as an inhibitory control, was reduced from 70 to 25%. PTX also reversed BACL-induced inhibition of gonadotropin-releasing hormone (GnRH)-elicited luteinizing hormone (LH) secretion in anterior pituitary cells from 15-day-old female rats. In addition, though working in a pituitary mixed cell population, in which only some cell types possess GABAB receptors, BACL (1·10-5 M) attenuated the forskolin-induced (0.5 μM) increase in cAMP. This effect was prevented by co-incubation with the antagonist 2 hydroxysaclofen and by preincubation with PTX. BACL (5·10-5 M) and DA (5·10-7 M) inhibited basal intracellular calcium concentrations ([Ca2+]i) in pituitary cells and the effect of the latter was significantly stronger. The effect of BACL on [Ca2+]i was abolished after preincubation with PTX. In the presence of the potassium channel blocking agents barium (200 μM and 1 mM) and tetraethylammonium (10 mM), BACL was still able to inhibit [Ca2+]i. Blockade of voltage-sensitive calcium channels (VSCC) with either verapamil (5·10-6 M) or nifedipine (1·10-6 M) completely abolished the effect of BACL on [Ca2+]i. In the presence of 12.5 mM potassium concentration baclofen significantly inhibited [Ca2+]i. In conclusion, our results describe the negative coupling of adenohypophyseal GABAB receptors to VSCC through PTX-sensitive G-proteins. These characteristics suggest a resemblance of these receptors to the typical presynaptic GABAB sites described in the central nervous system. Copyright © 2001 S. Karger AG, Basel.
title	GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects
title_short	GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects
title_full	GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects
title_fullStr	GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects
title_full_unstemmed	GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects
title_sort	gabab receptors in anterior pituitary cells: mechanism of action coupled to endocrine effects
publishDate	2001
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00283835_v73_n5_p334_LuxLantos http://hdl.handle.net/20.500.12110/paper_00283835_v73_n5_p334_LuxLantos
_version_	1768543265366212608

GABAB receptors in anterior pituitary cells: Mechanism of action coupled to endocrine effects

Ejemplares similares