An immunocytochemical study on the distribution of two G-protein-gated inward rectifier potassium channels (GIRK2 and GIRK4) in the adult rat brain

doi:10.1016/S0306-4522(97)00001-8

Neuroscience

Volume 80, Issue 2, 14 July 1997, Pages 345-357

https://doi.org/10.1016/S0306-4522(97)00001-8 Get rights and content

Abstract

G-protein-gated inward rectifier potassium channels mediate the synaptic actions of numerous neurotransmitters in the mammalian brain, and were recently shown to be candidates for genetic mutations leading to neuronal cell death. This report describes the localization of G-protein-gated inward rectifier potassium channel-2 and G-protein-gated inward rectifier potassium channel-4 proteins in the rat brain, as assessed by immunocytochemistry. G-protein-gated inward rectifier potassium channel-2 immunoreactivity was widely distributed throughout the brain, with the strongest staining seen in the hippocampus, septum, granule cell layer of the cerebellum, amygdala and substantia nigra pars compacta. In contrast, G-protein-gated inward rectifier potassium channel-4 immunoreactivity was restricted to some neuronal populations, such as Purkinje cells and neurons of the globus pallidus and the ventral pallidum. The presence of G-protein-gated inward rectifier potassium channel-2 immunoreactivity in substantia nigra pars compacta dopaminergic neurons was confirmed by showing its co-localization with tyrosine hydroxylase by double immunocytochemistry, and also by selectively lesioning dopaminergic neurons with the neurotoxin 6-hydroxydopamine. At the cellular level both proteins were localized in neuronal cell bodies and dendrites, but clear differences were seen in the degree of dendritic staining among neuronal groups. For some neuronal groups the staining of distal dendrites (notably dendritic spines) was strong, while for others the cell body and proximal dendrites were preferentially labelled. In addition, some of the results suggest that G-protein-gated inward rectifier potassium channel-2 protein could be localized in distal axonal terminal fields.

A knowledge of the distribution of G-protein-gated inward rectifier potassium channel proteins in the brain could help to elucidate their physiological roles and to evaluate their potential involvement in neurodegenerative processes in animal models and human diseases.

Section snippets

Brain samples and tissue preparation

Both normal and 6-hydroxydopamine (OHDA)-lesioned adult male Sprague–Dawley rats (Centre d'élevage R. Janvier, France) were used in this study. The experimental protocol was approved by the French Ministry of Agriculture and Fisheries. The rats were anaesthetized with pentobarbital (60 mg/kg i.p.) and perfused transcardially with cold saline followed by cold 0.1 M phosphate buffer (PB) containing 4% paraformaldehyde. Their brains were removed, postfixed for 2 h and placed in 0.1 M PB containing 15%

Results

Anti-GIRK2 antibodies produced a strong and widely distributed immunostaining throughout the brain, but the most intense labelling was seen in the hippocampus, granule cell layer of the cerebellum, septum, amygdala and SNc (Fig. 1A,C). Preabsorption of anti-GIRK2 antibodies with the GST-GIRK2 fusion protein effectively suppressed the immunostaining (Fig. 1B). In contrast, GIRK4 immunoreactivity was detected in a restricted number of structures. Preabsorption experiments also confirmed the

Discussion

The main findings of our study can be summarized as follows: (i) GIRK2 immunoreactivity is widely expressed by neurons in the adult rat brain, while GIRK4 immunoreactivity was found to be present in a limited number of CNS structures; (ii) GIRK2 immunoreactivity is present in the soma and dendrites of most mesencephalic dopaminergic neurons; (iii) different neuronal types could have distinct subcellular patterns of GIRK expression.

The results of this study are in general agreement with recent

Conclusions

This work demonstrates the expression of GIRK2 and GIRK4 proteins in CNS neurons. GIRK2 immunoreactivity is widely expressed throughout the brain, notably by mesencephalic dopaminergic neurons, while GIRK4 immunoreactivity is present in a limited number of neuronal groups. The staining pattern observed indicates the presence of GIRK2 in the soma and dendrites of most labelled neurons, and suggests its presence in the axonal endings of some cells. GIRK4 seems to be present mainly in the soma and

Acknowledgements

This work was supported by grants from INSERM and CNRS (France). We are indebted to Dr Fosset for his help in the preparation of the antibodies (CNRS, Association Française contre les Myopathies).

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An immunocytochemical study on the distribution of two G-protein-gated inward rectifier potassium channels (GIRK2 and GIRK4) in the adult rat brain

Abstract

Section snippets

Brain samples and tissue preparation

Results

Discussion

Conclusions

Acknowledgements

Brain Res.

Neuroscience

Molec. cell. Neurosci.

Curr. Opin. Neurobiol.

Neuron

Biochim. biophys. Acta

Neuroscience

Biochem. biophys. Res. Commun.

Neuron

Fedn Eur. biochem. Socs Lett.

J. biol. Chem.

Neuroscience

Biochem. biophys. Res. Commun.

A G-protein couples serotonin and GABAB receptors to the same channels in hippocampus

Science

Pharmacologically distinct actions of serotonin on single pyramidal neurons of the rat hippocampus recorded in vitro

J. Physiol.

The human homologue of the weaver mouse gene in familial and sporadic Parkinson's disease

Neuroscience

Uncoupling of cardiac muscarinic and β-adrenergic receptors from ion channels by a guanine nucleotide analogue

Nature

Ionic channels and their regulation by G protein subunits

A. Rev. Physiol.

Atrial G protein-activated K+ channel: expression cloning and molecular properties

Proc. natn. Acad. Sci. U.S.A.

Neurotensin excites basal forebrain cholinergic neurons: ionic and signal transduction mechanisms

Proc. natn. Acad. Sci. U.S.A.

GABAB-receptor-activated K+ current in voltage-clamped CA3 pyramidal cells in hippocampal cultures

Proc. natn. Acad. Sci. U.S.A.

Muscarinic agonists activate inwardly rectifying potassium conductance in medial pontine reticular formation neurons of the rat in vitro

J. Neurosci.

A G-protein couples serotonin and GABA_B receptors to the same channels in hippocampus

Atrial G protein-activated K⁺ channel: expression cloning and molecular properties

GABA_B-receptor-activated K⁺ current in voltage-clamped CA3 pyramidal cells in hippocampal cultures