Localization of the m2 muscarinic acetylcholine receptor protein and mRNA in cortical neurons of the normal and cholinergically deafferented rhesus monkey (original) (raw)
Related papers
1998
The purpose of our work was to investigate how the cholinergic environment influences the targeting and the intracellular trafficking of the muscarinic receptor m2 (m2R) in vivo. To address this question, we have used immunohistochemical approaches at light and electron microscopic levels to detect the m2R in control rats and rats treated with muscarinic receptor agonists. In control animals, m2Rs were located mostly at postsynaptic sites at the plasma membrane of perikarya and dendrites of cholinergic and NPY–somatostatin interneurons as autoreceptors and heteroreceptors, respectively. Presynaptic receptors were also detected in boutons. The m2Rs were usually detected at extrasynaptic sites, but they could be found rarely in association with symmetrical synapses, suggesting that the cholinergic transmission mediated by m2R occurs via synaptic and nonsynaptic mechanisms. The stimulation of muscarinic
The Journal of Comparative Neurology, 1995
The m2 muscarinic acetylcholine receptor gene is expressed at high levels in basal forebrain, but the paucity of information about localization of the encoded receptor protein has limited the understanding of cellular and subcellular mechanisms involved in cholinergic actions in this region. The present study sought to determine the cellular localization of m2 protein, its relationship to cholinergic neurons, and its pre-and postsynaptic distribution in the rat medial septum-diagonal band complex using immunocytochemistry with polyclonal rabbit antibodies and a newly developed rat monoclonal antibody specific to the m2 receptor. Light microscopic colocalization studies demonstrated that m2 was present in a subset of choline acetyltransferase immunoreactive neurons, in choline acetyltransferase-negative neurons, and in more neuropil elements than was choline acetyltransferase. Intraventricular injections of 192 IgG-saporin, an immunotoxin directed to the low-affinity nerve growth factor receptor, resulted in depletion of choline acetyltransferase-immunoreactive neurons in the medial septum-diagonal band complex, whereas m2 immunoreactivity in neurons and in the neuropil was unchanged. By electron microscopy, m2 receptor in medial septum-diagonal band complex was localized to the plasmalemma of a small population of small to medium-sized neurons, and it was also found in dendrites, axons, and axon terminals in the neuropil. Neurons expressing m2 immunoreactivity received synaptic contacts from unlabelled axon terminals. A small distinct subpopulation of large neurons, unlabelled by m2 immunoreactivity, received synaptic contacts from m2-immunoreactive terminals. Thus, m2 receptor is situated to mediate the local effects of acetylcholine on basal forebrain cholinergic and noncholinergic neurons and, also, at both pre-and postsynaptic sites.
European Journal of Pharmacology, 1989
Muscarinic acetylcholine receptors in intact, cultured explants of rat hippocampus were investigated in binding experiments with tritiated quinuclidinyl benzilate ([3H]QNB) as ligand. Dissociation constants (K j) were determined to 320-575 pM and maximal binding capacity (Bma x) to 67-87 fmol/explant. The K d s obtained in kinetic experiments were very similar. Hippocampal explants cultured alone contained more muscarinic receptors than hippocampal explants reinnervated by cholinergic fibers from co-cultured septal explants. Pretreatment of hippocampal explants with carbachol resulted in a down-regulation of receptor number which was counteracted by the simultaneous addition of atropine. Atropine added alone had no effect on receptor number in hippocampal explants cultured alone whereas it occasionally caused an up-regulation in co-cultured hippocampus. Displacement experiments with scopolamine and oxotremorine as competitors, showed that hippocampal explants cultured alone contain multiple types of muscarinic receptors. With atropine, pirenzepine and AF-DX 116, only one class of receptors could be detected.
Neurochemical Research, 1994
We employed radioligand binding autoradiography to determine the distributions of pre-and postsynaptic cholinergic radioligand binding sites in the brains of two species of bat, one species of shrew, and the rat. High affinity choline uptake sites were measured with [3H]hemicholinium, and presynaptic cholinergic vesicles were identified with [3H]vesamicol. Muscarinic cholinergic receptors were determined with [3H]scopolamine. The distribution patterns of the three cholinergic markers were simitar in all species examined, and identified known major cholinergic pathways on the basis of enrichments in both pre-and postsynaptic markers. In addition, there was excellent agreement, both within and across species, in the regional distributions of the two presynaptic cholinergic markers. Our results indicate that pharmacological identifiers of cholinergic pathways and synapses, including the cholinergic vesicle transport site, and the organizations of central nervous system cholinergic pathways are phylogenetically conserved among eutherian mammals.
The Journal of Comparative Neurology, 2001
The cellular and subcellular localization of muscarinic receptor proteins m1 and m2 was examined in the neostriatum of macaque monkeys by using light and electron microscopic immunocytochemical techniques. Double-labeling immunocytochemistry revealed m1 receptors in calbindin-D28k-positive medium spiny projection neurons. Muscarinic m1 labeling was dramatically more intense in the striatal matrix compartment in juvenile monkeys but more intense in striosomes in the adult caudate, suggesting that m1 expression undergoes a developmental age-dependent change. Ultrastructurally, m1 receptors were predominantly localized in asymmetric synapse-forming spines, indicating that these spines receive extrastriatal excitatory afferents. The association of m1-positive spines with lesion-induced degenerating prefronto-striatal axon terminals demonstrated that these afferents originate in part from the prefrontal cortex. The synaptic localization of m1 in these spines indicates a role of m1 in the modulation of excitatory neurotransmission. To a lesser extent, m1 was present in symmetric synapses, where it may also modulate inhibitory neurotransmission originating from local striatal neurons or the substantia nigra. Conversely, m2/choline acetyltransferase (ChAT) double labeling revealed that m2-positive neurons corresponded to large aspiny cholinergic interneurons and ultrastructurally, that the majority of m2 labeled axons formed symmetric synapses. The remarkable segregation of the m1 and m2 receptor proteins to projection and local circuit neurons suggests a functional segregation of m1 and m2 mediated cholinergic actions in the striatum: m1 receptors modulate extrinsic glutamatergic and monoaminergic afferents and intrinsic GABAergic afferents onto projection neurons, whereas m2 receptors regulate acetylcholine release from axons of cholinergic interneurons.
Acta neurobiologiae experimentalis, 1987
The influence of bilateral electrolytic lesions of different parts of the septum on muscarinic receptor binding in the hippocampus was studied within 14-21 days after operation. The effect of total septal lesion upon receptor binding was also investigated separately in the dorsal and ventral hippocampus and in five consecutive hippocampal parts along the septotemporal axis of the structure. The data indicate that: (i) differential response of muscarinic receptors, as revealed by a decrease, increase or lack of changes in the [3H]QNB binding depends on the site and extent of the lesion, (ii) lack of changes in muscarinic receptor binding can be spurious when the investigation is performed on the whole hippocampus, and masked by regional response differences, (iii) differential response of [3H]QNB binding sites in distinct parts of the hippocampus to total septal lesion may depend on the preexisting differences in the density of cholinergic innervation and of muscarinic receptors.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1998
The purpose of our work was to investigate how the cholinergic environment influences the targeting and the intracellular trafficking of the muscarinic receptor m2 (m2R) in vivo. To address this question, we have used immunohistochemical approaches at light and electron microscopic levels to detect the m2R in control rats and rats treated with muscarinic receptor agonists. In control animals, m2Rs were located mostly at postsynaptic sites at the plasma membrane of perikarya and dendrites of cholinergic and NPY-somatostatin interneurons as autoreceptors and heteroreceptors, respectively. Presynaptic receptors were also detected in boutons. The m2Rs were usually detected at extrasynaptic sites, but they could be found rarely in association with symmetrical synapses, suggesting that the cholinergic transmission mediated by m2R occurs via synaptic and nonsynaptic mechanisms. The stimulation of muscarinic receptors with oxotremorine provoked a dramatic alteration of m2R compartmentalizat...
Molecular Brain Research, 1994
In situ hybridization was used to compare the microscopic distribution in the rat brain of cells containing mRNA for choline acetyltransferase (CHAT) (i.e. cholinergic cells) with that of cells containing mRNA for the five subtypes of muscarinic receptors, in an attempt to establish the potential role as autoreceptors (i.e. muscarinic cholinoceptors present in cholinergic cells) of the different muscarinic receptor subtypes. [32P]a-dATP-labelled synthetic oligonucleotides were used as hybridization probes in serial sections. Transcripts for all five subtypes of muscarinic receptors were detected in cells co-distributing with ChAT mRNA-containing cells in one or more regions of the brain. Cells containing m2, m3, m4 or m5 mRNAs were observed in the regions of the basal forebrain where cholinergic cells are located (medial septum/diagonal band nuclei, ventral pallidum, basal nucleus of Meynert). m2, m3 and m5 mRNAs were abundant in the parabigeminal nucleus. m2, m3 and m4 transcripts were detected in the pedunculopontine and laterodorsal tegmental nuclei, ml, m2 and m3 mRNAs were present in several cranial nerve nuclei. The present results suggest that muscarinic autoreceptors belonging to the five subtypes cloned to date may exist.
Neuroscience, 1992
The goal of the present study was to identify the cells containing mRNA coding for the m2 subtype of m mcarinic cholinergic receptors in the rat brain. In siru hybridization histochemistry was used, with ohgonucleotides as hybridixation probes. The distribution of choline@ cells was examined in consecutive sections with probes complementary to choline acetyltransferase mRNA. Furthermore, the microscopic distribution of mumarini c cholinergic binding sites was examined with a non-selective ligand ([3H]N-methylscopolamine) and with ligands proposed to be M-selective ([3H&kenmpine) or M,-selective ([aH]oxotremorine-M). The majority of choline acetyltransferase mRNA-rich (i.e. cholmergic) cell groups (medial septum-diagonal band complex, nucleus basalii, pedunculopontine and laterodorsal tegmental nuclei, nucleus parabigeminalis, several motor nuclei of the brainstem, motoneurons of the spinal cord), also contained m2 mRNA, strongly suggesting that at least a fraction of these receptors may be presynaptic autoreceptors. A few groups of cholinergic cells were an exception to this fact: the medial habemtla and some cranial nerve nuclei (principal oculomotor, trochlear, abducens, dorsal motor nucleus of the vagus).