Muscarinic acetylcholine receptor‐expression in astrocytes in the cortex of young and aged rats

Abstract

The present report describes the cellular and subcellular distribution pattern of immunoreactivity to M35, a monoclonal antibody raised against purified muscarinic acetylcholine receptor protein, in astrocytes in the cerebral cortex of young and aged rats. Most M35-positive astrocytes were localized in the superficial layers of the cortex and part of the corpus callosum. At the ultrastructural level, immunoprecipitates were localized in the Golgi complexes, but the nucleus, rough endoplasmic reticulum, mitochondria, and microfilaments were generally free of labeling. Labeling was also present associated to the cell membrane, although without the characteristic immunoreactive postsynaptic membrane thickening found in neuronal structures. In aging rats of 30-34 months, the number of M35-labeled astrocytes doubled, whereas the neuronal staining slightly decreased in the same region in half of the animals studied. Fluorescent double-labeling for M35 and GFAP, an astrocytic microfilament protein, revealed that all M35-positive glial cells express GFAP and, conversely, that almost all GFAP glial cells were M35-immunostained. Based on the high incidence of coexpression of mAChRs and GFAP, both proteins may be functionally linked to each other. Rough semiquantitative estimates revealed that in young adult rats the GFAP/M35-immunoreactive astrocytes made up approximately one fifth of all cortical astrocytes. An important aspect of the presently demonstrated immunoreactivity of astroglia to mAChR proteins is its labeling in situ instead of in tissue culture. This finding may further support investigation, e.g., on anatomical relations of astroglia with neuronal and vascular elements, and its reactivity in experimental conditions.

Astrocyte Calcium Signaling Transforms Cholinergic Modulation to Cortical PlasticityIn Vivo

“…3B: stNBM 11 Ϯ 2% vs stNBM ϩ ATR 2.6 Ϯ 1.5%, p ϭ 0.02, 105 neurons in 3 mice for stNBM ϩATR). Astrocytes express mAChRs (Van Der Zee et al, 1993), and their activation leads to [Ca 2ϩ ] i elevation from internal stores (Shelton and McCarthy, 2000;Araque et al, 2002). In fact, in vivo iontophoretic injection of ACh into the barrel cortex induced [Ca 2ϩ ] i responses in 54 Ϯ 9% astrocytes in the imaging field (Fig.…”

Neuronal Nitric Oxide Synthase Expression is Induced in Neocortical Astrocytes after Spreading Depression

“…Differential expression of receptors and channels on astrocytes occur in anatomically distinct zones of the brain (Van der Zee et al, 1993) and functionally unique regions, such as at nodes of Ranvier (Black et al, 1989). Astrocytes also display morphologic diversity based on their laminar localization (Bailey and Shipley, 1993).…”

Distribution of AVP and Ca2+-dependent PKC-isozymes in the suprachiasmatic nucleus of the mouse and rabbit

“…Circadian timing is known to be disturbed in aging and age-related changes in glia are observed in the SCN [26,31,36]. Previously, Van der Zee and coworkers [51] described a significant increase in number and staining intensity of glial cells expressing abundant numbers of cholinergic receptors in the aging rat SCN, which represent reactive astrocytes [52]. In conclusion, these observations suggest that a high level of expression of proteins involved in signal transduction in astrocytes of the SCN may result in reduced clock function and weakening of the circadian pacemaker.…”