In situ determination of M1 and M2 muscarinic receptor binding sites and mRNAs in young and old rat brains.
Changes in M1, M2 receptor binding and mRNA in aged (25-26 months) rat brains were examined to determine whether decreases in receptors are due to declines in expression of corresponding mRNA levels. With aging, the M2 muscarinic receptor binding sites and m2 receptor mRNA were significantly decreased in the medial septum and diagonal band of Broca. In addition, M2 receptor binding was also reduced in the basal ganglia, CA3 field of the hippocampus, deeper layers of cortex, medial and central nuclei of amygdala, and thalamic nuclei. However, M1 binding was decreased in the basal ganglia, superficial layers of cortex, CA3 field of hippocampus and lateral nuclei of amygdala. There was no change in m1 receptor mRNA expression between any brain region of young and old rats. These studies suggest the reduction of the M2 receptor subtype during the transcriptional process, and alterations of M1 subtypes during translational or post-transcriptional periods.
Narang
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Neuropsychiatric Research Institute, Fargo, ND 58103, USA.
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001921:Brain / Q000254:growth & development* / Q000378:metabolism; D017403:In Situ Hybridization; D008297:Male; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000032:analysis*; D051381:Rats; D011916:Rats, Inbred F344; D011976:Receptors, Muscarinic / Q000032:analysis* / Q000235:genetics
D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D011976:Receptors, Muscarinic