title: Cholinergic and GABAergic neurons in the nucleus basalis region of young and aged rats.
abstract: Antibodies directed against choline acetyltransferase and glutamic acid decarboxylase were used in combination with recently developed stereological techniques to quantify changes in cholinergic, GABAergic, and total neuron number (Nissl-stain) within adjacent tissue sections through the horizontal limb/nucleus basalis in young (3 months, n = 6) and aged (27 months, n = 6) Fischer-344 male rats. Unbiased estimates of total neuron number within these regions were produced using a three-dimensional optical probe, the optical disector, in combination with a systematic random sampling scheme. Estimates of cell counts in immunostained tissue sections were conducted throughout the entire horizontal limb/nucleus basalis region. A significant 30% decrease in both cholinergic and total neuron number was detected in the aged animals; GABAergic neuron number remained unchanged. Total neuron number was significantly correlated with both cholinergic (r = 0.94) and glial cell number (r = 0.63), but not with GABAergic cell number. Based on neuron counts within an individual thick tissue section, the cholinergic neurons comprised only 11-15% of all neurons in the nucleus basalis of young and aged animals. Cholinergic neuron loss accounted for only 20% of the total age-related neuron loss within the horizontal limb/nucleus basalis in Fischer-344 male rats. These results indicate that age-related cholinergic neuron loss within the basal forebrain is reflected in reductions in total neuron number; however, GABAergic neurons, many of which project to the cortex, are unaffected by age. The magnitude of the age-related total neuron loss cannot be entirely accounted for by cholinergic cell loss. Therefore, an unidentified non-cholinergic, non-GABAergic component within the basal forebrain is also lost during aging and may contribute to the cognitive deficits previously ascribed to cholinergic dysfunction.
authors.affiliation: Department of Pharmacology and Sanders-Brown Center on Aging, University of Kentucky College of Medicine, Lexington 40536-0084, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Smith
authors.forename: R M
authors.initials: RM
authors.lastname: Booze
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D000906:Antibodies / Q000276:immunology; D002262:Carboxy-Lyases / Q000276:immunology; D002452:Cell Count; D016923:Cell Death; D002799:Cholinergic Fibers / Q000502:physiology*; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D013377:Substantia Innominata / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000906:Antibodies; D005680:gamma-Aminobutyric Acid; D002262:Carboxy-Lyases