title: The giant miniature endplate potentials frequency is increased in aged rats.
abstract: At the neuromuscular junction, spontaneous giant events (GMEPPs) are enhanced in different conditions when degenerative and/or remodeling processes take place, but no one investigated their incidence upon aging. In the present work, we evaluated evoked and spontaneous neuromuscular transmission events recorded from single muscle fibers. Phrenic-diaphragm preparations of 3-4, 12-16, 36-40 and 70-80 weeks old rat males were used. We found that the occurrence of GMEPPs significantly increases in aged rats. Moreover, in old rats the neuromuscular transmission was significantly impaired due to a significant decrease in the amplitude and quantal content of evoked endplate potentials. Interestingly, the number of observed EPPs failures were ∼ 3 times lower than the predicted value based on the quantal content. This discrepancy was not observed in infant or adult rats. The coincidence of a high GMEPPs frequency with a lower than expected EPPs failure rate suggests that GMEPPs events are needed to preserve effective neuromuscular transmission in aged animals.
authors.affiliation: Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Av. Professor Egas Moniz, 1649-028 Lisboa, Portugal; Unidade de Neurociências, Instituto de Medicina Molecular, Universidade de Lisboa, Av. Professor Egas Moniz, 1649-028 Lisboa, Portugal. Electronic address: pousinha@ipmc.cnrs.fr.
authors.forename: Paula A
authors.initials: PA
authors.lastname: Pousinha
authors.affiliation: Unidade de Neurociências, Instituto de Medicina Molecular, Universidade de Lisboa, Av. Professor Egas Moniz, 1649-028 Lisboa, Portugal; Museu Nacional de História Natural e da Ciência, University of Lisbon, Lisbon, Portugal. Electronic address: amcorreia@fc.ul.pt.
authors.forename: Alexandra M
authors.initials: AM
authors.lastname: Correia
authors.affiliation: Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Av. Professor Egas Moniz, 1649-028 Lisboa, Portugal; Unidade de Neurociências, Instituto de Medicina Molecular, Universidade de Lisboa, Av. Professor Egas Moniz, 1649-028 Lisboa, Portugal. Electronic address: anaseb@medicina.ulisboa.pt.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Sebastião
authors.affiliation: Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Av. Professor Egas Moniz, 1649-028 Lisboa, Portugal; Unidade de Neurociências, Instituto de Medicina Molecular, Universidade de Lisboa, Av. Professor Egas Moniz, 1649-028 Lisboa, Portugal. Electronic address: jaribeiro@medicina.ulisboa.pt.
authors.forename: Joaquim A
authors.initials: JA
authors.lastname: Ribeiro
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000375:Aging / Q000502:physiology*; D000818:Animals; D003964:Diaphragm / Q000294:innervation / Q000502:physiology; D008297:Male; D055369:Miniature Postsynaptic Potentials; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D009469:Neuromuscular Junction / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D017208:Rats, Wistar
chemical_list: D000109:Acetylcholine
keywords: Aging; GMEPPs; Neuromuscular junction; Neuromuscular transmission