title: Tonic adenosine neuromodulation is preserved in motor nerve endings of aged rats.
abstract: Neuromuscular transmission is decreased in aged subject. Since endogenous adenosine is a potent neuromodulator at motor nerve endings, either inhibiting via A(1) receptors or facilitating via A(2A) receptors acetylcholine release, we now investigated if the tonic effect of endogenous adenosine was modified at phrenic nerve endings of aged rats. The A(2A) receptor antagonist (ZM241385, 50 nM) inhibited (77 +/- 9%) and the A(1) receptor antagonist (DPCPX, 50 nM) facilitated (74 +/- 13%) acetylcholine release from young adult (6 weeks old) rat preparations, indicating a simultaneous tonic activation of A(2A) and A(1) receptors. Tonic modulation by adenosine was unaltered in aged (24 months old) rats, since ZM241385 (50 nM) inhibited (73 +/- 8%) and DPCPX (50 nM) facilitated (91 +/- 20%) acetylcholine release in aged animals similarly to young rats. This indicates that, in contrast to the central nervous system where adenosine neuromodulation is modified in aged animals, the control by adenosine of phrenic nerve function is preserved in aged animals.
authors.affiliation: Laboratory of Neurosciences, Faculty of Medicine, University of Lisbon, Av. Prof. Egas Moniz, Lisbon, Portugal.
authors.forename: M F
authors.initials: MF
authors.lastname: Pereira
authors.forename: R A
authors.initials: RA
authors.lastname: Cunha
authors.forename: J A
authors.initials: JA
authors.lastname: Ribeiro
mesh_terms: D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000378:metabolism; D000241:Adenosine / Q000502:physiology*; D000375:Aging / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009411:Nerve Endings / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology; D058915:Purinergic P1 Receptor Antagonists; D051381:Rats; D017208:Rats, Wistar; D014227:Triazines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology
chemical_list: D018377:Neurotransmitter Agents; D058915:Purinergic P1 Receptor Antagonists; D014227:Triazines; D014230:Triazoles; D014970:Xanthines; C097270:ZM 241385; C051360:1,3-dipropyl-8-cyclopentylxanthine; D000241:Adenosine; D000109:Acetylcholine