title: Adenosine A2A receptors interact with GABAergic pathways to modulate respiration in neonatal piglets.
abstract: GABA and adenosine contribute to respiratory inhibition in early postnatal life. In this study the adenosine A2A receptor agonist CGS21680 was used to evaluate adenosine receptor specificity and the interrelation of adenosine and GABA in the inhibition of inspiratory drive. In neonatal piglets (n = 10), CGS21680 was injected into the fourth ventricle resulting in apnea and/or decreased burst area and frequency of phrenic discharge. Phrenic burst area decreased to 58.9 +/- 8.6% (S.E.M.) after CGS21680 injection (control = 91.8 +/- 1.0%). Expiratory time increased 261.0 +/- 59.9% after CGS21680 from control (87.7 +/- 2.7%). When bicuculline was injected locally within the rostral ventrolateral medulla (n = 5), or into the fourth ventricle (n = 5), the CGS21680 induced inhibition of phrenic was abolished. To define expression of A2A receptor at the message level (mRNA), we employed in situ hybridization with a digoxigenin-coupled oligonucleotide. Adenosine A2A receptor mRNA was expressed in regions of the medulla oblongata known to contain GABAergic neurons. We conclude that GABAergic inputs affecting respiratory timing and inspiratory drive are modulated by activation of A2A receptors. These findings offer new insight into the mechanism whereby xanthine therapy diminishes apnea of prematurity.
authors.affiliation: Department of Pediatrics, Case Western Reserve University School of Medicine, Division of Neonatology, Suite 3100, 11100 Euclid Avenue, Cleveland, OH 44106, USA. cgwilson@po.cwru.edu
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Wilson
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Martin
authors.forename: Marwan
authors.initials: M
authors.lastname: Jaber
authors.forename: Jalal
authors.initials: J
authors.lastname: Abu-Shaweesh
authors.forename: Anjun
authors.initials: A
authors.lastname: Jafri
authors.forename: Musa A
authors.initials: MA
authors.lastname: Haxhiu
authors.forename: Syed
authors.initials: S
authors.lastname: Zaidi
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000502:physiology*; D058908:Adenosine A2 Receptor Agonists; D000818:Animals; D000831:Animals, Newborn; D001640:Bicuculline / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D008526:Medulla Oblongata / Q000166:cytology / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D010627:Phenethylamines / Q000494:pharmacology; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology*; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D018079:Receptors, GABA / Q000187:drug effects; D011983:Receptors, Purinergic / Q000187:drug effects; D015656:Respiratory Mechanics / Q000187:drug effects / Q000502:physiology*; D012137:Respiratory System / Q000294:innervation; D015398:Signal Transduction; D013552:Swine; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D058908:Adenosine A2 Receptor Agonists; D018756:GABA Antagonists; D010627:Phenethylamines; D043705:Receptor, Adenosine A2A; D018079:Receptors, GABA; D011983:Receptors, Purinergic; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D005680:gamma-Aminobutyric Acid; D000241:Adenosine; D001640:Bicuculline