title: Input-specific modulation of neurotransmitter release in the lateral horn of the spinal cord via adenosine receptors.
abstract: Activation of adenosine A2A receptors (A2ARs) in the CNS produces a variety of neuromodulatory actions dependent on the region and preparation examined. In autonomic regions of the spinal cord, A1R activation decreases excitatory synaptic transmission, but the effects of A2AR stimulation are unknown. We sought to determine the location and function of the A2ARs in the thoracic spinal cord, focusing on the intermediolateral cell column (IML). A2AR immunoreactivity was observed throughout the gray matter, with particularly dense immunostaining in regions containing sympathetic preganglionic neurons (SPNs), namely, the IML and intercalated nucleus. Electron microscopy revealed A2AR immunoreactivity within presynaptic terminals and in postsynaptic structures in the IML. To study the functional relevance of these A2ARs, visualized whole-cell patch-clamp recordings were made from electrophysiologically identified SPNs and interneurons within the IML. The A2AR agonist c2-[p-(carboxyethyl)phenethylamino]-5'-N-ethylcarboxyamidoadenosine (CGS 21680) had no significant effect on EPSPs but increased the amplitude of IPSPs elicited by stimulation of the lateral funiculus. These effects were attributable to activation of presynaptic A2ARs because CGS 21680 application altered the paired pulse ratio. Furthermore, neurons in the IML that have IPSPs increased via A2AR activation also receive excitatory inputs that are inhibited by A1R activation. These data show that activating A2ARs increase inhibitory but not excitatory transmission onto neurons in the IML. Simultaneous activation of A1Rs and A2ARs therefore could facilitate inhibition of the postsynaptic neuron, leading to an overall reduction of sympathetic nervous activity.
authors.affiliation: School of Biomedical Sciences, University of Leeds, Leeds LS2 9NQ, United Kingdom.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Brooke
authors.forename: Jim
authors.initials: J
authors.lastname: Deuchars
authors.forename: Susan A
authors.initials: SA
authors.lastname: Deuchars
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D000818:Animals; D002478:Cells, Cultured; D019706:Excitatory Postsynaptic Potentials; D007150:Immunohistochemistry; D007395:Interneurons / Q000502:physiology; D008297:Male; D009433:Neural Inhibition; D009474:Neurons / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D018377:Neurotransmitter Agents / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010627:Phenethylamines / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000737:chemistry; D051381:Rats; D043682:Receptor, Adenosine A1 / Q000032:analysis; D043705:Receptor, Adenosine A2A / Q000032:analysis / Q000502:physiology*; D013116:Spinal Cord / Q000737:chemistry / Q000166:cytology* / Q000502:physiology*; D014227:Triazines / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology
chemical_list: D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D018377:Neurotransmitter Agents; D010627:Phenethylamines; D043682:Receptor, Adenosine A1; D043705:Receptor, Adenosine A2A; D014227:Triazines; D014230:Triazoles; C097270:ZM 241385; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D000241:Adenosine