Adenosine inhibits basal forebrain cholinergic and noncholinergic neurons in vitro.
Adenosine has been proposed as a homeostatic "sleep factor" that promotes the transition from waking to sleep by affecting several sleep-wake regulatory systems. In the basal forebrain, adenosine accumulates during wakefulness and, when locally applied, suppresses neuronal activity and promotes sleep. However, the neuronal phenotype mediating these effects is unknown. We used whole-cell patch-clamp recordings in in vitro rat brain slices to investigate the effect of adenosine on identified cholinergic and noncholinergic neurons of the magnocellular preoptic nucleus and substantia innominata. Adenosine (0.5-100 microM) reduced the magnocellular preoptic nucleus and substantia innominata cholinergic neuronal firing rate by activating an inwardly rectifying potassium current that reversed at -82 mV and was blocked by barium (100 microM). Application of the A1 receptor antagonist 8-cyclo-pentyl-theophylline (200 nM) blocked the effects of adenosine. Adenosine was also tested on two groups of electrophysiologically distinct noncholinergic magnocellular preoptic nucleus and substantia innominata neurons. In the first group adenosine, via activation of postsynaptic A1 receptors, reduced spontaneous firing via inhibition of the hyperpolarization-activated cation current. Blocking the H-current with ZD7288 (20 microM) abolished adenosine effects on these neurons. The second group was not affected by adenosine. These results demonstrate that, in the magnocellular preoptic nucleus and substantia innominata region of the basal forebrain, adenosine inhibits both cholinergic neurons and a subset of noncholinergic neurons. Both of these effects occur via postsynaptic A1 receptors, but are mediated downstream by two separate mechanisms.
Arrigoni
E
E
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Room 814, 77 Louis Pasteur Avenue, Boston, MA 02115, USA. Earrigon@bidmc.harvard.edu
Chamberlin
N L
NL
Saper
C B
CB
McCarley
R W
RW
D000109:Acetylcholine / Q000378:metabolism*; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000241:Adenosine / Q000378:metabolism* / Q000494:pharmacology; D058907:Adenosine A1 Receptor Agonists; D058916:Adenosine A1 Receptor Antagonists; D000818:Animals; D002799:Cholinergic Fibers / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011301:Preoptic Area / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043682:Receptor, Adenosine A1 / Q000378:metabolism; D012890:Sleep / Q000187:drug effects / Q000502:physiology; D013377:Substantia Innominata / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D050051:Transient Receptor Potential Channels / Q000187:drug effects / Q000378:metabolism
D058907:Adenosine A1 Receptor Agonists; D058916:Adenosine A1 Receptor Antagonists; D015221:Potassium Channels; D043682:Receptor, Adenosine A1; D050051:Transient Receptor Potential Channels; D000241:Adenosine; D000109:Acetylcholine