title: Circadian variation of [3H]N6-(L-phenylisopropyl)adenosine binding in rat brain.
abstract: Since considerable recent experimental evidence suggests a role for the purine nucleoside adenosine in the regulation of mammalian sleep, circadian variations of adenosine receptor binding were examined in whole rat brain using [3H]N6-(L-phenylisopropyl)adenosine ([3H]L-PIA). These results demonstrate a significant circadian variation in the number of [3H]L-PIA binding sites (Bmax) with a maximum 3 h after the beginning of the dark phase of a 12 h light/12 h dark cycle, and a minimum 8 h later (P less than 0.025). The dissociation constant (Kd) of [3H]L-PIA at adenosine receptors did not exhibit any statistically significant circadian variation. These data indicate a daily rhythm in the number of adenosine receptors without a change in Kd and may support the hypothesized involvement of adenosine in the regulation of sleep in rats.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives*; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D002940:Circadian Rhythm; D007700:Kinetics; D008297:Male; D010660:Phenylisopropyladenosine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000032:analysis*; D011983:Receptors, Purinergic; D012890:Sleep / Q000502:physiology*; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D010660:Phenylisopropyladenosine; D000241:Adenosine