title: Circannual variation in opioid receptor sensitivity in mouse vas deferens.
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D004558:Electric Stimulation; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000494:pharmacology; D011957:Receptors, Opioid / Q000187:drug effects*; D012621:Seasons; D014649:Vas Deferens / Q000294:innervation*
chemical_list: D011957:Receptors, Opioid; D004744:Enkephalin, Methionine; C022118:enkephalinamide-Met, Ala(2)-; D009020:Morphine