title: CNS alpha 2-adrenoceptor induced mydriasis in conscious rats.
abstract: Clonidine (3-300 microgram/kg, i.p.) produced dose-dependent pupillary dilation in unanesthetized rats. At low levels of illumination (30 lux), this effect was similar to that seen in anesthetized animals but was diminished under higher ambient lighting conditions. alpha Methyldopa (60 mg/kg, i.p.) produced mydriasis that took several hours to develop and was prevented by pretreatment with a dopamine beta-hydroxylase inhibitor (FLA-63). Yohimbine antagonized pupillary dilation induced by both clonidine and methyldopa. These results demonstrate that mydriasis in the conscious rat can be an effective index of CNS alpha 2-adrenoceptor activation, particularly when measured under low lighting levels.
authors.affiliation: Department of Pharmacology, University of Oklahoma Health Sciences Center, Oklahoma City.
authors.forename: H D
authors.initials: HD
authors.lastname: Christensen
authors.forename: M
authors.initials: M
authors.lastname: Mutzig
authors.forename: M C
authors.initials: MC
authors.lastname: Koss
mesh_terms: D000758:Anesthesia; D000818:Animals; D005406:Bis(4-Methyl-1-Homopiperazinylthiocarbonyl)disulfide / Q000494:pharmacology; D002490:Central Nervous System / Q000187:drug effects / Q000502:physiology; D003000:Clonidine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008027:Light; D008297:Male; D008750:Methyldopa / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011292:Premedication; D011680:Pupil / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D011942:Receptors, Adrenergic, alpha; D005406:Bis(4-Methyl-1-Homopiperazinylthiocarbonyl)disulfide; D015016:Yohimbine; D008750:Methyldopa; D003000:Clonidine