title: Local administration of EAA antagonists blocks light-induced phase shifts and c-fos expression in hamster SCN.
abstract: Syrian hamsters were fitted with guide cannulas stereotaxically aimed at the suprachiasmatic nuclei (SCN) and housed in constant darkness in cages equipped with running wheels. Animals received 300-nl injections of either vehicle, CNQX, or MK-801 into the region of the SCN 5 min before a brief (10 min at 20 lx) light exposure. Local administration of either 1 mM CNQX or 1 mM MK-801 at circadian time (CT) 18 significantly inhibited light-induced phase advances (vehicle = 52 +/- 9 min; CNQX = 12 +/- 7 min; MK-801 = 12 +/- 5 min; P < 0.05 relative to vehicle+light group). The effects of both drugs were reversible and dose related. Injection of 1 mM MK-801 at CT13.5 resulted in a 71% inhibition of light-induced phase delays (vehicle = -51 +/- 6 min; MK-801 = -15 +/- 5 min; P < 0.05), while CNQX failed to significantly inhibit light-induced phase delays (-39 +/- 10 min). Local administration of either 1 mM CNQX or MK-801 into the SCN region reduced the number of Fos-immunoreactive cells relative to vehicle-injected controls by approximately 32 and 44%, respectively (vehicle = 951 +/- 79; CNQX = 643 +/- 135, P < 0.05; MK-801 = 533 +/- 143, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Circadian Neurobiology Research Group, Armstrong Laboratory (AL/CFTO), Brooks Air Force Base, Texas 78235.
authors.forename: M A
authors.initials: MA
authors.lastname: Rea
authors.forename: B
authors.initials: B
authors.lastname: Buckley
authors.forename: L M
authors.initials: LM
authors.lastname: Lutton
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000204:Activity Cycles / Q000187:drug effects; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects*; D006224:Cricetinae; D016291:Dizocilpine Maleate / Q000008:administration & dosage / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects*; D016762:Genes, fos / Q000187:drug effects*; D008027:Light; D008297:Male; D008647:Mesocricetus; D008845:Microinjections; D009043:Motor Activity / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000032:analysis / Q000096:biosynthesis; D011810:Quinoxalines / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D013238:Stereotaxic Techniques; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D011810:Quinoxalines; D016291:Dizocilpine Maleate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione