NMDA and non-NMDA receptor antagonists inhibit photic induction of Fos protein in the hamster suprachiasmatic nucleus.
We previously reported that systemic treatment with a noncompetitive antagonist affecting the NMDA subtype of excitatory amino acid (EAA) receptor, MK-801, inhibits photic induction of Fos-like immunoreactivity (Fos-lir) in the hamster suprachiasmatic nucleus (SCN). Because MK-801 blocks the Ca2+ channel associated with the NMDA receptor, it may also influence the activity of other transmitters acting through Ca2+ channels. To assess the specificity of these effects, we compared the effects on photic induction of Fos-lir of several treatments: central injection of a competitive NMDA antagonist, CPP; central injection of a non-NMDA antagonist, DNQX; and systemic injection of the non-competitive NMDA antagonist, ketamine. Fos-lir was induced in SCN cells of vehicle-injected hamsters exposed to a light pulse 4-5 h after dark onset. Pretreatment with CPP (greater than 2 nmoles) or ketamine (greater than 100 mg/kg) caused a dose-related inhibition of photic induction of Fos-lir in portions of the SCN. These treatments reduced Fos-lir mainly in the rostral SCN and ventrolateral, but not dorsolateral, portions of the caudal SCN. Pretreatment with DNQX (greater than 20 nmoles) also inhibited photic induction of Fos-lir in the same regions of the SCN. These results indicate that photic induction of Fos protein in a portion of the hamster SCN is regulated by both NMDA and non-NMDA types of EAA receptor.
Abe
H
H
Department of Psychology, Dalhousie University, Halifax, Nova Scotia, Canada.
Rusak
B
B
Robertson
H A
HA
D000818:Animals; D006224:Cricetinae; D005071:Evoked Potentials / Q000187:drug effects; D007649:Ketamine / Q000494:pharmacology; D008297:Male; D008647:Mesocricetus; D016761:Oncogene Proteins v-fos / Q000096:biosynthesis*; D009900:Optic Nerve / Q000502:physiology; D010775:Photic Stimulation; D010879:Piperazines / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface / Q000187:drug effects; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000378:metabolism*
D016761:Oncogene Proteins v-fos; D010879:Piperazines; D011810:Quinoxalines; D017459:Receptors, Amino Acid; D011956:Receptors, Cell Surface; D016194:Receptors, N-Methyl-D-Aspartate; C056723:FG 9041; D007649:Ketamine; C050592:3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid