title: Subchronic administration of MK-801 in the rat decreases cortical binding of [3H]D-AP5, suggesting down-regulation of the cortical N-methyl-D-aspartate receptors.
abstract: The effects of the subchronic administration of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine (MK-801) (0.5 mg/kg twice daily, 7 days) on N-methyl-D-aspartate, phencyclidine and sigma binding sites, behaviour and catecholamine turnover were investigated in the rat. Overt behaviours induced by MK-801 on day 7 were significantly altered relative to day 1 with subchronically treated rats not showing head weaving, goss ataxia or loss of hindlimb control: locomotion and sniffing were largely unaffected. The mean intensities of behaviour were 1.8 and 5.4 for days 7 and 1, respectively. Behavioural tolerance was accompanied by a significant reduction in the density of cortical N-methyl-D-aspartate receptors as measured by [3H]D-2-amino-5-phosphonopentanoic acid binding, while affinity was unchanged: the density of binding sites was 3.52 and 1.88 pmol/mg protein for saline- and MK-801-treated rats, respectively. The N-methyl-D-aspartate ion channel as measured by the binding of [3H]N-(1-[2-thienyl]cyclohexyl)piperidine was not affected by the schedule of MK-801. Additionally, changes were not observed to N-methyl-D-aspartate- or glycine-stimulated [3H]N-(1-[2-thienyl]cyclohexyl)piperidine binding or to sigma binding. Catecholamine turnover was unaltered in the nucleus accumbens septi after the schedule of MK-801. Our results demonstrate that the subchronic administration of MK-801 produces behavioural tolerance and down-regulation of N-methyl-D-aspartate binding sites and suggest differential regulation of the domains of the N-methyl-D-aspartate receptor-ionophore complex.
authors.affiliation: University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: D T
authors.initials: DT
authors.lastname: Manallack
authors.forename: D
authors.initials: D
authors.lastname: Lodge
authors.forename: P M
authors.initials: PM
authors.lastname: Beart
mesh_terms: D015763:2-Amino-5-phosphonovalerate; D000818:Animals; D000927:Anticonvulsants / Q000378:metabolism; D001259:Ataxia / Q000139:chemically induced; D002540:Cerebral Cortex / Q000378:metabolism*; D003986:Dibenzocycloheptenes / Q000494:pharmacology* / Q000633:toxicity; D016291:Dizocilpine Maleate; D004361:Drug Tolerance; D008297:Male; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000378:metabolism*; D014633:Valine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D000927:Anticonvulsants; D003986:Dibenzocycloheptenes; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D016291:Dizocilpine Maleate; D015763:2-Amino-5-phosphonovalerate; D014633:Valine