Time and brain region specific up-regulation of low affinity neuronal nicotinic receptors during chronic nicotine administration in mice.
We studied the effects of chronic oral nicotine on brain low affinity nicotine binding sites. Mice received nicotine in the drinking water for 4 or 7 weeks. Receptor binding was measured at 24 or 48 h after cessation of nicotine administration with [3H]methyllycaconitine, an antagonist in alpha7 and alpha3/alpha6beta2beta3* nicotinic receptors in striatum, midbrain, hippocampus and cortex. Chronic nicotine for 4 weeks resulted in a significant increase in the [3H]methyllycaconitine binding in the striatum and cortex, whereas after 7 weeks the increase in binding could be found in the hippocampus but not in the other brain areas studied. For comparison, high affinity nicotine binding sites (mostly alpha4beta2) were measured with [3H]epibatidine after 7-week chronic nicotine treatment. [3H]Epibatidine binding sites were increased in the hippocampus, midbrain and cortex, but not in the striatum. The up-regulation of [3H]methyllycaconitine binding was significant at 24 h but that of [3H]epibatidine binding sites was not observed until at 48 h after cessation of chronic nicotine. These results suggest that up-regulation of low affinity nicotine binding sites does occur during chronic nicotine administration. Furthermore, the low affinity and high affinity binding differ clearly as regards regions and duration suggesting that different nicotinic receptors respond differently to nicotine administration.
Nuutinen
Saara
S
Division of Pharmacology and Toxicology, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5 E), University of Helsinki, FIN-00014, Finland.
Ahtee
Liisa
L
Tuominen
Raimo K
RK
D000157:Aconitine / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D008297:Male; D008636:Mesencephalon / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology; D011725:Pyridines / Q000378:metabolism; D011869:Radioligand Assay; D011978:Receptors, Nicotinic / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium; D015854:Up-Regulation
D019086:Bridged Bicyclo Compounds, Heterocyclic; D018722:Nicotinic Agonists; D011725:Pyridines; D011978:Receptors, Nicotinic; D014316:Tritium; C054634:methyllycaconitine; D009538:Nicotine; C082748:epibatidine; D000157:Aconitine