title: Norepinephrine regulation of alpha-1 receptors and alpha-1-stimulated phosphoinositide hydrolysis in primary neuronal cultures.
abstract: Alpha-1 receptor density and alpha-1 receptor-stimulated phosphoinositide hydrolysis in neuronal primary cultures are regulated by exposure of the cells to the alpha-1 agonist norepinephrine (NE). Pretreatment of neuronal cultures with 10 microM NE caused a time- and concentration-dependent decrease in NE-stimulated accumulation of [3H]inositol phosphates. The maximal NE-stimulated inositide hydrolysis was decreased by approximately 80% after 2 hr of pretreatment with NE, and this loss of responsiveness was reversible over a period of 12 hr. NE pretreatment of neuronal cultures did not affect the muscarinic receptor stimulation of inositide hydrolysis. Neither the number of alpha-1 receptor recognition sites, assessed by measuring the specific binding of DL-[125I]-alpha-(3-iodohydroxyphenyl)-ethyl-aminomethyl tetralone ([125I]HEAT), nor the Ki for NE inhibition of [125I]HEAT binding were changed appreciably after treating neurons with NE for 2 hr. A time- and concentration-dependent decrease in alpha-1 receptor recognition sites occurred with longer periods of NE pretreatment. The maximal loss of 50 to 60% [125I]HEAT binding sites was seen after 14 hr of pretreatment with NE. The number of [125I]HEAT binding sites returned to control levels within 24 hr in parallel with the recovery of alpha-1-stimulated inositide hydrolysis after being down-regulated by a 24-hr exposure to NE. Cycloheximide (3.5 microM) blocked both the recovery of alpha-1 receptors and the recovery of alpha-1-stimulated inositide hydrolysis after 24 hr of NE pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, Louisiana State University Medical Center, New Orleans.
authors.forename: R A
authors.initials: RA
authors.lastname: Gonzales
authors.forename: F T
authors.initials: FT
authors.lastname: Crews
authors.forename: C
authors.initials: C
authors.lastname: Sumners
authors.forename: M K
authors.initials: MK
authors.lastname: Raizada
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006868:Hydrolysis; D009474:Neurons / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D010627:Phenethylamines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology; D051381:Rats; D011921:Rats, Inbred WKY; D011942:Receptors, Adrenergic, alpha / Q000032:analysis / Q000187:drug effects / Q000502:physiology*; D044024:Tetralones
chemical_list: D010627:Phenethylamines; D010716:Phosphatidylinositols; D011942:Receptors, Adrenergic, alpha; D044024:Tetralones; C048008:2-(beta-(3-iodo-4-hydroxyphenyl)ethylaminomethyl)tetralone; D003513:Cycloheximide; D011493:Protein Kinase C; D009638:Norepinephrine