title: Beta1 adrenergic receptor-mediated enhancement of hippocampal CA3 network activity.
abstract: Norepinephrine is an endogenous neurotransmitter distributed throughout the mammalian brain. In higher cortical structures such as the hippocampus, norepinephrine, via beta adrenergic receptor (AR) activation, has been shown to reinforce the cognitive processes of attention and memory. In this study, we investigated the effect of beta1AR activation on hippocampal cornu ammonis 3 (CA3) network activity. AR expression was first determined using immunocytochemistry with antibodies against beta1ARs, which were found to be exceptionally dense in hippocampal CA3 pyramidal neurons. CA3 network activity was then examined in vitro using field potential recordings in rat brain slices. The selective betaAR agonist isoproterenol caused an enhancement of hippocampal CA3 network activity, as measured by an increase in frequency of spontaneous burst discharges recorded in the CA3 region. In the presence of alphaAR blockade, concentration-response curves for isoproterenol, norepinephrine, and epinephrine suggested that a beta1AR was involved in this response, and the rank order of potency was isoproterenol > norepinephrine = epinephrine. Finally, equilibrium dissociation constants (pK(b)) of subtype-selective betaAR antagonists were functionally determined to characterize the AR subtype modulating hippocampal CA3 activity. The selective beta1AR antagonists atenolol and metoprolol blocked isoproterenol-induced enhancement, with apparent K(b) values of 85 +/- 36 and 3.9 +/- 1.7 nM, respectively. In contrast, the selective beta2AR antagonists ICI-118,551 and butoxamine inhibited isoproterenol-mediated enhancement with apparent low affinities (K(b) of 222 +/- 61 and 9268 +/- 512 nM, respectively). Together, this pharmacological profile of subtype-selective betaAR antagonists indicates that in this model, beta1AR activation is responsible for the enhanced hippocampal CA3 network activity initiated by isoproterenol.
authors.affiliation: Department of Pharmacology, Physiology and Therapeutics, School of Medicine and Health Sciences, University of North Dakota, 501 North Columbia Rd., Grand Forks, ND 58202-9037, USA.
authors.forename: Chris W D
authors.initials: CW
authors.lastname: Jurgens
authors.forename: Katie E
authors.initials: KE
authors.lastname: Rau
authors.forename: Chris A
authors.initials: CA
authors.lastname: Knudson
authors.forename: Jacob D
authors.initials: JD
authors.lastname: King
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Carr
authors.forename: James E
authors.initials: JE
authors.lastname: Porter
authors.forename: Van A
authors.initials: VA
authors.lastname: Doze
mesh_terms: D058665:Adrenergic beta-1 Receptor Agonists; D058671:Adrenergic beta-1 Receptor Antagonists; D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002395:Catecholamines / Q000494:pharmacology / Q000502:physiology; D004594:Electrophysiology; D006624:Hippocampus / Q000187:drug effects*; D007150:Immunohistochemistry; D007202:Indicators and Reagents; D007545:Isoproterenol / Q000494:pharmacology; D009415:Nerve Net / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D017966:Pyramidal Cells / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism*; D012044:Regression Analysis; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D058665:Adrenergic beta-1 Receptor Agonists; D058671:Adrenergic beta-1 Receptor Antagonists; D058666:Adrenergic beta-2 Receptor Agonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D002395:Catecholamines; D007202:Indicators and Reagents; D018342:Receptors, Adrenergic, beta-1; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D007545:Isoproterenol