Activation of Ih is necessary for patterning of mGluR and mAChR induced network activity in the hippocampal CA3 region.
Neuronal networks of the hippocampal CA3 region generate stereotyped patterns of electrical activity in response to activation of metabotropic glutamate receptors (mGluRs) or muscarinic acetylcholine receptors (mAChRs) that consist of intermittent episodes of prolonged oscillatory activity. In light of the slow kinetics of such network responses, we investigated the possible contribution of the hyperpolarisation-activated inward current (I(h)) in the generation and maintenance of hippocampal oscillatory states. Hippocampal 'mini-slice' experiments in which the main subfields of the hippocampus were isolated by transection of the connecting afferents revealed that the CA3 region was the primary generator of both mGluR and mAChR-mediated network responses. Subsequent patch-clamp experiments confirmed the presence of a prominent hyperpolarisation-activated inward current in the principal cells of the CA3 region that was sensitive to caesium chloride and the selective I(h) blocker ZD-7288.Furthermore, in the presence of mAChR or mGluR agonists these cells exhibited a slow membrane potential oscillation that was independent of AMPA receptor-mediated synaptic transmission. Blockade of I(h) suppressed this oscillation as well as mGluR and mAChR-induced theta based intermittent network oscillatory behaviour. These data support the idea that the I(h) pacemaker current is important in the generation of patterned neuronal activities in the hippocampus.
Cobb
S R
SR
Division of Neuroscience and Biomedical Systems, University of Glasgow, Glasgow, G12 8QQ, UK. s.cobb@bio.gla.ac.uk
Larkman
P M
PM
Bulters
D O
DO
Oliver
L
L
Gill
C H
CH
Davies
C H
CH
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D003515:Cycloleucine / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D006624:Hippocampus / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D009415:Nerve Net / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D013826:Theta Rhythm / Q000187:drug effects
D002316:Cardiotonic Agents; D018679:Cholinergic Agonists; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D011743:Pyrimidines; D011810:Quinoxalines; D018094:Receptors, Metabotropic Glutamate; D011976:Receptors, Muscarinic; D003515:Cycloleucine; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; C082246:ICI D2788; D002217:Carbachol