Further characterization of muscarinic agonist-induced epileptiform bursting activity in immature rat piriform cortex,

Whalley, B.J., Postlethwaite, M. and Constanti, A. (2005) Further characterization of muscarinic agonist-induced epileptiform bursting activity in immature rat piriform cortex,. Neuroscience, 134 (2). pp. 549-566. 10.1016/j.neuroscience.2005.04.018.

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DOI: 10.1016/j.neuroscience.2005.04.018

Abstract

The characteristics of muscarinic acetylcholine receptor agonist-induced epileptiform bursting seen in immature rat piriform cortex slices in vitro were further investigated using intracellular recording, with particular focus on its postnatal age-dependence (P+14-P+30), pharmacology, site(s) of origin and the likely contribution of the muscarinic acetylcholine receptor agonist-induced post-stimulus slow afterdepolarization and gap junction functionality toward its generation. The muscarinic agonist, oxotremorine-M (10 microM), induced rhythmic bursting only in immature piriform cortex slices; however, paroxysmal depolarizing shift amplitude, burst duration and burst incidence were inversely related to postnatal age. No significant age-dependent changes in neuronal membrane properties or postsynaptic muscarinic responsiveness accounted for this decline. Burst incidence was higher when recorded in anterior and posterior regions of the immature piriform cortex. In adult and immature neurones, oxotremorine-M effects were abolished by M1-, but not M2-muscarinic acetylcholine receptor-selective antagonists. Rostrocaudal lesions, between piriform cortex layers I and II, or layer III and endopiriform nucleus in adult or immature slices did not influence oxotremorine-M effects; however, the slow afterdepolarization in adult (but not immature) lesioned slices was abolished. Gap junction blockers (carbenoxolone or octanol) disrupted muscarinic bursting and diminished the slow afterdepolarization in immature slices, suggesting that gap junction connectivity was important for bursting. Our data show that neural networks within layers II-III function as primary oscillatory circuits for burst initiation in immature rat piriform cortex during persistent muscarinic receptor activation. Furthermore, we propose that muscarinic slow afterdepolarization induction and gap junction communication could contribute towards the increased epileptiform susceptibility of this brain area.

Item Type:Article
Uncontrolled Keywords:piriform cortex; muscarinic acetylcholine receptor; bursting activity; slow afterdepolarization; gap junctions; development
Departments, units and centres:Department of Pharmacology > Department of Pharmacology
ID Code:2512
Journal or Publication Title:Neuroscience
Deposited By:Library Staff
Deposited On:24 Nov 2011 17:03
Last Modified:24 Nov 2011 17:03

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