title: Muscarinic control of graded persistent activity in lateral amygdala neurons.
abstract: The cholinergic system is crucially involved in several cognitive processes including attention, learning and memory. Muscarinic actions have profound effects on the intrinsic firing pattern of neurons. In principal neurons of the entorhinal cortex (EC), muscarinic receptors activate an intrinsic cation current that causes multiple self-sustained spiking activity, which represents a potential mechanism for transiently sustaining information about novel items. The amygdala appears to be important for experience-dependent learning by emotional arousal, and cholinergic muscarinic influences are essential for the amygdala-mediated modulation of memory. Here we show that principal neurons from the lateral nucleus of the amygdala (LA) can generate intrinsic graded persistent activity that is similar to EC layer V cells. This firing behavior is linked to muscarinic activation of a calcium-sensitive non-specific cation current and can be mimicked by stimulation of cholinergic afferents that originate from the nucleus basalis of Meynert (n. M). Moreover, we demonstrate that the projections from the n. M. are essential and sufficient for the control and modulation of graded firing activity in LA neurons. We found that activation of these cholinergic afferents (i) is required to maintain and to increase firing rates in a graded manner, and (ii) is sufficient for the graded increases of stable discharge rates even without an associated up-regulation of Ca2+. The induction of persistent activity was blocked by flufenamic acid or 2-APB and remained intact after Ca2+-store depletion with thapsigargin. The internal ability of LA neurons to generate graded persistent activity could be essential for amygdala-mediated memory operations.
authors.affiliation: Interdisciplinary Center for Neurosciences (IZN), Department of Neuroanatomy, University of Heidelberg, Im Neuenheimer Feld 307, D-69120 Heidelberg, Germany. alexei.egorov@urz.uni-heidelberg.de
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Egorov
authors.forename: Klaus
authors.initials: K
authors.lastname: Unsicker
authors.forename: Oliver
authors.initials: O
authors.lastname: von Bohlen und Halbach
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000344:Afferent Pathways / Q000187:drug effects / Q000378:metabolism*; D000679:Amygdala / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D020532:Basal Nucleus of Meynert / Q000187:drug effects / Q000378:metabolism*; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002799:Cholinergic Fibers / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005439:Flufenamic Acid / Q000494:pharmacology; D008568:Memory / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009924:Organ Culture Techniques; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000893:Anti-Inflammatory Agents; D001896:Boron Compounds; D004791:Enzyme Inhibitors; D011976:Receptors, Muscarinic; D005439:Flufenamic Acid; C109986:2-aminoethoxydiphenyl borate; D000109:Acetylcholine; D002118:Calcium