title: M3 muscarinic receptor in the ventral medial prefrontal cortex modulating the expression of contextual fear conditioning in rats.
abstract: BACKGROUND
  Basal forebrain cholinergic neurons modulate the activation of cortical neurons by several stimuli such as fear and anxiety. However, the role of the muscarinic receptor in the medial prefrontal cortex (MPFC) in the modulation of the conditioned emotional response (CER) evoked in the model contextual conditioned fear remains unclear.
  
  
  OBJECTIVE
  The objective of this study is to test the hypothesis that inhibition of the muscarinic receptor in ventral MPFC modulates CER observed during animal's re-exposure to the aversive context.
  
  
  METHODS
  Rats implanted with cannulae aimed at the prelimbic (PL) or the infralimbic (IL) were submitted to a high-intensity contextual fear conditioning protocol. Before the test session, they received microinjections of the hemicholinium (choline reuptake blocker), atropine (muscarinic antagonist), J104129 fumarate (M1-M3 muscarinic antagonists), pirenzepine (M1 muscarinic antagonist), neostigmine (inhibitor acetylcholinesterase enzyme), or the systemic administration of the FG7142 (inverse benzodiazepine agonist). Additional independent groups received the neostigmine or FG7142 before the ineffective doses of J104129 fumarate in the low-intensity protocol of contextual fear conditioning.
  
  
  RESULTS
  In the high-intensity protocol, the administration of hemicholinium (1 nmol), atropine (0.06-6 nmol), J104129 fumarate (6 nmol), or pirenzepine (6 nmol) attenuated the expression of CER in rats. However, in the low-intensity protocol, only J10129 fumarate (0.06 nmol) reduced the expression of the CER. Finally, neostigmine (0.1-1 nmol) or FG7142 (8 mg/Kg) increased CER expression, an effect inhibited by the low dose of the J10129 fumarate.
  
  
  CONCLUSIONS
  These results indicated that the blockade of M3 muscarinic receptor in the vMPFC attenuates the CER expression.
authors.affiliation: Department of Pharmacology, Ribeirao Preto School of Medicine, University of Sao Paulo, Av. Bandeirantes, 3900, CEP: 14049-900, Ribeirao Preto, SP, Brazil.|Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: A G
authors.initials: AG
authors.lastname: Fedoce
authors.affiliation: Department of Pharmacology, Ribeirao Preto School of Medicine, University of Sao Paulo, Av. Bandeirantes, 3900, CEP: 14049-900, Ribeirao Preto, SP, Brazil.|Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: N C
authors.initials: NC
authors.lastname: Ferreira-Junior
authors.affiliation: Department of Pharmacology, Ribeirao Preto School of Medicine, University of Sao Paulo, Av. Bandeirantes, 3900, CEP: 14049-900, Ribeirao Preto, SP, Brazil.|Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: D G
authors.initials: DG
authors.lastname: Reis
authors.affiliation: Department of Pharmacology, Ribeirao Preto School of Medicine, University of Sao Paulo, Av. Bandeirantes, 3900, CEP: 14049-900, Ribeirao Preto, SP, Brazil.
authors.forename: F M A
authors.initials: FM
authors.lastname: Corrêa
authors.affiliation: Department of Pharmacology, Ribeirao Preto School of Medicine, University of Sao Paulo, Av. Bandeirantes, 3900, CEP: 14049-900, Ribeirao Preto, SP, Brazil. leoresstel@yahoo.com.br.|Center for Interdisciplinary Research on Applied Neurosciences (NAPNA), University of Sao Paulo, Sao Paulo, Brazil. leoresstel@yahoo.com.br.
authors.forename: L B M
authors.initials: LB
authors.lastname: Resstel
mesh_terms: D000818:Animals; D001569:Benzodiazepines / Q000819:agonists; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D003213:Conditioning, Psychological / Q000187:drug effects; D004644:Emotions; D005239:Fear / Q000523:psychology*; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000187:drug effects; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D043587:Receptor, Muscarinic M3 / Q000187:drug effects / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D002800:Cholinesterase Inhibitors; D018727:Muscarinic Antagonists; D043587:Receptor, Muscarinic M3; D001569:Benzodiazepines
keywords: Acetylcholine; Anxiety; Conditioned emotional response; Medial prefrontal cortex; Muscarinic receptor