title: Dopaminergic Modulation of Lateral Amygdala Neuronal Activity: Differential D1 and D2 Receptor Effects on Thalamic and Cortical Afferent Inputs.
abstract: BACKGROUND
  In auditory fear conditioning, the lateral nucleus of the amygdala (LA) integrates a conditioned stimulus (CS) from the auditory thalamus (MGN) and the auditory association cortex (Te3) with an aversive unconditioned stimulus. The thalamic input provides a basic version of the CS, while the cortical input provides a processed representation of the stimulus. Dopamine (DA) is released in the LA under heightened arousal during the presentation of the CS.
  
  
  METHODS
  In this study we examined how D1 or D2 receptor activation affects LA afferent-driven neuronal firing using in vivo extracellular single-unit recordings with local micro-iontophoretic drug application in anesthetized rats. LA neurons that were responsive (~50%) to electrical stimulation in either the MGN or the Te3 were tested by iontophoresis of either the D1 agonist, SKF38393, or the D2 agonist, quinpirole.
  
  
  RESULTS
  We found that most of the LA projection neurons exhibited either facilitatory or attenuating effects (changes in evoked probability >15% relative to baseline) on afferent input by activation of D1 or D2 receptors. In general, it required significantly higher stimulation current to evoke ~50% baseline responses to the cortical input. Activation of the D1 receptor showed no difference in modulation between the thalamic or cortical pathways. On the other hand, activation of the D2 receptor had a stronger inhibitory modulation of the cortical pathway, but a stronger excitatory modulation of the thalamic pathway.
  
  
  CONCLUSIONS
  Our results suggest that there is a shift in balance favoring the thalamic pathway in response to DA acting via the D2 receptor.
authors.affiliation: Departments of Neuroscience, Psychiatry, and Psychology, University of Pittsburgh, Pittsburgh, PA 15260 (Drs Chang and Grace). changch@pitt.edu.
authors.forename: Chun-Hui
authors.initials: CH
authors.lastname: Chang
authors.affiliation: Departments of Neuroscience, Psychiatry, and Psychology, University of Pittsburgh, Pittsburgh, PA 15260 (Drs Chang and Grace).
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Grace
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000679:Amygdala / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001303:Auditory Cortex / Q000187:drug effects / Q000502:physiology*; D001306:Auditory Pathways / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000378:metabolism; D018491:Dopamine Agonists / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology; D008297:Male; D008839:Microelectrodes; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D019257:Quinpirole / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000819:agonists / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000819:agonists / Q000378:metabolism*; D013788:Thalamus / Q000187:drug effects / Q000502:physiology*
chemical_list: D018491:Dopamine Agonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D019257:Quinpirole; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D004298:Dopamine
keywords: D1 receptor; D2 receptor; amygdala; auditory cortex; auditory thalamus; dopamine