title: Morphological and physiological evidence of a synaptic connection between the lateral parabrachial nucleus and neurons in the A7 catecholamine cell group in rats.
abstract: BACKGROUND
  The descending noradrenergic (NAergic) system is one of the important endogenous analgesia systems. It has been suggested that noxious stimuli could activate descending NAergic system; nevertheless, the underlying neuronal circuit remains unclear. As NAergic neurons in the A7 catecholamine cell group (A7) are a part of the descending NAergic system and the lateral parabrachial nucleus (LPB) is an important brainstem structure that relays ascending nociceptive signal, we aimed to test whether LPB neurons have direct synaptic contact with NAergic A7 neurons.
  
  
  RESULTS
  Stereotaxic injections of an anterograde tracer, biotinylated dextran-amine (BDA), were administered to LPB in rats. The BDA-labeled axonal terminals that have physical contacts with tyrosine hydroxylase-positive (presumed noadrenergic) neurons were identified in A7. Consistent with these morphological observations, the excitatory synaptic currents (EPSCs) were readily evoked in NAergic A7 neurons by extracellular stimulation of LPB. The EPSCs evoked by LPB stimulation were blocked by CNQX, a non-NMDA receptor blocker, and AP5, a selective NMDA receptor blocker, showing that LPB-A7 synaptic transmission is glutamatergic. Moreover, the amplitude of LPB-A7 EPSCs was significantly attenuated by DAMGO, a selective μ-opioid receptor agonist, which was associated with an increase in paired-pulse ratio.
  
  
  CONCLUSIONS
  Taken together, the above results showed direct synaptic connections between LPB and A7 catecholamine cell group, the function of which is subject to presynaptic modulation by μ-opioid receptors.
authors.affiliation: Department of Life Sciences, and Agricultural Biotechnology Center, National Chung Hsing University, Taichung, Taiwan. et099530@gmail.com.|Department of Nursing, Jen-Teh Junior College of Medicine, Nursing and Management, Miaoli, Taiwan. et099530@gmail.com.
authors.forename: Chia-Yi
authors.initials: CY
authors.lastname: Liu
authors.affiliation: Department of Biomedical Sciences, Chung Shan Medical University, 110, Chien-Kuo N. Rd, Sec. 1, Taichung, 402, Taiwan. menglam.lee@gmail.com.|Department of Medical Research, Chung Shan Medical University, Taichung, Taiwan. menglam.lee@gmail.com.
authors.forename: Meng-Lam
authors.initials: ML
authors.lastname: Lee
authors.affiliation: Department of Nursing, Hungkuang University, Taichung, Taiwan. jcsy01@sunrise.hk.edu.tw.
authors.forename: Chi-Sheng
authors.initials: CS
authors.lastname: Yang
authors.affiliation: Department of Life Sciences, and Agricultural Biotechnology Center, National Chung Hsing University, Taichung, Taiwan. chchen1@dragon.nchu.edu.tw.|Rong Hsing Research Center for Translational Medicine, and the iEGG Center, National Chung Hsing University, Taichung, Taiwan. chchen1@dragon.nchu.edu.tw.
authors.forename: Chuan-Mu
authors.initials: CM
authors.lastname: Chen
authors.affiliation: Department of Life Sciences, College of Life Science, National Taiwan University, Taipei, Taiwan. mymin@ntu.edu.tw.
authors.forename: Ming-Yuan
authors.initials: MY
authors.lastname: Min
authors.affiliation: Department of Biomedical Sciences, Chung Shan Medical University, 110, Chien-Kuo N. Rd, Sec. 1, Taichung, 402, Taiwan. hwy@csmu.edu.tw.|Department of Medical Research, Chung Shan Medical University, Taichung, Taiwan. hwy@csmu.edu.tw.
authors.forename: Hsiu-Wen
authors.initials: HW
authors.lastname: Yang
mesh_terms: D059331:Adrenergic Neurons / Q000166:cytology / Q000502:physiology; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D008297:Male; D065823:Parabrachial Nucleus / Q000166:cytology / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000502:physiology*
chemical_list: D002395:Catecholamines