title: Characterization of synapses in the rat subnucleus centralis of the nucleus tractus solitarius.
abstract: The nucleus tractus solitarius (NTS) receives subdiaphragmatic visceral sensory information via vagal A- or C-fibers. We have recently shown that, in contrast to cardiovascular NTS medialis neurons, which respond to either purinergic or vanilloid agonists, the majority of esophageal NTS centralis (cNTS) neurons respond to vanilloid agonists, whereas a smaller subset responds to both vanilloid and purinerigic agonists. The present study aimed to further investigate the neurochemical and synaptic characteristics of cNTS neurons using whole cell patch-clamp, single cell RT-PCR and immunohistochemistry. Excitatory postsynaptic currents (EPSCs) were evoked in cNTS by tractus solitarius stimulation, and in 19 of 64 neurons perfusion with the purinergic agonist αβ-methylene ATP (αβMeATP) increased the evoked EPSC amplitude significantly. Furthermore, neurons with αβMeATP-responsive synaptic inputs had different probabilities of release compared with nonresponsive neurons. Single cell RT-PCR revealed that 8 of 13 αβMeATP-responsive neurons expressed metabotropic glutamate receptor 8 (mGluR8) mRNA, which our previous studies have suggested is a marker of glutamatergic neurons, whereas only 3 of 13 expressed glutamic acid dehydroxylase, a marker of GABAergic neurons. A significantly lower proportion of αβMeATP-nonresponsive neurons expressed mGluR8 (2 of 30 neurons), whereas a greater proportion expressed glutamic acid dehydroxylase (12 of 30 neurons). Esophageal distension significantly increased the number of colocalized mGluR8- and c-Fos-immunoreactive neurons in the cNTS from 8.0 ± 4% to 20 ± 2.5%. These data indicate that cNTS comprises distinct neuronal subpopulations that can be distinguished based on their responses to purinergic agonists and that these subpopulations have distinct neurochemical and synaptic characteristics, suggesting that integration of sensory inputs from the esophagus relies on a discrete organization of synapses between vagal afferent fibers and cNTS neurons.
authors.affiliation: Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Tanja
authors.initials: T
authors.lastname: Babic
authors.affiliation: Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Jason
authors.initials: J
authors.lastname: Ambler
authors.affiliation: Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania.
authors.forename: Kirsteen N
authors.initials: KN
authors.lastname: Browning
authors.affiliation: Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, Pennsylvania rtravagli@hmc.psu.edu.
authors.forename: R Alberto
authors.initials: RA
authors.lastname: Travagli
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D004947:Esophagus / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D005968:Glutamate Decarboxylase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D058913:Purinergic Agonists / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D046509:Tissue Culture Techniques; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D058913:Purinergic Agonists; D012333:RNA, Messenger; D018094:Receptors, Metabotropic Glutamate; C111435:metabotropic glutamate receptor 8; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D000255:Adenosine Triphosphate; D005968:Glutamate Decarboxylase; C002630:alpha,beta-methyleneadenosine 5'-triphosphate
keywords: brain stem; electrophysiology; nucleus tractus solitarius; vagus