title: Contribution of different classes of glutamate receptors in the corticostriatal polysynaptic responses from striatal direct and indirect projection neurons.
abstract: BACKGROUND
  Previous work showed differences in the polysynaptic activation of GABAergic synapses during corticostriatal suprathreshold responses in direct and indirect striatal projection neurons (dSPNs and iSPNs). Here, we now show differences and similarities in the polysynaptic activation of cortical glutamatergic synapses on the same responses. Corticostriatal contacts have been extensively studied. However, several questions remain unanswered, e.g.: what are the differences and similarities in the responses to glutamate in dSPNs and iSPNs? Does glutamatergic synaptic activation exhibits a distribution of latencies over time in vitro? That would be a strong suggestion of polysynaptic cortical convergence. What is the role of kainate receptors in corticostriatal transmission? Current-clamp recordings were used to answer these questions. One hypothesis was: if prolonged synaptic activation distributed along time was present, then it would be mainly generated from the cortex, and not from the striatum.
  
  
  RESULTS
  By isolating responses from AMPA-receptors out of the complex suprathreshold response of SPNs, it is shown that a single cortical stimulus induces early and late synaptic activation lasting hundreds of milliseconds. Prolonged responses depended on cortical stimulation because they could not be elicited using intrastriatal stimulation, even if GABAergic transmission was blocked. Thus, the results are not explained by differences in evoked inhibition. Moreover, inhibitory participation was larger after cortical than after intrastriatal stimulation. A strong activation of interneurons was obtained from the cortex, demonstrating that polysynaptic activation includes the striatum. Prolonged kainate (KA) receptor responses were also elicited from the cortex. Responses of dSPNs and iSPNs did not depend on the cortical area stimulated. In contrast to AMPA-receptors, responses from NMDA- and KA-receptors do not exhibit early and late responses, but generate slow responses that contribute to plateau depolarizations.
  
  
  CONCLUSIONS
  As it has been established in previous physiological studies in vivo, synaptic invasion over different latencies, spanning hundreds of milliseconds after a single stimulus strongly indicates convergent polysynaptic activation. Interconnected cortical neurons converging on the same SPNs may explain prolonged corticostriatal responses. Glutamate receptors participation in these responses is described as well as differences and similarities between dSPNs and iSPNs.
authors.affiliation: División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, DF, México.
authors.forename: Bianca J
authors.initials: BJ
authors.lastname: Vizcarra-Chacón
authors.forename: Mario A
authors.initials: MA
authors.lastname: Arias-García
authors.forename: Maria B
authors.initials: MB
authors.lastname: Pérez-Ramírez
authors.forename: Edén
authors.initials: E
authors.lastname: Flores-Barrera
authors.forename: Dagoberto
authors.initials: D
authors.lastname: Tapia
authors.forename: Rene
authors.initials: R
authors.lastname: Drucker-Colin
authors.forename: José
authors.initials: J
authors.lastname: Bargas
authors.forename: Elvira
authors.initials: E
authors.lastname: Galarraga
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D001703:Biophysics; D002540:Cerebral Cortex / Q000166:cytology*; D003342:Corpus Striatum / Q000166:cytology*; D004558:Electric Stimulation; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D009434:Neural Pathways / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D017447:Receptors, Dopamine D1 / Q000235:genetics; D017448:Receptors, Dopamine D2 / Q000235:genetics; D017470:Receptors, Glutamate / Q000145:classification / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
chemical_list: D018683:Excitatory Amino Acid Agents; D058787:GABA-A Receptor Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D017470:Receptors, Glutamate; D049452:Green Fluorescent Proteins; D001640:Bicuculline