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This Article Full Text Full Text (PDF) All Versions of this Article: 92/4/2538    most recent 00372.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Sato, K. Articles by Momose-Sato, Y. Search for Related Content PubMed PubMed Citation Articles by Sato, K. Articles by Momose-Sato, Y.

Optical Mapping Reveals Developmental Dynamics of Mg²⁺-/APV-Sensitive Components of Glossopharyngeal Glutamatergic EPSPs in the Embryonic Chick NTS

Department of Physiology, Tokyo Medical and Dental University, Graduate School and Faculty of Medicine, Tokyo 113-8519, Japan

Submitted 12 April 2004; accepted in final form 26 May 2004

To examine whether there are any differences in functional organization between the glossopharyngeal nerve (N. IX)– and vagus nerve (N. X)–projecting areas in the nucleus of the tractus solitarius (NTS), we performed optical recording of neural responses evoked by N. IX stimulation in 5- to 9-day-old embryonic chick brain stem preparations and compared the results with those in our previous studies concerning the N. X-related NTS. First, we investigated DL-2-amino-5-phosphonovaleric acid (APV)/Mg²⁺ sensitivity of the glutamatergic excitatory postsynaptic potentials (EPSPs) in the N. IX-related NTS. In 7- to 9-day-old preparations, we found regional differences in the degree of both the APV-induced reduction and Mg²⁺-free–induced enhancement of the EPSPs. We constructed developmental maps of spatial patterns of the APV- and Mg²⁺-sensitive components and showed that functional expression of the N-methyl-D-aspartate (NMDA) receptor dynamically changed during development. Second, we studied initial expression of synaptic functions in the N. IX-related NTS. In 6-day-old preparations, although action potentials alone were usually detected in normal Ringer solution, small EPSPs were elicited in a Mg²⁺-free solution. This result suggests that the NMDA receptor–mediated synaptic function is latently generated in the N. IX-related NTS at the 6-day-old embryonic stage and that external Mg²⁺ regulates the onset of synaptic functions. Developmental patterns of APV/Mg²⁺ sensitivity and the stage of initial expression of the glossopharyngeal EPSP were similar to those of the N. X, suggesting that the developmental sequence of the synaptic function in the NTS is the same for the N. IX- and N. X-related NTS.