Glutamate neurotransmission plays critical roles in normal central nervous system (CNS) function, neurodegenerative diseases, and neurotrauma. We determined whether glutamate signaling could be evoked within the anesthetized normal adult rat CNS with clinically relevant peripheral stimulation and recorded (at >1. Hz) with glutamate-sensitive, ceramic microelectrode arrays (MEAs). Basal glutamate levels and both forelimb cutaneous and electrical stimulation-evoked glutamate release were measured within the cuneate nucleus, a relay of the mammalian dorsal columns somatosensory system. The MEAs with triangular, sharp-point tips were more effective at tissue penetration than the flat, blunt tips. Basal glutamate levels of 2.1 ± 4.4 μM (mean ± SD, n= 10 animals) were detected from 150 μm to 1200 μm below the brainstem dorsal surface. Cutaneous evoked glutamate signals showed an amplitude of 1.1 ± 1.1 μM and a duration of 7.3 ± 6.5. s (26 signals, n= 6). Electrically evoked signals, like cutaneous ones, were both rapid and slowly rising. Electrically evoked signals, especially those evoked by stimulation trains, were more reproducible and had an amplitude of 1.2 ± 1.4 μM, duration of 19.4 ± 17.3. s, and latency from stimulus onset of 21.3 ± 21.5. s (25 signals, n= 4). In contrast to cutaneous stimulation, glutamate signals evoked by electrical stimulation had longer durations and were recorded primarily in the middle and ventral cuneate nuclei. Importantly, both cutaneous and electrical stimulation of the contralateral forelimb and hindlimbs did not evoke glutamate signaling. With the use of MEAs, these results show, for the first time, somatosensory-pathway specific changes in glutamate levels during peripheral cutaneous and electrical stimulation.
|Number of pages||9|
|Journal||Journal of Neuroscience Methods|
|State||Published - Jul 15 2012|
Bibliographical noteFunding Information:
This research was supported by the Kentucky Spinal Cord and Head Injury Research Trust Grant 9-9 (Stephen M. Onifer) and by USPHS Grant DA 017186 , NSF Grant EEC-0310723 , DARPA Grant N66001-09-2080 (Greg A. Gerhardt). The funding source had no involvement in study design. Greg A. Gerhardt is sole proprietor of and Jorge E. Quintero serves as a consultant to Quanteon LLC. The technical and artistic expertises of Laura Whitnel-Smith, Joshua Eason, Daisy Ramos, and David Onifer are gratefully appreciated.
- Cutaneous stimulation
- Dorsal column nuclei
- Electrical stimulation
- Microelectrode array
- Spinal cord
ASJC Scopus subject areas
- Neuroscience (all)