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Front. Neuroanat. | doi: 10.3389/fnana.2018.00034

Stereological Estimates of Glutamatergic, GABAergic and Cholinergic Neurons in the Pedunculopontine and Laterodorsal Tegmental Nuclei in the Rat

  • 1Center for Applied Medical Research (CIMA), Universidad de Navarra, Spain
  • 2Department of Biochemistry and Genetics, School of Science, Universidad de Navarra, Spain
  • 3Anatomy Department, School of Medicine, Universidad de Navarra, Spain

The pedunculopontine (PPN) and laterodorsal (LDT) tegmental nuclei are functionally associated brainstem structures implicated in behavioral state control and sensorimotor integration. The PPN is also involved in gait and posture, while the LDT plays a role in reward. Both nuclei comprise characteristic cholinergic neurons intermingled with glutamatergic and GABAergic cells whose absolute numbers in the rat have been only partly established. Here we sought to determine the complete phenotypical profile of each nucleus to investigate potential differences between them. Counts were obtained using stereological methods after the simultaneous visualization of cholinergic and either glutamatergic or GABAergic cells. The two isoforms of glutamic acid decarboxylase (GAD), GAD65 and GAD67, were separately analyzed. Dual in situ hybridization revealed coexpression of GAD65 and GAD67 mRNAs in  90% of GAD-positive cells in both nuclei; thus, the estimated mean numbers of 1) cholinergic, 2) glutamatergic and 3) GABAergic cells in PPN and LDT, respectively, were 1) 3,360 and 3,650; 2) 5,910 and 5,190; and 3) 4,439 and 7,599. These data reveal significant differences between PPN and LDT in their relative phenotypical composition, which may underlie some of the functional differences observed between them. The estimation of glutamatergic cells was significantly higher in the caudal PPN, supporting the reported functional rostrocaudal segregation in this nucleus. Finally, a small subset of cholinergic neurons (8% in PPN, 5% in LDT) also expressed the glutamatergic marker Vglut2, providing anatomical evidence for a potential corelease of transmitters at specific target areas.

Keywords: : basal ganglia, GAD65, GAD67, VGLUT2, Gait, Reward

Received: 24 Dec 2017; Accepted: 16 Apr 2018.

Edited by:

Javier Blesa, Centro Integral en Neurociencias A.C. HM CINAC, Spain

Reviewed by:

Juan Mena-Segovia, Rutgers University, The State University of New Jersey, United States
María García-Amado, Universidad Autonoma de Madrid, Spain  

Copyright: © 2018 Luquin, Huerta, Aymerich and Mengual. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: PhD. Elisa Mengual, Universidad de Navarra, Center for Applied Medical Research (CIMA), Avda. Pío XII 55, Pamplona, 31008, Navarra, Spain, emp@unav.es