Dendritic Projections and Dye-Coupling in Dopaminergic Neurons of the Substantia Nigra Examined in Horizontal Brain Slices From Young Rats

• Published in: Journal of neurophysiology 2003-10, Vol.90 (4), p.2531-2535
• Main Authors: Lin, John Y, van Wyk, Michiel, Bowala, Tharushini K, Teo, Min-Yau, Lipski, Janusz
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn; Biotin - analogs & derivatives; Biotin - analysis; Dendrites - chemistry; Dendrites - physiology; Dopamine - analysis; Dopamine - physiology; Fluorescent Dyes - analysis; Isoquinolines - analysis; Neural Pathways - chemistry; Neural Pathways - cytology; Neural Pathways - physiology; Neurons - chemistry; Neurons - cytology; Neurons - physiology; Rats; Rats, Wistar; Staining and Labeling - methods; Substantia Nigra - chemistry; Substantia Nigra - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00020.2003

Division of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, Private Bag 92-019 New Zealand Submitted 10 January 2003; accepted in final form 7 June 2003 We examined the rostro-caudal dendritic spread of striatally projecting dopaminergic neurons of the Substantia Nigra pars compacta (SNc) and investigated the presence of dye-coupling after labeling these cells with a mixture of lucifer yellow (LY) and neurobiotin (NB) or with LY alone. Whole cell recordings were made from horizontal brain slices (400 µm) obtained from P5-P20 rats. SNc neurons retrogradely labeled with Fluoro-Gold and located in the region containing tyrosine hydroxylase-immunoreactive cells displayed I h current and other properties characteristic of SNc neurons. To prevent extracellular leakage, dyes were introduced into patch pipettes after the establishment of whole cell configuration, and cells were filled under visual control. In contrast to previous studies conducted in coronal sections that identified dendritic projections of SNc neurons mainly in the medio-lateral and ventral directions, almost all neurons labeled in our study (53/54) additionally displayed a large rostro-caudal dendritic span (649 ± 219 µm). Dye-coupling between SNc neurons was not observed under basal conditions, in the presence of gap junction "openers" (forskolin, trimethylamine), or after neurons were filled with LY using sharp intracellular microelectrodes. As a "positive control," dye-coupling was demonstrated in four hippocampal dentate gyrus neurons that were filled using the same patch pipette technique. In addition, none of the tested SNc cells ( n = 12) showed expression of connexin 36 (the "neuronal" connexin) when tested with single-cell RT-PCR. In conclusion, this study revealed extensive rostro-caudal dendritic projections of SNc neurons. Under our in vitro conditions, no evidence was found for dye-coupling among these neurons. Address for reprint requests and other correspondence: J. Lipski, Div. of Physiology, Faculty of Medical and Health Sciences, Univ. of Auckland, Private Bag 92-019, Auckland, New Zealand (E-mail: j.lipski{at}auckland.ac.nz ).