Electrophysiological and immunocytochemical characterization of GABA and dopamine neurons in the substantia nigra of the rat
Section snippets
Electrophysiology
Slices were prepared from male Sprague–Dawley rats (Harlan: 60–150 g) using previously described methods.19, 81Briefly, the rats were anaesthetized with methoxyflurane and decapitated. The brain was removed and placed in ice-cold artificial cerebrospinal fluid (ACSF), the composition of which was (mM): NaCl 124, KCl 2.5, NaHCO3 26, NaH2PO4 1.24, MgSO4 1.3, CaCl2 2.4, glucose 10. Sagittal sections (400–500 μm) were cut on a Lancer Series 2000 Vibratome, and were maintained in ACSF at room
Results
A total of 34 neurons recorded from the SN were selected for analysis, of which 22 were from the SNr and 11 from the SNc.
Discussion
The aim of this study was to provide an electrophysiological characterization of neurons within the SNr and the SNc based upon a combination of electrophysiological, morphological and immunocytochemical data. We found two classes of neurons within the SNr: GABA and dopamine neurons. The GABA neurons have a very different electrophysiological profile from the dopamine neurons: the dopamine neurons from the SNr, on the other hand, appear to form an electrophysiologically homogeneous population
Conclusion
In sum, projection neurons within the SNr could be divided into two classes, i.e. GABA or dopamine neurons, based upon electrophysiology, immunocytochemistry and morphology; the SNc contained only dopamine neurons. The dopamine neurons in the two regions of the SN were found not to be different in any of the parameters studied. On the other hand, the GABA neurons were different in their morphology from the dopamine neurons, and additionally displayed very different electrophysiological
Acknowledgements
The authors wish to express their gratitude to Dr Jang-Yen Wu for the kind gift of the anti-GAD antibody. We would also like to thank Dr Dietmar Plenz for his helpful comments and criticisms. This study was supported by USPHS grants NS 20702, NS 26473, and the National Parkinson Foundation.
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Present Address: Department of Psychiatry, Mie University, School of Medicine, Mie, Japan.