Slow Oscillatory Firing: A Major Firing Pattern of Dopamine Neurons in the Ventral Tegmental Area

• Published in: Journal of neurophysiology 2005-11, Vol.94 (5), p.3516-3522
• Main Author: Shi, Wei-Xing
• Format: Article
• Language: English
• Subjects: Action Potentials - physiology; Animals; Biological Clocks - physiology; Dopamine - metabolism; Male; Neurons - physiology; Rats; Rats, Sprague-Dawley; Synaptic Transmission - physiology; Ventral Tegmental Area - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00317.2005

Neuropsychopharmacological Research Unit, Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut Submitted 28 March 2005; accepted in final form 14 July 2005 Using spectral analysis and in vivo single-unit recording in rats, the present study revealed a pronounced slow oscillation (SO) in the firing activity of about half the dopamine (DA) neurons recorded in the ventral tegmental area. DA neurons in this group tended to fire repetitive spike clusters, making them appear to be rhythmic bursting cells. However, only some of these burst-like events met the traditional "80/160 ms" burst criteria entirely. The observation that the SO could be found in nonbursting DA cells, occurred at frequencies different from those of bursts, and persisted after bursts were digitally removed from spike trains further supports the suggestion that the SO is different from the traditionally defined bursting. Interspike intervals (ISIs) had been thought to be bimodally distributed in bursting DA neurons. This study found that some nonbursting DA cells also had a bimodal ISI distribution and a significant number of bursting cells did not. In the majority of cells where less than half the spikes occurred in bursts, a bimodal ISI distribution was highly predictive of the presence of the SO. Results further showed that the generation of the SO required forebrain inputs to DA neurons but not the adrenergic 1 receptor activation responsible for psychostimulant-induced increases in the SO. Taken together, these results suggest that the SO is distinct from the traditionally defined bursting and represents a major firing pattern of DA neurons in the ventral tegmental area. Address for reprint requests and other correspondence: W.-X. Shi, Neuropsychopharmacological Research Unit, Yale University School of Medicine, 300 George St., Rm. 8300C, New Haven, CT 06511 (E-mail: wei-xing.shi{at}yale.edu )