Oscillatory firing of dopamine neurons: Differences between cells in the substantia nigra and ventral tegmental area

Abstract

Neuronal oscillations have been suggested to play an important role in information processing in the brain. Using spectral analysis, we have recently shown that the repetitive burst-like firing in many dopamine (DA) neurons in the ventral tegmental area (VTA) can be described as a slow oscillation (SO) in firing rate. In this study, we examined whether DA neurons in the adjacent substantia nigra (SN) also display a SO. DA neurons were recorded extracellularly using the cells/track technique in chloral hydrate-anesthetized rats. Spectral analysis showed that firing patterns of SN DA neurons exhibited a SO similar to that observed in VTA DA neurons. The amplitude of the SO, however, was much reduced in the SN compared with that in the VTA and so was the number of DA neurons qualified as high-SO cells. In high-SO DA neurons, the amplitude of the SO was strongly correlated with the degree of bursting, and this correlation was observed in both the VTA and SN. In low-SO cells, however, the SO was more significantly correlated with the variability of firing than with firing rate and bursting. Since the generation of the SO depends on afferent inputs to DA neurons, a better understanding of its difference between the SN and VTA may provide important insights into the neural networks that control DA neurons in the two areas.

Effects of l-DOPA on Nigral Dopamine Neurons and Local Field Potential: Comparison with Apomorphine and Muscimol

“…Thus, in 6-hydroxydopamine-lesioned rats, L-DOPA decreased both the firing rate and bursting in the remaining SN DA neurons (Harden and Grace, 1995). The decrease in bursting suggests that L-DOPA also inhibits synaptic input to DA cells in lesioned animals because burst firing in DA neurons depends on synaptic input and is partially correlated with CV and SO (Shi et al, 2004(Shi et al, , 2005Zhang et al, 2008). Apomorphine also inhibited DA cells in 6-hydroxydopamine-lesioned rats (Bilbao et al, 2006).…”

Estrogen regulates responses of dopamine neurons in the ventral tegmental area to cocaine

“…The electrode was placed into VTA through a small burr hole in the skull (3.0 mm anterior to the lambda and 0.5-0.9 mm lateral to the midline) by an electro-microdriver. DA neurons were identified at a depth of 6.5-8.5 mm from the cortical surface according to the commonly used criteria (Grace and Bunney 1983b;Zhang et al 2007) as follows: a biphasic (positive-negative) or triphasic (positivenegative-positive) spike waveform with a duration of greater than 3.0 ms, a broad initial positive phase (>1 ms, measured from the start of action potential to the negative trough), an initial segment-somatodendritic break in the initial positive phase, and a slow firing rate (<10 spikes/s). In addition, DA neurons can also be distinguished from non-DA neurons by the characteristic low-pitched sound that they produce on an audio monitor.…”

“…The present work is designed to investigate, in details, how ovarian hormones regulate the activity of VTA DA neurons and their responses to cocaine. In addition to the classical firing patterns of DA neurons, we included slow oscillation (SO), a recently identified firing pattern for DA neurons (Shi 2005;Zhang et al 2007), in the experiments. In vivo spectral analysis has revealed SO in approximately half of DA neurons in the VTA.…”

Cannabinoid CB 2 receptors modulate midbrain dopamine neuronal activity and dopamine-related behavior in mice

“…In addition, paired t tests were used to analyze some electrophysiological data, as described previously (30,31). FRs and burst firing were determined every 10 s, as described previously (57,58).…”