Jul 29, 1998

Do silent dopaminergic neurons exist in rat substantia nigra in vivo?

M Dai, J M Tepper


A subpopulation of inactive or "silent" dopaminergic neurons has been reported to exist in vivo in rat substantia nigra, comprising up to 50% of nigral dopaminergic neurons. The existence of this large proportion of silent neurons has been inferred from various experimental manipulations, but never demonstrated directly. In the present study, striatal or medial forebrain bundle stimulation was used to activate antidromically substantia nigra dopaminergic neurons in vivo. Antidromic spikes of dopaminergic neurons observed by extracellular single-unit recordings in the absence of spontaneous activity were employed as indicators of the presence of a silent cell. A total of 312 dopamine neurons were recorded, including 190 neurons that could be antidromically activated from the striatum and/or the medial forebrain bundle. All neurons exhibited spontaneous activity. The firing rates were unimodally distributed about the mean of 4 spikes/s, and very few cells were observed to fire at less than 0.5 spikes/s. The numbers of spontaneously active and antidromically activated dopaminergic neurons per track were recorded and compared with the number of antidromically responding silent dopaminergic neurons per track after systemic apomorphi...Continue Reading

Mentioned in this Paper

Resting Potentials
Substantia Nigra Structure
Structure of Median Forebrain Bundle
Antipsychotic Agents
Voltage-Clamp Techniques
Cell Density
Dopamine Measurement

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