Phasic firing time locked to cocaine self-infusion and locomotion: dissociable firing patterns of single nucleus accumbens neurons in the rat

  • Peoples L
  • Gee F
  • Bibi R
 et al. 
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Abstract

The activity of single nucleus accumbens (NAcc) neurons of rats was extracellularly recorded during intravenous cocaine self-administration sessions (0.7 mg/kg per infusion, fixed ratio 1). We reported previously that NAcc neurons showed a change, usually a decrease, in firing rate during the first 1 min after the cocaine-reinforced lever press. This postpress change was followed by a progressive reversal of that change, which began within the first 2 min after the press and was not complete until the last 1 min before the next lever press (termed the change + progressive reversal firing pattern). In the present study we documented a regular pattern of locomotion that occurred in parallel with the change + progressive reversal firing pattern. This observation suggested that discharges time locked to locomotion may determine the change + progressive reversal firing pattern. However, 55% of the neurons failed to show firing time locked to locomotion that could have contributed to the change + progressive reversal firing pattern. Moreover, for all neurons, the change + progressive reversal firing pattern was apparent even if the calculation of firing rate excluded all periods of locomotion. The present data showed that the change + progressive reversal firing pattern is not solely attributable to phasic changes in firing time locked to the execution of locomotion. The change + progressive reversal firing pattern closely mirrors changes in drug level and dopamine overflow observed by previous researchers and may thus be a component of the neurophysiological mechanism by which drug level regulates drug-taking behavior during an ongoing self-administration session.

Author-supplied keywords

  • Action Potentials/drug effects
  • Animals
  • Behavior, Animal/drug effects
  • Cocaine-Related Disorders/physiopathology
  • Cocaine/*pharmacology
  • Dopamine Uptake Inhibitors/*pharmacology
  • Electrophysiology
  • Locomotion/*drug effects
  • Motivation
  • Neurons/*drug effects/physiology
  • Nucleus Accumbens/*cytology/drug effects/physiolog
  • Rats
  • Rats, Inbred Strains
  • Reaction Time/drug effects
  • Reward
  • Self Administration
  • Stereotyped Behavior/drug effects

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Authors

  • L L Peoples

  • F Gee

  • R Bibi

  • M O West

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