Psychopharmacology

, Volume 191, Issue 3, pp 653–667

Differential neurochemical and behavioral adaptation to cocaine after response contingent and noncontingent exposure in the rat

  • Daniele Lecca
  • Fabio Cacciapaglia
  • Valentina Valentini
  • Elio Acquas
  • Gaetano Di Chiara
Original Investigation

DOI: 10.1007/s00213-006-0496-y

Cite this article as:
Lecca, D., Cacciapaglia, F., Valentini, V. et al. Psychopharmacology (2007) 191: 653. doi:10.1007/s00213-006-0496-y
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Abstract

Rationale

In naive rats, passive administration of drugs of abuse preferentially increases extracellular dopamine (DA) in the nucleus accumbens (NAc) shell as compared to the core. Repeated exposure to the same drugs results in behavioral and biochemical sensitization characterized by stereotyped activity and reduction of the shell/core DA response ratio.

Objectives

The aim of this work is to study the neurochemical and behavioral effects of response-contingent vs response-noncontingent drug administration in rats, who were bilaterally implanted with chronic intracerebral guide cannulae and trained to self-administer cocaine by nose poking in daily 1-h sessions for 3 weeks (5 days/week). Nose poking in the active hole by master rats resulted in intravenous injection of cocaine (0.25 mg/kg) in master rats and in rats yoked to them. Dialysate DA was monitored before, during, and for 30 min after cocaine availability on alternate days by inserting the probe into the NAc shell and core. Stereotyped and non-stereotyped behavior was recorded during the sessions.

Results

In master rats, dialysate DA increased preferentially in the NAc shell during cocaine self-administration throughout the 3 weeks of cocaine exposure. In yoked rats, DA increased preferentially in the shell but to a lesser extent than in master rats. With continued exposure to cocaine, the shell/core ratio of DA changes decreased progressively and, on the third week, was reversed so that DA increased more in the core than in the shell. Yoked rats showed a progressive and faster increase in stereotyped behaviors than master rats.

Conclusions

Response-noncontingent cocaine administration is particularly prone, compared to response-contingent administration, to induce behavioral and biochemical sensitization.

Keywords

Self-administrationMaster ratsYoked ratsMicrodialysisCocaineDopamineNucleus accumbens shellNucleus accumbens coreNon-stereotyped behaviorStereotyped behavior

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Daniele Lecca
    • 1
    • 2
  • Fabio Cacciapaglia
    • 1
  • Valentina Valentini
    • 1
    • 2
  • Elio Acquas
    • 1
    • 2
  • Gaetano Di Chiara
    • 1
    • 2
    • 3
  1. 1.Department of ToxicologyUniversity of CagliariCagliariItaly
  2. 2.Centre of Excellence for Studies on the Neurobiology of AddictionUniversity of CagliariCagliariItaly
  3. 3.Institute of NeuroscienceConsiglio Nazionale delle Ricerche (CNR), Section of CagliariCagliariItaly