Ventral tegmental analgesia in two strains of rats: effects of amphetamine, naloxone and parachlorophenylalanine

Brain Res. 1984 May 21;300(1):1-8. doi: 10.1016/0006-8993(84)91334-9.


Pain sensitivity and analgesia induced by the stimulation of the ventral tegmentum (VT) were studied in 72 male rats of two lines, LC2-Hi and LC2-Lo, genetically selected for high and low rates of lateral hypothalamic self-stimulation, respectively. LC2-Lo rats were more sensitive to acute peripheral pain and developed a stronger analgesia than their LC2-Hi counterparts. In order to assess the pharmacological substrate of ventral tegmental stimulation-induced analgesia (VT-SIA), the effects of amphetamine (AMP, 21 animals), naloxone (NX, 24 animals) and parachlorophenylalanine (PCPA, 27 animals) injections were studied. VT-SIA was found to be clearly decreased by PCPA, slightly decreased by AMP and not significantly affected by NX. Ventral tegmental self-stimulation ( VTSS ) was increased by PCPA treatment. The comparison of VTSS and VT-SIA did not reveal any correlation between both phenomena. These data suggest that VT-SIA may be mediated by serotonin while catecholamines may have a modulatory role in this analgesia and that VTSS and VT-SIA seem to be governed by different neuronal systems.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amphetamine / pharmacology
  • Animals
  • Dopamine / physiology*
  • Endorphins / physiology*
  • Fenclonine / pharmacology
  • Male
  • Naloxone / pharmacology
  • Pain / physiopathology*
  • Rats
  • Rats, Inbred Strains
  • Serotonin / physiology*
  • Species Specificity
  • Synaptic Transmission
  • Tegmentum Mesencephali / physiopathology*


  • Endorphins
  • Serotonin
  • Naloxone
  • Amphetamine
  • Fenclonine
  • Dopamine