Assessment of the neural substrate for intracranial self-stimulation by the postreinforcement pause technique.
The poststimulation excitability of neurons mediating intracranial self-stimulation (ICSS) was evaluated by the paired-pulse method. Stimulus effectiveness was assessed by the postreinforcement pause (PRP) and by frequency threshold (FT) determinations in 7 rats performing ICSS in the medial forebrain bundle (MFB) and in the ventral tegmental area (VTA). Stimulus effectiveness values were minimal at conditioning-test (C-T) pulse intervals of 0.6 and 0.8 ms for MFB and VTA animals, respectively, because of neuronal refractoriness. Local potential summation could account for the increase in effectiveness at very short C-T intervals, and an additional peak of enhanced effectiveness at a C-T interval of 2.0 ms, perhaps reflecting synaptic events, was observed only in VTA animals with the PRP method. Important advantages of the PRP method were that the C-T interval was the only stimulus parameter that was varied, and the behavioral output of the animal remained relatively constant.
West
C H
CH
Department of Psychiatry, Georgia Mental Health Institute, Emory University School of Medicine, Atlanta 30306.
Michael
R P
RP
D000818:Animals; D001143:Arousal / Q000502:physiology*; D001931:Brain Mapping; D008297:Male; D008474:Medial Forebrain Bundle / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology*; D012653:Self Stimulation / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology; D013681:Tegmentum Mesencephali / Q000502:physiology