[Abstract Title]. - Society for Neuroscience

Authors: *P. SCHWEINHARDT 1 , M. CEKO 1 , M. LEYTON 2 , M. BUSHNELL 1 ;
1 Ctr. for Res. on Pain, 2 Psychiatry, McGill Univ., Montreal, QC, Canada
Abstract: Increased striatal dopamine (DA) transmission in animals decreases pain behaviors. In
comparison, the functional significance of DA for pain perception in humans remains unknown.
To investigate the association in humans, we hypothesized that depleting brain DA would
increase pain sensitivity, and that individual differences in this response would be related to
putative monoamine-associated personality traits.
16 healthy young males took part in a double-blind crossover study. Acute DA depletion was
achieved by administering an amino acid mixture deficient in the DA precursors, phenylalanine
and tyrosine. In the control condition, subjects ingested a nutritionally balanced mixture. Pain
testing (short heat stimuli) was performed both before (Pre) and 5 hrs after ingestion of each
mixture (Post). Pain intensity was rated from 0 to 200 (0 - no sensation, 100 - pain threshold, 200
- worst pain tolerable). Personality traits were assessed with the Temperament and Character
Inventory (TCI), the BIS/BAS scale, and the Temporal Experience of Pleasure Scale (TEPS). To
test for an effect of DA depletion on pain perception, we compared difference scores (Post-Pre)
between the two conditions (Post-Pre) depleted vs. (Post-Pre) control. The changes in pain
intensity in the depleted condition relative to the control condition were then correlated with the
personality trait scores.
The mean (SD) pain intensity ratings were: control condition Pre: 148 (17.2), Post: 142(32.5);
depleted condition Pre: 150 (12.5), Post: 153 (24.4). The change in pain sensitivity did not differ
significantly between the two conditions (p=0.29). However, individual differences in the effect
of DA depletion correlated negatively with Anticipatory Pleasure scores (AP, TEPS) (r=-0.67,
p=0.009) and positively with Harm Avoidance scores (HA, TCI) (r=0.54, p=0.044). A median
split indicated that DA depletion significantly increased pain sensitivity in subjects with high
(p=0.043) but not low HA scores (p=0.45), and at the trend level in subjects with low (p=0.069)
but not high AP scores (p=0.46).
In conclusion, DA depletion had no significant effect on pain perception on a group level.
However, personality traits thought to be related to endogenous DA function influenced
significantly changes in pain sensitivity following DA depletion. The observation that low AP
subjects are more vulnerable to the pain enhancing effects of DA depletion supports the
proposition that DA has analgesic properties in humans and that these susceptible subjects may
have a low DA trait.
Disclosures: P. Schweinhardt, None; M. Ceko, None; M. Leyton, None; M. Bushnell, None.
Poster
266. Pain: Psychophysics and Behavior
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 266.12/FF6