Progressive behavioral response to repeated d-amphetamine challenge: further evidence for sensitization in humans.
BACKGROUND
Behavioral sensitization is the process whereby intermittent stimulant exposure produces a time-dependent, enduring, and progressive behavioral response. Although animal models of sensitization are well established, the phenomenon has been relatively little studied in humans. In a previous study, we reported enhanced responses following a second as compared to a first amphetamine dose in eye-blink rate and ratings of increased motor activity/energy, increased speech, and elevated mood in normal human volunteers. This current study extends those findings in a new sample of normal volunteers.


METHODS
Eleven normal human volunteers were administered three single oral doses of d-amphetamine (0.25 mg/kg) at 48-hour intervals, alternating with matched placebo in a randomized, double-blind trial. Hourly behavioral ratings included eye-blink rate, symptoms (elevated mood, increased speech, increased motor activity/energy), and subjective drug effects.


RESULTS
Eye-blink rate and increased motor activity/energy ratings progressively increased following each challenge with the third amphetamine dose response significantly greater than all other conditions 4 hours postadministration. Similar, although less pronounced, responses were observed for elevated mood and subjective drug effect.


CONCLUSIONS
These results provide further evidence for sensitization of some amphetamine-induced behaviors in human subjects.
Strakowski
S M
SM
Department of Psychiatry, University of Cincinnati College of Medicine, OH 45267-0559, USA.
Sax
K W
KW
D000293:Adolescent; D000328:Adult; D000339:Affect / Q000187:drug effects*; D001767:Blinking / Q000187:drug effects*; D003913:Dextroamphetamine / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011597:Psychomotor Performance / Q000187:drug effects*; D013060:Speech / Q000187:drug effects*
D003913:Dextroamphetamine