In this study, 21 non-treatment-seeking cigarette smokers were recruited to investigate the effects of acute stress on brain function and nicotine seeking/self-administration behavior.
Non-treatment-seeking cigarette smoking individuals were recruited from the Detroit, MI area. Individuals were screened for cardiovascular, neurological, and psychiatric contraindications. 21 healthy smokers completed two oral pre-treatment experimental sessions (on separate non-consecutive days) in randomized order under double-blind conditions: placebo (lactose) and stress (54mg yohimbine and 10mg hydrocortisone). Yohimbine + hydrocortisone elicit a neurochemical and physiological response that mimics a 'natural' stressor. Placebo and stress sessions were identical and started at 11am. Upon arrival, subject sobriety was confirmed with expired breath alcohol measurement (\<.02%). At 11:30am, each subject smoked 6 cigarette puffs (preferred brand; provided by study) over 5 minutes to control for recent nicotine exposure. Throughout each experimental session, subjects periodically completed self-reported measures of cigarette craving, nicotine withdrawal symptoms, affect, and anxiety, and vital signs were measured. Subjects self-administered (swallowed) oral doses of yohimbine (or placebo) at 11:45am and hydrocortisone (or placebo) at 12:15pm. At 1pm, subjects completed a 60-min neuroimaging scan which included: 1) T1-weighted structural scan, 2) proton functional magnetic resonance spectroscopy (fMRS) acquisition from the left prefrontal cortex during a letter 2-back working memory paradigm, and 3) functional magnetic resonance imaging (fMRI) acquisition during an N-back paradigm yoked with cigarette cues. At 2:30pm, subjects completed an 11-trial choice progressive ratio task in which they could earn cigarette puffs (preferred brand; provided by study) or money. At 3pm, subjects self-administered earned cigarette puffs (video monitored). Subjects remained on site until 4pm discharge.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Enrollment
21
54mg of yohimbine powder was encapsulated in a generic opaque capsule and swallowed with water.
10mg hydrocortisone was encapsulated in a generic opaque capsule and swallowed with water.
Lactose powder was encapsulated in generic opaque capsules identical to those used during the acute stress session. Lactose doses weighed the same as the acute stress session doses (54mg and 10mg, respectively).
Wayne State University
Detroit, Michigan, United States
Cigarette puff vs. money choice task
Participants could earn (via computer mouse 'clicks') money or cigarette puffs (preferred brand; provided by the study) across 11 independent choice trials. At the start of each trial, subjects selected either money or cigarette puffs on a computer screen. After each selection, subjects could earn one unit of that selection by satisfying the computer 'mouse' click requirement. The click requirement increased with each successive unit earned separately for cigarette puffs and money following a progressive ratio schedule (5, 12, 33, 100, 180, 340, 540, 835, 1220, 1660, and 2275 'mouse' clicks; identical schedule for both options and experimental sessions). Units were $0.25 money and 1 cigarette puff. Earned cigarette puffs were smoked at the end of the task and earned money was applied to the subject's study payment. The task was completed between 2:30pm and 3pm for each session.
Time frame: 30 minutes
Letter 2-back task
Participants completed 5 blocks of a letter 2-back working memory task during proton functional magnetic resonance spectroscopy data acquisition from the left dorsolateral prefrontal cortex. The 2-back task consisted of a neurochemistry normalization period (passive viewing of a 3Hz flashing checkerboard; 208s) and alternating periods of passive visual fixation (centered fixation cross; 32s) and letter 2-back (64s; 4s instructions \['2-back'\], 20 letters \[3s/letter; 500ms on screen; 2500ms blank screen\], 6 target letters). Changes in neurochemistry as quantified using LCModel were the primary outcome variable. 2-back response accuracy (% correct) and response latency (ms) were secondary outcomes.
Time frame: 12 minutes
Cigarette-cued letter N-back task
Participants completed a neutral image vs. cigarette smoking-related image cued letter N-back task during functional magnetic resonance imaging acquisition. The task consisted of pseudo-randomly ordered blocks of 0-, 1-, and 2-back with either cigarette cues or matched neutral images behind each letter. Two 32s blocks of each task permutation were collected separated by 16s of blank screen (to minimize carry-over effects). Patterns of brain activation throughout the task was the primary outcome measure while N-back response accuracy (% correct) and response latency (ms) were secondary outcomes.
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Time frame: 15 minutes