Person:

Lukas, Scott

Although many studies have shown that cognitive effect expectancies are associated with drug use and drug treatment outcomes, few studies have compared effect expectancies with drug response following drug challenge. Healthy male and female volunteers (n = 19, ages 21-35) who reported using cocaine 1-4 times per month completed the Cocaine Effect Expectancy Questionnaire (CEEQ: [Schafer, J. and Brown, S.A. (199 1). Marijuana and cocaine effect expectancies and drug use patterns. Journal of Consulting and Clinical Psychology, 59, 558-565.]), were challenged with cocaine (0.9 mg/kg, i.n.), then completed a series of visual analog scales (VAS) and the Addiction Research Center Inventory (ARCI) at 15 min intervals for 3 h following cocaine administration. Significant positive correlations were found between global negative expectancies and peak responses on the VAS measures "Good," "Happy," "High," "Stimulated," and "Desire to Use Cocaine," and on the LSD subscale of the ARCI post-cocaine administration, and between global positive expectancies and the MBG subscale of the ARCI, and on VAS items "Anxious" and "Good" post-cocaine administration. Global positive expectancies also were positively correlated with peak systolic blood pressure, and global negative expectancies with peak heart rate after cocaine administration. These results suggest that negative and positive effect expectancies both play a complex role in the subjective experience of cocaine effects, and thus likely in the progression of non-use to recreational use, in the transition to abuse, and in individualized treatment strategies.

In rodents, corticosterone (cortisol in humans) facilitates cocaine self-administration purportedly via enhancement of dopaminergic activity in the brain. This study sought to assess central dopaminergic effects of cortisol in humans and to compare them to those of cocaine. Twelve cocaine-dependent individuals received an intravenous bolus of cortisol (0.5 and 0.2 mg/kg; n=6 for each dose) and cocaine (0.2 mg/kg) in a double-blind randomized placebo-controlled and counterbalanced fashion. Their plasma was assayed over the next 120 min for prolactin and growth hormone (GH), which are two neuroendocrine indices of dopaminergic function. Cortisol injections produced significant increases in GH, while cocaine resulted in significant decreases in prolactin. Placebo administration was associated with gradual declines in prolactin, but the levels at the 90- and 120-min time points were significantly lower after cocaine than after placebo infusion. These different neuroendocrine response profiles point to important differences between dopaminergic effects of cortisol and cocaine.

Numerous reports have documented a high occurrence of sleep difficulties in drug-dependent populations, prompting researchers to characterize sleep profiles and physiology in drug abusing populations. This mini-review examines studies indicating that drug-dependent populations exhibit alterations in sleep homeostatic and restoration processes in response to sleep deprivation. Sleep deprivation is a principal sleep research tool that results in marked physiological challenge, which provides a means to examine sleep homeostatic processes in response to extended wakefulness. A report from our laboratory demonstrated that following recovery sleep from sleep deprivation, brain high-energy phosphates particularly beta–nucleoside triphosphate (beta-NTP) are markedly increased as measured with phosphorus magnetic resonance spectroscopy (MRS). A more recent study examined the effects of sleep deprivation in opiate-dependent methadone-maintained (MM) subjects. The study demonstrated increases in brain beta-NTP following recovery sleep. Interestingly, these increases were of a markedly greater magnitude in MM subjects compared to control subjects. A similar study examined sleep deprivation in cocaine-dependent subjects demonstrating that cocaine-dependent subjects exhibit greater increases in brain beta-NTP following recovery sleep when compared to control subjects. The studies suggest that sleep deprivation in both MM subjects and cocaine-dependent subjects is characterized by greater changes in brain ATP levels than control subjects. Greater enhancements in brain ATP following recovery sleep may reflect a greater disruption to or impact of sleep deprivation in drug dependent subjects, whereby sleep restoration processes may be unable to properly regulate brain ATP and maintain brain high-energy equilibrium. These studies support the notion of a greater susceptibility to sleep loss in drug dependent populations. Additional sleep studies in drug abusing populations are needed, particularly those that examine potential differential effects of sleep deprivation.