The anticipation of a cocaine fix and the actual craving to abuse the drug are two closely related phenomena, according to new evidence published today in the online open access journal Substance Abuse Treatment, Prevention, and Policy.
The study, by Rinah Yamamoto and colleagues at McLean Hospital in Belmont, Massachusetts assessed the suspected link by contrasting reactions to varying perceived availability of the drug. The researchers suggest that more appropriate care could be given if the degree of dependency and abuse were assessed in a natural environment with a potential access to the drug, rather than in a clinical setting.
Yamamoto explains that craving, is an intense and often irrepressible urge to seek and consume the drug, which can result in relapses even after extended periods of abstinence. In searching for effective therapies, understanding how craving, cognition and motivation are entwined is essential.
The researchers administered intravenous cocaine (0.2 mg/kg) to individuals with cocaine dependence who were not seeking treatment. "Unblinded" participants knew for certain they would receive cocaine, while the "blinded" group knew there was a 33 percent chance of getting the drug. The researchers obtained subjective ratings of craving, high, rush and low from the volunteers along with their heart rate and blood pressure measurements. Measurements were collected prior to cocaine administration and every minute for 20 minutes thereafter.
The results showed that several hours prior to the infusion all volunteers had similar craving scores. However, those volunteers who knew they were to receive a cocaine infusion said they felt a greater craving immediately prior to the receipt of cocaine than the "blinded" volunteers who did not know whether the infusion was placebo or the genuine drug. The team also found that the unblinded subjects experienced a more rapid onset of high and rush cocaine responses along with significantly higher cocaine-induced heart rate elevations.
The findings suggest that the cocaine expectancy state modulates the user's subjective and objective responses to the drug. These data are consistent with the previous studies demonstrating that drug-induced elevated dopamine concentrations in the brain may prime drug users to associate the cues around the source of dopamine boost (e.g., cocaine) with the pleasure experienced once the drug is taken.
Effects of perceived cocaine availability on subjective and objective responses to the drug
Rinah T Yamamoto, Katherine H Karlsgodt, David Rott, Scott E Lukas and Igor Elman
Substance Abuse Treatment, Prevention, and Policy (in press)
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Laura Neves (Press Office, McLean Hospital)
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