The reinforcing and subjective effects of morphine were determined in five human volunteers with histories of i.v. heroin abuse. Subjects responded under a second-order schedule of i.m. injection. Under this schedule, every 100 lever presses produced a brief stimulus light [fixed ratio (FR) 100:s]; the 30th completion of the FR 100 requirement turned on the light for 15 min and the subject rece...

Orexin plays a crucial role in drug-seeking behavior. The lateral hypothalamus (LH) is a central region that produces orexin, and its projections to the ventral tegmental area (VTA) play an important role in reward and addiction-related behaviors. In this study, we investigated the role of LH stimulation and the involvement of the orexin-1 receptor (Ox1r) in the VTA in relation to morphine sens...

Morphine administration causes long-lasting neural changes in the brain that underpin the behavioral abnormalities, and the relationship between structural changes and behavioral symptoms is obscure. In present study, the elevated plus-maze and transmission electron microscope were applied to validate the anxiety-like behaviors and synaptic ultrastructural changes in the hippocampi of rats amon...

BACKGROUND This study was undertaken to identify predictors of the prescription of strong opioids, which are important for the management of severe cancer pain, by Korean physicians. METHODS A questionnaire based on a hypothetical case designed to assess the prescription of morphine by physicians was administered to 800 specialists in the Korea Cancer Association, of whom 147 (18.4%) responde...

Dopamine neurons in the ventral tegmental area (VTA) are a key target of addictive drugs, and neuroplasticity in this region may underlie some of the core features of addiction. From the very first exposure, all drugs of abuse induce synaptic plasticity in the VTA. However, it is not well understood how this diverse group of drugs brings about common synaptic change. Orexin (also known as hypoc...

BACKGROUND Previous clinical studies have not examined the relationship between nicotine abstinence and opioid use for postoperative analgesia. This may be important because tobacco smokers are routinely required to abstain from smoking just before and during acute post-surgical recovery. This study investigated IV morphine self-administration [patient controlled analgesia (PCA)], subjective pa...

Increasing evidence suggests that in addition to the mesoaccumbens dopamine (DA) system other neurotransmitter and brain systems are also involved in opiate addiction. Recent evidence points to a major involvement of brain norepinephrine (NE) in the behavioral and central effects of opiates and, more specifically, indicates that NE in the prefrontal cortex may have a critical role in rewarding ...

In this pilot study, we used functional magnetic resonance imaging (fMRI) to study the effects of morphine in 8 healthy, opioid-naïve volunteers. Intravenous small-dose morphine (4 mg/70 kg) or saline was administered to volunteers undergoing a fMRI scan. Infusion of morphine, but not saline, elicited mild euphoria without aversive symptoms and resulted in positive signal changes in reward stru...

Self-administration of addictive drugs is a widely used tool for studying behavioral, neurobiological, and genetic factors in addiction. However, how locomotor activity is affected during self-administration of addictive drugs has not been extensively studied. In our present study, we tested the locomotor activity levels during acquisition, extinction and reinstatement of morphine self-administ...