Primarily, rats have served as subjects in Delta(9)-tetrahydrocannabinol's (THC) discrimination studies although other species such as monkeys and pigeons have been used. While the introduction of the knockout and transgenic mice has vastly stimulated the study of the discriminative stimulus effects of drugs there is only a single published report of mice trained to discriminate THC. Thus, this...
Central cannabinoid receptors are thought to mediate neural oscillations and are localized to brain regions implicated in auditory P50 sensory gating, including the hippocampus and neocortex. The current study therefore examined if neural oscillations evoked by the paired clicks (S1, S2) are associated with impaired P50 gating reported in cannabis users. Seventeen heavy cannabis users and 16...
Marijuana and hashish are the illicit drugs most frequently used by human adolescents. Given the continued neurodevelopment throughout adolescence, adolescents may be more vulnerable than adults to certain neural consequences of heavy marijuana use. This study aimed to assess whether an experimental model of adolescent chronic exposure to Delta9-tetrahydrocannabinol (THC), may induce lasting...
Cannabis has been reported as a likely risk factor for the development of psychosis, and a gene × environment interaction with the catechol-O-methyltransferase (COMT) gene has been proposed. Moreover, COMT has been separately linked to affective symptoms in psychosis. Despite a high rate of cannabis abuse and affective symptoms in African Americans, no studies exploring a relationship between...
BACKGROUND: We conducted a systematic review to assess the evidence for specific effects of cannabis on brain structure and function. The review focuses on the cognitive changes associated with acute and chronic use of the drug. METHOD: We reviewed literature reporting neuroimaging studies of chronic or acute cannabis use published up until January 2009. The search was conducted using Medline,...
The association between cannabis use and psychosis has long been recognized. Recent advances in knowledge about cannabinoid receptor function have renewed interest in this association. Converging lines of evidence suggest that cannabinoids can produce a full range of transient schizophrenia-like positive, negative, and cognitive symptoms in some healthy individuals. Also clear is that in...
Regular use of illegal drugs is suspected to cause cognitive impairments. Two substances have received heightened attention: 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') and delta-9-tetrahydrocannabinol (THC or 'cannabis'). Preclinical evidence, as well as human studies examining regular ecstasy consumers, indicated that ecstasy use may have negative effects on learning, verbal memory...
Cannabis is the most widely used illegitimate substance in the world, and the number of users has increased by 10% over the last decade worldwide. Therefore, it is important to review the evidence on psychoactive properties of cannabis and its possible association with schizophrenia spectrum disorders (SSD). We searched MEDLINE with the key words cannabis and schizophrenia. The search was...
We are reporting improvement of symptoms of schizophrenia in a small group of patients who received the cannabinoid agonist dronabinol (synthetic Delta-9-tetrahydrocannabinol). Before this report, cannabinoids had usually been associated with worsening of psychotic symptoms. In a heuristic, compassionate use study, we found that 4 of 6 treatment-refractory patients with severe chronic...
BackgroundEpidemiological evidence suggests a link between cannabis use and psychosis. A variety of factors have been proposed to mediate an individual's vulnerability to the harmful effects of the drug, one of which is their psychosis proneness. We hypothesized that highly psychosis-prone individuals would report more marked psychotic experiences under the acute influence of cannabis.MethodA...
We recently demonstrated that Delta(9)-tetrahydrocannabinol (THC) chronic administration in female adolescent rats induces alterations in the emotional circuit ending in depressive-like behavior in adulthood. Since cognitive dysfunction is a major component of depression, we assessed in these animals at adulthood different forms of memory. Adolescent female rats were treated with THC or its...
Abstract: Introduction and Aims. Little is known about motives or expectancies for cannabis use in psychotic populations, despite these cognitive factors being a central focus of the treatment for substance misuse in psychosis. This study examined the relationship between cannabis use expectancies, cannabis use and psychotic symptoms among cannabis using psychotic inpatients. A secondary aim...
Performance impairment during Delta(9)-tetrahydrocannabinol (THC) intoxication has been well described in occasional cannabis users. It is less clear whether tolerance develops to the impairing effects of THC in heavy users of cannabis. The aim of the present study was to assess neurocognitive performance during acute THC intoxication in occasional and heavy users. Twenty-four subjects (12...
Anandamide and Delta(9)-tetrahydrocannabinol (Delta(9)-THC) sometimes produce different discriminative stimulus effects and, therefore, appear to differ in their mechanism of action. In order to understand the widespread use of cannabis and the therapeutic potential of cannabinoids, mechanisms responsible for behavioral effects need to be identified. Drug discrimination was used to compare the...
Delta(9)-tetrahydrocannabinol (THC), the principal psychoactive ingredient in marijuana, acts as a partial agonist on presynaptic cannabinoid type 1 (CB1) receptors to inhibit neurotransmitter release. Here, we report that THC inhibits excitatory neurotransmission between cultured rat hippocampal neurons in a manner highly sensitive to stimulus rate. THC (1 microM) inhibited excitatory...
Preclinical evidence suggests that non-cannabinoid neurotransmitter systems are involved in the behavioral and physiological effects of cannabinoids, but relatively little research has been conducted in humans. The aims of this study were to assess whether oral Delta(9)-tetrahydrocannabinol (Delta(9)-THC) would function as a discriminative stimulus in humans and to examine the substitution...
CONTEXT: Cannabis sativa use can impair verbal learning, provoke acute psychosis, and increase the risk of schizophrenia. It is unclear where C. sativa acts in the human brain to modulate verbal learning and to induce psychotic symptoms. OBJECTIVES: To investigate the effects of 2 main psychoactive constituents of C. sativa, Delta9-tetrahydrocannabinol (Delta9-THC) and cannabidiol, on regional...
Impaired verbal memory is common in MDMA (Ecstasy) polydrug users. The contributions of Ecstasy or polydrug exposure to reduced verbal memory are unclear, as is the neural basis for this cognitive deficit. Ecstasy users have reduced gray matter in brain regions mediating verbal memory (BA 18, 21 and 45). N-acetylaspartate (NAA) as a neuronal marker and myoinositol (mI) as a glial marker are...
The influence of cannabis on mental health receives growing scientific and political attention. An increasing demand for treatment of cannabis dependence has refueled the discussion about the addictive potential of cannabis. A key feature of all addictive drugs is the ability to increase synaptic dopamine levels in the striatum, a mechanism involved in their rewarding and motivating effects....
It is unclear whether impairment in decision making, measured by the Iowa Gambling Task (IGT), in addiction is substance-induced or the consequence of personality structure. Analysis of the IGT, the Tridimensional Personality Questionnaire (TPQ) and cannabinoids in hair and urine were performed in 13 cannabis users and matched controls. Hair Delta(9)-tetrahydrocannabinol (THC) correlated...