Effects of acute oral Delta9-tetrahydrocannabinol and standardized cannabis extract on the auditory P300 event-related potential in healthy volunteers

Reduced amplitudes of auditory evoked P300 are a robust finding in schizophrenic patients, indicating deficient attentional resource allocation and active working memory. Delta9-Tetrahydrocannabinol (Delta9-THC), the main active constituent of Cannabis sativa, has been known to acutely impair cognitive abilities in several domains, particularly in memory and attention. Given the psychotic-like effects of Delta9-THC, a cannabinoid hypothesis of schizophrenia has been proposed. This prospective, double-blind, placebo-controlled cross-over study investigated the acute effects of cannabinoids on P300 amplitude in 20 healthy volunteers (age 28.2+/-3.1 years, 10 male) by comparing Delta9-THC and standardized cannabis extract containing Delta9-THC and cannabidiol (CBD). P300 waves were recorded during a choice reaction task. As expected, Delta9-THC revealed a significant reduction of P300 amplitude at midline frontal, central, and parietal electrodes. CBD has been known to abolish many of the psychotropic effects of Delta9-THC, but, unexpectedly, failed to demonstrate a reversal of Delta9-THC-induced P300 reduction. Moreover, there were no correlations between cannabinoid plasma concentrations and P300 parameters. These data suggest that Delta(9)-THC may lead to acute impairment of attentional functioning and working memory. It can be speculated whether the lack of effect of CBD may be due to an insufficient dose used or to an involvement of neurotransmitter systems in P300 generation which are not influenced by CBD.

Acute effects of Delta9-tetrahydrocannabinol and standardized cannabis extract on the auditory evoked mismatch negativity

Reduced amplitudes of auditory evoked mismatch negativity (MMN) have often been found in schizophrenic patients, indicating deficient auditory information processing and working memory. Cannabis-induced psychotic states may resemble schizophrenia. Currently, there are discussions focusing on the close relationship between cannabis, the endocannabinoid and dopaminergic system, and the onset of schizophrenic psychosis. This study investigated the effects of cannabis on MMN amplitude in 22 healthy volunteers (age 28+/-6 years, 11 male) by comparing Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and standardized cannabis extract containing Delta(9)-THC and cannabidiol (CBD) in a prospective, double-blind, placebo-controlled cross-over design. The MMNs resulting from 1000 auditory stimuli were recorded by 32 channel EEG. The standard stimuli were 1000 Hz, 80 dB SPL, and 100 ms duration. The deviant stimuli differed in frequency (1500 Hz). Significantly greater MMN amplitude values at central electrodes were found under cannabis extract, but not under Delta(9)-THC. There were no significant differences between MMN amplitudes at frontal electrodes. MMN amplitudes at central electrodes were significantly correlated with 11-OH-THC concentration, the most important psychoactive metabolite of Delta(9)-THC. Since the main difference between Delta(9)-THC and standardized cannabis extract is CBD, which seems to have neuroprotective and anti-psychotic properties, it can be speculated whether the greater MMN amplitude that may imply higher cortical activation and cognitive performance is related to the positive effects of CBD. This effect may be relevant for auditory cortex activity in particular because only MMN amplitudes at the central, but not at the frontal electrodes were enhanced under cannabis.

Simultaneous and sensitive analysis of THC, 11-OH-THC, THC-COOH, CBD, and CBN by GC-MS in plasma after oral application of small doses of THC and cannabis extract

Besides the psychoactive Delta(9)-tetrahydrocannabinol (THC), hashish and marijuana as well as cannabis-based medicine extracts contain varying amounts of cannabidiol (CBD) and of the degradation product cannabinol (CBN). The additional determination of these compounds is interesting from forensic and medical points of view because it can be used for further proof of cannabis exposure and because CBD is known to modify the effects of THC. Therefore, a method for the simultaneous quantitative determination of THC, its metabolites 11-hydroxy-Delta(9)-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol (THC-COOH), CBD and CBN from plasma was developed. The method was based on automatic solid-phase extraction with C(18) ec columns, derivatization with N,O-bistrimethylsilyltrifluoroacetamide (BSTFA), and gas chromatography-electron impact ionization-mass spectrometry (GC-EI-MS) with deuterated standards. The limits of detection were between 0.15 and 0.29 ng/mL for THC, 11-OH-THC, THC-COOH, and CBD and 1.1 ng/mL for CBN. The method was applied in a prospective pharmacokinetic study after single oral administration of 10 mg THC alone or together with 5.4 mg CBD in cannabis extract. The maximum plasma concentrations after cannabis extract administration ranged between 1.2 and 10.3 ng/mL (mean 4.05 ng/mL) for THC, 1.8 and 12.3 ng/mL (mean 4.9 ng/mL) for 11-OH-THC, 19 and 71 ng/mL (mean 35 ng/mL) for THC-COOH, and 0.2 and 2.6 ng/mL (mean 0.95 ng/mg) for CBD. The peak concentrations (mean values) of THC, 11-OH-THC, THC-COOH, and CBD were observed at 56, 82, 115, and 60 min, respectively, after intake. CBN was not detected. Caused by the strong first-pass metabolism, the concentrations of the metabolites were increased during the first hours after drug administration when compared to literature data for smoking. Therefore, the concentration ratio 11-OH-THC/THC was discussed as a criterion for distinguishing oral from inhalative cannabis consumption.

Oculomotor effects of delta-9-tetrahydrocannabinol in humans: implications for the functional neuroanatomy of the brain cannabinoid system

The significance of cannabinoid signaling for human cognition and motor control is still poorly understood. Here, we have investigated acute behavioral effects of oral delta-9-tetrahydrocannabinol (THC) with oculomotor paradigms in 12 healthy human subjects. Compared to baseline testing: (i) THC increased latencies of reflexive visually guided saccades, while their accuracy was not affected; (ii) latencies of memory-guided saccades were unaffected, but THC modulated accuracy of these eye movements by increasing average gain and gain variability; (iii) frequency of anticipated memory-guided saccades and antisaccade errors was increased; (iv) the saccade amplitude/peak velocity relationships were not affected. These results show that THC acts on selected aspects of saccade control, namely spatial attention shifts, fine tuning of volitional saccades, spatial working memory and inhibition of inappropriate saccades. The pattern of effects suggests modulation of neuronal activity in substantia nigra pars reticulata and/or dorsolateral prefrontal cortex and sparing of the eye fields and the final motor pathway for saccades. Behaviorally, our findings reflect the distribution of CB-1 cannabinoid receptors in the human neocortex, basal ganglia and brainstem and provide evidence for participation of the cannabinoidergic system in high level control of saccades and associated cognitive functions. Saccadic eye movements may provide an objective measure of motor and cognitive effects of cannabinoids.

Decreased plasma levels of amitriptyline and its metabolites on comedication with an extract from St. John's wort ( Hypericum perforatum )

Extracts of St. John's wort ( Hypericum perforatum ) became increasingly popular as easily available remedies for mild to moderate depression. Comedication with hypericum extract was recently shown to drastically reduce plasma concentration of ciclosporin, digoxin, and indinavir. We investigated the possible interaction of hypericum extract LI160 with amitriptyline. Both antidepressants have a high probability of concomitant use. Twelve patients requiring amitriptyline treatment received a single dose of hypericum extract (900 mg) at day 1, continued by a 12-to 14-day treatment with retarded amitriptyline (75 mg twice daily). Then hypericum (900 mg/day) was added for another 14 to 16 days. Steady-state pharmacokinetics of amitriptyline were compared before and after multiple-dose treatment with hypericum extract. Furthermore, comparisons were made for single-dose kinetics of hypericum-extract ingredients hypericin, pseudohypericin, and hyperforin between the first day of concomitant treatment and LI160 alone. Multiple-dose comedication with LI160 led to a statistically significant decrease in the area under the plasma concentration-time curve within one dosing interval of amitriptyline by 22% ( p = 0.03) and nortriptyline by 41% ( p = 0.002), as well as of all hydroxylated metabolites, except for 10-E-hydroxynortriptyline. Plasma levels of amitriptyline and hydroxylated metabolites gradually decreased, whereas nortriptyline concentrations were already markedly decreased after 3 days of cotreatment with hypericum. Cumulative urinary amounts of amitriptyline and metabolites decreased to the same extent as plasma concentrations upon hypericum comedication. Induction of cytochrome P-450 enzymes or drug transporters (P-glycoprotein) by St. John's wort extract may explain this pharmacokinetic interaction. Physicians should be aware of this interaction when treating patients with amitriptyline.

Nitric oxide synthase is increased following small intestinal transplantation in the rat

Transplantation of the small intestine is a neural model that could include extrinsic denervation, loss of intrinsic enteric neurons, or loss of intrinsic neural pathways. Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity was measured in normal rat ileum, ileum 3 months after resection of the jejunum, and ileum 3 months after isotransplantation of the ileum. The distribution of NADPH diaphorase activity and immunoreactive neuronal nitric oxide synthase were examined. Nicotinamide adenine dinucleotide phosphate diaphorase activity was increased in transplanted ileum (16.5+/-3.5 mU/mg protein) compared to normal controls (6.6+/-0.7) and resection controls (6.8+/-0.6) (P < 0.05, ANOVA). Histologically, NADPH diaphorase activity and immunoreactive nitric oxide synthase appeared increased within nerve cell bodies following transplantation. These findings may represent an adaptive response of the enteric nervous system to extrinsic denervation. Loss of intrinsic neural pathways was not supported as a mechanism.

Distribution of muscarinic receptor subtypes in rat small intestine

Despite its great promise, small intestinal transplantation in some patients is complicated by difficult postoperative management. The reasons for this are complex. In a rat model of small intestinal transplantation, frequencies of migrating myoelectric complexes during fasting are reduced in ileal isografts and muscarinic receptor density is decreased. We hypothesized that the distribution of muscarinic 1 receptors localized to enteric neurons is altered after small intestinal transplantation. Distal small intestine was orthotopically transplanted in Lewis-to-Lewis donor-recipient combinations. At 3 months, transplanted and normal ileum was obtained to prepare membrane fractions. [N-methyl-3H]Scopolamine served as ligand, while scopolamine methylbromide, pirenzepine, and methoctramine were used in competitive homologous and heterologous displacement experiments. Receptor subtype models were examined by nonlinear regression analysis. In normal and transplanted ileum, heterologous displacement was consistent with three site models (P < 0.05). In normals, the muscarinic 1 receptor subtype was most abundant, with a relative distribution of 69 to 78%. There was a relative distribution of 13 to 16% for muscarinic 3 receptor subtype. After transplantation, the muscarinic 1 subtype decreased to a mean of 45% but the muscarinic 3 subtype increased to a mean of 42%. Using pirenzepine, mean pKD values were not different between the two groups. It is concluded that the decrease in muscarinic 1 receptor subtype after transplantation could be related to neuronal cell loss or to downregulation of the expression of muscarinic 1 receptors. The results did not support defective posttranslational processing of receptor proteins.

Expression of mRNA for vasoactive intestinal peptide in rat small intestine

Transplantation of small intestine is a neural model that permits studies of expression of the neuropeptide, vasoactive intestinal peptide, following extrinsic denervation, transection of intrinsic neural pathways, and an ischemic interval. Tissue levels of vasoactive intestinal peptide were examined at 3 months in ileum from a sham operation, in ileum after resection of proximal small intestine, in ileum after resection of proximal small intestine and extrinsic denervation, in ileum after resection of proximal small intestine and 30 min of ischemia, and in ileum obtained 3 months after ileal isografting in Lewis-to-Lewis combinations. Vasoactive intestinal peptide levels were increased in transplanted rat ileum, resection controls, denervation controls, and ischemic controls compared to sham-operated ileum (pANOVA < 0.01). The increased levels of this peptide were highest in denervation controls and lowest in ischemic controls. Northern blot analysis using rat vasoactive intestinal peptide cDNA identified a single 1.7-kb transcript in normal and transplanted rat ileum. The density of vasoactive intestinal peptide transcripts was increased in transplanted ileum (8450 +/- 540) compared to normal ileum (5790 +/- 620) (P < 0.01), and the ratio of this transcript to glyceraldehyde-3-phosphate dehydrogenase density units was also increased in transplanted ileum (0.81 +/- 0.08) compared to normal ileum (0.40 +/- 0.07; P < 0.01). Enhanced transcriptional regulation was the likely mechanism for increased tissue vasoactive intestinal peptide. The increased tissue levels appeared to be a response to extrinsic denervation and transection of intrinsic neural pathways, while an ischemic interval appeared to decrease tissue levels of the peptide.