The gamma-aminobutyric acid system in rat cerebellum during cannabinoid-induced cataleptoid state

Effect of cannabis on glutamate signalling in the brain: A systematic review of human and animal evidence

Use of cannabis or delta-9-tetrahydrocannabinol (Δ9-THC), its main psychoactive ingredient, is associated with psychotic symptoms or disorder. However, the neurochemical mechanism that may underlie this psychotomimetic effect is poorly understood. Although dopaminergic dysfunction is generally recognized as the final common pathway in psychosis, evidence of the effects of Δ9-THC or cannabis use on dopaminergic measures in the brain is equivocal. In fact, it is thought that cannabis or Δ9-THC may not act on dopamine firing directly but indirectly by altering glutamate neurotransmission. Here we systematically review all studies examining acute and chronic effects of cannabis or Δ9-THC on glutamate signalling in both animals and man. Limited research carried out in humans tends to support the evidence that chronic cannabis use reduces levels of glutamate-derived metabolites in both cortical and subcortical brain areas. Research in animals tends to consistently suggest that Δ9-THC depresses glutamate synaptic transmission via CB1 receptor activation, affecting glutamate release, inhibiting receptors and transporters function, reducing enzyme activity, and disrupting glutamate synaptic plasticity after prolonged exposure.

Olfactory Hallucinations without Clinical Motor Activity: A Comparison of Unirhinal with Birhinal Phantosmia

Olfactory hallucinations without subsequent myoclonic activity have not been well characterized or understood. Herein we describe, in a retrospective study, two major forms of olfactory hallucinations labeled phantosmias: one, unirhinal, the other, birhinal. To describe these disorders we performed several procedures to elucidate similarities and differences between these processes. From 1272, patients evaluated for taste and smell dysfunction at The Taste and Smell Clinic, Washington, DC with clinical history, neurological and otolaryngological examinations, evaluations of taste and smell function, EEG and neuroradiological studies 40 exhibited cyclic unirhinal phantosmia (CUP) usually without hyposmia whereas 88 exhibited non-cyclic birhinal phantosmia with associated symptomology (BPAS) with hyposmia. Patients with CUP developed phantosmia spontaneously or after laughing, coughing or shouting initially with spontaneous inhibition and subsequently with Valsalva maneuvers, sleep or nasal water inhalation; they had frequent EEG changes usually ipsilateral sharp waves. Patients with BPAS developed phantosmia secondary to several clinical events usually after hyposmia onset with few EEG changes; their phantosmia could not be initiated or inhibited by any physiological maneuver. CUP is uncommonly encountered and represents a newly defined clinical syndrome. BPAS is commonly encountered, has been observed previously but has not been clearly defined. Mechanisms responsible for phantosmia in each group were related to decreased gamma-aminobutyric acid (GABA) activity in specific brain regions. Treatment which activated brain GABA inhibited phantosmia in both groups.

Pretreatment with delta 1-tetrahydrocannabinol and psychoactive drugs: effects on uptake of biogenic amines and on behavior

Injection of delta 1-tetrahydrocannabinol (THC) into mice increased the uptake into brain synaptosomes of radioactive DA, NE, 5-HT and GABA, with the effect on GABA being the greatest; uptake of leucine was not stimulated, indicating that THC does not facilitate the transport of amino acids in general. The effect of THC was stereospecific because pretreatment with the non-psychoactive isomer, (+) delta 6-THC had no effect on uptake of DA into cortical synaptosomes. The effect on DA uptake was correlated with psychoactive potency. THC enhanced uptake more than did SP-111 (a water soluble ester of THC but less potent than THC) and much more than cannabidiol (a non-psychoactive ingredient of marijuana). THC increased the uptake of DA into striatal synaptosomes but much less than into cortical synaptosomes. The enhancing effect of THC on uptake in cortex showed tolerance after chronic (1 week) treatment with THC. Catecholaminergic receptor antagonists (chlorpromazine, propranolol), like THC, stimulated the uptake of DA or NE into cortical synaptosomer. In contrast, pretreatment with MAO (pargyline) or uptake (tricyclic antidepressants) inhibitors, or with amphetamine, decreased uptake. Thus THC does not inhibit MAO uptake, or stimulate the release of catecholamines but may interact with a receptor. The notion of a THC--receptor interaction is supported by behavioral experiments.

Effect of cannabinoids on the turnover rate of acetylcholine in rat hippocampus, striatum and cortex

The effects of delta9-tetrahydrocannabinol (delta9-THC), the major psychoactive compound of marijuana, and cannabidiol (CBD), a non-psychoactive component, on the acetylcholine (ACh) concentration and the turnover rate of ACh (TRACh) have been studied in various regions of the rat brain. Neither delta9-THC doses from 0.2 to 10 mg/kg nor CBD (10 OR 20 MG/KG) alter the ACh concentration in the brain areas examined 30 min, after the intravenous injection. However, delta9-THC (doses from 0.2 to 10 mg/kg) causes a marked dose-related decrease in the TRACh in hippocampus whereas CBD is without effect in this brain region even when 20 mg/kg is given. Furthermore, high doses of delta9-THC (5 mg/kg) and CBD (20 mg/kg) that produce a significant decrease in the TRACh of striatum fail to change the TRACh in parietal cortex. The low doses of delta9-THC required to reduce hippocampal TRACh suggest that an action on these cholinergic mechanisms may play a role in the psychotomimetic activity of delta9-THC.