1995 ICRS Symposium on Cannabis and the Cannabinoids

Robert C. Clarke

International Hemp Association
P. O. Box 75007
1070 AA Amsterdam
The Netherlands

          The 1995 Symposium on Cannabis and the Cannabinoids sponsored by the International Cannabis Research Society (ICRS) was held at the Regal McCormick Ranch at Scottsdale, Arizona, USA from June 8-10.  Nearly 80 Cannabis researchers from around the world convened to share primary research papers covering a wide range of topics including the chemistry, biochemistry, and metabolism of cannabinoids; the characterization of the cannabinoid receptors and associated G-proteins; the endogenous ligands and antagonists associated with the cannabinoid receptors; investigations of the immunological, pharmacological, and physiological actions of cannabinoids; the effects of chronic exposure to cannabinoids; and the effects of cannabinoids on human behavior.
          The research presented at the 1995 ICRS symposium represents international cooperation between 45 universities and private companies from Australia, Canada, Finland, France, Hungary, Israel, Italy, Japan, Korea, The Netherlands, Scotland, Spain, and the United States.  Twenty-five of the 64 papers presented (nearly 40%) were collaborative efforts between two or more laboratories.  Basic cannabinoid research has been largely sponsored by government agencies such as the United States National Institute on Drug Abuse.  Since there has been little interest shown in the cannabinoids by the highly competitive pharmaceutical industry, there have been fewer of the limitations on collaborative effort so often imposed by proprietary considerations.
          Cannabis and its cannabinoid compounds have been under study by researchers worldwide since the 1960s when the recreational use of Cannabis drugs began to gain popularity in the West.  The basic structures and activities of the naturally occurring cannabinoids and synthetic cannabinoids created in chemistry laboratories were elucidated during the 1970s.  The physiological and psychological effects of cannabinoids on animal and human subjects were extensively studied during the 1970s and 1980s.  However, few new insights into the mechanisms of cannabinoid actions on the body and the brain were being realized.  By the early 1990s the field of cannabinoid research lacked momentum and direction.  Then three key discoveries radically changed the face of cannabinoid research.  The discovery of the cannabinoid receptor (1992), the isolation and synthesis of anandamide, the naturally occurring ligand (receptor binding molecule) produced in the brain (1993), and the synthesis of an antagonist (receptor blocking molecule) to the cannabinoid ligands (1994), providing tools making it possible to study the effects of cannabinoids from the inside out.  Without these basic tools no viable models could be proposed by which to measure new theories.
          The vibrant field of cannabinoid research is now advancing rapidly on many new fronts.  As researchers probe deeper into the mechanisms of the interaction between the cannabinoid receptor and its various ligands, they move ever closer to understanding the relationship between humans and Cannabis.
          The specific topics of the papers presented at the 1995 ICRS symposium reflect the underlying research interests of the majority of ICRS members in developing a deeper understanding of the complex relationship between Cannabis and humans.  Brief summaries of the presentations most likely to be of interest to IHA members are given below.  Many presentations have been omitted from this brief review in the interest of conserving space.

June 8  Chemistry

          Marcus Tius (University of Hawaii) opened the Chemistry Session with his research on the synthesis of hybrid cannabinoid molecules incorporating features of both the classical cannabinoids (naturally occurring cannabinoids and synthetic molecules modeled on their structure) such as THC and non-classical cannabinoids (non-natural cannabinoid molecules derived from other chemical structures that induce cannabinoid effects) such as CP 55,940.  Many of these hybrid cannabinoids were found to bind with the brain cannabinoid receptor CB1.  New hybrid cannabinoids can be used as probes to elucidate the structures and functions of the cannabinoid receptors and may also prove to have medical applications.
          Alexandros Makriyannis (University of Connecticut) began the report of his findings concerning the synthesis of hexahydrocannabinol analogs and their binding behavior with receptors by explaining how new cannabinoid probes are being used to investigate the structure of the cannabinoid receptors.  The probes that he and his colleagues have developed bind irreversibly to the receptor and allow the receptor proteins to be cleaved into discrete subunits.  These protein subunits can then be subjected to further analysis in order to determine their detailed structure and the way in which they function in forming the receptor.
          John Huffman and Julia Lainton (Clemson University) gave two papers on the synthesis of several methyl and dimethyl-heptyl substituted side chain analogs of delta-8- THC.  Pharmacologically the analogs were of equal or greater potency than the natural cannabinoid delta-8-THC.
          Raj Razdan (Organix Inc.) presented a synthesis of the cannabinoid antagonist SR 141716A.  The SR 141716A antagonist binds with the cannabinoid receptor and significantly limits the effects of delta-9-THC the primary psycho-active compound in Cannabis.  Chemists at Sanofi Recherche first described SR 141716A at the 1994 ICRS symposium in Montreal, Canada.  Their discovery met with great enthusiasm and now two syntheses have been presented.

Biochemistry and Metabolism

          Herbert Seltzman (Research Triangle Institute) presented a second synthesis of SR 141716A, as well as the tritium labeled molecule, and an elucidation of the antagonist's structure.  The cannabinoid antagonist SR 141716A and its radio labeled analog will be used in studies of the cannabinoid receptors.
          Dale Deutsch (State University of New York at Stony Brook) reported on a new assay technique for anandamide amidase activity.  Anandamide is a compound produced in brain tissue that binds to the cannabinoid receptors and may modulate such psychologically and physiologically related functions as control of mood and the sensations of contentment and euphoria.  Anandamide amidase is the enzyme at the site of the cannabinoid receptors that breaks down (hydrolyzes) the anandamide molecule into its precursor molecule arachadonic acid and thereby clears the cannabinoid receptors so they can be stimulated again.  The new assay technique allows much faster determination of the location of the cannabinoid receptors in brain tissue as indicated by the hydrolysis of anandamide.
          Sumner Burstein (University of Massachusetts Medical School) presented his theory that categorizes anandamide, and other endogenous cannabinoid ligands (compounds that bind to receptors) yet to be discovered, as members of a novel group of eicosanoid compounds.  In this light he presented a theoretical model for the biosynthesis and mode of action of anandamide involving a positive feedback mechanism where anandamide synthesis triggers additional anandamide synthesis.  This model can be used as a framework within which to explore the evolution of the anandamide pathway in humans.
          Cecelia Hillard (Medical College of Wisconsin) reported on research using brain cell cultures to study the uptake of anandamide and its breakdown by cells.  Anandamide is absorbed rapidly by cells, is only broken down within the cell, and breaks down quite slowly.  The assay technique developed using these cell lines is being used to identify the specific locations of anandamide's actions amongst the myriad cellular components.  Initial results indicate that cell fractions containing myelin or microsomal membranes exhibit the greatest breakdown of anandamide.
          Aidan Hampson (University of California at San Francisco) offered strong data indicating that anandamide is broken down in the brain through the action of a lipoxygenase.  The lipoxygenase pathway is suggested as a third pathway, in addition to the previously elucidated anandamide amidase and cytochrome P450 pathways, that brain cells use to break down anandamide.  The structures of various anandamide lipoxygenase metabolites were shown, and some of these compounds were found to have a very high affinity for the cannabinoid receptor.

Receptors and G-Proteins

          Patty Reggio and Daniel Bramblett (Kennesaw State College) gave two papers and a poster showing the results of detailed studies into the mechanism of action of the cannabinoid receptors.  Through the determination of amino acid sequences in the receptor proteins and advanced computer assisted modeling techniques, the cannabinoid receptors can now be visualized as a membrane-bound docking site encircled by 7 nearly parallel helical protein subunits.  The cannabinoid ligand molecules enter the circular opening between the protein helices and bind temporarily to several of the amino acid bases that form the long protein chains.  When a ligand binds to the receptor it causes the proteins to bend, and this change in shape triggers a chemical change that activates the G-protein attached to the inner side of the membrane.  The G-protein then detaches from the receptor and is transported to wherever in the organ the message from the receptor is intended to have its effect.
          Brian Thomas (Research Triangle Institute) showed computer generated structural models for the eicosanoid, classical cannabinoid, and non-classical cannabinoid classes of molecules and compared the structural requirements of these molecules in terms of their having cannabimimetic (Cannabis-like) activity.  Structural studies allow pharmaceutical chemists to design molecules with a high likelihood of having cannabimimetic activity that mimics one of the beneficial actions of a natural cannabinoid.
          Abby Parrill (University of Arizona) also showed a computerized structural analysis of apparently dissimilar cannabinoids looking for hidden structural similarities that may be required for the molecular to be active.
          Denise Pettit (Medical College of Virginia) presented an assay of CB1 receptor activity using melanophore cells that change color dramatically in the presence of compounds that activate the CB1 cannabinoid receptor.  This technique could prove useful for mapping the sites of active receptors and as an assay of activity for novel ligands and antagonists.
          Steven Childers (Bowman Gray School of Medicine) presented a comparison of the opioid and cannabinoid receptors in terms of receptor density and the activity of their associated G-protein effectors.  The activity of G-protein coupled receptors does not correspond to the number of receptors available.  Data also indicate that cannabinoid receptors are not as efficiently coupled to their associated G-proteins as are the opioid receptors.

June 9  Receptors

          Roger Pertwee (University of Aberdeen, Scotland) presented further evidence that CB1 receptors, usually characterized as the brain cannabinoid receptors, are also found in the mouse vas deferens.  The presence of the CB1 receptor in tissues other than the brain could indicate that cannabinoid receptors are somehow involved in basic physiological functions.
          David Shire (Sanofi Recherche, France) reported on Sanofi's continuing research to characterize the CB1 and CB2 receptors, and a new variant receptor CB1A discovered during the cloning of the CB1 receptor using their cannabinoid antagonist SR 141716A.  Data indicate that the amino-terminal region of the CB1 receptor may play a part in the receptor's recognition of the antagonist.
          David Compton (Medical College of Virginia) presented additional characterization of the CB2 receptor in terms of its affinity for various ligands.  Cannabinoid ligands can be divided into three groups: CB1 selective ligands; CB2 selective ligands; and ligands with low selectivity.

Pharmacology and Nociception

          William Martin (Brown University) presented research showing that anandamide plays a role in antinociception (analgesia and sedation) and Jennelle Durnett-Richardson (University of Minnesota) showed that anandamide has its effect in the spinal chord.  Sandra Welch (Medical College of Virginia) demonstrated that anandamide and THC have different mechanisms by which they induce antinociception and tolerance.  Aron Lichtman (Medical College of Virginia) presented evidence that SR 141716A antagonizes the antinociceptive effects of cannabinoids.

Physiology and Pharmacology

          Sam Deadwyler (Wake Forest University) brought us up to date on his investigations of the mode of action of cannabinoids through their regulation of the potassium A-currents.  Potassium currents are pathways through which electrical signals are transmitted through cells and form a link in the communication system within the body.
          David Compton (Medical College of Virginia) showed that the structures of certain active indole derivatives of non-classical cannabinoids can suggest templates for the development of new cannabinoids with specific pharmacological activities.
          Ken Mackie (University of Washington and Panlabs) showed evidence that the CB1 receptor is phosphorylated by protein kinase C and that this mechanism may be involved in the receptor's action.

June 10  Chronic Exposure

          Stacie Cook (Medical College of Virginia) reported that rats develop a pharmacological tolerance to extremely high doses of THC, that the tolerance to THC was not as great as tolerance to CP 55,940, and that no tolerance developed to anandamide.
          Wensheng Lang (University of Connecticut) presented a model for the transport of cannabimimetic agents across the blood brain barrier involving (i) an "on" step from the blood into the membranes (ii) a "flip-flop" step within the membrane where the orientation of the polar ends of the cannabinoid molecules are reversed, and (iii) an "off" step from the membrane into the brain tissues.
          Dave Pate (HortaPharm, Amsterdam) presented research performed during development of a cyclodextrin delivery system for administering cannabinoids to the eyes, lowering the high intraocular pressure associated with glaucoma.  Several novel anandamide analogs were found to cause a minimal initial hypertensive effect (increased ocular pressure) followed by a significant hypotensive phase (lowered ocular pressure).  This paper illustrated that the recently discovered anandamides may have promising medical uses.
          Julian Romero (Complutense University, Spain) presented evidence that chronic exposure to anandamide causes down-regulation of the CB1 receptor and that the rapid breakdown of anandamide counteracts the desensitization.  Investigations along these lines are leading to a better understanding of the tolerance to cannabinoid compounds.

Endogenous Ligands and Antagonists

          Ester Fride (Hebrew Univer-sity, Israel) presented the results of research into the effects of very low doses of anandamide on the behavior of rats.  The effects produced by very low doses of anandamide are opposite from the effects of high doses.  Also, the effects of very low doses of anandamide are easier to detect than the effects of very low doses of delta-9-THC.  The hypothesis that low doses of anandamide activate the G-protein signaling pathway is currently being tested.
          Amruthesh Shivachar, Jenny Wiley and Mario Aceto (Medical College of Virginia) and Mike Walker (Brown University) all gave papers on research using the cannabinoid antagonist SR 141716A to block the effects of anandamide, delta-9-THC, CP 55,940 or WIN 55,212-2 either to investigate the actions of the antagonist itself or to precipitate withdrawal in investigations of tolerance to cannabinoids.

Human Behavior

          Mario Peres-Reyes (Univer-sity of North Carolina) reviewed his earlier clinical research confirming that there is no significant correlation between the condition of red eyes and the amount of THC a person has been exposed to.  He also cautioned that the use of red eyes as a criterion for deciding if a person is under the influence of THC is not reliable.
          Rik Musty (University of Vermont) pointed out that the data from a study of light and heavy marijuana users with either above average or below average self esteem suggest that marijuana smokers are well adjusted to life as measured by the Sense of Coherence Scale (SOC).  This research also shows that regardless of the amount of marijuana consumed both groups with low self esteem had lower SOC scores.  It is unlikely that marijuana use alone leads to the poor adjustment to life experienced in marijuana users seeking treatment, and that their poor adjustment to life is more likely a result of depression.

Poster Session

          Fourteen posters covered many of the same fields of study represented by the oral presentations.  Nancy Buckley and Eva Mezey (National Institutes of Neurological Diseases and Stroke) presented a poster on the cellular location of the non-brain cannabinoid receptor CB2 found in spleen tissue.  The discovery that the CB2 receptor is localized to the lymphocytes, but is not found in the macrophages, may help to explain the immunosuppressive effects of THC and suggests that certain CB2 receptor agonists (receptor stimulating compounds) might be used to stimulate certain immune responses.  Amy Herring et. al. (Michigan State University) also presented evidence that the CB2 receptor is active in splenocytes which suggests that the CB2 receptor is involved in the modulation of the immune system by cannabinoid compounds.  The possible effects of cannabinoids on the immune system is currently being actively explored by several research teams.
          Helen McIntosh and Allyn Howlett (Saint Louis University School of Medicine) presented investigations into the turnover time of the CB1 receptor.  Since the rate of turnover or synthesis of new receptors to replace exhausted and no longer active receptors is known to influence drug tolerance, this line of research may prove useful in understanding the mechanism of cannabinoid tolerance.
          Alexandros Makriyannis et al. presented research with potent inhibitors of anandamide hydro-lysis that showed antinociceptive (analgesic and calmative) activity.  When anandamide breakdown by amidase is inhibited, and an antagonist is also administered, antinociception is attenuated, indicating that the antinociceptive effects of the cannabinoids are mediated by the cannabinoid receptor.
          Murielle Rinaldi-Carmona et al. (Sanofi Recherche, France) presented the newest stage in Sanofi's development of their orally active cannabinoid antagonist molecule SR 141716A.  Data indicate that SR 141716A competitively displaces the CP 55,940 and WIN 55,212-2 non-classical cannabinoids and delta-9- THC while it non-competitively displaces anandamide.  Tritiated radio-labeled SR 141716A was shown to be an effective tool for labeling the brain cannabinoid receptors both in vitro and in vivo.
          Kang Tsou et al. (Brown University) reported that their research with CP55,940 provides evidence that cannabinoids suppress pain by affecting the processing of pain signals in the spine.

The International Cannabis Research Society is an organization of Cannabis researchers established in 1990 whose main focus is on cannabinoid chemistry and pharmacology.  ICRS members and their research teams have made the key discoveries that now fuel the resurgent interest in Cannabis and cannabinoid research.  If you are interested in learning more about the ICRS contact Dr. Rik Musty, 31121 Lakeview Avenue, Red Wing, MN, USA 55066, <Mrik@aol.com>