Drugs and Behaviour - Andy Parrott
Lecture 3: Cannabis – 10th October 2016
Cannabis: Overview
- Cannabis: Historical introduction
- Modes of administration: Smoking, drinking, food.
- Neuropharmacology: Anandamide receptor
- Subjective aspects: Mood effects
- Dependence: Physical & psychological aspects.
- Cognitive and psychomotor aspects: Acute & chronic
- Psychiatric aspects: Schizophrenia and others?
- Medicinal uses: Multiple sclerosis, analgesia, glaucoma
Cannabis: Historical Overview
Cannabis sativa: Grows as a weed in many parts of the world.
First pharmacopoeia (Shen Nung, in China, 2737BC) a ‘superior herb’ for
many ailments.
Victorian Europe. Paris club of hashish eaters.
USA: Not illegal until the mid-1920s.
Hippie culture and pop music from the mid-1960s.
UK: Decreasing usage in 2010s
USA decriminalization: Local states vs. federal govt.
World Health Org: 2012, 2016 reports on its damaging effects.
Overview from core book: For centuries beliefs cannabis were based on
personal anecdotes and reflected sociocultural wisdom. Then, in the 20th
Century during the rise of empirical pharmacology, the main focus was on the
development of new disorder-specific compounds; this led to cannabinoids
,being ignored as possible therapeutic agents. It was then widely used for
recreational purposes and has remained the most popular illicit recreational
drug. Some governments view it as a ‘gateway drug’ in that it leads to harder,
more damaging compounds.
The active ingredients of smoked or ingested cannabis are several
cannabinoids including THC; these bind to the cannabinoid receptors that
increase hyperpolarisation, inhibiting neuronal activity in a dose-dependent
manner.
In Westernised societies, many recreational users develop intensive patterns of
use, when drug taking predominates over other more useful activities
amotivational syndrome.
Administration Modes
The plant grows easily in most places. Can smoke the leaves or take the resin.
THC is the psychoactive ingredient and cannabidiol has oxidative stress
properties need a balance between them so you can the psychoactive
effects as well as the beneficial effects of cannabis.
Marijuana (grass) Dried leaves, or hashish resin - smoked. Bhang as a
drink or infusion. Also taken in foods and cakes
Wild plant: Leaves and female buds contain 1-2% THC (active ingredient,
see later), other parts even less.
Sensemilla strain in mid-1970s: 6-8% THC.
Skunk & modern varieties: 13-18% THC, low in cannabidiol.
24 hour lights, cont Fertilizer, hydroponics, large valuable plants
1960s cannabis quite mild – balance of THC and cannabidiol
Today powerful & noxious…. excess THC over cannbidiol
, Spice: Artificial cannabinoids – can prove fatal (Schifano, 2013), very
addictive, use in Swansea Prison (Anderson, 2015). Spice is the highest
in concentration and danger; it is a total agonist to the anandamide
receptor.
Anandamide (N -arachidonoyl-ethanolamine, AEA) was the first
endogenous ligand of cannabinoid receptors to be discovered.
It is an endogenous analogue of tetrahydrocannabinol. Anandamide
plays an important role in the regulation of appetite, pleasure and
reward, and elevated levels may increase the pleasure experienced on
consumption of food.
Anandamide has been found in chocolate, and is thought to be partly
responsible for the intense enjoyment experienced while eating it.
Anandamide may also be partly responsible for pain regulation and sleep
patterns.
Cannabidiol is one of the least active cannabinoids identified in cannabis.
Thought to have a wide scope of potential medical applications due to
clinical reports showing a lack of side effects, particularly a lack of
psychoactivity.
It also has non-interference with several psychomotor learning and
psychological functions.
Neuropharmacology
Main constituents: delta-9-tetrahydrocannabinol (THC), delta-8-THC,
cannabinol and cannabidiol.