Biol 2217B: Opium and Cannabis Lecture Notes

Overview of Opioids and Cannabis

  • Opioids and Endorphins: Both modulate pain in the human body.
  • Cannabis: Used for thousands of years for drugs and fiber.
  • Endocannabinoid System: Regulates several neurological pathways; however, many specific effects remain unclear.

Four Steps of Pain Processing

  • Transduction:
    • A stimulus causes cell damage.
    • This leads to the release of sensitizing chemicals (e.g., histamine in allergic reactions).
    • Nociceptors (pain receptors) generate an action potential.
  • Transmission:
    • The action potential travels to the brain for processing.
    • Various neurotransmitters involved include:
    • Glutamate
    • Substance P
  • Perception:
    • The brain processes the pain signals.
  • Modulation:
    • Action potential moves down the spinal cord.
    • Neurotransmitters like endorphins are released to inhibit pain impulses (Quock 2022).

Mechanism of Pain Modulation

  • Endorphins Release:
    • Opioid neurons release endorphins into the synapse.
    • Opioid Receptors: Located on both presynaptic and postsynaptic sides.
    • Presynaptic: Inhibits the release of pain-causing neurotransmitters.
    • Postsynaptic: Inhibits the formation of action potentials.

Neurotransmitters Involved

  • Dopamine: Acts as a reward hormone.
  • GABA (Gamma-Aminobutyric Acid): Inhibitory, modulates dopamine activity.
  • MOR (Mu Opioid Receptor): Inhibits GABA.
  • β-EP (Beta-Endorphins): Activate MOR and are involved in the pain modulation process.

Side Effects of Opioids

  • Central Nervous System:
    • Hallucination, Confusion, Dizziness, Loss of Appetite, Drowsiness, Headaches.
  • Skin: Hives, Rash, Sweating, Itching.
  • Respiratory: Difficulty and slowed breathing.
  • Intestinal: Constipation.
  • Cardiac: Variations in heart rate (fast or slow).

Cannabis Overview

  • Cannabis Family: Canabaceae, includes:
    • C. sativa: Common for recreational marijuana; some cultivars low in cannabinoids for hemp production.
    • C. indica: Strains for recreational use and hashish production.
    • C. ruderalis: Low THC content; often hybridized.

Historical Use of Hemp and Cannabis

  • Hemp Uses (1600-1900):
    • Clothing for the poor.
    • Sails and ropes for ships.
    • Paper production.
  • Tobacco Spread:
    • Introduced to Europe by Columbus (1492) and other explorers.
  • Cannabis Use:
    • Medical use in China for 5,000 years.
    • Hashish popularized in the Middle East and Europe during 1100-1600.

The Endocannabinoid System

  • Functions: Regulates appetite, sleep, mood, pain, and other pathways.
  • Key Components:
    • Anandamide (AEA) & 2-Arachidonoylglycerol (2-AG) as significant endocannabinoids.
    • Receptors:
    • CB1: Primarily in the CNS.
    • CB2: Primarily on immune cells.

Retrograde Signaling and Its Modulation

  • Mechanism of Action:
    • Endocannabinoids are produced by postsynaptic neurons and travel backward to inhibit neurotransmitter production, affecting pain pathways.
    • In appetite pathways, they stimulate appetite by reducing inhibitory effects of GABA neurons.

Phytocannabinoids

  • THC: Psychoactive component of cannabis, binds to and activates CB1 receptors.
  • CBD: Non-psychoactive, interacts with the nervous system; may change receptor conformation for THC binding.

Physiological Effects of Cannabis

  • Common Effects:
    • Decreased intra-ocular pressure, Mouth dryness, Heart rate increase, Muscular relaxation, Sensation of heat/cold in the skin.

Next Steps

  • Tutorial 5: Next week; no required reading.
  • Background Reading:
    • Quock, R. (2022) on drugs and behavior.
    • Hashim, N. (2017) on hemp and the global economy.