Notes%20for%20neuro.pdf

Psychopharmacology

• Definition: The study of how psychoactive drugs interact with the brain.

Atropine: Overview

• Derived from Atropa belladonna (deadly nightshade).

• Noted for its dual nature: poisonous and medicinal effects.

• First isolated in 1831.

Effects and Uses

• Mechanism: Antagonist at muscarinic acetylcholine receptors (mAChRs), classified as a parasympatholytic.

• Medical Uses:

  • Slows intestinal motility: Treats diarrhea and spastic colon.

  • Dilation of pupils: Historically used in ophthalmology; replaced by shorter-acting drugs in present.

• Anticholinergic effects include:

  • Increased heart rate.

  • Dilation of lung airways.

  • Dry mouth.

  • Difficulty urinating.

Historical and Mythological Context

• Genus name "Atropa" alludes to the mythological Fates (Moirai):

  • Clotho: Spins the thread of life.

  • Lachesis: Measures the thread of life.

  • Atropos: Cuts the thread of life (death); referred directly to the plant's poisonous aspects.

• Species name "belladonna": Meaning "beautiful woman"; historically used to enhance beauty via pupil dilation.

Psychoactive Effects

• Atropine crosses the blood-brain barrier, leading to:

  • Altered consciousness, including dream-like and hallucinatory states.

  • Higher doses can result in disorientation, confusion, and intense hallucinations.

  • Amnesia is a common occurrence.

  • The relationship between mAChR antagonism and psychoactive effects remains unknown.

Comparison of Atropine and Ipratropium

• Ipratropium has an additional isopropyl group attached to nitrogen, making it a charged quaternary amine.

• This alteration renders ipratropium hydrophilic, preventing it from crossing the blood-brain barrier.

• Used as a parasympatholytic (e.g., in inhalers) without CNS side effects.

Psychoactive Drugs: Popularity Rankings

• Top Five Psychoactive Drugs:

  1. Caffeine

     • Principal psychoactive in coffee, tea, cacao, etc.; widely consumed globally.

  2. Ethanol (ethyl alcohol)

     • Produced via fermentation of plant sugars; primary psychoactive in alcoholic beverages.

  3. Nicotine

     • Principal psychoactive in tobacco; often inhaled through smoke.

  4. Areca Nut (betel nut)

     • Contains arecoline; provides relaxation and mental stimulation; widely used in Southeast Asia.

  5. Cannabis

     • Includes marijuana and hashish; its psychoactive component is THC; usage prevalence is difficult to quantify due to legal restrictions.

Chemical Complexity of Plants

• Plants synthesize complex chemical profiles beyond singular substances.

• Each plant has unique constituents that may produce physiological effects.

• Different forms of caffeine-containing plants can yield varying psychoactive effects.

Ethnobotany and the History of Drugs

• Ethnobotany studies human relationships with plant resources throughout history.

• Understanding the medicinal and poisonous properties of plants is essential.

• Indigenous peoples have historically valued the unique powers of plants; traditional healers (herbalists, shamans) utilized their knowledge for healing.

• The relationship between psychoactive substances and the mind-brain interplay points to significant implications for psychopharmacology.