NEUC61 Chapter 9

What are the three most well-known plant sources for caffeine?

coffee, tea, and cacao

What is the most widely used psychoactive drug in the world?

Caffeine

What does caffeine stimulate in the body?

• Central nervous system - increase wakefulness and alertness

• Cardiovascular System - increasing heart rate and blood pressure

Which receptors does caffeine act at?

adenosine receptors as an antagonist

When caffeine reaches adenosine receptors, what three things does it antagonize?

1. Heart - slows heart rate

2. Blood vessels - vasodilation, or opens them

3. Brain - decreases neuronal excitability

What does blocking the normal neuronal inhibitory effect of adenosine produce and why?

neuronal excitation because the usual balance between excitation and inhibition is altered

Adenosine’s action at adenosine receptors results in activation of what?

G-proteins —> which affect adenylate cyclase and impact intracellular cAMP concentration —> which changes the activity of protein kinases and alters the opening of K+ channels —> leading to a hyperpolarization of the membrane and decreased neuronal excitability

What does the action of caffeine work to prevent?

Adenosine’s action at adenosine receptors — this reduces the inhibition that would normally be present in the brain, thus making neurons more excitable.

What is the major known neurochemical effect of nicotine?

To bind as an agonist at nicotinic acetylcholine receptors (nAChRs)

What effects does nicotine cause in the brain?

Behavioral effects related to relaxation, alertness, and focused attention

How are nAChRs at the neuromuscular junction different from the nAChRs of the CNS?

nAChRs at the neuromuscular junction have different amino acid sequences than CNS ones, and are less sensitive to nicotine binding

Alcohol

refers the two-carbon ethyl alcohol, called ethanol

How is ethanol formed in alcoholic beverages?

Yeast eats sugar during the process of fermentation, and creates ethanol as a waste product

Sedative-hypnotics

a class of drugs that in low doses produce relaxing effects and in high doses produce a hypnotic effect.

What are the effects of sedative-hypnotics?

relaxation, impaired judgement and coordination, loss of consciousness, and even death

Barbiturates

often used to treat anxiety and insomnia, and were the first synthetic drugs introduced in medicine classified by a certain molecular structure

Anasthetics

category of sedative-hypnotics that induce loss of sensation

How do local anasthetics induce sensation loss?

by interfering with voltage-gated sodium channels, which alters the propagation of nerve signals locally

How do general anasthetics induce sensation loss?

act in the brain to reduce CNS neural activity, producing a loss of consciousness and awareness of sensory experience

(1) Describe sedative-hypnotic drugs’ neurochemical mechanism of action in the brain

all sedative-hypnotic drugs act on ionotropic GABA receptors, facilitating the action of GABA at the receptor

(2) Describe sedative-hypnotic drugs’ neurochemical mechanism of action in the brain

Action of GABA at the receptor increases inhibition in the CNS by increasing GABA-induced CI- flow into cells

(3) Describe sedative-hypnotic drugs’ neurochemical mechanism of action in the brain

Increased GABA-induced CI- flow into cells creates relaxing, anxiety-reducing effects. Too much GABAergic inhibition may lead to death.

Opium

comes from the opium poppy, and reduces perception of pain, supresses cough, and slows motile muscle action of the intestines

Why is diacetylmorphine more potent than morphine?

Acetyl groups are less polar than hydroxyl groups, so they cross the blood-brain barrier better — they can enter the brain more efficiently

What was the first instance of a completely synthetic opioid

methadone

Endorphins

endogenous opioid neurotransmitters, made of chains of amino acids (polypeptides)

What is the major neurochemical effect of coaine?

blocking or inhibiting reuptake transporters for neurotransmitters —> neurotransmitters are slowed in leaving the synaptic cleft —> will have a greater effect at the synapse AFTER their release —> cocaine results in excessive activity at all synapses in the nervous system that use norepinephrine or dopamine as a neurotransmitter