Opiods

What are propeptides and their role in opioid production?

Propeptides are larger peptides that are broken down into smaller active opioids and processed by specific enzymes to form active peptides that bind to opioid receptors.

What are endorphins?

Endorphins are a class of peptides that activate opioid receptors.

How are propeptides processed in the nervous system?

Propeptides are manufactured in the soma, cleaved by enzymes, packaged in vesicles, and processed during transport down the axon before release at the synapse.

What types of synaptic vesicles are found in axon terminals?

Axon terminals contain small clear vesicles and large dense core vesicles.

What are the three major classes of opioid receptors and their functions?

Mu (μ) receptors - responsible for analgesic effects; Delta (δ) receptors - involved in mood modulation; Kappa (κ) receptors - role in pain relief and can produce dysphoria.

What characterizes pain?

Pain is defined as unpleasant sensory or emotional experiences in response to tissue damage.

What is the function of the ascending pain pathway?

The ascending pain pathway sends pain signals from the body to the brain for pain perception.

What is the purpose of the descending pain pathway?

The descending pain pathway modulates or reduces pain by sending signals from the brain to the body.

How is dopamine synthesized?

Dopamine is synthesized from the precursor amino acid tyrosine through the action of tyrosine hydroxylase.

What distinguishes dopamine-producing neurons from norepinephrine-producing neurons?

Dopamine neurons express tyrosine hydroxylase and AADC, while norepinephrine neurons possess DBH to synthesize norepinephrine.

What are the two ways dopamine is removed from the synaptic cleft?

Dopamine is removed through degradation (by MAO and COMT) and reuptake mechanisms.

What are the main types of dopamine receptors?

There are five main types, categorized as D1-like (D1, D5) which are usually excitatory, and D2-like (D2-D4) which are usually inhibitory.

What is the Nigrostriatal pathway and its significance?

The Nigrostriatal pathway comprises connections from the substantia nigra to the striatum, crucial for movement regulation and affected in Parkinson's disease.

What are the effects of cocaine on neurotransmission?

Cocaine antagonizes dopamine receptors and blocks dopamine reuptake, increasing dopamine levels in the synapse.

How do amphetamines influence dopamine levels?

Amphetamines are imported into presynaptic terminals and cause the dopamine transporter to release large amounts of dopamine into the synapse.

What are therapeutic uses of amphetamines?

Amphetamines are used to treat disorders including obesity, narcolepsy, and ADHD when properly dosed.

What are the side effects of chronic amphetamine use?

Chronic use can lead to neurotoxicity in the nigrostriatal pathway and damage to dopamine neurons.