6 - Peptides, Opioids, Adenosine, Nitric

Peptides

consist of two or more amino acids linked together by peptide bonds

• most of these serves as neuromodulators, some act as neurotransmitters

precurser molecules

All other peptides that have been studied so far are produces from _____ ______

Large polypeptides

these precursers are ___ _______ that are broken into pieces by special enzymes

Neurons

Release several different peptides

Endogenous opioids

One of the best known families of peptides

Endogenous

Means produced from within

Opioid

Means like opium

Opiates

Reduce pain because they have direct effects

Opiates

Drugs such as opium, morphine, heroin

Pert, Snowman, & Synder

Discovered that neurons in a localized region of the brain contain specialized receptors that responds to opiates

Enkephalins

From the Greek word enkephalos which means “in the head”

Enkephalins

The natural ligands for the receptors that were discovered soon after the discovery of opiate receptor

Enkephalins

Are only two members of endogenous opioids

• Mu

• Delta

• Kappa

3 Different types of Opiate Receptor:

• Analgesia

• another inhibits special-typical defensive responses such as fleeing and hiding

• another stimulates a system of neurons involved in reinforcement (reward)

Effects of Opiates:

Stimulates a system of neurons involved in reinforcement (reward)

The last effect explain why opiates are often abused:

Adenosine

is a nucleoside which is a combination of ribose and adenine that serves as a neuromodulator in the brain

Adenosine

Are released when cells are short of fuel or oxygen

Adenosine

the release of this activates receptors on nearby blood vessels and causes them to dilate, increasing the flow of blood and helping bring more of the needed substances to the region

Nucleoside

A compound that consists of a sugar molecule bound with a purine or pyrimidine base

Glial cells & neurons

Releases adenosine when cells are short of fuel or oxygen

inhibitory effects

Because adenosine receptors suppress neural activity, adenosine and other adenosine receptor agonist have generally _____ ____ on behavior

Adenosine receptors

Some investigators even believe that ______ _____ may be involved in the control of sleep

Caffeine

Blocks adenosine receptors and hence produces excitatory effects

Caffeine

a bitter-tasting alkaloid found in coffee, tea, cocoa beans, and other plants

NO

is a soluble gas that is produced by the activity of an enzyme found in certain neurons

NO

is used as a messenger in many parts of the body

NO

it is involved in the control of the muscles in the wall of the intestines

• it dilate blood vessels in regions of the brain that become metabolically active

NO

it stimulates the changes in blood vessels that produce penile erection

• also play a role in establishment of neural changes that are produced by learning