Atypical Neurotransmitters: Purines, Cannabinoids, and Nitric Oxide

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Questions and Answers

What is the classification of glutamate, aspartate, and D-serine?

Amino acids (correct)

Peptides

Purines

Monoamines

Which of the following is NOT a gasotransmitter?

Carbon monoxide

Adenosine (correct)

Nitric oxide

Hydrogen sulfide

What is the term used to describe the nerves that release ATP or related molecules?

Adrenergic

Purinergic (correct)

Neurotransmittergic

Cholinergic

What is the name of the peptide that is released by nonadrenergic, noncholinergic (NANC) nerves?

ATP Signup and view all the answers

Which of the following is a type of monoamine?

Dopamine Signup and view all the answers

What is the name of the neurotransmitter that is synthesized and stored in nerve terminals?

ATP Signup and view all the answers

What is the name of the neurotransmitter that is released during nerve stimulation?

ATP Signup and view all the answers

What is the term used to describe the breakdown of ATP by ectoenzymes?

Ectoenzymatic breakdown Signup and view all the answers

What is the role of ATP as a cotransmitter in sympathetic nerves?

Supplying visceral organs and blood vessels Signup and view all the answers

What is the primary function of postjunctional P2-purinoceptors?

Mediating purinergic transmission Signup and view all the answers

What is the effect of low concentrations of methylxanthines on P1-purinoceptors?

Selective antagonism Signup and view all the answers

Which of the following is a selective agonist of P2-purinoceptors?

ATP Signup and view all the answers

What is the effect of suramin on P2-purinoceptors?

Antagonism Signup and view all the answers

How many subclasses of P1-purinoceptors are recognized so far?

4 Signup and view all the answers

What is the role of ATP in the urinary bladder?

Causing atropine-resistant excitation Signup and view all the answers

What is the effect of occupation of P1-purinoceptors on an adenylate cyclase system?

Activation Signup and view all the answers

What is the function of P2X purinoceptors in vascular and visceral smooth muscles?

Contraction Signup and view all the answers

Which type of receptors are selective to ADP on platelets?

P2T Signup and view all the answers

What is the response of P2Y purinoceptors on endothelial cells?

Vasodilation Signup and view all the answers

What is the function of P2Y purinoceptors in vascular and visceral smooth muscles?

Relaxation Signup and view all the answers

What is the role of ATP in sympathetic nerves?

Cotransmitter Signup and view all the answers

What is the effect of suramin and PPADS on sympathetic nerve stimulation responses?

Block the response Signup and view all the answers

What is the role of ATP in parasympathetic neurons in the bladder?

Cotransmitter Signup and view all the answers

How many subclasses of P2Y purinoceptors have been identified in mammals?

8 Signup and view all the answers

What is the primary function of CB1 receptors in the human body?

Regulating respiratory and cardiovascular functions Signup and view all the answers

Which part of the brain does not have CB1 receptors?

Medulla oblongata Signup and view all the answers

What is the name of the primary psychoactive compound in cannabis?

Tetrahydrocannabinol (THC) Signup and view all the answers

What is the total number of cannabinoids isolated from cannabis?

113 Signup and view all the answers

Where are CB1 receptors also found in the human body, besides the brain?

Anterior eye and retina Signup and view all the answers

Which type of cannabinoids are produced naturally in the body by animals?

Endocannabinoids Signup and view all the answers

What is the name of the receptor that is absent in the medulla oblongata?

CB1 Signup and view all the answers

What is the function of adenosine in the CNS?

Modulating the release of excitatory transmitters Signup and view all the answers

What is the effect of Sildenafil citrate on penile erections?

It enhances signaling through the nitric oxide pathway Signup and view all the answers

What is the function of nitric oxide in vessel homeostasis?

It inhibits vascular smooth muscle contraction and growth Signup and view all the answers

What is the effect of high salt intake on nitric oxide production in patients with essential hypertension?

It attenuates nitric oxide production Signup and view all the answers

Which of the following is an effect of nitric oxide?

Vasodilatation Signup and view all the answers

What is the role of nitric oxide in the immune response?

It is generated by phagocytes as part of the immune response Signup and view all the answers

Which of the following is a condition in which nitric oxide might serve as an inflammometer?

Asthma Signup and view all the answers

What is the effect of nitroglycerin and amyl nitrite on the body?

They dilate blood vessels Signup and view all the answers

What is the effect of minoxidil on the body?

It dilates blood vessels Signup and view all the answers

What is the common characteristic of humans with atherosclerosis, diabetes, or hypertension?

They have impaired nitric oxide pathways Signup and view all the answers

Study Notes

XBHY P2 Purinoceptors

Divided into 2 main families: P2X purinoceptor family (7 subclasses) and P2Y purinoceptor family (8 subclasses)
P2X mediates fast responses via ligand-gated ion channels, while P2Y mediates slower responses via G proteins

Functions of P2X and P2Y

P2X mediates contraction of vascular and visceral smooth muscles
P2Y mediates relaxation of vascular and visceral smooth muscles, including vasodilation via P2Y receptors on endothelial cells, releasing nitric oxide (NO)

Other Purinoceptors

P2T-purinoceptors (ADP-selective receptors on platelets)
P2Z-purinoceptors (open non-selective pores in mast cells, macrophages, and lymphocytes of the immune system)
P2U purinoceptors (responsive to UTP and ATP)
P2D-purinoceptors (subtype responsive to diadenosine polyphosphates)

Sympathetic and Parasympathetic Nerves

Sympathetic nerves: NE and ATP act as cotransmitters, released from sympathetic nerves in variable proportions depending on tissue and species
Parasympathetic nerves: ACh and ATP appear to be cotransmitters in parasympathetic neurons in the bladder

Functions of Purinergic Transmission

Vasodilation, neurotransmission, production of reactive nitrogen intermediates, and penile erections
Nitric oxide (NO) pathway is involved in vasodilation and is affected in certain diseases (e.g., atherosclerosis, diabetes, hypertension)

Nitric Oxide (NO)

Generates reactive nitrogen intermediates
Inhibits vascular smooth muscle contraction and growth, platelet aggregation, and leukocyte adhesion to the endothelium
Impaired NO pathways are seen in certain diseases (e.g., atherosclerosis, diabetes, hypertension)
High salt intake attenuates NO production in patients with essential hypertension

Cannabinoids

A class of diverse chemical compounds that act on cannabinoid receptors in cells, altering neurotransmitter release in the brain
Include endocannabinoids (produced naturally in the body), phytocannabinoids (found in cannabis and some other plants), and synthetic cannabinoids
Notable cannabinoids: THC (primary psychoactive compound in cannabis), CBD (major constituent of the plant)

Cannabinoid Receptors

2 types: CB1 and CB2
CB1 receptors are primarily found centrally in the brain (basal ganglia, limbic system, hippocampus, cerebellum, and reproductive systems) and are responsible for respiratory and cardiovascular functions
CB2 receptors are found in the immune system