Ganglionic Blockers

Question 1

How do ganglionic blockers act differently than atropine (a muscarinic blocker)?

Answer 1

They act on NICOTINIC Receptors to prevent ACh from binding

Question 2

What is the primary function of the ganglionic blockers?

Answer 2

Reduce Hypertension by Suppressing overactive sympathetic nerves

Question 3

What two main drugs act as ganglionic blockers?

Answer 3

Mecamylamine
Trimethaphan

These drugs are not commonly used to treat hypertension anymore because of their global effects

Question 4

Specifically what receptor is acted on my Mecamylamine and Trimethaphan?
• Location?

Answer 4

Cholinergic Nn receptors found in:
• Autonomic Ganglia
• Adrenal Medulla

***These are distinct from the receptors found on the neuromuscular junction

Question 5

What is responsible for creating the EPSP?

Answer 5

EPSP:
• Nn nicotinic acetylcholine receptors (nAChRs) bind 2 molecule of ACh
• Receptor is a Na+ channel that opens when ACh binds and Na+ rushes down the concentration gradient

Question 6

What receptor signaling causes the IPSP and slow EPSP?

• what modulates the effects of the EPSP?

Answer 6

IPSP - created by M2 receptor (that block Ca++ L-type channel, Allows K+ in, and increases Negative Threshold via If)

slow EPSP - created by M1 receptor
• effects modulated by SIF cells and/or sensory terminals

Question 7

Determine if the following have more of a sympathetic or parasympathetic tone:
• Arterioles
• Veins
• Heart

Answer 7

Arterioles:
• Sympathetic (adrenergic)

Veins:
• Sympathetic (adrenergic)

Heart:
• Parasympathetic (cholinergic)

Question 8

Determine the effects of a ganlionic blockade of:
• Arterioles
• Veins
• Heart

Answer 8

Arterioles:
• Blocking normal sympathetic tone would result in vasodilation, increased peripheral blood flow and hypotension

Veins:
• Blocking normal sympathetic tone would result in dilation, peripheral pooling of blood, decreased venous return, decreased cardiac output

Heart:
• Blocking normal parasympathetic tone would cause Tachycardia

Question 9

How do trimethaphan and mecamylamine work to block the Nn receptors?
• Result of blocking on action potentials?

Answer 9

• Competitive inhibition by binding to one of the two ACh binding sites prevents the Na+ channel from opening
• No Na+ channel opening means NO EPSP

Question 10

In what conditions is trimethaphan used?

Answer 10

• Intraoperative Hypertensive Emergencies
• Malignant Hypertension
• Acute Dissecting Aortic Aneurysm

Question 11

What is mecamylamine used to treat?

Answer 11

• Nicotine-responsive neurological diseases (e.g. Tourette’s)
• Cocaine and Nicotine addictions

**No longer used to treat Hypertension

Question 12

What adverse effect is unique to Trimethaphan?

Answer 12

Causes HISTAMINE release leading to BRONCHOCONSTRICTION

Really bad for asthmatics

Question 13

What are some adverse effects common to Trimethaphan and mecamylamine?

Answer 13

• Postural hypotension, Tachycardia, Arrhythmias
• Blurred Vision, Double Vision
• Dry Mouth, Constipation
• Urinary Retention, Impotence
• Drowsiness, Siezures, Hallucinations
• Neuromuscular Blockade