Toxicology 2

Question 1

What is the mechanism of action of the pyridine alkaloids?

Answer 1

Activate the nicotinic cholinergic receptors. At lower doses they activate the sympathetic nervous system. However, at higher doses they lead to ganglionic paralysis and a total block.

Question 2

What is the mechanism of action of the tropane alkaloids?

Answer 2

They block the parasympathetic nervous system leading to dominance of the sympathetic nervous system (the sympathetic signs will dominate)

Question 3

What is the mechanism of action of the indole alkaloids?

Answer 3

Inhibit the breakdown of serotonin by serotonin by monoamine oxidase disrupting nerve function

Question 4

What is the effect of the steroidal alkaloids?

Answer 4

Intact glycoalkaloid = GIT irritant but it is not absorbed Free alkaloid = crosses the blood brain barrier (has some anticholinesterase activity)

Question 5

What is the mechanism of action of the pyrrolizidine alkaloids?

Answer 5

Hepatotoxicity

Question 6

What is a plant that could have caused the condition seen below?

Answer 6

Common Heliotrope

Question 7

What is the mechanism of action of fluroacetate?

Answer 7

Mechanism of action:

1. Fluoroacetate is converted to Fluoroacetate CoA and that then enters the TCA cycle to produce Fluorocitrate
2. Fluorocitrate inhibits the enzyme aconitate hydratase (preventing conversion of citrate to aconitate)
3. Also irreversibly inhibits citrate transport out of the mitochondria

Question 8

What are the clinical signs that are observed from fluoroacetate poisining?

Answer 8

heart failure and nervous signs

Question 9

What is the effect of intact glycosides?

Answer 9

Intact glycoside acts like a detergent causing irritation of the gastrointestinal tract

Question 10

What is the effect of the Azoxyglycosides?

Answer 10

MAM and diazomethane - methylating agents (heaptotoxins and carcinogens)

Question 11

What is the mechanism of action of the cardiac glycosides?

Answer 11

decrease the activity of the sodium pump causing decreased conductivity of the myocardium and subsequent arrythmias and premature systole

Question 12

What plant has the potential to induce cyanide poisionings?

Answer 12

Sorghum

Question 13

What is the action of the nitrates/nitrites?

Answer 13

vasodilatory via nitrous oxide: pulmonary and central hypotension results in decreased cardiac output

oxidised haemoglobin: converts Fe2+ to Fe3+, red oxyhaemoglobin leading to chocolate brown methaemoglobin and decreased oxygen to tissues

respiratory defiency: dyspnoea, cyanosis, rapid to weak pulse trembling

Question 14

What is the mechanism of action of the oxalates?

Answer 14

1. Bundles of small crystalline needles (raphides) cause local irritation through the penetration into mucous membranes causing
2. Souble salts of sodium and potassium can cause functional hypocalcaemia