Autonomic Nervous Systems
Hypotension, bradycardia, respiratory depression, and muscle weakness, all unresponsive to atropine and neostigmine, would most likely be due to: (LQ)
a. Nicotine is a drug that initially stimulates and then blocks nicotinic muscular (Nm) (skeletal muscle) and nicotinic neural (Nn) (parasympathetic ganglia) cholinergic receptors.
b. Blockade of the sympathetic division of the autonomic nervous system (ANS) results in arteriolar vasodilation, bradycardia, and hypotension.
c. This is an example of depolarization block. Blockade at the neuromuscular junction leads to muscle weakness and respiratory depression caused by interference with the function of the diaphragm and intercostal muscles.
d. Atropine, a muscarinic receptor blocker, would be an effective antagonist, as would neostigmine, a cholinesterase inhibitor.
e. Pilocarpine and isoflurophate are cholinomimetics and can be antagonized by atropine; the effects of tubocurarine can be inhibited by neostigmine. Diazoxide, a vasodilator, would cause tachycardia, rather than bradycardia.