A volunteer receives a single dose of a ganglion-blocking drug that antagonises nicotinic receptors at all autonomic ganglia. Which combination of cardiovascular changes is expected?

• A No change in either parameter because both limbs are blocked equally
• B Hypertension with bradycardia
• C Hypertension with tachycardia
• D Hypotension with tachycardia ✓

Explanation

Blocking all ganglia abolishes sympathetic vasoconstrictor tone, dropping blood pressure. In the supine resting state the sinoatrial node is under dominant vagal restraint, so removing parasympathetic tone unmasks the intrinsic rate and heart rate rises, giving tachycardia. Option A is wrong because the two divisions exert opposite tonic effects, so equal blockade does not cancel out; the net result mirrors loss of both tones.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

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