1. E. The principal neurotransmitter released from preganglionic nerve terminals in all autonomic ganglia is acetylcholine. It acts on the postganglionic cell body to activate a nicotinic-cholinergic receptor resulting in a fast EPSP. Dopamine or norepinephrine or both are the mediators released from SIF cells or interneurons. Neuropeptide Y is a peptide neurotransmitter. Angiotensin and serotonin are modulatory mediators. These last three contribute to the late very slow EPSP.
2. C. The slow EPSP results from activation of muscarinic-cholinergic receptors on SIF cells or in-
terneurons, which release norepinephrine or dopamine from their terminals. These catecholamines then cause a slow IPSP in the ganglionic cell body. Therefore, both the slow EPSP and subsequent slow IPSP would be prevented by the muscarinic antagonist atropine. Prazosin is an ar adrenergic antagonist; sumatriptan is a serotonin 5HT1D agonist; losartan is an angiotensin receptor antagonist; and chlorpromazine is a dopamine antagonist. Only atropine would block both the slow EPSP and the slow IPSP.
3. B. The receptor contributing to the slow EPSP is a muscarinic-cholinergic receptor and is activated by ACh. The nicotinic-cholinergic receptor mediates the fast EPSP, an a-receptor may mediate the slow IPSP, and a P2X receptor and a (3-adrenergic receptor do not appear to be involved in the complex action potentials seen at autonomic ganglia.
4. C. Trimethaphan is a ganglionic blocking agent that will lower blood pressure very rapidly. Hydralazine is a vasodilator; hydrochlorothiazide and spirono-lactone are diuretics; and methyldopa is a sympa-tholytic acting in the central nervous system. All of these drugs are used clinically as antihypertensive agents. None work as rapidly as trimethaphan. Clinically, however, either nitroprusside or clonidine is used much more commonly than trimethaphan in this situation.
5. E. The effect of ganglionic blockade depends upon the predominant autonomic tone exerted within various organ systems. Since the activity of the parasympathetic nervous system predominates in the eye, the effect of ganglionic blockade is mydriasis, not miosis. Similarly, stimulation of the genital tract and urinary retention would be decreased. Since sympathetic nervous system activity predominates in blood vessels and the ventricles, vasodila-tion and a decreased cardiac output would follow ganglionic blockade.
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