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Heart rate response by "drug X' alone and when given pretreatment with the listed drugs:
(Pretreatment with)........ ("Drug X" HR response)
NONE.....................................Decr
Mecamylamine....................... NO change from normal HR
Prazosin................................ NO change from normal HR
Atropin.................................. NO change from normal HR
Propronolol............................ Decr
Identify the "Drug X"
A-Methoxamine
B-Epinephrine
C-Physostigmine
D-Norepinephrine
E-Acetylcholine
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If propranolol decrease the HR -means the agonist has to have the same receptors B1 and B2 .
The ONLY one with both B1 and B2 is EPI...
NE has only B1 beside the alfa,but propranolol will not decrease .
W/o much thinging I will go with EPI..
Antonella
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This is how it is for "Epinephrine"
(Pretreatment with)........ ("Drug X" HR response)
NONE.....................................Incr
Mecamylamine....................... Incr
Prazosin................................ Incr
Atropin.................................. Incr
Propronolol............................ NO change from normal HR
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Acetylcholine slows the heart rate when functioning as an inhibitory neurotransmitter. However, acetylcholine also behaves as an excitatory neurotransmitter at neuromuscular junctions.
Methoxamine is an α1-adrenergic receptor agonist,[1] similar in structure to phenylephrine and 2,5-DMA. It induces vasoconstriction of skin and splanchnic blood vessels, thereby increasing peripheral vascular resistance and raising mean arterial blood pressure. Because of its hypertensive effects, it may evoke a compensatory reflex bradycardia via the baroreceptors.
so if we give methoxamine with propranol bradycardia will still persist as after dec the bp due to methoxamine propranol will itself cause bradycardia instead the Q says that there is normal hr.
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"A" is correct
Thank u all.
