Adrenaline drugs blocking 3-adrenoceptor

Adrenaline, noradrenaline Beta-adrenoceptor blocking drugs Potentiation of hypertensive effect. 

Sympatholytic drugs are a group of drugs, which decrease the activity of the sympathetic nervous system, mainly by blocking the action of adrenaline and noradrenaline at adrenoceptors. 

If one set of these responses can be blocked (antagonised) by a drug that does not affect the other responses (e.g. propranolol blocks the increase in heart rate produced by adrenaline, but not the dilation of the pupil evoked by adrenaline) then this is good evidence that adrenoceptors in the pupil are not the same as those in the heart. 

These drugs selectively block the P-adrenoceptor effects of noradrenaline (norepinephrine) and adrenaline (epinephrine). They may be pure antagonists or may have some agonist activity in addition (when they are described as partial agonists). 

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