Why (and how) do certain drugs such as LSD, MDMA and BZP enlarge the pupils of the user?

Answer 1

Mydriasis is the term for excessive dilation of the pupil due to disease or drugs. To explain, there are two types of muscles that control the size of the iris: circular and radial. The former is innervated by the parasympathetic nervous system, the latter by the sympathetic nervous system. Sympathetic stimulation of Alpha 1 adrenergic receptors causes the contraction of the radial muscle, and subsequent DILATION of the iris. Mydriasis depends on this adrenaline agent. LSD, cocaine, and the like inhibit the re-uptake of NOR-ADRENALINE within a nerve synapse. As an experiment, if a solution of cocaine is dropped into the eye, noradrenaline is no longer reabsorbed by the neurons, and its levels increase. Noradrenaline, the neurotransmitter for the sympathetic nervous system, causes dilation of the pupil that may last for hours or days. Another drug known to cause mydriasis is MDMA (Ecstasy) and BZP.

Answer 2

Marilyn B gave the best answer.

Answer 3

we can just see it