Atropine sulfate monohydrate (Atropine sulfate hydrate), the sulfate salt of atropine, is a competitive muscarinic acetylcholine receptor antagonist.

mAChR:2.5 nM

Atropine increases the release of the neurotransmitter dopamine into the superfusate in vitro at 100-500 mM and into the vitreous in vivo at 250 mg. Atropine induces spreading depression (SD) in the in vitro preparation. Atropine reduces the ERG b- and d-wave, leads to damped oscillations of RPE potentials, and reverses the ERG c-wave. Atropine suppresses myopia only at doses at which severe nonspecific side effects are observed in the retina. [1]

Atropine (1.0 mg/kg, i.p.), but not methylatropine (1.0 mg/kg, i.p.), prevents the enhancement of retention induced by both doses of the anticholinesterase when given immediately after training in mice. [2] Atropine administration effectively prevents bradycardia and second-degree heart block but induces pulsus alternans and hypertension in dogs. [3] Atropine has no effect on handling-induced acetylcholine output in the presence of 10 nM neostigmine, but causes greater and longer increases in the presence of 100 nM and 1000 nM neostigmine in rats. [4] Atropine not only blocks the rapid eye movement (REM) sleep increases induced by CGS but it also tends to decrease REM sleep compared to atropine preceding saline in rats. [5] Atropine decreases the time to exhaustion by 67% in intact rats and by 96.2% in adrenodemedullated (ADM) and also reduces the exercise-induced pituitary prolactin (PRL) release in both intact (50%) and ADM rats (90%). [6]