Why does high level of atropine cause vasodilation?

Atropine is an anticholinergic drug that blocks the muscarinic cholinoreceptors of the parasympathetic nervous system. One of the effects of parasympathetic stimulation is vasodilation, so blocking these receptors can lead to vasoconstriction. However, at high doses, atropine can cause vasodilation due to its antihistamine and antiserotonin effects. Histamine and serotonin are both vasodilators, so blocking their receptors can lead to vasoconstriction. However, at high doses, atropine can block the receptors for these substances, leading to vasodilation. Additionally, atropine can cause the release of catecholamines, such as epinephrine and norepinephrine, which can also cause vasodilation.