Which substance is known to slow down the respiratory centers in the brain and can lead to overdose?

Heroin

Heroin intake significantly interferes with social and occupational functioning. Most abusers further develop a dependence on heroin, revolving their lives around the substance, building up a tolerance for it, and experiencing a withdrawal reaction when they stop taking it. The most direct danger of heroin abuse is an overdose, which slows down the respiratory centres in the brain, almost paralysing breathing, and in many cases causing death.