Indirect-acting refers to a type of drug or substance that does not directly bind to its target receptor but instead influences the activity of other molecules or systems in the body. These substances often enhance or inhibit the release of neurotransmitters or hormones, leading to a secondary effect on the target cells. For example, in the context of pharmacology, indirect-acting agents can increase the levels of certain neurotransmitters, such as dopamine or serotonin, by preventing their breakdown or reuptake. This mechanism can be beneficial in treating conditions like depression or attention deficit hyperactivity disorder (ADHD).