Do Substances Affect the Brain?

Any substance tends to activate the brain, right? It doesn't actually like create new neurocircuitry. So for example, when I use cocaine, the reason it's so addictive is because it's activating circuitry that's already there. Even in the case of DMT, we know that, for example, DMT activates 5-HT2A, a particular serotonergic receptor.