Final answer:
Some substances of abuse, including alcohol, cocaine, nicotine, and cannabis, have the ability to cross the blood-brain barrier and directly affect the central nervous system.
Step-by-step explanation:
Some substances of abuse can pass through the blood-brain barrier (BBB) including alcohol, cocaine, nicotine, and cannabis. The BBB is a critical structure that protects the central nervous system (CNS) by regulating the entry of compounds. However, this barrier also poses a significant challenge for drug delivery targeting the CNS. Substances such as glucose and amino acids can pass through the BBB, supporting essential brain functions, but most drugs and large molecules cannot. Specific drugs, especially those with small molecules and lipophilic properties, are able to penetrate the BBB. This is why substances of abuse like alcohol, which can influence the GABA neurotransmitter system, and cocaine, which affects dopamine neurotransmission, can have direct effects on the CNS.