Registered Practical Nurse (RPN) Practice Test

What is the most common nociceptive transmitter released in response to noxious stimuli?

1. Adrenaline

2. Substance P

3. Dopamine

4. Serotonin

The correct answer is: Substance P

Substance P is recognized as one of the most common nociceptive transmitters involved in the transmission of pain signals. It is found primarily in the central and peripheral nervous systems and plays a crucial role in pain perception by facilitating the communication of pain-related signals from sensory neurons to the spinal cord and brain. When noxious stimuli — such as injury or inflammation — are detected, substance P is released from primary afferent nerve fibers. This release contributes to sensations of pain and can also enhance the inflammatory response, magnifying the perception of pain. The presence of substance P in areas such as the dorsal horn of the spinal cord is critical for the development of pain pathways and for central sensitization, where neurons become hyper-responsive, leading to increased pain sensitivity. The other substances mentioned have different primary roles in the body. Adrenaline, also known as epinephrine, is primarily involved in the fight-or-flight response and not directly associated with nociceptive signaling. Dopamine functions mainly in the brain’s reward system and motor control rather than pain transmission. Serotonin is primarily known for its role in mood regulation and can influence pain but is not the primary transmitter in nociception like substance P.