**Core Concept**
The relief of pain by massage and application of liniments to painful areas in the body is attributed to the stimulation of the gate control theory of pain, which involves the activation of certain nerve fibers that inhibit the transmission of pain signals to the brain. This phenomenon is mediated by the release of endogenous opioids and other neurotransmitters.

**Why the Correct Answer is Right**
The gate control theory of pain, proposed by Ronald Melzack and Patrick Wall, suggests that certain nerve fibers can modulate the transmission of pain signals to the brain. Massage and application of liniments stimulate the activation of large-diameter A-beta nerve fibers, which are non-nociceptive in nature. These fibers release neurotransmitters such as substance P, which inhibits the transmission of pain signals to the brain via the activation of inhibitory interneurons. This results in the relief of pain.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the underlying mechanism of pain relief by massage and application of liniments. While the release of endorphins may play a role in pain relief, it is not the primary mechanism involved in the gate control theory of pain.
* **Option B:** This option is incorrect because it is a distractor and does not accurately describe the mechanism of pain relief by massage and application of liniments. The release of histamine is not directly involved in the gate control theory of pain.
* **Option D:** This option is incorrect because it is a distractor and does not accurately describe the mechanism of pain relief by massage and application of liniments. The release of prostaglandins is not directly involved in the gate control theory of pain.

**Clinical Pearl / High-Yield Fact**
The gate control theory of pain is an important concept in pain management, and understanding its mechanisms can help clinicians develop effective treatment strategies for patients with chronic pain.

**Correct Answer:** C.