Surgery Godfather

Chapter 2185: Chapter 1433: Monkey’s Pain Sensation Test

By the third week post-surgery, M7’s recovery entered a critical phase.

According to the pattern Eva observed in previous mouse experiments, this week should be the end of the "silent phase," where the original cells are slowly maturing after being activated. On the surface, there is no visible functional improvement, but significant changes are occurring on the tissue level. Scar formation begins, the expression of CTGF gradually increases, and FG-3019 should start to be effective this week.

But M7 isn’t a mouse, its injury is more severe, its spinal structure more complex, and its recovery cycle could be entirely different.

"We might need to recalibrate the time window," Eva said at the morning meeting on the seventeenth day post-surgery. Her laptop displayed M7’s daily behavior records, "Look at this indicator, the spontaneous activity frequency of M7’s right leg has been slowly increasing from the tenth day post-surgery but stopped in the past three days."

She enlarged the chart so everyone could see the curve that leveled off after climbing.

"What does this mean?" Tang Shun asked.

"It suggests that the original cells may have been activated, but the scar is starting to ’lock’ them," Eva said. "Normal nerve plasticity requires axons to pass through the injury area, but if the scar becomes too dense, the axons can’t pass through, and functions will stagnate. In mice, this stagnation period appears at the end of the third week to early in the fourth week, lasting around seven to ten days, followed by a burst of recovery. If our hypothesis is correct, M7 should experience a similar surge in two weeks."

"Two weeks?" Manstein frowned, "That means we have to wait fourteen days to know if we’re on the right track?"

"Unless we can observe histological changes without euthanizing the animal," Lina said, "but that would require live imaging, and we don’t have that equipment right now."

The meeting room fell silent for a moment. Yang Ping looked at the chart, at the curve in the plateau phase, like a diver in slow motion, suspended in mid-air, unsure when they would fall.

"We don’t need to wait for histological changes," he suddenly said, "What we need is another indicator."

"What indicator?"

"Pain!"

Everyone looked at him, Weber leaned slightly forward, like an old wolf scenting prey.

"After spinal cord injury, neuropathic pain is one of the earliest sensory functions to recover," Yang Ping said. "Because the plasticity of pain pathways is stronger than motor pathways, it responds faster to microenvironment changes. If the original cell activation strategy is really working, M7 should first recover pain perception, then touch and proprioception, and finally motor function."

"So if motor function surges in two weeks, that means pain and touch should have already recovered earlier?" Manstein asked.

"Yes! But we haven’t systematically assessed M7’s sensory function because we assume the response of primates to pain stimuli is too complex and hard to standardize, unlike humans, who can quantify their pain response to some extent."

"Maybe we can standardize it," Fritz suddenly spoke, his voice still light, but this time everyone quieted down to listen to him, "M7 is afraid of chili, use chili to test M7’s pain."

"What?" Tang Shun turned his head.

"Once I brought a chili back from the cafeteria and accidentally dropped it near a cage. After smelling it, it stepped back two steps and kept staring at the chili for a long time, refusing to approach. The next day, I brought the chili near it again, and it still avoided it."

"That’s smell, not pain," Lina said.

"Fritz insisted, "I’ve specifically studied it. By cutting the chili open and contacting the sensitive skin, it grimaced in pain. Later, after rigorous research, I found that chili could be used for primate pain assessment, and I even created a quantifiable evaluation form."

Yang Ping looked at Fritz for a few seconds, then smiled: "Fritz, you’re the strangest scientist I’ve ever met. Others use fluorescent proteins, and you use chili peppers."

Fritz’s face reddened again, but he didn’t lower his head. Instead, he looked at Yang Ping and earnestly said: "Science doesn’t always need complex things; sometimes kitchen supplies can work, as long as they’re useful."

Weber let out a short laugh.

"Fritz is right, using chili to test pain perception, though unconventional, is logically sound. The question is, is your quantification method mature? It is a monkey after all."

"We can compare two stimuli," Lina immediately responded, "One is a harmless stimulus, like a banana; the other is a harmful chemical stimulus, like capsaicin. If M7 only reacts to capsaicin and the reaction intensity increases over time, it would be well explained."

"This design is good," Eva said, "Adding a mechanical stimulus with Von Frey fibers to test mechanical pain thresholds. Although primate pain testing isn’t as standardized as it is for rodents, M7 is adapted to the operating environment, so we can try."

Yang Ping stood up and drew a table on the whiteboard, three columns and three rows. The horizontal axis was harmless stimuli, harmful chemical stimuli, and mechanical stimuli, while the vertical axis was pre-surgery baseline, early post-surgery, and the current stage.

"We need three sets of data," he said, "Baseline data to show that M7 had normal responses to capsaicin and Von Frey before the injury; data from the first three weeks post-surgery to show the injury caused sensory function loss; and then current stage data, if recovery is present, there should be changes in response thresholds."

"We didn’t test before the surgery," Tang Shun said, "M7 was trained by someone else and sent to us; we don’t have its baseline data."

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