This situation arose in the current book I am reading and
I want to know your views on this topic.

Suppose that certain experiments are thought to be needed to develop better means of coping with an extreme pain in humans. These experiments would involve performing a variety of procedures that would be very painful to the experimental subjects. The subjects would have to be vertebrates. Species closer to humans in evolutionary terms might give more meaningful results, but it is not known exactly what traits of laboratory animals are most relevent. Because the information about the neutral response would be crucial, subjects would receve no pain medication. The subjects would be temporarily paralyzed to keep them from flailing about.

What, if any, species would it be ethically acceptable to use in such experiments? Is it morally relevent whether the subjects are mammals?

Would intelligence of members of that species be morally relevant to the decision, and if so, how?

Would the presence or absence of a complex social system in which members care for other members of the species be a morally relevant factor to consider?

Would it be morally relevant that one canidate species resembled humans closely?

Would it be relevant that some particular individuals had once been human pets? If so, would it be better or worse to use those individuals?

What do you think?