Electrical stimulation of the periaqueductal gray (PAG) produces __________. analgesia acetylcholine serotonin pain

### a. analgesia

## Step1: Understanding the question### The question is asking about the effect of electrical stimulation on the periaqueductal gray (PAG). The PAG is a part of the brain that is involved in the modulation of pain.## Step2: Identifying the role of PAG### The PAG is known to play a role in the modulation of pain. It is involved in the control of pain perception and can produce analgesia, which is the relief from pain.## Step3: Answering the question### Given the role of the PAG in pain modulation, it is logical to conclude that electrical stimulation of the PAG would produce analgesia.