Final answer:
Electrical stimulation of the periaqueductal gray in animals can have various effects, such as regulating heart rate, controlling pain, and modulating behavior.
Step-by-step explanation:
Electrical stimulation of the periaqueductal gray in animals results in the activation of parasympathetic central neurons in the Edinger-Westphal nucleus of the midbrain. This activation can have various effects on different physiological functions, such as regulating heart rate, controlling pain, and modulating behavior. For example, in some animal studies, electrical stimulation of the periaqueductal gray has been shown to induce analgesia, reducing pain perception.