New class of neurotransmitters.
D000818:Animals; D004745:Enkephalins / Q000502:physiology; D006801:Humans; D018377:Neurotransmitter Agents / Q000502:physiology*; D011687:Purines / Q000502:physiology
D004745:Enkephalins; D018377:Neurotransmitter Agents; D011687:Purines