Which of the following neurotransmitters are present in both CNS and peripheral nervous system? (Select All that Apply.)

A. Oxytocin is primarily a hormone and neurotransmitter in the central nervous system. It plays roles in social bonding, reproduction, and maternal behaviors but is not a primary neurotransmitter in the peripheral nervous system (PNS). B. Norepinephrine functions as a neurotransmitter in both the CNS and PNS. In the CNS, it is involved in arousal, attention, and mood regulation. In the PNS, norepinephrine is a major neurotransmitter of the sympathetic nervous system, mediating the "fight or flight" response through effects on the heart, blood vessels, and other organs. C. Acetylcholine is present in both the CNS and PNS. In the CNS, it contributes to learning, memory, and attention, while in the PNS, it is the primary neurotransmitter of the somatic nervous system (stimulating skeletal muscles) and the parasympathetic nervous system (controlling smooth muscles and glandular activity). D. Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the CNS but is not a significant neurotransmitter in the PNS. Its function is largely restricted to modulating neuronal excitability within the brain and spinal cord.