Final answer:
The false statement regarding vertebrate neurotransmitters is that many receptors for biogenic amines mediate fast ionic responses in the CNS. Option 2 is correct.
Step-by-step explanation:
In regard to vertebrate neurotransmitters, the false statement among the options provided is Statement 2: "In the CNS, many receptors for biogenic amines mediate fast ionic responses." Biogenic amines include neurotransmitters like dopamine and serotonin, which are derived from amino acids but no longer have the carboxyl groups and thus are not amino acids themselves.
While biogenic amines do have receptors that can mediate ionic responses, they are more commonly known for their role in modulating various cellular functions, such as gene transcription and metabolic processes, rather than fast synaptic ionic responses.
Most fast synaptic responses are mediated by amino acid neurotransmitters, such as glutamate and GABA, which bind to ionotropic receptors leading to rapid changes in ion flow across the neuronal membrane. Glutamate is particularly noted for being the principal excitatory neurotransmitter in the CNS, functioning through ionotropic receptors such as AMPA, NMDA, and kainate receptors, which facilitate fast excitatory transmission.
The other statements provided as options are all generally true: Statement 1 notes that most synapses in the CNS use amino acid neurotransmitters like glutamate and GABA, Statement 3 is correct in saying that biogenic amines are found in relatively few neurons in the CNS, Statement 4 correctly states that a neuroactive peptide may be co-released with other neurotransmitters, and Statement 5 is also true by indicating that peptides are present in a substantial number of CNS neurons.