Research suggests that a neurotransmitter, may be a major contributor to the development of schizophrenia.

Dopamine.

Explanation:

Dopamine is a neurotransmitter and generally excitatory in nature. Dopamine is present at the adrenal medulla and in the nerve endings as well. Dopamine is also known as prolactin-inhibiting hormone.

The dopamine acts as inhibitory neurotransmitter in the schizophrenia. The dopamine improper functioning in mesolimbic and prefrontal brain regions makes the schizophrenia condition most drastic.

Thus, the answer is dopamine.

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