Method of effecting neuroprotection using soluble neuregulin isoforms

A method of treating a subject suffering from schizophrenia, comprising intravenously administering to the subject a recombinant soluble Type I Neuregulin-1 β isoform which is an about 15 to about 35 kD N-terminal fragment of Type I Neuregulin-1 β, wherein the recombinant soluble Type I Neuregulin-1 β isoform is the first 245, 246, 247, 248, 249, or 250 amino acids of Type I Neuregulin-1 β and is administered in an amount of about 400 ng/kg to about 600 ng/kg body weight of the subject to be treated.