Lead researcher Dr Fang Liu from the Centre for Addiction and Mental Health (CAMH) in Toronto previously developed a protein peptide that provided a highly targeted approach to treating depression that she hopes will have minimal side effects.
The peptide was just as effective in relieving symptoms when compared to a conventional antidepressant in animal testing.
However, the peptide had to be injected into the brain. Taken orally, it would not cross the blood-brain barrier in sufficient concentrations.
"Clinically, we needed to find a non-invasive, convenient method to deliver this peptide treatment," said Liu.
The nasal delivery system, developed by US company Impel NeuroPharma, was shown to deliver the peptide to the right part of the brain. It also relieved depression-like symptoms in animals.
"This study marks the first time a peptide treatment has been delivered through nasal passageways to treat depression," said Liu, Professor in the University of Toronto's Department of Psychiatry.
The peptide treatment interferes with the binding of two dopamine receptors - the D1 and D2 receptor complex.
Liu's team had found that this binding was higher in the brains of people with major depression. Disrupting the binding led to the anti-depressant effects.
The peptide is an entirely new approach to treating depression, which has previously relied on medications that primarily block serotonin or norepinephrine transporters.
Depression, the most common form of mental illness, is one of the leading causes of disability globally. More than 50 per cent of people living with depression do not respond to first-line medication treatment, researchers said.
The study appears in the journal Neuropsychopharmacology.


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