The Oxytocin-Induced Placebo Effect in Laboratory Animals: Implications for the Cellular and Molecular Substrates of the Placebo Response
an endogenous neuropeptide found in mammals, is produced by the paraventricular nucleus
of the hypothalamus. Its primary effects in most mammals, including rats and humans,
span a wide range of physiological functions, including social behavior and bonding.
Oxytocin is also involved in a host of ancillary effects including food intake/satiety,
sedation, and movement. Howev... read moreer, it is a peptide not known to directly stimulate
dopamine release in the brain so it can be considered a good candidate to study the role
of central dopamine in the placebo response without the apparent confounding effects of
a dopamine-releasing drug. The present study considers the role of oxytocin in inducing
a placebo response when the peptide is substituted by an inert substance over several
days. The behavioral effects assessed include food intake and locomotor activity
following either intraperitoneal oxytocin or its substitution by a saline injection. The
primary hypothesis of the study was that oxytocin decreases food intake and locomotion
in rats and that effect is also observed when oxytocin is substituted by saline after
the animal is trained to expect a neuropeptide injection. The experiment was carried out
over a 20-day trial period designed to include a baseline period at the beginning and a
"placebo" period at the end. It utilized a 1 mg/kg dose of oxytocin given to male
Sprague-Dawley rats. Results showed a modest decrease in both total movement and food
intake after both oxytocin and placebo saline sessions and indicated that a protocol
with a non-dopaminergic drug like oxytocin could potentially distinguish between strong
and weak placebo responders.
Thesis (M.S.)--Tufts University, 2017.
Submitted to the Dept. of Pharmacology & Experimental Therapeutics.
Advisor: Emmanuel Pothos.
Keyword: Pharmacology.read less