Abstract
There is evidence of the therapeutic potential of intranasal oxytocin for the treatment of pain and various psychiatric disorders, however, there is scant evidence that oxytocin reaches the brain. We quantified the concentration and distribution pattern of [125I]-radiolabeled oxytocin in the brains and peripheral tissues of rats after intranasal delivery using gamma counting and autoradiography, respectively. Radiolabel was detected in high concentrations in the trigeminal and olfactory nerves as well as in brain regions along their trajectories. Considerable concentrations were observed in the blood, however, relatively low levels of radiolabel were measured in peripheral tissues. The addition of a mucoadhesive did not enhance brain concentrations. These results provide support for intranasal OT reaching the brain via the olfactory and trigeminal neural pathways. These findings will inform the design and interpretation of clinical studies with intranasal oxytocin.
Highlights
A growing body of research highlights the potential for the neuropeptide oxytocin (OT) in the treatment of a wide range of central nervous system (CNS) disorders, spanning autism to chronic pain [1, 2]
In order to circumvent the restrictions of the blood–brain barrier (BBB), many clinical researchers have utilized the noninvasive intranasal delivery route in the hopes of enhancing OT brain penetration by bypassing the BBB [4]
Intranasal delivery of large molecular weight drugs and proteins resulted in substantial brain penetration via transport along the perivascular space of blood vessels associated with olfactory and trigeminal nerves [5]
Summary
A growing body of research highlights the potential for the neuropeptide oxytocin (OT) in the treatment of a wide range of central nervous system (CNS) disorders, spanning autism to chronic pain [1, 2]. Oral delivery of peptide therapeutics leads to limited absorption due in part to degradation in the gut, injections are not favored for chronic daily use, and both delivery methods typically result in limited CNS penetration for large molecules like OT (molecular weight = 1007.19 Da) [3]. Intranasal delivery of large molecular weight drugs and proteins resulted in substantial brain penetration via transport along the perivascular space of blood vessels associated with olfactory and trigeminal nerves [5]. Thorne et al [6] reported that intranasal, but not intravenous, delivery of radioiodinated insulin-like growth factorI (7.65 kDa) rapidly (
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