Oxytocin is actually supposed to have the opposite effect. Oxytocin is supposed to stimulate the release of GABA, an inhibitory neurotransmitter.
Oxytocin is the hormone the allows a mother to bond with her baby, and also to produce milk. It's also the hormone that enables "pair bonding" between two mates after sex, increasing the changes they bond and stay together (evolutionary adaptive monogamy). Oxytocin is also elevated in those who take MDMA / Ecstasy, thus the "love" everyone experiences for each other when taking the drug.
Are you able to find that article and provide a link?
Generally, the anxiety after orgasm is the stimulation of the sympathetic fight-of-flight response which is part of the overall POIS series of symptoms.
There is a great thread on this forum about the "POIS Cascade" and the science behind it seems to be an over-binding of norepinephrine to the alpha 1 receptors (which are part of the sympathetic nervous system, hence the cascade).
https://poiscenter.com/forums/index.php?topic=2502.0From everything I read on this forum and beyond, the overall reaction (and continued negative feedback loop) is likely due to the continued rise in adrenaline / norepinephrine from arousal / orgasm, and subsequent lack of hormones and conversion pathways to keep this rise in check like everyone else does upon orgasm.
For those suffering more in relation to anxiety / fight-or-flight activation / euro-transmitter burnout (depression / derealization) my understanding it's too much of the inflammatory Prostaglandin E2 / COX2 and not enough Prostaglandin E1/E3 and Nitric Oxide to counter-balance. It's very likely that "low" oxytocin after orgasm is more related to POIS conditions.
For those who suffer more in the realm of "flu-like symptoms" (congestion, etc) it's more about the h1H histamine receptor binding and over-stimulation.