Vampiric kiss with effects similar to nitrogen narcosis

Question

My story has vampires in it. Within my story's universe, I want a human kissing one mouth-to-mouth to result in nitrogen narcosis-like symptoms for said human, and for said symptoms to intensify as long as the kiss is maintained.

For reference: nitrogen narcosis is caused by inhaling nitrogen gas at a high pressure. As the pressure increases, the victim - among several other symptoms - slowly looses their consciousness and ability to think clearly, up until they pass out and/or die.

Unfortunately, nitrogen narcosis won't work as an explanation for this, since I want to write a somewhat biologically plausible vampire. A form of life that's...

• compatible with Earthly biology

and

• contains nitrogen gas under many atmospheres of pressure - for instance, to be lethal, the nitrogen gas's pressure has to exceed at least 10 atmospheres -

...doesn't seem remotely (let alone "somewhat") plausible to me. Moreover, I don't think releasing a gas at 10 atmospheres of pressure within kissing range of a human - and doing under sea-level atmospheric conditions - would be safe for said human.

What biological mechanism would cause a kiss with a vampire to - as long as the kiss is held - slowly afflict the other participant with symptoms of nitrogen narcosis, and how can such a thing work without being incompatible with Earthly biology?

The nitrogen narcosis-like effect needs to wear off over a week at most and half a minute at least.

Acceptable answers can be anything that could possibly exist within the limits of Earth-based biochemistry, but please don't make ones based on non-biological technology or magic - these vampires were bioengineered, not cybernetically altered or summoned from Hell.

• Good answers will be biologically plausible, or at least not cite things like "magical knockout gas".

• Better answers will cite a specific biological mechanism, and why the answerer believes said mechanism will mimic the effects of nitrogen narcosis.

• The best answers will do all of the above, as well as specifically explain the pathophysiology of how their mechanism slowly shuts down the human brain. For instance, such an explanation for nitrogen narcosis would state that it

appears to be the direct effect of gas dissolving into nerve membranes and causing temporary disruption in nerve transmissions.

Answer 1

Just use a regular biological toxin.

There's no reason to get overwhelmed with trying to work specific elements like nitrogen gas into the vampire's biology when all you need is a regular old neurotoxin that has the same effects. The world is filled with animals, plants, and fungi with nerve-affecting properties, from opiates to hallucinogens, and any of those could plausibly develop in a living creature, since they already did.

The biggest question is how such an effect would evolve, but it makes sense for a vampire (who feeds on living blood) to produce a toxin that can render their prey dazed without killing them. It could have started as a simple pain-blocker (vampire bats and mosquitoes both produce pain-dulling chemicals in their saliva so their sleeping prey doesn't react when they are bitten), similar to opium which works by blocking nerve transmissions.

If that nerve blocker becomes stronger, it could develop into a toxin that slows down the entire nervous system, first helping to keep its sleeping prey asleep, and later increasing to the point where it could render prey dazed even when awake. This could evolve into the practice of maintaining control over a herd of human "cattle" and feed off of each one a small amount without killing them (and being forced to find new prey). Opiates are also addictive, which would certainly be beneficial for vampires that use them for this purpose.

Answer 2

There's a whole range of NMDA receptor antagonist chemicals out there, which cover a number of anaesthetics which are known to induce a dissociative state.

These have a whole range of effects, some of which are enjoyable and lead to recreational use of some of these pharmaceuticals (such as ketamine) but perhaps most usefully for predatory purposes:

• Ataxia and catalepsy, interfering with voluntary muscle control and co-ordination.
• Confusion, memory and cognitive impairment and amnesia.
• Derealization, where the world and events in seem to be come separated or unreal.
• Analgesia and unconsciousness.

This combination of a euphoric high, loss of muscle co-ordination and a general unwillingness or inability to fight back followed by the possibility of being unable to remember what happened at all seems ideal for vampirism purposes.

Whilst L.Dutch's suggestion of nitrous oxide is an NMDA receptor antagonist (and was in fact my first thought of how to answer this question, but I was too slow, so L.Dutch got my +1 instead) there are others which are much stronger with much more pronounced effects. People on high-dose nitrous might giggle a lot and forget what they're doing but the effects are shallow and quickly shrugged off and memory effects are limited or absent. By comparison, someone deep in the k-hole isn't going to be shrugging anything off for some time.

Answer 3

Your vampires might be exhaling nitrous oxide (aka laughing gas) during the kiss.

Recreational inhalation of nitrous oxide, with the purpose of causing euphoria and/or slight hallucinations, began as a phenomenon for the British upper class in 1799, known as "laughing gas parties".

Starting in the nineteenth century, widespread availability of the gas for medical and culinary purposes allowed the recreational use to expand greatly throughout the world. In the United Kingdom, as of 2014, nitrous oxide was estimated to be used by almost half a million young people at nightspots, festivals and parties.

In this way the more the kissed one is kissed, the more becomes intoxicated.

Note that at higher doses the gas acts as an analgesic, which might be a good thing for a vampire wanting to have lunch.