In behavioural tests of anxiety , a low dose of N
2 O is an effective anxiolytic , and this anti-anxiety effect is associated with enhanced activity of GABA A receptors, as it is partially reversed by benzodiazepine receptor antagonists . Mirroring this, animals that have developed tolerance to the anxiolytic effects of benzodiazepines are partially tolerant to N
2 O .  Indeed, in humans given 30% N
2 O , benzodiazepine receptor antagonists reduced the subjective reports of feeling "high", but did not alter psychomotor performance, in human clinical studies. 
My Vet worked the flight deck and complained of working on A-4Js who returned with oily residue that “he was told was AO by the pilots.” Let’s analyze this. A-4s were busy destroying downtown Hanoi and the Paul Doumer Bridge for the most part. We were not running Ranchhand spray ops over downtown Hanoi. Having worked in FAC, I personally know we controlled every aircraft in our area of operations. We didn’t have C-123s at 2,500 feet spraying AO while we were clearing in A-1s hot with ordnance free below 1,500 feet underneath them. What the Vet saw and probably smelled was jettisoned JP-4 (130 AVGAS w/ Kerosene). We often added kerosene, or, for that matter, any contaminated petroleum distillate, in a one-to-one mixture to AO. That was the prescribed recipe. To this day, we know categorically that no AO spray operations were conducted from carriers or any other naval vessels in the So. China Sea. Sorry, sailors. No sail.
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