oxide have been known to vary, based on several factors, including settings and individual differences; however, from his discussion, Jay (2008) suggests that it has been reliably known to induce the following states and sensations: Intoxication Euphoria/dysphoria Spatial disorientation Temporal disorientation Reduced pain sensitivity A minority of users also will present with uncontrolled vocalisations and muscular spasms. These effects generally disappear minutes after removal of the nitrous oxide source. Anxiolytic effect In behavioural tests of anxiety, a low dose of is an effective anxiolytic, and this anti-anxiety effect is associated with enhanced activity of GABA 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 . Indeed, in humans given 30% , benzodiazepine receptor antagonists reduced the subjective reports of feeling "high", but did not alter psychomotor performance, in human clinical studies. Analgesic effect The analgesic effects of are linked to the interaction between the endogenous opioid system and the descending noradrenergic system. When animals are given morphine chronically, they develop tolerance to its pain-killing effects, and this also renders the animals tolerant to the analgesic effects of . Administration of antibodies that bind and block the activity of some endogenous opioids (not β-endorphin) also block the antinociceptive effects of . Drugs that inhibit the breakdown of endogenous opioids also potentiate the antinociceptive effects of . Several experiments have shown that opioid receptor antagonists applied directly to the brain block the antinociceptive effects of , but these drugs have no effect when injected into the spinal cord. Apart from an indirect action, nitrous oxide, like morphine also interacts directly with the endogenous opioid system by binding at opioid receptor binding sites. Conversely, α-adrenoceptor antagonists block the pain-reducing effects of when given directly to the spinal cord, but not when applied directly to the brain. Indeed, α-adrenoceptor knockout mice or animals depleted in norepinephrine are nearly completely resistant to the antinociceptive effects of . Apparently -induced release of endogenous opioids causes disinhibition of brainstem noradrenergic neurons, which release norepinephrine into the spinal cord and inhibit pain signalling. Exactly how causes the release of endogenous opioid peptides remains uncertain. Properties and reactions Nitrous oxide is a colourless gas with a faint, sweet odour. Nitrous oxide supports combustion by releasing the dipolar bonded oxygen radical, and can thus relight a glowing splint. is inert at room