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.