Olfactory cues from an oxytocin-injected male rat can induce anti-nociception in its cagemates.

We recently demonstrated an olfactorily induced tail skin temperature drop in saline-injected rats exposed to an oxytocin-injected cagemate, an effect abolished by olfactory impairment. Treatment with oxytocin may induce both nociceptive and anti-nociceptive effects. The contrasting effects likely depend on the model and dosage used. Here we report an increased hindpaw withdrawal latency in response to nociceptive heat following the subcutaneous administration of oxytocin (1 mg/kg). An increased withdrawal response latency was also found in the untreated cagemates of an oxytocin-treated rat. The anti-nociceptive effect was abolished in oxytocin-antagonist-injected cagemates. Our results suggests that an olfactorily induced oxytocinergic mechanism is activated in the cagemates of an oxytocin-injected rat promoting anti-nociception.