The participation of oxytocin in the abirritation of lateral habenular nucleus on normal adult rats

• Lateral habenular nucleus (LHN) may be a new target of oxytocin׳s analgesia in CNS.
• Provide new theoretical basis for the neuropeptides׳ in clinical application.
• Oxytocin may play a role in the development and repair of central nervous system.

This paper probes into the participation of different concentrations of oxytocin in the pain regulation of lateral habenular nucleus on normal adult rats. The detailed experiment steps are as follows: microinject 1.25, 2.5, and 5 nmol of oxytocin to three adult rats׳ lateral habenular nucleus, and measure the hind paw withdrawal latency (HWL) after 5, 10, 15, 20, 30, 45 and 60 min with hot plate and pressure plate test as the indicator of algesia. At the same time, another group of adult rats were injected with normal saline as a control to observe the participation of oxytocin in the pain regulation of lateral habenular nucleus. Through the oxytocin microinjection, the HWL of rats was significantly prolonged, compared with the control group. According to the experimental results, the HWL of thermo stimulation on the left paw of the rats between OT group and the control group (injected with normal saline) showed no difference (p>0.05) after a microinjection of 1.25 nmol in LHb, while the HWL of thermo stimulation on the left paw of the rats showed significant difference (p<0.01; p<0.01) after a microinjection of 2.5 and 5 nmol in LHb; The HWL of thermo stimulation on the right paw of the rats between OT group and the control group (injected with normal saline) showed significant difference, slight difference and significant difference (p<0.01; p<0.05; p<0.01) after a microinjection of 1.25, 2.5 and 5.0 nmol in LHb; The HWL of mechanical stimulation both on the left paw of the rats after a microinjection of 2.5 nmol and on the right paw of the rats after a microinjection of 5 nmol showed significant differences (p<0.01; p<0.01), and all the rest showed extremely significant differences (p<0.001). This experiment shows that oxytocin has significant abirritational effect on the lateral habenular nucleus of adult rats, which is dose dependent, especially after OT was injected for 15 min.