Sciatica caused by pseudomyxoma peritonei

Developing a trans-multisynaptic tracer to map the neural circuit of recovered sciatic nerve after treatment with nerve growth factor

Nerve growth factor (NGF) has been shown to support the survival and differentiation of neurons. In this study, we first developed a retrograde trans-multisynaptic tracer PRV580 expressing the mCherry fluorescent protein based on pseudorabies virus Bartha strain to map the neural circuit of sciatic nerve. Secondly, the newly developed PRV580 was used to map the neural circuit of the recovering sciatic nerve upon treatment with NGF. Our results showed that red signals from PRV580 were observed in various brain regions. Among these regions, many areas of the pyramidal system and the extra-pyramidal system had been mapped, accounting for as much as 56.8 % of the total inputs. Furthermore, we found that NGF could significantly increase the ratio of total input (29.05 %) compared to PBS (3.65 %), indicating that NGF indeed can aid in the repair of injured sciatic nerve. These findings indicated that NGF has therapeutic ability for the treatment of peripheral nerve injuries and virus-based tracers can be used to monitor the recovery.

Acute pressure on the sciatic nerve results in rapid inhibition of the wide dynamic range neuronal response

Background

Acute pressure on the sciatic nerve has recently been reported to provide rapid short-term relief of pain in patients with various pathologies. Wide dynamic range (WDR) neurons transmit nociceptive information from the dorsal horn to higher brain centers. In the present study, we examined the effect of a 2-min application of sciatic nerve pressure on WDR neuronal activity in anesthetized male Sprague–Dawley rats.

Results

Experiments were carried out on 41 male Sprague–Dawley albino rats weighing 160–280 grams. Dorsal horn WDR neurons were identified on the basis of characteristic responses to mechanical stimuli applied to the cutaneous receptive field. Acute pressure was applied for 2 min to the sciatic nerve using a small vascular clip. The responses of WDR neurons to three mechanical stimuli applied to the cutaneous receptive field were recorded before, and 2, 5 and 20 min after cessation of the 2-min pressure application on the sciatic nerve. Two-min pressure applied to the sciatic nerve caused rapid attenuation of the WDR response to pinching, pressure and brushing stimuli applied to the cutaneous receptive field. Maximal attenuation of the WDR response to pinching and pressure was noted 5 min after release of the 2-min pressure on the sciatic nerve. The mean firing rate decreased from 31.7±1.7 Hz to 13±1.4 Hz upon pinching (p < 0.001), from 31.2±2.3 Hz to 10.9±1.4 Hz (p < 0.001) when pressure was applied, and from 18.9±1.2 Hz to 7.6±1.1 Hz (p < 0.001) upon brushing. Thereafter, the mean firing rates gradually recovered.

Conclusions

Our results indicate that acute pressure applied to the sciatic nerve exerts a rapid inhibitory effect on the WDR response to both noxious and innocuous stimuli. Our results may partially explain the rapid analgesic effect of acute sciatic nerve pressure noted in clinical studies, and also suggest a new model for the study of pain.