Nocistatin and nociceptin/orphanin FQ (N/OFQ) are two neuropeptides which may have opposite effects in several biological functions but their neuro-anatomical sites of interaction are not fully clear. We investigated interaction between the effect of intracerebroventricular (i.c.v.) injection of nocistatin and N/OFQ, on c-Fos expression in the mouse thalamus, using c-Fos immunohistochemistry. We found that co-injection of nocistatin with N/OFQ significantly modulates c-Fos expression in the thalamus. The present study strongly suggests that "Nocistatin-Nociceptin" interaction system in the thalamus may be the promising neuromodulatory sites in the investigation of unlocking their possible therapeutic circuit in nociception, memory and anxiety.
The study on the efficacy of oral analgesics reported that no single class of drug is effective in post-surgical dental pain. Pain following removal of third molar is most commonly used and widely accepted acute pain model for assessing the analgesic effect of drugs in humans. Reports demonstrated that analgesic efficacy in the human dental model is highly predictive. The high incidence of false-negative findings in analgesic investigations hinders the process of molecular discovery. Molecular mechanism of post-surgical pain is not known. More importantly, the animal model for postoperative dental pain is not well established. In an attempt to discover an effective post-surgical dental pain blocker with acceptable side effects, it is essential to elucidate the molecular mechanism of post-operative dental pain. The present study investigated mandibular molars extraction in rat as an animal model for the post-operative dental pain in central nervous system. Using c-Fos immunohistochemistry, we demonstrated that pre administration of GBP (150 mg/kg. i.p) significantly (p< 0.01) neutralized the surgical molar extraction induced c-Fos expression bilaterally in rat hypothalamus. Present results indicate that pain after surgical molar extraction might follow novel neural pathways therefore difficult to treat with existing anti-nociceptive drugs.
A growing body of evidence suggests the existence of a functional interaction between gabapentin (GBP)-morphine system. However, the neuro-anatomical sites and molecular mechanism of action of gabapentin-morphine interaction to prevent and reverse morphine side effects as well as enhancement of the analgesic effect of morphine is not clear. Therefore, we examined the combined effects of GBP-morphine on acute morphine-induced c-Fos expression in rat nucleus accumbens. The combined effect of GBP-morphine was examined by means of c-Fos immunohistochemistry. A single intraperitoneal injection (i.p.) of morphine (10 mg/kg), saline (control), and co-injection of GBP (150 mg/kg) with morphine (5 mg/kg) was administered under anesthesia. The deeply anesthetized rats were perfused transcardially with 4% paraformaldehyde 2 h after drugs administration. Serial 40 μm thick sections of brain were cut and processed by immunohistochemistry to locate and quantify the sites and number of neurons with c-Fos immunoreactivity. Detection of c-Fos protein was performed using the peroxidase-antiperoxidase detection protocol. The present study demonstrated that, administration of GBP (150 mg/kg, i.p.) in combination with morphine (5 mg/kg, i.p.) significantly (p < 0.01) attenuated the acute morphine (5 mg/kg, i.p.)-induced c-Fos expression in the rat nucleus accumbens shell. Present results showed that GBP-morphine combination action prevented the acute morphine-induced c-Fos expression in rat nucleus accumbens. Moreover, this study provides first evidence of neuro-anatomical site and that GBP neutralized the morphine-induced activation of rat nucleus accumbens shell.