Maybe the newcomer is an impostor and not a member of the family after all, or perhaps his quirks must be understood and explained before he can be accepted. But their research showed that the new peptide intensified the sense of pain. Intrigued by the possibility that there might be a subfamily of opioid molecules with effects diametrically opposite those of other members, NCRR grantee Dr. Sukhbir S. Mokha decided to investigate. Within moments of receiving a painful stimulus, an intricate network of signals springs into action inside the body, relaying the message from the source to the spinal cord and brain. Dr. Sukbir Mokha found that nociceptin, a brain peptide, apparently dampens neural responses to painful stimuli.
Trigeminal neurons sense stimuli to the face such as a pinch on the cheek.
In contrast, scientists in the two independent research groups that first studied nociceptin reported in 1995 that the peptide enhanced the response to pain when injected into the brains of mice. The Meharry researchers also found that nociceptin reduced the responses evoked by stimulation of another type of receptor called the NMDA-receptor, which plays a key role in mediating pain signals and in generating the chronic pain that follows nerve injuries or inflammation. The responses evoked by certain non-NMDA receptors were also similarly dampened. The pores open and close when neurotransmitters that are released in response to pain or other stimuli bind to receptors. According to Dr. Mokha, researchers in Sweden and Britain have also shown that nociceptin inhibits spinal cord reflexes and responses of spinal cord neurons to painful stimuli.