TY - JOUR
T1 - Itch and analgesia resulting from intrathecal application of morphine
T2 - Contrasting effects on different populations of trigeminothalamic tract neurons
AU - Moser, Hannah R.
AU - Giesler, Glenn J.
PY - 2013/4/3
Y1 - 2013/4/3
N2 - Intrathecal application of morphine is among the most powerful methods used to treat severe chronic pain. However, this approach commonly produces itch sufficiently severe that patients are forced to choose between relief of pain or itch. The neuronal populations responsible for processing and transmitting information underlying itch caused by intrathecal application of morphine have not been identified and characterized. We describe two populations of antidromically identified trigeminothalamic tract (VTT) neurons in anesthetized rats that are differentially affected by morphine and explain several aspects of opioid-induced itch and analgesia. We found that intrathecal application of morphine increased ongoing activity of itch-responsive VTT neurons. In addition, intrathecal application of morphine increased responses to pruritogens injected into the skin and greatly heightened responses to innocuous mechanical stimuli. In contrast, the ongoing activity and responses to noxious pinches in nociceptiveVTTneurons were frequently inhibited by the same dose of morphine. These results reveal that i.t. application of morphine affects specific subpopulations of VTT neurons in ways that may produce itch, hyperknesis, alloknesis, and analgesia.
AB - Intrathecal application of morphine is among the most powerful methods used to treat severe chronic pain. However, this approach commonly produces itch sufficiently severe that patients are forced to choose between relief of pain or itch. The neuronal populations responsible for processing and transmitting information underlying itch caused by intrathecal application of morphine have not been identified and characterized. We describe two populations of antidromically identified trigeminothalamic tract (VTT) neurons in anesthetized rats that are differentially affected by morphine and explain several aspects of opioid-induced itch and analgesia. We found that intrathecal application of morphine increased ongoing activity of itch-responsive VTT neurons. In addition, intrathecal application of morphine increased responses to pruritogens injected into the skin and greatly heightened responses to innocuous mechanical stimuli. In contrast, the ongoing activity and responses to noxious pinches in nociceptiveVTTneurons were frequently inhibited by the same dose of morphine. These results reveal that i.t. application of morphine affects specific subpopulations of VTT neurons in ways that may produce itch, hyperknesis, alloknesis, and analgesia.
UR - http://www.scopus.com/inward/record.url?scp=84876002238&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84876002238&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.0216-13.2013
DO - 10.1523/JNEUROSCI.0216-13.2013
M3 - Article
C2 - 23554490
AN - SCOPUS:84876002238
SN - 0270-6474
VL - 33
SP - 6093
EP - 6101
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 14
ER -