The action of opioid on the hyperpolarization-activated cation current (Ih) in substantia gelatinosa neurons were investigated by using whole-cell voltage-clamp recording in rat spinal brain slices. Hyperpolarizing voltage steps revealed slowly activating currents in a subgroup of neurons. The half-maximal activation and the reversal potential of the current were compatible to neuronal Ih. DAMGO (1 muM), a selective-opioid agonist, reduced the amplitude of Ih reversibly. This reduction was dose-dependent and was blocked by CTOP (2 muM), a selective mu-opioid antagonist. DAMGO shifted the voltage dependence of activation to more hyperpolarized potential. Cesium (1 mM) or ZD 7288 (100 muM) blocked Ih and the currents inhibited by cesium, ZD 7288 and DAMGO shared a similar time and voltage dependence. These results suggest that activation of mu-opioid receptor by DAMGO can inhibit Ih in a subgroup of rat substantia gelatinosa neurons.
Animals ; Brain ; Cesium ; Enkephalin, Ala(2)-MePhe(4)-Gly(5)- ; Neurons* ; Rats* ; Substantia Gelatinosa*

Epidural injection of 2.0 mg morphine with distilled water or 0.9 % normal saline 10 ml were given to a bladder cancer patient with severe chronic intraetable pain which radiated from low abdomen to gluteal and low leg region. The patient had absolute pain relief which began 2~3 minutes to onset, with 3~5 minutes of peak of action and was effective for 20~25 hours (mean 24 hours) without complications or continuous care as an ambulatory patient. It is suggested that the morphine reached the subarachinoid space through the membrane and produced its effect by direct action on the specific opiate receptors in the substantia gelatinosa of the posterior horn of the spinal cord.
Abdomen ; Animals ; Horns ; Humans ; Injections, Epidural ; Leg ; Membranes ; Morphine* ; Receptors, Opioid ; Spinal Cord ; Substantia Gelatinosa ; Urinary Bladder Neoplasms ; Water

The KA1 kainate receptor (KAR) subunit in the substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been implicated in the processing of nociceptive information from the orofacial region. This study compared the expression of the KA1 KAR subunit in the SG of the Vc in juvenile, prepubescent and adult mice. RT-PCR, Western blot and immunohistochemistry analyses were used to examine the expression level in SG area. The expression levels of the KA1 KAR subunit mRNA and protein were higher in juvenile mice than in prepubescent or adult mice. Quantitative data revealed that the KA1 KAR subunit mRNA and protein were expressed at levels approximately two and three times higher, respectively, in juvenile mice than in adult mice. A similar expression pattern of the KA1 KAR subunit was observed in an immunohistochemical study that showed higher expression in the juvenile (59%) than those of adult (35%) mice. These results show that the KA1 KAR subunits are expressed in the SG of the Vc in mice and that the expression level of the KA1 KAR subunit decreases gradually with postnatal development. These findings suggest that age-dependent KA1 KAR subunit expression can be a potential mechanism of age-dependent pain perception.
Age Factors ; Animals ; Gene Expression Profiling ; *Gene Expression Regulation, Developmental ; Mice ; Receptors, Kainic Acid/*metabolism ; Substantia Gelatinosa/*metabolism

Caudal narcotic analgesia was assessed after the injection of 3mg morphine diluted in 30ml(physiologic) saline into the sacral canal in 15 patients after upper abdominal surgery, in 20 patients after lower abdominal surgery under general anesthesia, and in 20 patients after perianal surgery under caudal block. Pain relief was evaluated by the subsequent need for systemic analgesics. All cases had considerable relief from pain and the morphine was effective for 12 or more hours. There were no significant differences between pain relief of the upper abdominal and lower abdominal surgery group, upper abdomianl and perianal surgery group, and lower abdominal and perianal surgery group (p>0.05, p>0.05, p>0.05). It is suggested that the morphine, which was administered into the sacral, cannal, reached the subarachnoid space and produced it's effect by direct action on the specific opiate receptors in the substantia gelatinosa of the posterior horn cell of the spinal cord. Consequently, whether analgesia from epidural narcotics appears to be segmental in distribution or not is still in controveray.
Analgesia ; Analgesics ; Anesthesia, General ; Humans ; Morphine* ; Narcotics ; Pain, Postoperative* ; Posterior Horn Cells ; Receptors, Opioid ; Spinal Cord ; Subarachnoid Space ; Substantia Gelatinosa

Epidural injection of 2-4mg morphine for 7-14 days were given to 18 patients with severe chronic pain. All cases except 2 arachnoiditis had considerable amelioration of pain, which commenced within 2-3min, reached a peak in 10-20min, and was effective for 6-72 hours. Using sensory evoked potentials(SEP) examination for pre-and post-morphine epidural infusion in 18 pain patients, we found the morphine inhibited the action of spinal pain receptor system. It is suggested that morphine reached the subarachnoid space and produced its effect by direct action on the specific opiate receptors in the substantia gelatinosa of the posterior horn cell of the spinal cord.
Arachnoid ; Arachnoiditis ; Chronic Pain* ; Humans ; Injections, Epidural ; Morphine* ; Nociceptors ; Posterior Horn Cells ; Receptors, Opioid ; Spinal Cord ; Subarachnoid Space ; Substantia Gelatinosa

OBJECTIVETo investigate the effect of minocycline on hyperpolarization-activated current (Ih) in the substantia gelatinosa (SG) neurons in rat spinal dorsal horn.

METHODSIn vitro spinal cord transverse slices were prepared from 3-5-week-old male Sprague-Dawley rats. Using whole-cell patch clamp technique, Ih currents were recorded before and after bath application of minocycline (1-300 µmol/L) to the SG neurons.

RESULTSIh currents were observed in nearly 50% of the recorded neurons, and were blocked by Ih blocker CsCl and ZD7288. Minocycline rapidly and reversibly reduced the amplitude of Ih and decreased the current density in a concentration-dependent manner with an IC50 of 34 µmol/L.

CONCLUSIONMinocycline suppresses the excitability of SG neurons through inhibiting the amplitude and current density of Ih and thereby contributes to pain modulation.

Animals ; Male ; Minocycline ; pharmacology ; Neurons ; drug effects ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Substantia Gelatinosa ; cytology

The lamina II, also called the substantia gelatinosa (SG), of the trigeminal subnucleus caudalis (Vc), is thought to play an essential role in the control of orofacial nociception. Glycine and serotonin (5-hydroxytryptamine, 5-HT) are the important neurotransmitters that have the individual parts on the modulation of nociceptive transmission. However, the electrophysiological effects of 5-HT on the glycine receptors on SG neurons of the Vc have not been well studied yet. For this reason, we applied the whole-cell patch clamp technique to explore the interaction of intracellular signal transduction between 5-HT and the glycine receptors on SG neurons of the Vc in mice. In nine of 13 neurons tested (69.2%), pretreatment with 5-HT potentiated glycine-induced current (I(Gly)). Firstly, we examined with a 5-HT₁ receptor agonist (8-OH-DPAT, 5-HT(1/7) agonist, co-applied with SB-269970, 5-HT₇ antagonist) and antagonist (WAY-100635), but 5-HT₁ receptor agonist did not increase IGly and in the presence of 5-HT₁ antagonist, the potentiation of 5-HT on I(Gly) still happened. However, an agonist (α-methyl-5-HT) and antagonist (ketanserin) of the 5-HT₂ receptor mimicked and inhibited the enhancing effect of 5-HT on I(Gly) in the SG neurons, respectively. We also verified the role of the 5-HT₇ receptor by using a 5-HT₇ antagonist (SB-269970) but it also did not block the enhancement of 5-HT on I(Gly). Our study demonstrated that 5-HT facilitated I(Gly) in the SG neurons of the Vc through the 5-HT₂ receptor. The interaction between 5-HT and glycine appears to have a significant role in modulating the transmission of the nociceptive pathway.
Animals ; Glycine ; Mice ; Neurons ; Neurotransmitter Agents ; Nociception ; Patch-Clamp Techniques ; Receptors, Glycine ; Serotonin ; Signal Transduction ; Substantia Gelatinosa

Nitric Oxide (NO) is an important signaling molecule in the nociceptive process. Our previous study suggested that high concentrations of sodium nitroprusside (SNP), a NO donor, induce a membrane hyperpolarization and outward current through large conductances calcium-activated potassium (BKca) channels in substantia gelatinosa (SG) neurons. In this study, patch clamp recording in spinal slices was used to investigate the sources of Ca2+ that induces Ca2+-activated potassium currents. Application of SNP induced a membrane hyperpolarization, which was significantly inhibited by hemoglobin and 2-(4-carboxyphenyl) -4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide potassium salt (c-PTIO), NO scavengers. SNP-induced hyperpolarization was decreased in the presence of charybdotoxin, a selective BKCa channel blocker. In addition, SNP-induced response was significantly blocked by pretreatment of thapsigargin which can remove Ca2+ in endoplasmic reticulum, and decreased by pretreatment of dentrolene, a ryanodine receptors (RyR) blocker. These data suggested that NO induces a membrane hyperpolarization through BKca channels, which are activated by intracellular Ca2+ increase via activation of RyR of Ca2+ stores.
Animals ; Calcium* ; Charybdotoxin ; Endoplasmic Reticulum ; Humans ; Membranes ; Neurons* ; Nitric Oxide ; Nitroprusside ; Potassium ; Rats* ; Ryanodine Receptor Calcium Release Channel ; Ryanodine* ; Substantia Gelatinosa* ; Thapsigargin ; Tissue Donors

After the identification by Snyder of specific opiate receptors it the substantia gelatinosa of the posterior horn of the spinal cord, Behar et al. reported that small doses of epidural morphine are effective in treatment of acute and chronic pain. We have administered 3~5 mg of epidural morphine as a single dose with 1.5~2 % lidocaine to 40 patients as a continuous lumber epidural anesthesia and to 20 patients as a single caudal anesthesia. All the patients had remarkable relief of pain and we can confirm that there was no loss of sensation to temperature, touch or pinprick. However the dosage (3. 4 or 5 mg) of morphine administrated did not affect the duration of postoperative pain relief. Arterial blood pressure and heart rate were measured up to 15 minutes after morphine injection at 5 minutes intervals, but were not significantly changed. PaO2, PaCO2 pH and base excess were also not significantly changed.
Anesthesia, Caudal ; Anesthesia, Epidural ; Animals ; Arterial Pressure ; Chronic Pain ; Heart Rate ; Horns ; Humans ; Hydrogen-Ion Concentration ; Lidocaine ; Morphine* ; Pain, Postoperative* ; Receptors, Opioid ; Sensation ; Spinal Cord ; Substantia Gelatinosa

In an attempt to relieve postoperative pain after lumbar epidural anesthesia, a small dose of morphine with lidocaine was administered into the lumbar epidural space. It is suggested that the morphine reaehed the subarachnoidal space and produced its effect by direct action on the specific opiate receptors in the substantia gelatinosa of the posterior horn of the spinal cord. Epidural anesthesia was done in l25 cases from June 1979 through March 1980. These cases were divided into two groups (Control group and Morphine group). The Control group was 46 cases which were injected with 2% lidocaine, and the Morphine group was 79 cases which west injected with 2% lidocaine and morphine (3. 5~6. 5mg). 0.1% epinephrine 0.1mL was mixed to each 10ml of 2% lidocaine in all of both groups, The results of this study were as follows: 1) The cases complaining pain within 12 hours after epidural anesthesia were 36/46(78.2 %) in the Control group and 11/79(13.9%) in the Morphine group. 2) A variable single dose of morphine did not affect the duration of postoperative pain relief. 3) The time of recovery of spontaneous voiding was similar in Control and Morphine groups. Within 24 hours, spontaneous voiding was recovered in 34/46(73,9%) of the Control group and in 64/79(81.0%) of the Morphine group. 4) Blood pressure changed a little within 30 minutes after epidural anesthesia in both groups(56.5% in the Control group and 54.4% in the Morphine group). 5) Complications were similar in both groups except for nausea and vomiting, which occurred more in the Morphine group(8.9% & 7. 6) than in the control group (4.4% & none).
Anesthesia, Conduction* ; Anesthesia, Epidural ; Animals ; Blood Pressure ; Clinical Study* ; Epidural Space ; Epinephrine ; Horns ; Lidocaine ; Morphine* ; Nausea ; Pain, Postoperative* ; Receptors, Opioid ; Spinal Cord ; Substantia Gelatinosa ; Vomiting