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*

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

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

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

Substantia gelatinosa (SG) neurons receive synaptic inputs from primary afferent Adelta- and C-fibers, where nociceptive information is integrated and modulated by numerous neurotransmitters or neuromodulators. A number of studies were dedicated to the molecular mechanism underlying the modulation of excitability or synaptic plasticity in SG neurons and revealed that second messengers, such as cAMP and cGMP, play an important role. Recently, cAMP and cGMP were shown to downregulate each other in heart muscle cells. However, involvement of the crosstalk between cAMP and cGMP in neurons is yet to be addressed. Therefore, we investigated whether interaction between cAMP and cGMP modulates synaptic plasticity in SG neurons using slice patch clamp recording from rats. Synaptic activity was measured by excitatory post-synaptic currents (EPSCs) elicited by stimulation onto dorsal root entry zone. Application of 1 mM of 8-bromoadenosine 3,5-cyclic monophosphate (8-Br-cAMP) or 8-bromoguanosine 3,5-cyclic monophosphate (8-Br-cGMP) for 15 minutes increased EPSCs, which were maintained for 30 minutes. However, simultaneous application of 8-Br-cAMP and 8-Br-cGMP failed to increase EPSCs, which suggested antagonistic cross-talk between two second messengers. Application of 3-isobutyl-1-methylxanthine (IBMX) that prevents degradation of cAMP and cGMP by blocking phosphodiesterase (PDE) increased EPSCs. Co-application of cAMP/cGMP along with IBMX induced additional increase in EPSCs. These results suggest that second messengers, cAMP and cGMP, might contribute to development of chronic pain through the mutual regulation of the signal transduction.
1-Methyl-3-isobutylxanthine ; Adenosine ; Animals ; Chronic Pain ; Guanosine ; Myocytes, Cardiac ; Neurons ; Neurotransmitter Agents ; Plastics ; Rats ; Second Messenger Systems ; Signal Transduction ; Spinal Nerve Roots ; Substantia Gelatinosa

In an attempt to find out the effect of epidural administration with morphine on postoperative pain relief, a small dose of morphine with a local anesthetic(lidocaine) was administered into the epidural space, either by lumbar or caudal approach. Morphine injected into the epidural space has been suggested to produce it's effect by direct action on the specific oplate receptor in the substantia gelatinosa of the posterior horn of the spinal cord. 90 patients who were anesthetized under epidural block in the Pusan Paik's Hospital, INJE Medical College, from May 1980 trhough Jan. 1981 were divided into the groups "Lidocaine alone" and "Lidocaine + Morphine". The number of patients of patients of the lumbar approach was 73 (81.1%) and of the caudal approach was 17(18.9%). The group "Lidocaine alone" numbered 45 cases which were injected with 2% lidocaine into the epidural space as an anesthetic. Group "Lidocaine + Morphine" also numbered 45 cases and received 2mg of morphine with 500 mg of 2% lidocaine as an epidural anesthetic. 0.2mg of 0.1% epinephrine was mixed to the anesthetic solution in all the above cases. The results of this study are as follows: 1) Alteration of arterial blood pressure during anesthesia was minimal within 30 minutes after injection of the epidural anesthetic in both groups. 2) Duration of postoperative pain relief in the group "Lidocaine + Morphine" was significantly extended comparing it to that in the group "Lidocaine alone". 3) Between the two groups, no significant difference was noted in recovery of spontaneous volding. 4) Complications were similar in both groups except for nausea and vomiting which occurred more frequently in the group "Lidocaine + Morphine"(8.9% and 6.7%, respectively) than in the group "Lidocaine alone" (2.2% and none, respectively). Any signs of CNS depression or neurologic sequelae were not observed.
Anesthesia ; Anesthesia, Epidural* ; Animals ; Arterial Pressure ; Busan ; Depression ; Epidural Space ; Epinephrine ; Horns ; Humans ; Lidocaine ; Morphine* ; Nausea ; Pain, Postoperative* ; Spinal Cord ; Substantia Gelatinosa ; Vomiting