No abstract

No abstract

Serotoninergic modulation of GABAergic mIPSCs was investigated in immature (postnatal 12-16-days old) rat CA3 pyramidal neurons using a conventional whole-cell patch clamp technique. Serotonin or 5-hydroxytryptamine (5-HT) (10 lmol/L) transiently and explosively increased mIPSC frequency with a small increase in the current amplitude. However, 5-HT did not affect the GABA-induced postsynaptic currents, indicating that 5-HT acts presynaptically to facilitate the probability of spontaneous GABA release. The 5-HT action on GABAergic mIPSC frequency was completely blocked by 100 nmol/L MDL72222, a selective 5-HT 3 receptor antagonist, and mimicked by mCPBG, a selective 5-HT 3 receptor agonist. The 5-HT action on GABAergic mIPSC frequency was completely occluded either in the presence of 200 lmol/L Cd 2+ or in the Na + -free external solution, suggesting that the 5-HT 3 receptor-mediated facilitation of mIPSC frequency requires a Ca 2+ influx passing through voltagedependent Ca 2+ channels from the extracellular space, and that presynaptic 5-HT 3 receptors are less permeable to Ca 2+ . The 5-HT action on mIPSC frequency in the absence or presence of extracellular Na + gradually increased with postnatal development. Such a developmental change in the 5-HT 3 receptor-mediated facilitation of GABAergic transmission would play important roles in the regulation of excitability as well as development in CA3 pyramidal neurons. Address correspondence and reprint requests to Il-Sung JANG, PhD, Department of Pharmacology, School of Dentistry, Kyungpook National University, 188-1, Samduk-dong, 2-Ga, Jung-gu, Daegu 700-412, Republic of Korea. E-mail: jis7619@mail.knu.ac.krAbbreviations used: [Ca 2+ ] i, intracellular Ca 2+ concentration; 5-HT, serotonin or 5-hydroxytryptamine; 8-OH-DPAT, (±)-8-hydroxy-2-dipropylaminotetralin; APV, DL-2-amino-5-phosphonovaleric acid; CNQX, 6-cyano-7-nitroquinozaline-2,3-dione disodium; CP 93129, 1,4-Dihydro-3-(1,2,3,6-tetrahydro-4-pyridinyl)-5H-pyrrolo[3,2-b]pyridine-5-one; DRG, dorsal root ganglia; K-S test, Kolmogorov-Smirnov test; mCPBG, m-chlorophenylbiguanide; MDL72222, tropanyl 3,5-dichlorobenzoate; mIPSCs, spontaneous miniature inhibitory postsynaptic currents; Ro 60-0175, (aS)-6-chloro-5-fluoro-a-methyl-1H-indole-1-ethanamine; RS 67506, 1-(4-Amino-5-chloro-2-methoxyphenyl)-3-[1-2-methylsulfonylaminoethyl-4-piperidinyl]-1-propanone; sIPSPs, spontaneous inhibitory postsynaptic potentials; TTX, tetrodotoxin; VDCC, voltage-dependent Ca 2+ channel.

Although anticonvulsant drugs that block voltage-dependent Na+ channels have been widely used for neuropathic pain, including peripheral nerve injury-induced pain, much less is known about the actions of these drugs on immature trigeminal ganglion (TG) neurons. Here we report the effects of carbamazepine (CBZ) and amitriptyline (ATL) on tetrodotoxin-resistant (TTX-R) Na' channels expressed on immature rat TG neurons. TTX-R Na+ currents (I(Na)) were recorded in the presence of 300 nM TTX by use of a conventional whole-cell patch clamp method. Both CBZ and ATL inhibited TTX-R I(Na) in a concentration-dependent manner, but ATL was more potent. While CBZ and ATL did not affect the overall voltage-activation relationship of TTX-R Na+ channels, both drugs shifted the voltage-activation relationship to the left, indicating that they inhibited TTX-R Na+ channels more efficiently at depolarized membrane potentials. ATL showed a profound use-dependent blockade of TTX-R I(Na), but CBZ had little effect. The present results suggest that both CBZ and ATL, common drugs used for treating neuropathic pain, efficiently inhibit TTX-R Na+ channels expressed on immature TG neurons, and that these drugs might be useful for the treatment of trigeminal nerve injury-induced neuropathic pain, as well as the inhibition of ongoing central sensitization, even during immature periods.

Fruit and vegetable processing industries produce substantial quantities of phenolic-rich by-products that could be potential sources of natural antioxidants. The measurement of antioxidant activity in plant materials is mostly limited to extraction-based procedures that have several limitations. In this study, a relatively new direct approach, the QUENCHER (quick, easy, new, cheap, and reproducible) procedure was applied to measure total antioxidant capacity in pomegranate fruit by-products, including peel, pith, carpellary membranes, and seeds. Freeze-dried ground samples were directly mixed with free radical solvents in a single operation rather than separating the extract from solid samples. Efficacy of the direct procedure was evaluated against a routine extraction-based procedure using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS); 2,2-diphenyl-1-picrylhydrazyl (DPPH); and ferric reducing antioxidant power assays. Pomegranate peel showed the highest total antioxidant capacity, followed by pith, carpellary membranes, and seeds. Total antioxidant capacity values determined by the direct procedure were significantly higher (P < 0.05) than those measured by the extraction procedure. The obvious advantages of the QUENCHER procedure over extraction-based procedures are that it would reduce the complexity of separating bound phenolics and antioxidant compounds, as well as the time and conditions required for unit extraction operations. The conversion of industrial waste into valuable ingredients would be advantageous for development of pomegranate supplements and added-value products.