• International Journal of Oral Biology
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• 제34권4호
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• pp.191-197
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• 2009

Somatostatin (SST) is a known neuromodulator of the central nervous system. The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) receives many thinmyelinated $A{\delta}$-fiber and unmyelinated C primary afferent fibers and is involved in nociceptive processing. Many studies have demonstrated that SST plays a pivotal role in pain modulation in the spinal cord. However, little is yet known about the direct effects of SST on the SG neurons of the Vc in adult mice. In our present study, we investigated the direct membrane effects of SST and a type 2 SST receptor agonist, seglitide (SEG), on the SG neurons of the Vc using a gramicidin-perforated current clamp in adult mice. The majority (53%, n = 27/51) of the adult SG neurons were hyperpolarized by SST (300 nM) but no differences were found in the hyperpolarization response rate between males and females. When SST was applied successively, the second response was smaller ($76{\pm}9.5%$, n=19), suggesting that SST receptors are desensitized by repeated application. SST-induced hyperpolarization was also maintained under conditions where presynaptic events were blocked ($75{\pm}1.0%$, n=5), suggesting that this neuromodulator exerts direct effects upon postsynaptic SG neurons. SEG was further found to induce membrane hyperpolarization of the SG neurons of the Vc. These results collectively demonstrate that SST inhibits the SG neuronal activities of the Vc in adult mice with no gender bias, and that these effects are mediated via a type 2 SST receptor, suggesting that this is a potential target for orofacial pain modulation.

• The Korean Journal of Physiology and Pharmacology
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• 제15권5호
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• pp.285-289
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• 2011

Shilajit, a medicine herb commonly used in Ayurveda, has been reported to contain at least 85 minerals in ionic form that act on a variety of chemical, biological, and physical stressors. The substantia gelatinosa (SG) neurons of the trigeminal subnucleus caudalis (Vc) are involved in orofacial nociceptive processing. Shilajit has been reported to be an injury and muscular pain reliever but there have been few functional studies of the effect of Shilajit on the SG neurons of the Vc. Therefore, whole cell and gramicidin-perfotrated patch clamp studies were performed to examine the action mechanism of Shilajit on the SG neurons of Vc from mouse brainstem slices. In the whole cell patch clamp mode, Shilajit induced short-lived and repeatable inward currents under the condition of a high chloride pipette solution on all the SG neurons tested. The Shilajit-induced inward currents were concentration dependent and maintained in the presence of tetrodotoxin (TTX), a voltage gated $Na^+$ channel blocker, CNQX, a non-NMDA glutamate receptor antagonist, and AP5, an NMDA receptor antagonist. The Shilajit-induced responses were partially suppressed by picrotoxin, a $GABA_A$ receptor antagonist, and totally blocked in the presence of strychnine, a glycine receptor antagonist, however not affected by mecamylamine hydrochloride (MCH), a nicotinic acetylcholine receptor antagonist. Under the potassium gluconate pipette solution at holding potential 0 mV, Shilajit induced repeatable outward current. These results show that Shilajit has inhibitory effects on the SG neurons of Vc through chloride ion channels by activation of the glycine receptor and $GABA_A$ receptor, indicating that Shilajit contains sedating ingredients for the central nervous system. These results also suggest that Shilajit may be a potential target for modulating orofacial pain processing.