Ji-Shuo Li

Immunocytochemical localization of μ-opioid receptor in primary afferent neurons containing substance P or calcitonin gene-related peptide. A light and electron microscope study in the rat

Co-expression of mu-opioid receptor-like immunoreactivity (MOR-LI) with substance P (SP)- or calcitonin gene-related (CGRP)-LI was observed in rat trigeminal and dorsal root ganglion neurons. In particular, MOR-LI was found in axon terminals with SP- or CGRP-LI in laminae I and II of the medullary and spinal dorsal horns. MOR may be implicated in modulation of release of SP and CGRP from primary sensory afferents.

Spatial and temporal expression of c-Fos protein in the spinal cord of anesthetized rat induced by subcutaneous bee venom injection.

In order to study central neuronal components involved in subcutaneous (s.c.) bee venom-induced persistent pain (a new tonic pain model), we use Fos immunostaining technique to study the spatial and temporal patterns of neuronal activity in the spinal cord of anesthetized rats. Following intraplantar bee venom injection, Fos-like immunoreactive (ir) neurons were only seen from L1 to S3 rostrocaudally with distinct distribution at L4-5 segments. At segments of L1-2 and S1-3, Fos-ir labelings were diffusely and symmetrically distributed on both sides of the gray matter; however, at L4-5 segments, Fos-ir neurons were densely localized in medial portion of laminae I-II, less densely in laminae V-VI and a few in laminae VII and X ipsilateral to the injection side. No Fos labeling was seen in ventral horn of the spinal cord at L4-5 segments. Fos protein began to express only within lamina I at 0.5 h, but increased over the whole dorsal horn at 1 h and reached peak labeling at 2 h after bee venom. Expression of c-Fos in laminae I-II decreased at 4 h, and completely disappeared at 24 h, however, labeling in laminae V-VI disappeared much slowly and existed even at 96 h after bee venom. Within laminae III-IV, Fos-ir neurons could not be seen at 0.5 h, but began to be seen at 1 h and appeared to exist even at 24 h after bee venom. Systemic morphine suppressed c-Fos expression dose-dependently in both superficial and deep layers of dorsal horn and the latter region was much more sensitive to morphine than the former one. The present results demonstrated that prolonged neuronal activities in superficial and deep layers of dorsal horn were essential to mediation of bee venom induced tonic pain and may have different roles in generation and/or modulation of spontaneous pain and hyperalgesia and allodynia.

Monosynaptic connections between neurons of trigeminal mesencephalic nucleus and jaw-closing motoneurons in the rat: an intracellular horseradish peroxidase labelling study.

In order to confirm the monosynaptic connections of muscle spindle-mediated jaw stretch reflexes, 8 neurons of trigeminal mesencephalic nucleus innervating masseteric muscle spindles were identified electrophysiologically and stained intracellularly with horseradish peroxidase. These axon terminals projected to ipsilateral dorsal and dorsolateral divisions of trigeminal motor nucleus and extensive premotor areas. Under electron microscope, labeled terminals made monosynaptic contacts predominantly with dendrites in the jaw-closing motoneuron pools. One labeled and many non-labeled terminals were frequently observed to converge simultaneously on one dendrite in the area. However, it was of particular interest that 28% of the labeled terminals constituted the intermediate component of axo-axodendritic synaptic triads. The present study confirmed, for the first time, monosynaptic connections between jaw-closing muscle spindle afferents and jaw-closing motoneurons. These findings also provided ultrastructural evidence for the monosynaptic excitation of muscle spindle-mediated jaw stretch reflexes which received presynaptic and postsynaptic inhibitions of the premotor neurons from other sources.

Substance P receptor (NK1)-immunoreactive neurons projecting to the periaqueductal gray: distribution in the spinal trigeminal nucleus and the spinal cord of the rat

Substance P receptor (SPR)-immunoreactive neurons projecting to the periaqueductal gray (PAG) were examined in the rat spinal trigeminal nucleus and spinal cord by a retrograde tracing method combined with immunofluorescence histochemistry. After injection of Fluoro-gold (FG) into the PAG, SPR-immunoreactive neurons labeled with FG were observed mainly in the lateral spinal nucleus and lamina I of the medullary and spinal dorsal horns and additionally in laminae V and X of the spinal cord.

The distribution and origin of axon terminals with NADPH diaphorase activity in the nucleus of the solitary tract of the rat

The distribution and origin of axon terminals containing nitric oxide synthase (NOS) were examined in the nucleus of the solitary tract (NST) of the rat by NADPH diaphorase histochemistry combined with nodose ganglionectomy. Axon terminals with NADPH diaphorase activity were densely distributed in the middle and caudal part of the NST. After removal of the nodose ganglion (NG), most of the axon terminals with NADPH activity in the NST were eliminated on the ipsilateral side. These results indicated that most of the axon terminals with NADPH diaphorase in the NST derive from the primary afferent neurons in the NG, and that NOS may be richly contained in the central terminals of NG neurons to produce nitric oxide as a transmitter.

The brain-derived neurotrophic factor is associated with alcohol dependence-related depression and antidepressant response

Brain-derived neurotrophic factor (BDNF) plays an essential role in neuronal survival, proliferation, and synaptic remodeling and modulates the function of many other neurotransmitters. Additionally, it likely underlies neurodegenerative and psychiatric disorders, including alcohol dependence-related depression (AD-D). Here, we investigated the possible association between three single nucleotide polymorphisms (SNPs) of the BDNF gene (rs13306221, rs6265, rs16917204) and AD-D. Of 548 patients with alcohol dependence (AD), 166 had AD-D and 312 healthy controls. Response to 8-week sertraline treatment was also assessed. The frequency of the A allele of rs6265 (Val66Met) was significantly higher in AD-D patients than in the healthy controls (p=0.009 after Bonferroni correction). The analysis revealed a strong association between the rs6265 genotype distribution and AD-D (p=0.005 after Bonferroni correction), and the A allele of rs6265 was significantly overrepresented in AD-D patients compared to AD without depression (AD-nD) patients (p=0.001 after Bonferroni correction). Additionally, carriers of the A allele of rs6265 responded better to sertraline treatment (p=0.001). Our results suggested a novel association between BDNF rs6265 and AD-D. These findings might lead to earlier detection of AD-D, perhaps providing better tools for clinical care of these patients in the future.

Modulation of the glycine response by Ca2+-permeable AMPA receptors in rat spinal neurones.

1 In acutely isolated rat sacral dorsal commisural nucleus (SDCN) neurones, application of kainate (KA) reversibly potentiated glycine‐evoked Cl− currents (IGly) in a concentration‐dependent manner. 2 The cellular events underlying the interaction between non‐NMDA receptors and glycine receptors were studied by using nystatin‐perforated patch and cell‐attached single‐channel recording modes. 3 The action of KA was not accompanied by a shift in the reversal potential for IGly. In dose‐response curves, KA potentiated IGly without significantly changing glycine binding affinity. 4 GYKI 52466 blocked while NS‐102 had no effect on the KA‐induced potentiation of IGly. 5 The potentiation was reduced when KA was applied in a Ca2+‐free extracellular solution or in the presence of BAPTA AM, and was independent of the activation of voltage‐dependent Ca2+ channels. 6 Pretreatment with KN‐62, a selective Ca2+‐calmodulin‐dependent protein kinase II (CaMKII) inhibitor, abolished the action of KA. Inhibition of calcineurin converted the KA‐induced potentiation to a sustained one. 7 Single‐channel recordings revealed that KA decreased the mean closing time of glycine‐gated single‐channel activity, resulting in an increase in the probability of channel opening. 8 It is proposed that Ca2+ entry through AMPA receptors modulates the glycine receptor function via coactivation of CaMKII and calcineurin in SDCN neurones. This interaction may provide a new postsynaptic mechanism for control of inhibitory synaptic signalling and represent one of the important regulatory mechanisms of spinal nociception.

Taurine-activated chloride currents in the rat sacral dorsal commissural neurons

The electrophysiological and pharmacological properties of taurine (Tau)-activated Cl- currents (ITau) were investigated in the dissociated rat sacral dorsal commissural nucleus (SDCN) neurons using the nystatin perforated patch recording configuration under voltage-clamp conditions. The reversal potential of ITau was close to the Cl- equilibrium potential. The ITau was not affected by a preceding GABA response but cross-desensitized by a preceding glycine (Gly) response. Strychnine (STR), picrotoxin (PIC), bicuculline (BIC) and Zn2+ suppressed the ITau in a concentration-dependent manner. The pharmacology of the ITau and Gly-induced response (IGly) was similar, though Zn2+ inhibition on ITau differed from that on IGly in being much slower in recovery. Serotonin potentiated the ITau via protein kinase C. The results indicate that both Tau and Gly act on a strychnine-sensitive site to open the same Cl- channels in the SDCN neurons, and suggest that Tau may act as a functional neurotransmitter in the mammalian SDCN.

Expression of c-fos protein in substance P receptor-like immunoreactive neurons in response to noxious stimuli on the urinary bladder: an observation in the lumbosacral cord segments of the rat

Chemical irritation of the urinary bladder with formalin in the rat induced c-fos protein-like immunoreactivity in more than 80% of substance P receptor-like immunoreactive (SPR-LI) neurons of the dorsal commissural nucleus, sacral parasympathetic nucleus and lamina I in the 6th lumbar and 1st sacral cord segments. These neurons with SPR-LI may receive noxious information from the urinary bladder through the primary afferent fibers with substance P.

Co-localization of μ-opioid receptor-like immunoreactivity with substance P-LI, calcitonin gene-related peptide-LI and nitric oxide synthase-LI in vagal and glossopharyngeal afferent neurons of the rat

Co-localization of mu-opioid receptor (MOR)-like immunoreactivity (-LI) with substance P (SP)-LI, calcitonin gene-related peptide (CGRP)-LI and nitric oxide synthase (NOS)-LI in the nodose, petrosal and jugular ganglia was examined in the rat by a double immunofluorescence histochemical method. About 0.6%, 41% and 95% of neurons with MOR-LI, respectively, in the nodose, petrosal and jugular ganglia showed SP-LI; about 2%, 51% and 66% of MOR-like immunoreactive neurons displayed CGRP-LI in the nodose, petrosal and jugular ganglia, respectively. In addition, about 59% of MOR-like immunoreactive neurons in the nodose ganglia displayed NOS-LI, whereas no NOS-LI was detected in the petrosal or jugular ganglion. These data provide evidence for co-localization of MOR-LI with SP-LI, CGRP-LI and NOS-LI in the vagal and glossopharyngeal afferent neurons, and suggest that MOR may regulate the release of SP, CGRP and nitric oxide from the visceral primary afferent terminals in the nucleus of the solitary tract of the rat.