Primary afferent-driven presynaptic inhibition of C-fiber inputs to spinal lamina I neurons.

Presynaptic inhibition of primary afferent terminals is a powerful mechanism for controlling sensory information flow into the spinal cord. Lamina I is the major spinal nociceptive projecting area and monosynaptic input from C-fibers to this region represents a direct pathway for transmitting pain signals to supraspinal centers. Here we used an isolated spinal cord preparation to show that this pathway is under control of the afferent-driven GABAergic presynaptic inhibition. Presynaptic inhibition of C-fiber input to lamina I projection and local-circuit neurons is mediated by recruitment of Aß-, Aδ- and C-afferents. C-fiber-driven inhibition of C-fibers functions as a feedforward mechanism, by which the homotypic afferents control sensory information flow into the spinal cord and regulate degree of the primary nociceptive afferent activation needed to excite the second order neurons. The presynaptic inhibition of C-fiber input to lamina I neurons may be mediated by both synaptic and non-synaptic mechanisms, and its occurrence and extent are quite heterogeneous. This heterogeneity is likely to be reflective of involvement of lamina I neurons in diverse circuitries processing specific modalities of sensory information in the superficial dorsal horn. Thus, our results implicate both low- and high-threshold afferents in the modulation of C-fiber input into the spinal cord.

Characterization of functional subgroups among genetically identified cholinergic neurons in the pedunculopontine nucleus.

The pedunculopontine nucleus (PPN) is a part of the reticular activating system which is composed of cholinergic, glutamatergic and GABAergic neurons. Early electrophysiological studies characterized and grouped PPN neurons based on certain functional properties (i.e., the presence or absence of the A-current, spike latency, and low threshold spikes). Although other electrophysiological characteristics of these neurons were also described (as high threshold membrane potential oscillations, great differences in spontaneous firing rate and the presence or absence of the M-current), systematic assessment of these properties and correlation of them with morphological markers are still missing. In this work, we conducted electrophysiological experiments on brain slices of genetically identified cholinergic neurons in the PPN. Electrophysiological properties were compared with rostrocaudal location of the neuronal soma and selected morphometric features obtained with post hoc reconstruction. We found that functional subgroups had different proportions in the rostral and caudal subregions of the nucleus. Neurons with A-current can be divided to early-firing and late-firing neurons, where the latter type was found exclusively in the caudal subregion. Similar to this, different parameters of high threshold membrane potential oscillations also showed characteristic rostrocaudal distribution. Furthermore, based on our data, we propose that high threshold oscillations rather emerge from neuronal somata and not from the proximal dendrites. In summary, we demonstrated the existence and spatial distribution of functional subgroups of genetically identified PPN cholinergic neurons, which are in accordance with differences found in projection and in vivo functional findings of the subregions. Being aware of functional differences of PPN subregions will help the design and analysis of experiments using genetically encoded opto- and chemogenetic markers for in vivo experiments.

Direct presynaptic and indirect astrocyte-mediated mechanisms both contribute to endocannabinoid signaling in the pedunculopontine nucleus of mice.

The pedunculopontine nucleus (PPN), a cholinergic nucleus of the reticular activating system, is known to be involved in the regulation of sleep and wakefulness. Endogenous and exogenous cannabinoids, by systemic or local administration to the pedunculopontine nucleus, can both influence sleep. We previously demonstrated that activation of astrocytes by cannabinoid type 1 (CB1) receptor agonists was able to modulate the membrane potential of PPN neurons, even in the presence of blockers of fast synaptic neurotransmission. In the present work, we provide evidence that synaptic inputs of PPN neurons are also affected by activation of presynaptic and astrocytic CB1 receptors. Using slice electrophysiology combined with calcium imaging, optogenetics and immunohistochemistry, we revealed a direct presynaptic inhibitory action on inhibitory postsynaptic currents, along with a mild increase of excitatory postsynaptic currents during CB1 receptor stimulation. Besides inhibition of excitatory and inhibitory neurotransmission through stimulation of presynaptic CB1 receptors, astrocyte- and mGluR-dependent tonic inhibition and excitation also developed. The mild stimulatory action of CB1 receptor activation on excitatory neurotransmission is the combination of astrocyte-dependent tonic excitation on excitatory neurons and the canonical presynaptic CB1 receptor activation and consequential inhibition of excitatory synaptic neurotransmission, whereas the astrocyte-dependent stimulatory action was not observed in inhibitory neurotransmission within the PPN. Our findings demonstrate that endocannabinoids act in the PPN via a dual pathway, consisting of a direct presynaptic and an indirect, astrocyte-mediated component, regulating synaptic strength and neuronal activity via independent mechanisms.

Effects of temperature and light intensity on flowering of barley (Hordeum vulgare L.).

In order to analyse the effects of temperature (9-22 degreesC) and light intensity (170-576 micromol m(-2) s(-1)) on plant development two barley varieties with contrasting seasonal growth habits were included in a series of experiments consisting of controlled environment tests. The effect of constant (18 degrees C) and daily fluctuating (18/16 degrees C) temperature with a long photoperiod was also examined in a set of barley varieties including winter, facultative and spring barleys. Dicktoo with facultative growth habit was more sensitive to unfavourable conditions than Kompolti korai with winter growth habit; the flowering of Dicktoo was significantly delayed by sub- and supra-optimal temperatures and low light intensity accompanied by higher or fluctuating temperatures. The optimal temperature at flowering was also significantly lower for Dicktoo than for Kompolti korai (16.0 degrees C vs. 21.0 degrees C, respectively). Plant development was the fastest when there was no fluctuating environmental factor in the growing conditions and was significantly delayed with application of photo cycle. The addition of thermo cycle to photo cycle had an even stronger delaying effect. Facultative barleys were the most sensitive, followed by winter barleys, while spring barleys the least sensitive to the introduction of thermo cycle.

Effects of photo and thermo cycles on flowering time in barley: a genetical phenomics approach.

The effects of synchronous photo (16 h daylength) and thermo (2 degrees C daily fluctuation) cycles on flowering time were compared with constant light and temperature treatments using two barley mapping populations derived from the facultative cultivar 'Dicktoo'. The 'Dicktoo'x'Morex' (spring) population (DM) segregates for functional differences in alleles of candidate genes for VRN-H1, VRN-H3, PPD-H1, and PPD-H2. The first two loci are associated with the vernalization response and the latter two with photoperiod sensitivity. The 'Dicktoo'x'Kompolti korai' (winter) population (DK) has a known functional polymorphism only at VRN-H2, a locus associated with vernalization sensitivity. Flowering time in both populations was accelerated when there was no fluctuating factor in the environment and was delayed to the greatest extent with the application of synchronous photo and thermo cycles. Alleles at VRN-H1, VRN-H2, PPD-H1, and PPD-H2--and their interactions--were found to be significant determinants of the increase/decrease in days to flower. Under synchronous photo and thermo cycles, plants with the Dicktoo (recessive) VRN-H1 allele flowered significantly later than those with the Kompolti korai (recessive) or Morex (dominant) VRN-H1 alleles. The Dicktoo VRN-H1 allele, together with the late-flowering allele at PPD-H1 and PPD-H2, led to the greatest delay. The application of synchronous photo and thermo cycles changed the epistatic interaction between VRN-H2 and VRN-H1: plants with Dicktoo type VRN-H1 flowered late, regardless of the allele phase at VRN-H2. Our results are novel in demonstrating the large effects of minor variations in environmental signals on flowering time: for example, a 2 degrees C thermo cycle caused a delay in flowering time of 70 d as compared to a constant temperature.

Indication for hyperbaric oxygen treatment as a predictor of tympanostomy tube placement.

INTRODUCTION: Hyperbaric oxygen therapy (HBO2) has been utilized for many years for a multitude of disease entities. One commonly encountered side-effect is otic barotrauma. OBJECTIVE: To determine if patients with specific disease processes are at increased risk of requiring tympanostomy tubes during HBO2. METHODS: Data was obtained from Jan. 2000 to Dec. 2004, retrospectively. The requirement for tympanostomy tubes during a course of HBO2 was established. RESULTS: 325 met inclusion criteria. Fifteen percent of patients overall (95% CI= 11-19%) required tympanostomy tubes. Tubes were required in: 5% necrotizing soft tissue infection (p=0.33); 10% failed/threatened graft (p=0.39); 15% problem wounds; 17% chronic refractory osteomyelitis (CRO) (p=0.64); 22% soft tissue radionecrosis (STRN)/osteoradionecrosis (ORN) (p=0.02); 33% of crush injuries (p=0.10). Twenty-nine percent of nasopharyngeal radiation injury patients (p=0.001) and 10% of the non-nasopharyngeal radiation patients (p=0.36) received tympanostomy tubes. CONCLUSION: A significant increase in tympanostomy tubes were required in nasopharyngeal radiation injury patients.

Positional relationships between photoperiod response QTL and photoreceptor and vernalization genes in barley.

Winterhardiness has three primary components: photoperiod (day length) sensitivity, vernalization response, and low temperature tolerance. Photoperiod and vernalization regulate the vegetative to reproductive phase transition, and photoperiod regulates expression of key vernalization genes. Using two barley mapping populations, we mapped six individual photoperiod response QTL and determined their positional relationship to the phytochrome and cryptochrome photoreceptor gene families and the vernalization regulatory genes HvBM5A, ZCCT-H, and HvVRT-2. Of the six photoreceptors mapped in the current study (HvPhyA and HvPhyB to 4HS, HvPhyC to 5HL, HvCry1a and HvCry2 to 6HS, and HvCry1b to 2HL), only HvPhyC coincided with a photoperiod response QTL. We recently mapped the candidate genes for the 5HL VRN-H1 (HvBM5A) and 4HL VRN-H2 (ZCCT-H) loci, and in this study, we mapped HvVRT-2, the barley TaVRT-2 ortholog (a wheat flowering repressor regulated by vernalization and photoperiod) to 7HS. Each of these three vernalization genes is located in chromosome regions determining small photoperiod response QTL effects. HvBM5A and HvPhyC are closely linked on 5HL and therefore are currently both positional candidates for the same photoperiod effect. The coincidence of photoperiod-responsive vernalization genes with photoperiod QTL suggests vernalization genes should also be considered candidates for photoperiod effects.

P boutons in lamina IX of the rodent spinal cord express high levels of glutamic acid decarboxylase-65 and originate from cells in deep medial dorsal horn.

Presynaptic inhibition of primary muscle spindle (group Ia) afferent terminals in motor nuclei of the spinal cord plays an important role in regulating motor output and is produced by a population of GABAergic axon terminals known as P boutons. Despite extensive investigation, the cells that mediate this control have not yet been identified. In this work, we use immunocytochemistry with confocal microscopy and EM to demonstrate that P boutons can be distinguished from other GABAergic terminals in the ventral horn of rat and mouse spinal cord by their high level of the glutamic acid decarboxylase (GAD) 65 isoform of GAD. By carrying out retrograde labeling from lamina IX in mice that express green fluorescent protein under the control of the GAD65 promoter, we provide evidence that the cells of origin of the P boutons are located in the medial part of laminae V and VI. Our results suggest that P boutons represent the major output of these cells within the ventral horn and are consistent with the view that presynaptic inhibition of proprioceptive afferents is mediated by specific populations of interneurons. They also provide a means of identifying P boutons that will be important in studies of the organization of presynaptic control of Ia afferents.

The Vrn-H2 locus is a major determinant of flowering time in a facultative x winter growth habit barley (Hordeum vulgare L.) mapping population.

With the aim of dissecting the genetic determinants of flowering time, vernalization response, and photoperiod sensitivity, we mapped the candidate genes for Vrn-H2 and Vrn-H1 in a facultative x winter barley mapping population and determined their relationships with flowering time and vernalization via QTL analysis. The Vrn-H2 candidate ZCCT-H genes were completely missing from the facultative parent and present in the winter barley parent. This gene was the major determinant of flowering time under long photoperiods in controlled environment experiments, irrespective of vernalization, and under spring-sown field experiments. It was the sole determinant of vernalization response, but the effect of the deletion was modulated by photoperiods when the vernalization requirement was fulfilled. There was no effect under short photoperiods. The Vrn-H1 candidate gene (HvBM5A) was mapped based on a microsatellite polymorphism we identified in the promoter of this gene. Otherwise, the HvBM5A alleles for the two parents were identical. Therefore, the significant flowering time QTL effect associated with this locus suggests tight linkage rather than pleiotropy. This QTL effect was smaller in magnitude than those associated with the Vrn-H2 locus and was significant in two-way interactions with Vrn-H2. The Vrn-H1 locus had no effect on vernalization response. Our results support the Vrn-H2/Vrn-H1 repressor/structural gene model for vernalization response in barley and suggest that photoperiod may also affect the Vrn genes or tightly linked loci.

The demographics of e-mail for emergency medicine research.

Escalating costs of research combined with increasing use of e-mail by emergency physicians (EP), justifies studying whether electronic surveying (ES) is a valid methodology for research. Our primary study object is to delineate the demographics of EP with e-mail. Secondary objectives are to ascertain ES response rates and to identify response bias between "individual" versus "bulk" e-mailings. The 1999 American College of Emergency Physicians Membership Guide identified a pool of e-mail addresses. Of the 1,752 EP surveyed, 1,386 (79%) had valid e-mail addresses and 574 responded. A response rate of 41% questions the validity of ES for research. Demographic data of EP regarding mean age (38.2 years); gender (82.4% men); title (86.8% MD); practice (87% ED); practice location (49.6% urban); training (56% EM residency); research participation (65.5%); screening e-mail (7%); is representative of EP overall. Finally, comparison of individual versus bulk e-mail to survey participants showed a 13.6% (5.5-21.7; 95% CI) improvement in overall response.

Triage nurse application of the Ottawa knee rule.

OBJECTIVE: To determine interobserver agreement between triage registered nurses (RNs) and emergency physicians (EPs) regarding indication for knee radiographs by applying the Ottawa knee rule (OKR) and individual components of the rule. METHODS: This was a prospective, observational study in a suburban, teaching emergency department. The study enrolled a convenience sample of patients aged >17 years with traumatic knee injuries less than one week old. Patients with prior knee surgery or distracting conditions were excluded. Before study initiation, the RNs and EPs were in-serviced in the OKR. Nurses and EPs independently examined each patient for OKR criteria, blinded to the other's assessment. Knee radiographs were ordered at the discretion of the EP and were interpreted by board-certified radiologists. All patients received follow-up with a structured telephone interview to identify any undetected fractures. Kappa was calculated for each component and the overall application of the OKR to assess interobserver agreement. RESULTS: Ninety-six patients were enrolled. The mean age was 39.6 +/- 18.7 years; 50% were male. Eight patients (8%) had knee fractures. Interobserver agreements between the RNs and EPs for individual components of the OKR were: age > or =55 years (kappa = 0.97); inability to weight bear (kappa = 0.51); inability to bend knee to 90 degrees (kappa = 0.52); fibular head tenderness (kappa = 0.45); and isolated patellar tenderness (kappa = 0.40). The EPs and RNs agreed with OKR criteria for x-ray 71% of the time (kappa = 0.41). CONCLUSIONS: The only criterion that resulted in almost perfect agreement between the RNs and EPs was patient age; agreement for the other four criteria and the overall decision to order x-rays was moderate.

Storage temperatures of medications on an air medical helicopter.

INTRODUCTION: The safety and efficacy of medications stored on air medical helicopters may be adversely affected by extreme temperatures. The purpose of this study was to determine whether temperatures inside an air medical helicopter drug box were within the U.S. Pharmacopeia recommendations for controlled room temperature. This is defined as a temperature between 15 degrees and 30 degrees C (59 degrees and 86 degrees F) with a mean kinetic temperature of less than 25 degrees C (77 degrees F). An additional goal was to determine whether time/temperature indicator labels can reliably monitor mean kinetic temperatures. METHODS: Temperatures were monitored with miniature electronic temperature recorders and color-changing time/temperature indicator labels. RESULTS: The mean kinetic temperatures for the summer and winter periods were 25.1 degrees C (77.2 degrees F) and 12.7 degrees C (54.8 degrees F), respectively. In the summer, the electronic recorders logged temperatures exceeding 25 degrees C (59 degrees F) 37% of the time and more than 30 degrees C (86 degrees F) 6% of the time. In the winter, temperatures less than 15 degrees C (59 degrees F) were recorded 83% of the time. The mean kinetic temperatures obtained from the electronic recorder and the time/temperature indicator labels differed by less than 0.7 degree C (1.3 degrees F). The results show that medications on an air medical helicopter are subject to temperatures out of the recommended range and that time/temperature indicator labels can reliably monitor mean kinetic temperatures.

Cell surface domain specific postsynaptic currents evoked by identified GABAergic neurones in rat hippocampus in vitro.

1. Inhibitory postsynaptic currents (IPSCs) evoked in CA1 pyramidal cells (n = 46) by identified interneurones (n = 43) located in str. oriens were recorded in order to compare their functional properties and to determine the effect of synapse location on the apparent IPSC kinetics as recorded using somatic voltage clamp at -70 mV and nearly symmetrical [Cl-]. 2. Five types of visualised presynaptic interneurone, oriens-lacunosum moleculare (O-LMC), basket (BC), axo-axonic (AAC), bistratified (BiC) and oriens-bistratified (O-BiC) cells, were distinguished by immunocytochemistry and/or synapse location using light and electron microscopy. 3. Somatostatin immunoreactive O-LMCs, innervating the most distal dendritic shafts and spines, evoked the smallest amplitude (26 +/- 10 pA, s.e.m., n = 8) and slowest IPSCs (10-90 % rise time, 6.2 +/- 0.6 ms; decay, 20.8 +/- 1.7 ms, n = 8), with no paired-pulse modulation of the second IPSC (93 +/- 4 %) at 100 ms interspike interval. In contrast, parvalbumin-positive AACs evoked larger amplitude (308 +/- 103 pA, n = 7) and kinetically faster (rise time, 0.8 +/- 0.1 ms; decay 11.2 +/- 0.9 ms, n = 7) IPSCs showing paired-pulse depression (to 68 +/- 5 %, n = 6). Parvalbumin- or CCK-positive BCs (n = 9) terminating on soma/dendrites, BiCs (n = 4) and O-BiCs (n = 7) innervating dendrites evoked IPSCs with intermediate kinetic parameters. The properties of IPSCs and sensitivity to bicuculline indicated that they were mediated by GABAA receptors. 4. In three cases, kinetically complex, multiphasic IPSCs, evoked by an action potential in the recorded basket cells, suggested that coupled interneurones, possibly through electrotonic junctions, converged on the same postsynaptic neurone. 5. The population of O-BiCs (4 of 4 somatostatin positive) characterised in this study had horizontal dendrites restricted to str. oriens/alveus and innervated stratum radiatum and oriens. Other BiCs had radial dendrites as described earlier. The parameters of IPSCs evoked by BiCs and O-BiCs showed the largest cell to cell variation, and a single interneurone could evoke both small and slow as well as large and relatively fast IPSCs. 6. The kinetic properties of the somatically recorded postsynaptic current are correlated with the innervated cell surface domain. A significant correlation of rise and decay times for the overall population of unitary IPSCs suggests that electrotonic filtering of distal responses is a major factor for the location and cell type specific differences of unitary IPSCs, but molecular heterogeneity of postsynaptic GABAA receptors may also contribute to the observed kinetic differences. Furthermore, domain specific differences in the short-term plasticity of the postsynaptic response indicate a differentiation of interneurones in activity-dependent responses.

Safety and efficacy of diclofenac ophthalmic solution in the treatment of corneal abrasions.

STUDY OBJECTIVE: To determine whether the use of diclofenac ophthalmic solution is a safe and effective analgesic in the treatment of traumatic corneal abrasions in the emergency department. METHODS: We conducted a prospective, randomized, double-blinded, placebo-controlled clinical trial. Consenting consecutive patients with corneal abrasions who presented to a community-based ED from August through February 1998 were randomly assigned to receive either diclofenac or control vehicle drops. Pain relief was measured using a visual Numeric Pain Intensity Scale (NPIS) before and after treatment. Exclusion criteria were as follows: age younger than 18 years, pregnancy, history of glaucoma, ocular infection, recent eye surgery, other signs of ocular trauma, narcotics within 6 hours, minimal pain (NPIS score <3), and any allergy to diclofenac or nonsteroidal anti-inflammatory drugs. Patients were discharged with study drug or control vehicle solution, a topical antibiotic, oxycodone-acetaminophen as a rescue analgesic, and a pain diary. The outcome measurements were improvement in NPIS score 2 hours after treatment, use of oxycodone-acetaminophen, and occurrence of any adverse effects. RESULTS: Forty-nine patients were enrolled in the study; 25 received diclofenac and 24 received control vehicle drops. Both groups were similar in gender, age, pretreatment pain duration, NPIS score, and analgesic use. There was significantly greater improvement in the 2-hour NPIS score in the diclofenac group (3.1; 95% confidence interval [CI] 2.3 to 4) compared with the control group (1.0; 95% CI 0.1 to 2.0). The difference between the 2 groups was 2.1+/-1.3 (95% CI 0.8 to 3.4). There was a trend toward fewer patients taking rescue oxycodone-acetaminophen in the diclofenac group (20%; 95% CI 4% to 36%) versus the control group (42%; 95% CI 22% to 62%). Other than transient mild stinging, there were no complications associated with diclofenac use. CONCLUSION: Diclofenac ophthalmic solution appears to be a safe and effective analgesic in the treatment of traumatic corneal abrasions in the ED.

Droperidol for acute migraine headache.

The use of intramuscular droperidol to treat acute migraine headache has not been previously reported in the emergency medicine literature. It is a promising therapy for migraine. The authors performed a pilot review of all patients receiving droperidol for migraine in our emergency department (ED) to evaluate its efficacy. We used a retrospective case series, in a suburban ED with an annual patient census of 48,000. All patients with a discharge diagnosis of migraine headache who were treated with i.m. droperidol during a consecutive 5-month period in our ED were identified. All patients received droperidol 2.5 mg intramuscular. As per ED protocol, their clinical progress was closely followed and documented at 30 minutes after drug administration (t30). Demographic and clinical variables were recorded on a standardized, closed-question, data collection instrument. The primary outcome measurement was relief of symptoms at t30 to the point that the patient felt well enough to go home without further ED intervention (symptomatic relief). Thirty-seven patients were treated (84% female), with an ED diagnosis of acute migraine with droperidol during the study period. The mean age was 36 +/- 12 years. Analgesics had been used within 24 hours before ED presentation by 62% of patients. At t30, 30 (81%) patients had symptomatic relief, 2 (5%) felt partial relief but required rescue medication, and 5 (14%) had no relief of symptoms. Drowsiness (14%) and mild akathisia (8%) were the only adverse reactions observed following drug administration. Droperidol 2.5 mg intramuscular may be a safe and effective therapy for the ED management of acute migraine headache. Randomized, controlled trials are warranted to further validate the findings of this preliminary study.

Immunohistochemical localization of neurokinin-l receptor in the lumbar spinal cord of young rats: morphology and distribution.

The type and distribution of neurokinin-1 (NK-1) receptor-expressing neurones were studied in young (14-day-old) rats' lumbar spinal cord using pre-embedding immunohistochemistry. The heaviest immunoreactivity was observed in the middle part and lateral fourth of lamina I where the great majority of immunoreactive perikarya represented fusiform and multipolar cells. In lamina II the middle and medial part showed moderate immunoreactivity, most of the cells resembled stalked cells. In lamina III the labelled perikarya were evenly distributed, while those in lamina IV accumulated mainly in the lateral part. In both laminae most of the labelled neurones represented central cells, the rest of them belonged to the antenna-type cells with long dorsally directed dendrites penetrating the superficial laminae. The immunoreactivity in laminae V-VII was uniform and relatively weak. In lamina VIII the immunopositive perikarya were encountered only rarely while in lamina IX virtually all motoneurones showed weak immunoreactivity. Lamina X contained small, multipolar and fusiform labelled perikarya. In conclusion, we found that the general appearance of the NK-1 receptor immunostaining and the major type of NK-I receptor-expressing neurones were similar to that found previously in adult spinal cord. Using the same method as Brown and colleagues the number of labelled NK- 1 receptor immunoreactive cells was similar in young and adult animals except lamina I where the number of immunoreactive neurones was twice that in adults.

Neurokinin-1 receptor expression in dorsal root ganglion neurons of young rats.

The expression of neurokinin-1 receptors was studied in the fourth lumbar dorsal root ganglia of young rats using immunohistochemical and electrophysiological techniques. Use of a specific immunoserum raised against the C-terminal fragment of rat neurokinin-1 receptor revealed immunoreactivity in 32 +/- 1.5% of dorsal root ganglion neurons. The diameter of the majority of the neurokinin-1 receptor immunostained neurons was smaller than 30 microm. Double immunohistochemical labelling using neurokinin-1 receptor and substance P antibodies revealed that about 1/3 of the neurokinin-1 receptor expressing neuron contains substance P. Likewise, about 1/3 of the substance P producing DRG cells expressed the neurokinin-1 receptor. Superfusion of substance P (1 microM) to an in vitro preparation of the fourth lumbar dorsal root ganglion induced a reversible long-lasting depolarization as measured by extracellular suction electrodes attached to the dorsal roots. This response to substance P was only partially antagonized by the selective neurokinin-1 receptor antagonist RP 67580 (1 microM). Intracellular recordings distinguished between Aalpha/beta-, Adelta- and C-sub-types of ganglion neurons. Superfusion of substance P (1 microM) evoked excitatory responses in Adelta- and C-type neurons. These results demonstrate the expression of functional neurokinin-1 receptors on a subpopulation of Adelta- and C-type sensory ganglion neurons. Our data suggest the possible physiological importance of peripheral neurokinin-1 receptors located on dorsal root ganglion neurons.

Alterations of substance P immunoreactivity in lumbar and thoracic segments of rat spinal cord in ultraviolet irradiation induced hyperalgesia of the hindpaw.

Substance P immunostaining was quantified on sections from the 4th-5th lumbar and midthoracic spinal segments of rats at the peak of hyperalgesia following ultraviolet irradiation-induced inflammation of one hindpaw. The area of the immunostaining in the lumbar dorsal horn was significantly decreased on both sides by 50%, while in the thoracic spinal cord, it was increased by 18% on the contralateral and stayed unchanged on the ipsilateral side.

Sub-population of capsaicin sensitive primary afferent neurons in thoracic, lumbar and sacral dorsal root ganglion in young rats revealed by stimulated cobalt uptake.

The number of dorsal root ganglion (DRG) neurons, the relative number of capsaicin sensitive DRG cells and the diameter distribution of these neurons were investigated in the thoracic 11, lumbar 5 and sacral 1 DRG ganglia in young rats. The capsaicin sensitivity of DRG cells was shown by the stimulated cobalt uptake technique in in vitro conditions. Cobalt labelled and non-labelled neurons were counted using the dissector method. Our results show that the total number of DRG cells in the Th11, L5 and S1 segments (4200-6500 per ganglion) were not significantly different from each other and about 8% of these cells were capsaicin sensitive in the segments studied. These findings also show that the capsaicin sensitive DRG cells belong to the small diameter DRG cell population. Control experiments on neonatally capsaicin injected animals indicate that the capsaicin stimulated cobalt uptake provides selective and specific staining of capsaicin sensitive DRG neurons.