Dermatomal/segmental somatosensory evoked potential evaluation of L5/S1 unilateral/unilevel radiculopathies

Dermatomal and segmental somatosensory evoked potentials (SEPs) have been reported to be of diagnostic utility in unilateral/unilevel L5 and S1 radiculopathies. This investigation employs history, physical examination, imaging studies, and electrodiagnostic medicine evaluations to clearly define unilateral/unilevel L5 or S1 nerve root compromise. Inclusion criteria require all of the preceding diagnostic methods to corroborate a specific nerve root lesion. Regression equation analysis for cortical P1 latencies evaluating age and height based on comparable patient and control reference populations reveals segmental and dermatomal sensitivities for L5 radiculopathies to be 70% and 50%, respectively, at 90% confidence intervals. Similar sensitivities are obtained for 2 standard deviation mean cortical P1 latencies. Side-to-side cortical P1 latency difference data reveal segmental and dermatomal sensitivities for L5 radiculopathies to be 40% at 2 standard deviations. Regression equation analysis for age and height regarding segmental and dermatomal studies for S1 radiculopathies reveal sensitivities of 30% and 20%, respectively, at 90% confidence intervals. Similar data are delineated for 2 standard deviation mean cortical P1 latencies. Side-to-side cortical P1 latency difference data reveal segmental and dermatomal sensitivities for S1 radiculopathies to be 50% and 10%, respectively, at two standard deviations. The clinical utility of both segmental and dermatomal SEPs are questionable in patients with known unilateral/unilevel L5 and S1 nerve root compromise. © 1996 John Wiley & Sons, Inc.     

脑脊液中检测结核分枝杆菌特异性抗原对结核性脑膜炎的诊断意义

目的 应用改进的斑点酶联免疫吸附法(Dot ELISA)检测脑脊液中结核分枝杆菌特异性抗原培养滤液蛋白10(CFP10)和6000早期分泌性抗原靶(ESAT-6),评价其在结核性脑膜炎(TBM)中的诊断价值.方法 收集111例患者的脑脊液,其中58例临床诊断为TBM,53例非TBM,应用Dot ELISA法分别检测脑脊液中CFP10和ESAT-6并进行分析.结果 检测CFP10抗原的敏感度为93.1%,特异度为92.5%;检测ESAT-6抗原的敏感度为91.4%,特异度为94.3%.两项检测的敏感度和特异度均普遍高于针对结核分枝杆菌菌体或菌体物质进行检测的同类研究,如抗酸染色、结核分枝杆菌培养、聚合酶链反应等.结论 应用改进的Dot ELISA法检测脑脊液中CFP10和ESAT-6对诊断TBM有很高的敏感度和特异度,为结核分枝杆菌特异度抗原用于临床结核病诊断提供了依据.

Abstract：

Objective To evaluate the detection of culture filtrate protein 10 (CFP10) and 6000 early secretory antigenic target (ESAT-6) in cerebrospinal fluid to be used in diagnosing tuberculous meningitis. Methods Dot enzyme linked immunosorbent assay ( Dot ELISA) method that was improved by applying concentrated cerebrospinal fluid was used to detect CFP10 and ESAT-6 in cerebrospinal fluid to analyze small protein antigen secreted by M. tuberculosis. Cerebrospinal fluid of 111 subjects were collected,in which 58 specimens were clinically diagnosed as tuberculous meningitis and 53 as non-tuberculous.CFP10 and ESAT-6 were detected in cerebrospinal fluid using Dot ELISA method and the results were analyzed. Results The sensitivities of detecting CFP10 and ESAT-6 antigen were 93.1% and 91.4% respectively, and the specificities were 92. 5% and 94. 3% respectively. The sensitivities and specificities are generally higher compared with the other methods of detecting M. tuberculosis or materials of M. tuberculosis by acid-fast staining or mycobacterium tuberculosis culture and polymerase chain reaction.Conclusions Using Dot ELISA method to detect CFP10 and ESAT-6 in cerebrospinal fluid to diagnose tuberculous meningitis has a high sensitivity and specificity. Our study provided the evidence of detecting the specific antigen of M. tuberculosis to be used in diagnosing tuberculosis.     

Cholecystokinin concentrations and peptide immunoreactivity in the intact and deafferented medullary dorsal horn of the rat.

To further address the hypothesis that cholecystokinin (CCK) in the medullary dorsal horn (MDH) arises from intrinsic or higher-order neurons, CCK-8-specific radioimmunoassay (RIA) and immunohistochemical (IHC) experiments were carried out in adult rats after trigeminal tractotomy. RIA of punches from deafferented superficial layers of the MDH revealed no significant change in CCK levels vs. the control right side. In this same area, IHC revealed modest reductions in CCK, gastrin, and substance P staining. Calcitonin gene-related peptide (CGRP) staining was reduced substantially. Gastrin immunoreactive cell bodies, present normally in inner lamina II, were reduced in number. RIA and IHC methods were also used to assess MDH CCK concentrations in adult rats subjected to left infraorbital nerve section at birth. The left medulla contained significantly higher levels of CCK than the control right medulla (1.27 +/- 0.19 vs. 0.97 +/- 0.11 ng/mg protein). IHC revealed a dense band of CCK-like staining in laminae I and II ipsi- and contralateral to the lesion. Thus, neonatal deafferentation elevates medullary CCK. To determine if the neonatal lesion-induced increase in medullary CCK is due to primary afferent or higher-order reorganization, RIA and IHC experiments were run after infraorbital nerve section at birth and trigeminal tractotomy in adulthood. RIA revealed no significant change in CCK levels caudal to the tractotomy, although they were higher than control levels in 9 of 12 cases. IHC revealed modest reductions in CCK, substance P, and gastrin staining that resembled the reductions observed in tractotomy-alone cases. These data suggest that 1) most MDH CCK is of non-primary afferent origin, 2) gastrin immunoreactivity in layer II probably originates in CCK-containing cells intrinsic to layer II, the expression of which is dependent upon trigeminal primary afferent input, 3) neonatal V deafferentation induces increased CCK in the superficial MDH, reflecting reorganized intrinsic or higher-order inputs, and 4) higher-order substance P in the MDH is robust.     

Antigenic differences between neurological and diabetic patients with anti-glutamic acid decarboxylase antibodies

Antibodies to glutamic acid decarboxylase (GADAb) are found in Stiff-Person syndrome, type 1 diabetes, cerebellar ataxia and other neurological disorders (such as epilepsy and myoclonus) involving the GABAergic ways. GADAb are usually detected by immunohistochemistry (IHC), radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA). This study analysed the serum of 14 patients with neurological disorders who were positive by IHC for GADAb. The performance of a commercial RIA was compared with in-house immunoblotting and ELISA methods using recombinant GAD65 (rGAD65). RIA was positive in 14 of 14, immunoblotting was positive in seven of 14 and ELISA in 12 of 14. There was no correlation between the RIA result and the ELISA optical densities. Using a sodium thiocyanate chaotrope system with ELISA to determine antibody affinity, we found no significant correlation between antibody affinity and the RIA result. A consensus should be defined concerning which assay could be used as the gold standard for detecting GADAb. The most intriguing finding was that GAD antibodies from uncomplicated diabetics do not appear to recognize GAD in frozen sections from the rat cerebellum, whereas GAD antibodies from neurologically compromised diabetics do. A working proposal is therefore that type 1 diabetic patients with unusual neurological symptoms should be tested for GADAb both by RIA and IHC.     

The distribution of substance P in turtle nervous system: a radioimmunoassay and immunohistochemical study

The distribution of a substance P-like material in turtle brain, spinal cord, dorsal root ganglion, and retina was determined using radioimmunoassay (RIA) and immunohistochemistry. High levels of a substance P-like material were found in turtle neural tissue, particularly in basal telencephalon, hypothalamus, and tegmentum. In many regions, the concentration of a substance P-like material in turtle nervous tissue was found to be similar, in a region-to-region comparison, to that previously reported for birds and mammals, particularly for the more "phylogenetically conservative" parts of the nervous system (such as the basal ganglia, tegmentum, and hypothalamus). The slopes of substance P RIA dose-response curves for tissue extracts from nearly all regions of the turtle nervous system examined were parallel to a standard dose-response curve for synthetic substance P (SP). The immunohistochemical results, with anti-substance P antisera from guinea pig or rabbit, or with a monoclonal antibody, were consistent with the RIA data. Regions showing high concentration of an SP-like material by RIA were observed to contain numerous neurons and/or fibers containing an SP-like material. The immunohistochemical results provide evidence for the presence in turtle of numerous SP-containing pathways, several of which (e.g., an SP-containing strionigral pathway, an SP-containing striopallidal pathway and an SP-containing dorsal root ganglia-spinal dorsal horn pathway), have been described in birds and mammals. The present results thus suggest that the neuropeptide SP has had a largely stable evolutionary history as a transmitter or modulatory agent during amniote brain evolution.     

A double antibody sandwich microELISA for measuring human platelet factor 4

With the aim of investigating patients with a higher risk of thrombosis we developed a method for determining platelet factor 4 (PF4) in human plasma. Using the double antibody sandwich ELISA technique we set up a test system that allows the determination of PF4 concentrations in plasma samples from 1 to 100 ng/ml. This method is more sensitive and as specific as commercially available RIA kits, but has the advantage of being cheaper and less time consuming. Furthermore the ELISA does not require radioactive materials. The complete reaction is carried out in microtiter wells, and an ELISA-reader connected to an Apple computer does all the calculations needed for quantitative measurements.     

Comparative effects of neonatal hypothyroidism and euthyroidism on TRH and substance P content of lumbar spinal cord in saline and PCPA-treated rats

The effects of neonatal thyroidectomy and thyroid hormone replacement therapy on the content of substance P and TRH in the lumbar segment of the rat spinal cord were studied. The peptide content of discrete spinal cord regions removed by punches of frozen serial slices was measured by RIA. Animals receiving T4 replacement therapy were indistinguishable from normal littermates. In hypothyroid animals without PCPA-treatment, levels of TRH and substance P were significantly increased by 100% in the ventral and the dorsal lumbar spinal cord, respectively. Inhibition of serotonin biosynthesis by PCPA increased by 90% the substance P content in the dorsal horn of euthyroid rats and abolished completely the stimulatory effect of hypothyroidism on the TRH content of the ventral horn. These findings suggest the existence of a physiological relationship between substance P and TRH with the serotoninergic system in the rat spinal cord and that thyroid hormone is implicated in the normal development of the peptide-containing neurons in the rat spinal cord.     

Immunohistochemical and biochemical analysis of serotonin and substance P colocalization in the nucleus tractus solitarii and associated afferent ganglia of the rat

In a previous study of afferent projections to the nucleus tractus solitarii (NTS), it was shown that over half of the retrogradely-labelled neurons in the nucleus raphe pallidus contained serotonin-immunoreactivity and over half of these neurons contained substance P-immunoreactivity, suggesting that these two putative neurotransmitters are colocalized in NTS-afferent neurons. The objectives of the present study were to 1) directly determine if varicosities in the NTS, the area postrema (AP), and the dorsal motor nucleus of the vagus nerve (DMN) do contain both transmitters, 2) determine if primary afferent neurons in the nodose and pretrosal ganglia might also colocalize serotonin and substance P, and 3) quantify the amount of substance P that is contained in serotonergic varicosities in the NTS. Distributions and colocalization of substance P and serotonin in the NTS were studied using dual-color immunohistochemistry, while the quantity of substance P in serotonergic varicosities was assessed by radioimmunoassay (RIA) using micropunches from the NTS of 5,7-dihydroxytryptamine-(5,7 DHT-) and vehicle-treated rats. Varicosities that contained both serotonin- and substance P-immunoreactivity were found in the NTS, the DMN, and the AP. Double-labelled varicosities were common in the NTS and DMN (i.e., qualitatively similar to the density seen in the hypoglossal nucleus and in the ventral horn of the cervical spinal cord); however, the vast majority of the varicosities in these autonomic areas only displayed immunoreactivity for one or the other of these transmitters. This paucity of doubly-labelled varicosities, in comparison to the number of singly-labelled varicosities, was reflected in the lack of a significant decrease in substance P levels as determined by RIA of micropunches taken from caudal and intermediate levels of the NTS in 5,7 DHT- and vehicle-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuropeptides and γ-Aminobutyric acid in the vestibular nuclei of the rat: an immunohistochemical analysis. I. Distribution

The distributions of substance P, Leu-enkephalin and γ-aminobutyric acid (GABA) containing structures in the rat vestibular nuclei were investigated by means of an indirect immunofluorescent method using specific antisera to substance P, Leu-enkephalin and glutamic acid decar☐ylase (GAD), respectively.Numerous positive neurons and fibers containing these three substances were found in the medical vestibular nucleus. Most of them were situated in the caudal part of the nucleus and those in the rostral part were concentrated dorsally. In the descending vestibular nucleus, a large number of substance P, Leu-enkephalin and GAD containing neurons were evenly distributed among longitudinally directing fiber bundles. A number of positive fibers with these substances were also observed. The lateral vestibular nucleus contained numerous coarse GAD-immunoreactive fibers surrounding Deiters' neurons, while substance P-immunoreactive and Leu-enkephalin-immunoreactive fibers were rather poorly distributed in this nucleus as well as in the superior vestibular nucleus.     

Neuropeptides and gamma-aminobutyric acid in the vestibular nuclei of the rat: an immunohistochemical analysis. I. Distribution

The distribution of substance P, Leu-enkephalin and gamma-aminobutyric acid (GABA) containing structures in the rat vestibular nuclei were investigated by means of an indirect immunofluorescent method using specific antisera to substance P, Leu-enkephalin and glutamic acid decarboxylase (GAD), respectively. Numerous positive neurons and fibers containing these three substances were found in the medial vestibular nucleus. Most of them were situated in the caudal part of the nucleus and those in the rostral part were concentrated dorsally. In the descending vestibular nucleus, a large number of substance P, Leu-enkephalin and GAD containing neurons were evenly distributed among longitudinally directing fiber bundles. A number of positive fibers with these substances were also observed. The lateral vestibular nucleus contained numerous coarse GAD-immunoreactive fibers surrounding Deiters' neurons, while substance P-immunoreactive and Leu-enkephalin-immunoreactive fibers were rather poorly distributed in this nucleus as well as in the superior vestibular nucleus.     

Clinical correlates of enzyme-immunoassay versus radioimmunoassay measurements of antibody against acetylcholine receptor in patients with myasthenia gravis

Antibody against human nicotinic acetylcholine receptor [Ab(AcChR)] was measured in the sera obtained from 55 patients with myasthenia gravis (MG) using both radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA). By at least one assay, 91% of the patients had elevated Ab(AcChR). We found no correlation between the amount of Ab(AcChR) measured by RIA and that measured by ELISA. Patient subpopulations defined by ELISA- or RIA-measured Ab(AcChR) were associated with different disease durations. All of those who had high Ab(AcChR) levels by both assays had experienced symptoms for less than 2 years. 87% of those with high Ab(AcChR) levels by ELISA had had MG for less than 4 years. Those patients with high Ab(AcChR) only by RIA had a mean disease duration of over 8 years. With regard to correlations of Ab(AcChR) with patient age and sex, females under 50 years of age had high levels of Ab(AcChR) by RIA, but had lower levels by ELISA, whereas men over 50 had high Ab(AcChR) levels by ELISA. Using either assay, no relationship was established between concentrations of Ab(AcChR) and the patient's functional status, previous thymectomy, or current therapy. In this study, 16% of the MG patients with elevated Ab(AcChR) would have been considered within the non-disease range of Ab(AcChR) had only the RIA been performed, thus recommending the routine use of both assays for diagnostic purposes.     

Serum substance P levels in patients with chronic schizophrenia treated with typical or atypical antipsychotics

Aspiration pneumonia is a major cause of death in patients with dysphagia, often accompanied by psychiatric symptoms. The inhibition of swallowing and cough reflexes, which contribute to a significant risk for aspiration, may be related to decreased levels of substance P. Clinical studies indicate a strong association of an increased mortality in psychiatric patients with the use of antipsychotics. The present study documented fewer positive episodes of swallowing reflex in patients treated with haloperidol for schizophrenia (7/11; 63.6%) than those treated with risperidone (10/11; 90.9%). In addition, patients treated with risperidone had serum substance P levels comparable with control subjects (29.0 +/- 7.8 pg/mL, 29.6 +/- 7.6, respectively; p = 0.9), while patients treated with haloperidol had significantly lower serum substance P levels (20.6 +/- 5.5 pg/mL; p < 0.01). Among patients on haloperidol, those with negative episodes of reflex (4/11; 36.4%) had serum substance P levels at 15.8 +/-1.0 pg/mL, in contrast with those with positive episodes (7/11; 63.6%) who had serum levels at 23.4 +/- 4.9 pg/mL. However, in the patient group treated with risperidone, serum substance P levels in the majority of patients with positive episodes of reflexes (10/11, 90.9%; 30.1 +/- 7.2 pg/mL) was found to be as high as in control subjects, all with positive episodes (5/5, 100%; 29.6 +/- 7.6 pg/mL) (p = 0.866), and higher than in one patient with negative reflex (1/11, 9.1%; 18.0 +/- 0.0 pg/mL). These results suggest that the decreased serum substance P levels are strongly associated with the use of haloperidol, as well as decreased swallowing reflexes. This suggests that serum substance P levels may be a useful predictive marker for the increased risk of developing aspiration, or subsequently aspiration pneumonia. Moreover, this increased incidence of aspiration may contribute to an increased mortality in patients following antipsychotic therapy. Risperidone, which has little influence on serum substance P productions, may be a more appropriate first-line drug of choice for treatment of schizophrenia.     

Substance P and serotonin act synergistically to activate a cation permeability in a neuronal cell line

Both substance P and, to a lesser degree, serotonin activate cation permeability in neuroblastoma x glioma hybrid cells, as determined by measurement of [14C]guanidinium uptake. Serotonin potentiates the action of substance P by shifting the concentration-effect curve of substance P to the left. The EC50 value for the synergistic effect of serotonin was around 0.3 microM. Dopamine and noradrenaline displayed comparable activity, albeit only at 50 and 130 times higher concentrations, respectively. The order of potency of various substance P-analogues was not changed by serotonin, indicating that the specificity of the substance P site on the hybrid cells was not affected by serotonin. Various other neurotransmitters and peptides had no effect on the response of the hybrid cells to substance P. The serotonin receptor interacting with the substance P receptor may be classified as a 5-HT3-receptor since methysergide, cimetidine, and ketanserin were ineffective, but two inhibitors specific for 5-HT3-receptors, ICS 205-930 (3 alpha-tropanyl-1H-indole-3-carboxylic acid ester) and MDL 72222 (1 alpha H,3 alpha,5 alpha H-tropan-3-yl-3,5-dichlorobenzoate), blocked the effect of serotonin at nanomolar concentrations. However, the two serotonin antagonists might also be blocking the ion permeability, since at higher concentrations they fully inhibited the stimulation of guanidinium uptake by substance P or by substance P plus serotonin. The synergism between substance P and serotonin on the hybrid cells offers the opportunity to study the mechanism of interaction of neurotransmitter receptors on a permanent neuronal cell line.     

Sensory neuropeptidergic pattern in tendon, ligament and joint capsule. A study in the rat.

The normal occurrence of sensory neuropeptides in tendons, ligaments and joint capsules in the rat was analyzed by immunohistochemistry and radioimmunoassay (RIA). Nerve fibres immunoreactive to substance P (SP), calcitonin gene-related peptide (CGRP), neurokinin A, galanin and somatostatin were identified in the Achilles tendon as well as the collateral ligaments and joint capsule of the knee. The neuropeptidergic fibres were predominantly found in the epiligament and paratenon. However, SP- and CGRP-positive fibres were also seen in the proper ligament and tendon tissues. RIA showed higher concentrations of SP and CGRP in tendons than in ligaments and capsules. The morphological and quantitative data obtained on sensory neuropeptides in normal tendons, ligaments and joint capsules may be used as a reference for tissue analysis in painful and inflammatory conditions of the locomotor apparatus.     

Isocratic reverse-phase HPLC separation and RIA used in the analysis of neuropeptides in brain tissue.

A reverse-phase, high-performance liquid chromatographic (HPLC) method was employed to separate and characterise five neuropeptides from complex mixtures, with important advantages over methods employed earlier using combined HPLC-RIA studies. Peptides were separated using 0.5M pyridine-0.5M formic acid buffer, pH 4, containing propan-l-ol 14% (met-enkephalin, leu-enkephalin, neurotensin) or 20% (CCK-8-S, substance P) at a flow rate of 1.0 ml/min. Isocratic conditions, and volatile solvents, resulted in a highly reproducible method, producing samples in a form designed for subsequent RIA. The application and importance of the procedure is demonstrated by comparison of the measurements of apparent peptide levels in crude brain extracts with those of authentic peptides as determined after HPLC purification.     

Different reinnervation patterns in the celiac/mesenteric and superior cervical ganglia following guanethidine sympathectomy in adult rats

We sought to determine whether chronic guanethidine (Gu) treatment in adult rats produces depletion of sympathetic neurons and hyperinnervation by sensory neuropeptides in the celiac/superior mesenteric (C/SMG) ganglion. Rats received Gu 40 mg/kg per day i.p or saline for 5 weeks. Upon completion of treatment, the C/SMG and the superior cervical ganglion (SCG) were examined for neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP) and vasoactive intestinal polypeptide (VIP), both by immunocytochemistry (ICC) and radioimmunoassay (RIA). Gu produced marked depletion of NPY-containing neurons and NPY content in the C/SMG, similar to that in the SCG (−89 ± 2vs.−92 ± 4%, respectively). SP and CGRP immunoreactivities were significantly higher iontrol C/SMG as compared with SCG; after Gu treatment, there was no significant increase in either SP or CGRP in the C/SMG, however, both increased in the SCG. In contrast, VIP levels were similar in the SCG and C/SMG in controls and increased in the C/SMG but not in the SCG after Gu treatment. Thus, in adult rats, the C/SMG is as susceptible as the SCG to Gu treatment; the different pattern of hyperinnervation by SP, CGRP and VIP of the C/SMG as compared with the SCG may reflect the different sources for these neuropeptides in prevertebral as compared with paravertebral ganglia.     

Histamine and tumor necrosis factor-alpha production from purified rat brain mast cells mediated by substance P

The effect of cytokines and neuropeptides on neuroimmune functions has not been completely elucidated and recent evidence suggests an important role for these molecules linking the neuroimmune system and inflammatory events. The aim of this study was to analyse the effect of substance P (SP) on a pure population of hypothalamic brain mast cell (BMC). A pure population of BMC challenged with 10(-8) M SP gave 78% histamine release (HR) and secreted 600 pg/ml of tumor necrosis factor-alpha (TNF-alpha) as determined by ELISA. The production of TNF-alpha mRNA, measured by a competitive RT-PCR, was 14 times higher than that in unstimulated cells. The secretion of histamine and TNF-alpha from BMC after stimulation with SP supports the hypothesis that these mediators could induce an initial response in neuroinflammatory diseases.     

Deliberate self-harm and childhood hyperactivity in junior high school students

The present study aimed to explore the status of deliberate self-harm (DSH) among junior high-school students, and investigate the relationship between DSH and substance use and childhood hyperactivity. Subjects were 239 boys (mean age = 14.16 years, SD = 0.67) and 238 girls (14.22, 0.68) from a junior high-school in Kanagawa, Japan. A self-reporting questionnaire consisting of original questions on self-cutting, self-hitting, and tobacco and alcohol use was employed with the Wender Utah Rating Scale (WURS) for assessing childhood hyperactivity. Overall, 8.00% and 27.70% of males and 9.30% and 12.20% of females reported self-cutting and self-hitting, respectively. Regarding substance use, 33.10% and 74.10% of males and 14.30% and 63.40% of females reported tobacco and alcohol use, respectively. Comparisons of WURS scores between those with and without experience of problematic behaviors revealed that with all problematic behaviors in both genders, scores of those with experience were significantly higher than those without (P < 0.01 except for self-cutting in females, P < 0.05). The present study indicated that DSH is an important problem, even among children as young as junior high-school age. An association between DSH and childhood hyperactivity was also suggested.     

Substance P and neurokinin A in the cat carotid body: localization, exogenous effects and changes in content in response to arterial pO2

In the present work we studied the occurrence of substance P (SP) and neurokinin A (NKA) in the carotid bodies of cats by means of immunocytochemistry and radioimmunoassay (RIA). We also compared the exogenous effects of SP and NKA on carotid body sensory discharge. SP- and NKA-like immunoreactivities (SP-LI; NKA-LI) were seen in many glomus cells and in a sparse plexus of fine fibers. The SP-LI containing glomus cells and fibers also exhibited NKA-LI, suggesting that both these tachykinins coexist in the carotid body. Chemoreceptor discharge increased both by SP and NKA in a dose-dependent manner. The peak excitation produced by SP and NKA was the same when the effects were compared on an equimolar basis. The tachykinin content of the carotid bodies varied with changes in arterial pO2. During normoxia, SP and NKA levels were 57 +/- 8 and 85 +/- 14 fmol/mg, respectively. When the animals were exposed for 1 h to 100% O2, SP content was unchanged (51 +/- 4 fmol/mg), whereas NKA levels were significantly lower than during normoxia (29 +/- 3 fmol/mg, P less than 0.01). Following 1 h of hypoxia, SP content of the carotid body was 146 +/- 20 fmol/mg, a value higher than that obtained during normoxia and hyperoxia. NKA levels, on the other hand, were not significantly different from normoxic values. These results indicate that the cat carotid body (1) contains both SP and NKA, (2) both peptides augment neural discharge of the carotid body and (3) their levels in the carotid body are substantially altered by arterial oxygen, the natural stimulus to the chemoreceptors.