Biomedical subjects

R M Kream

Publications and source records attributed to R M Kream.

At least 19 recordsLinked to original sources

PubMed1999

Behavioral sensitization to cocaine after a brief social defeat stress: c-fos expression in the PAG.

The experiments explored the nature and time course of changes in behavior and Fos expression in the periaqueductal grey area (PAG) in response to an injection of cocaine that was given following a single episode of social defeat stress. Social defeat stress was defined as an intruder mouse's response to an aggressive resident mouse. First, the intruder was briefly attacked, and secondly, it was threatened while protected by a perforated cage for 20 min. Plasma corticosterone levels rose after the beginning of the confrontation and remained elevated during the protected phase. In a first experiment, separate groups of intruder and control mice were challenged once with cocaine (20, 30, or 40 mg/kg) or saline. During tests for motor activity, behavioral measurements were obtained via (1) photobeam interruptions, (2) tracking of movements via image analysis, and (3) quantitative ethological analysis of postures and acts via videorecords. Several indices of ambulatory or horizontal forward locomotion confirmed the stimulant effects of cocaine. In a further experiment, separate groups of mice were challenged with 40 mg/kg cocaine at one time point, either during the social stress or 3, 5, 7 or 9 days thereafter. A cocaine challenge significantly increased locomotion 5 and 7 days after a brief social defeat stress, in excess of the level that is seen in non-stressed animals. Further experiments used immunohistochemical assays of sections through the caudal ventrolateral PAG and showed a significant increase in Fos-like immunoreactivity (Fos-LI) 1 h after the social stress experience or after cocaine. Importantly, concurrent administration of cocaine with social defeat stress produced inhibition of Fos expression throughout the PAG. A partial to complete recovery of cocaine-induced Fos expression was observed 5-7 days after social defeat stress. The results suggest that a single social stress episode is sufficient to engender a delayed sensitization of stimulant hyperactivity. The initial inhibition of Fos expression by concurrent social stress and cocaine may point to a relevant initiating event in the process of sensitization to stimulants.

Aggression↗

PubMed1999

Alterations in neuropeptide Y, tyrosine hydroxylase, and Y-receptor subtype distribution following spinal nerve injury to rats.

Recent animal models of experimental nerve injury have proven useful in evaluating potential sympathetic involvement in neuropathic pain syndromes. We have employed a widely adopted unilateral L5/L6 spinal nerve ligation model to compare the development of mechanical allodynia with neurochemical changes both at the site of peripheral nerve injury and in the dorsal root ganglia (DRG). We have focused on the expression of neuropeptide Y (NPY), a well-studied regulatory peptide and phenotypic marker of sympathetic neurons, and functionally related Y-receptor binding sites following nerve injury. In sympathetic neurons, NPY is colocalized and coreleased with norepinephrine (NE) at peripheral sites of action. Furthermore, NPY gene expression is induced within the population of medium- and large-diameter DRG neurons of the A beta-fiber class after experimental nerve injury. We therefore hypothesized that concurrent alterations in NPY and NE expression by sympathetic and sensory neurons may be a contributing factor to sympathetically-maintained neuropathic conditions. Animals with unilateral L5/L6 spinal nerve ligation developed mechanical allodynia of the hind paw ipsilateral to the site of injury that persisted until sacrifice at postoperative day 10. A significant induction of preproneuropeptide Y-encoding (PPNPY) mRNA, as detected by in situ hybridization histochemistry (ISHH), occurred in populations of medium- and large-diameter DRG neurons ipsilateral to the site of injury. Immunohistochemical analysis indicated a marked decline in the number of labeled sympathetic axons positive for tyrosine hydroxylase-like and NPY-like immunoreactivities (TH-LI and NPY-LI, respectively) proximal to the site of nerve injury and almost complete elimination of immunopositive fibers distal to the site of ligation. Whereas, the extent of colocalization of NPY-LI to TH-LI-positive sympathetic axons in unaffected L4 or L5 nerve segments exceeded 80%, this figure declined to approximately 50% in regenerating axons of ligated spinal nerve L5. The portion of NPY-LI that was not colocalized to sympathetic TH-LI-positive fibers was most likely contributed by regenerating sensory axons, consistent with marked de novo synthesis of NPY by DRG neurons. In end bulb axon terminals, i.e. morphological profiles characteristic of neuromas, NPY-LI-positive elements that were not colocalized to TH-LI-positive sympathetic elements appeared to be spatially segregated from those of sympathetic origin with colocalized TH-LI and NPY-LI. Receptor autoradiography indicated that small- and medium-diameter DRG somata of the C-fiber class normally express both Y1 and Y2 receptor subtypes. The pattern of the distribution of Y-receptor binding sites appeared to be relatively unaffected by spinal nerve ligation. In contrast, there was a marked increase in the density of Y2 receptor binding sites in the proximal segment of ligated spinal nerve L5, consistent with previously published data indicating differential transport of the Y2 autoregulatory receptor subtype to nerve terminals. Induction of NPY gene expression in injured DRG neurons is consistent with appearance of NPY-LI-positive end bulbs derived from regenerating sensory axons that are found in developing neuromas containing a relatively high density of transported prejunctional Y2 receptors. Newly established functional interactions of spatially segregated sensory- and sympathetically-derived end bulbs in developing neuromas may enhance neuronal hyperexcitability engendered by aberrant electrical activity at the site of injury. Injury-related alterations in the regulatory activities of NPY released within the DRG at somally-distributed Y-receptors may also contribute to the development and/or persistence of symptoms characteristic of sympathetically-maintained pain. Finally, at later times NPY-mediated modulation of NE release from invading sympathetic axon terminals within the DRG may affect the extent of alpha2 rece

Animals↗

PubMed1998

Behavioral sensitization to cocaine after a brief social stress is accompanied by changes in fos expression in the murine brainstem.

The objective of the present study was to determine how c-fos gene expression in brainstem structures after a brief episode of social defeat stress is related to behavioral sensitization to cocaine challenge. Social stress was defined as defeat in a brief confrontation with an aggressive resident mouse and subsequent 20-min exposure to the resident's threats behind a protective screen. Mice were treated with cocaine (40 mg/kg, i.p.) immediately or 1 week after social defeat stress. Fos-like immunoreactive (Fos-LI) cell nuclei were analyzed in the ventral tegmental area (VTA), dorsal raphe nucleus (DR), periaqueductal grey area (PAG) and locus coeruleus (LC). One episode of social stress induced behavioral sensitization to cocaine as indicated by an augmented locomotor response to a challenge injection 7 days after a single defeat. In naive mice, social stress markedly increased the number of Fos-LI nuclei in the DR, PAG and LC, but not in the VTA. Similarly, cocaine administration resulted in a significantly increased number of Fos-LI nuclei in the same areas. Administration of cocaine immediately following social defeat significantly reduced the number of Fos-LI nuclei in the DR, PAG and LC. Cocaine-induced Fos expression returned in the PAG and DR, but not in the LC, 1 week after social stress. In conclusion, the present results suggest that the presence of brainstem Fos be related to the ability to express stress-induced behavioral sensitization to cocaine.

Anesthetics, Local↗

PubMed1998

Reduced levels of substance P in the brains of Cpe(fat)/Cpe(fat) mice.

This study examines the role of carboxypeptidase E (CPE) in processing pro tachykinin to form the final bioactive amidated undecapeptide, substance P (SP) in various rat brain regions. Cpe(fat)/Cpe(fat) mice brain tissue was analyzed for total SP forms (including intermediates), and final amidated SP was compared to Cpe+/Cpe+ and Cpe+/Cpe- controls. In all brain regions tested by radioimmunoassay, amidated fully processed SP was more than fivefold lower in Cpe(fat)/Cpe(fat) mice than in controls whereas total SP species levels were unchanged. This demonstrates that CPE is required for normal SP proteolytic processing. Substance P has numerous functions in the brain; therefore, SP deficiency due to the CPE mutation may contribute to the obese phenotype or even to other phenotypes not yet described in Cpe(fat)/Cpe(fat) mice.

Animals↗

PubMed1998

Increased expression of substance P receptor-encoding mRNA in bladder biopsies from patients with interstitial cystitis.

OBJECTIVES: To determine whether substance P (SP, also known as neurokinin 1, NK1) receptors are differentially expressed in bladder biopsies from patients with interstitial cystitis (IC) compared with matched controls. MATERIALS AND METHODS: Cold-cup biopsies were taken during routine diagnostic cystoscopy. NK1-receptor expression was assessed using a quantitative analysis of NK1-receptor-encoding mRNA in bladder biopsies from patients and controls using in situ hybridization histochemistry (ISHH) combined with autoradiographic image analysis. RESULTS: Autoradiographic signal indicating the presence of NK1-encoding mRNA was localized to detrusor muscle, urothelium and vascular structures. In the bladder vasculature, the signal was predominantly associated with endothelial cells. NK1 receptor-encoding mRNA within the vascular endothelium was increased in the biopsies obtained from patients with IC. CONCLUSION: Increased levels of NK1 receptor-encoding mRNA within the bladder vascular endothelium suggests the up-regulation of NK1 receptor as a putative factor in the pathogenesis of pain related to IC. Increased responsiveness to SP released from the perivascular sensory terminals may result in a local cascade of neurogenic inflammatory responses which trigger the pathophysiological changes, including pain, characteristic of IC.

Adult↗

PubMed1998

Differential immediate-early gene expression in ovine brain after cardiopulmonary bypass and hypothermic circulatory arrest.

BACKGROUND: This study determined the induction profiles of immediate-early genes in the ovine brain after cardiopulmonary bypass (CPB) and hypothermic circulatory arrest (HCA), and the effects of the noncompetitive N-methyl-D-aspartate antagonist, aptiganel, on immediate-early gene expression, neuronal necrosis, and functional outcome. METHODS: Cannulas were inserted into isoflurane-anesthetized neonatal lambs undergoing CPB. One group received 2.5 mg/kg intravenous aptiganel. Animals underwent 90 or 120 min of HCA at 16 degrees C, were rewarmed to 38 degrees C, and were weaned from CPB. One hour after CPB was discontinued, brain perfusion was fixed and removed for immunohistochemical analysis in one half of the animals. The other half survived 2 or 3 days before their brains were evaluated for neuronal degeneration. Data were analyzed using analysis of variance; P < 0.05 was considered significant. RESULTS: Cardiopulmonary bypass and HCA differentially induced c-Jun and Fos proteins in the hippocampal formation, with c-Jun expression increasing with the duration of HCA, whereas Fos protein expressions were greatest after 90 min of HCA. The c-Jun protein was expressed in all neurons except the dentate gyrus. The Fos proteins were expressed in all neurons, including the dentate gyrus. Neuronal necrosis was observed in CA1 (73%) and CA3 (29%) neurons but not in the dentate gyrus after 120 min of HCA. Aptiganel completely inhibited c-Jun expression (P < 0.001) but not Fos, improved functional outcome, and attenuated neuronal necrosis (P < 0.05). CONCLUSIONS: The c-Jun and c-Fos proteins are expressed differentially in hippocampal neurons after CPB and HCA. Expression of c-Jun is associated with neuronal necrosis, whereas Fos protein expression is associated with survival. Aptiganel inhibits c-Jun expression, attenuates neuronal necrosis, and improves outcome.

Anesthesia, General↗

PubMed1997

Immediate-early gene expression in ovine brain after hypothermic circulatory arrest: effects of aptiganel.

BACKGROUND: Altered gene expression occurs in the brain after global ischemia. We have developed a model to examine the effects of cardiopulmonary bypass and hypothermic circulatory arrest (HCA) on the induction of the immediate-early gene c-fos in the brains of neonatal lambs. We then tested the effects of the noncompetitive N-methyl-D-aspartate antagonist, aptiganel hydrochloride (Cerestat), on c-fos expression and neuronal injury. METHODS: Neonatal lambs (weight, 4 to 6 kg) anesthetized with isoflurane were supported by cardiopulmonary bypass, subjected to 90 or 120 minutes of HCA at 15 degrees C, and rewarmed on bypass to 38 degrees C. One hour after cardiopulmonary bypass was terminated, the brains were perfusion fixed and removed for in situ hybridization and immunohistochemical analysis. Some animals survived 3 days before their brains were removed to examine for neuronal necrosis. One group of lambs (n = 20) received aptiganel (2.5 mg/kg). A second group (n = 25) received saline vehicle only. RESULTS: Increasing duration of HCA induced a corresponding increase in c-fos messenger RNA expression throughout the hippocampal formation and cortex. However, Fos protein synthesis peaked after 90 minutes of HCA and decreased significantly (p < 0.01) after 120 minutes of HCA. Aptiganel administration caused a significant decrease in (p < 0.001) c-fos messenger RNA expression and Fos protein synthesis after 90 minutes of HCA and preserved Fos protein synthesis after 120 minutes of HCA. Neuronal necrosis was observed in the brains of vehicle-treated lambs after 120 minutes of HCA but was significantly decreased (p < 0.05) in the lambs given aptiganel. CONCLUSIONS: These experiments indicate that the transcriptional processes of immediate-early genes remain intact, whereas translational processes are impaired after prolonged HCA. The inability to synthesize Fos proteins after 120 minutes of HCA was associated with neuronal degeneration. Aptiganel preserved translational processes and caused a significant improvement in the neurologic outcome.

Animals↗

PubMed1997

Differential effect of central versus parenteral administration of morphine sulfate on regional concentrations of reduced glutathione in rat brain.

Prior studies in rodents have shown significant depletion of reduced glutathione (GSH) in peripheral organs following acute systemic or central administration of opioids. However, little information exists on whether opioid administration affects concentrations of brain GSH. Recently, clinical observations have indicated acute declines of GSH concentrations in the cerebrospinal fluid of cancer patients after acute intracerebroventricular (ICV) morphine which may contribute to the development of organic behavioral brain syndromes associated with central opioid analgesia. Collectively these data led us to investigate the affect of acute systemic and central morphine on regional concentrations of GSH in rat brain. Systemic morphine had no effect on GSH concentrations in selected brain areas. In contrast, ICV morphine resulted in selective GSH depletion in the caudate nucleus, consistent with concurrent excitatory locomotive behavior. This change may have reflected morphine-induced oxidative stress together with increased metabolic activity within the extrapyramidal system.

Analgesics, Opioid↗

PubMed1996

Streptozotocin-induced diabetes produces a decrease in pituitary substance P content and preprotachykinin mRNA.

Complications arising from diabetes mellitus include hormonal dysfunctions such as impairment in the regulation of gonadatroph and corticotroph secretion. Preprotachykinin (PPT) mRNA encoding the peptide substance P (SP), has been localized in the anterior pituitary. The goal of this study was to determine if streptozotocin (STZ)-induced diabetes affects the SP content or PPT mRNA level in the pituitary of male rats. We injected STZ (55 mg/kg) to 6-week-old rats which developed hyperglycemia (blood glucose > 400 mg/dl) by 6 weeks post-injection. SP-like immunoreactivity in the pituitary dropped 54%. In situ hybridization was performed using a PPT-specific oligonucleotide with signal intensity differences semi-quantified using an image analysis system. Normal pituitary had a regional distribution of PPT mRNA, with no detectable signal in the posterior or intermediate lobes, while the anterior lobe displayed a distinctive pattern of labeled cells arranged in clusters. In diabetic rats there was a 23% decrease in the PPT-mRNA hybridization signal compared to controls (P < 0.05). The changes observed in PPT gene expression and SP content may be additional factors participating in the hormonal complications seen in diabetes mellitus.

Animals↗

PubMed1996

Streptozotocin-induced diabetes is associated with altered expression of peptide-encoding mRNAs in rat sensory neurons.

Major complications arising from diabetes mellitus include neuropathic pain and altered peripheral inflammatory responses. Somatostatin (SOM), calcitenin gene-related peptide (CGRP), and substance P (SP) are neuropeptides that modulate pain responses transmitted by primary sensory afferents, the cell bodies of which are located in the dorsal root ganglion (DRG). Thus, the goal of the present study was to determine whether the diabetic condition is associated with altered neuropeptide gene expression in lumbar DRG of the rat. We employed an established animal model in which streptozotocin (STZ, 55 mg/kg) is administered to 6 week-old rats. The hallmark symptoms of hyperglycemia (blood glucose > 400 mg/dl), polydipsia, polyuria, and severe weight loss were maximal at 6 weeks postadministration, at which time animals were sacrificed. For determination of peptide encoding mRNAs distributed in DRG neurons, in situ hybridization histochemistry utilizing S-end-labeled oligonucleotides complimentary to sequences of preprosomatostatin (PPSOM), preprocalcitonin gene related peptide (PPCGRP), preprotachykinin (PPT), or preproneuropeptide Y (PPNPY) mRNA was performed. Silver grains were detected overlying DRG cells by autoradiography on sections of tissue counterstained with thionin. Semiquantitative analysis of differences in silver grain signal were made using an image analysis system, which expressed signals as fCi/microns2. In diabetic rats there was a significant decrease in DRG PPSOM (54%, p < 0.01), and PPCGRP (33%. p < 0.05) mRNA hybridization from the normal values PPT mRNA hybridization signal and SP-like immunoreactivity were not significantly changed in diabetic rat DRGs compared to control. In contrast, there was an increase in the number of cells labeled with PPNPY hybridization in DRG from diabetic rats. These data suggest that CGRP and SOM synthesis in primary sensory neurons is reduced in STZ-induced diabetic rats. These changes could contribute to the painful neuropathies and altered inflammatory responses seen in diabetes mellitus.

Animals↗

PubMed1996

Immediate-early gene expression in ovine brain after cardiopulmonary bypass and hypothermic circulatory arrest.

BACKGROUND: Cardiopulmonary bypass (CPB) and hypothermic circulatory arrest (HCA) are associated with neurological injury. Altered immediate-early gene expression occurs rapidly in the brain in response to ischemia, hypoxia, and severe metabolic stress, which results in long-term changes in the molecular phenotype of neurons. This study determined the effects of CPB and HCA on the expression of the immediate-early gene c-fos. METHODS: Neonatal lambs were subjected to 2 h of CPB at 38 degrees C (n = 4) or 60 min (n = 6), 90 min (n = 7), and 120 min (n = 6) of HCA at 15 degrees C. One hour after terminating CPB at 38 degrees C, the brains were analyzed for FOS-encoding mRNA and FOS-like immunoreactivity in the hippocampal formation. Other animals (n = 15), subjected to the same CPB and HCA protocol, were allowed to survive 3-5 days before their brains were examined for dead neurons. RESULTS: Minimal c-fos mRNA and FOS proteins were observed in neurons of animals subjected to normothermic bypass and of those that served as controls. Non-neuronal FOS proteins were observed in the choroid plexus, ependyma, and blood vessels at all times, including normothermic CPB, but not in the control animals without CPB. The magnitude of c-fos mRNA expression in hippocampal neurons increased directly with the duration of HCA. In contrast, expression of FOS proteins peaked after 90 min of HCA and declined significantly thereafter. Dead neurons were seen in surviving animals after 2 h of HCA only. CONCLUSIONS: Cardiopulmonary bypass and HCA alter immediate-early gene expression in the brain. Translational processes are impaired after 120 min of HCA and correlate with neuron death in the hippocampus.

Animals↗

PubMed1996

Calcium currents in a pituitary cell line (AtT-20): differential roles in stimulus-secretion coupling.

The purpose of the present investigation was to identify voltage-dependent calcium channel subtypes that control the release of ACTH in AtT-20 cells, a clonal mouse pituitary cell line. Using the perforated patch-clamp technique, we identified dihydropyridine (nimodipine)-, omega-Agatoxin IVA-, and omega-Conotoxin MVIIC-sensitive calcium currents. No omega-Conotoxin GVIA-sensitive currents are present in these cells. There also existed a considerable resistant component to the recorded inward current that was inhibited by cadmium, a nonselective calcium channel antagonist. Using RIA, we examined the contributions of each of the pharmacologically distinct calcium channel populations to CRH- or potassium chloride (KCI)-stimulated release of ACTH at various time intervals (10 sec to 60 min). We found that nimodipine markedly inhibited ACTH release at all intervals tested, whereas omega-Agatoxin IVA, omega-Conotoxin MVIIC, and omega-Conotoxin GVIA had no significant effect. Moreover, the inhibition by nimodipine was comparable to that seen after cadmium application, and the effects of these two antagonists were not additive. These data suggest that although AtT-20 cells possess dihydropyridine-, omega-Agatoxin IVA-, and omega-Conotoxin MVIIC-sensitive calcium channels as well as a considerable toxin-resistant current, only the dihydropyridine-sensitive calcium channels appear to be coupled to CRH- or KCI-induced ACTH release.

Adrenocorticotropic Hormone↗

PubMed1995

Increased number of substance P positive nerve fibres in interstitial cystitis.

OBJECTIVE: To explore the presence of the neuropeptide substance P (SP) in the bladders of rats and humans and to investigate its relationship to mast cells (MCs) in interstitial cystitis (IC), a bladder disorder which occurs mostly in women and is characterized by frequency of voiding, nocturia and debilitating suprapubic pain. PATIENTS, MATERIALS AND METHODS: Bladder biopsies from eight women with untreated IC (mean age 36 years, range 29-58) and five control patients with no IC were analysed and compared with each other and with bladder tissue from 12 rats. Immunohistochemistry and image analysis were used to examine the density of SP-positive nerve fibres and their relationship with MCs. RESULTS: SP-containing nerve fibres were present in the bladder of both rats and humans. They were increased only in the submucosa, but not in the detrusor, of IC patients and were frequently seen in juxtaposition to MCs. CONCLUSION: SP, a neuropeptide secreted from sensory nerve endings, has been implicated in the pathophysiology of pain and has been shown to trigger MC secretion. Moreover, MC secretion by SP is augmented by oestradiol and bladder MCs have been shown to express high affinity oestrogen receptors. A functional relationship between SP and MCs may explain the pathophysiology of the neuro-inflammatory and painful nature of IC.

Adult↗

PubMed1994

Effect of chronic DDC treatment on LHRH and substance P amidation processes in the rat.

We examined the effects of chronic diethyldithiocarbamate (DDC) treatment on the concentrations of methionine-enkephalin, mature and unamidated forms (-Gly) of luteinizing hormone releasing hormone (LHRH) and substance P (SP) in various regions of the central nervous system (CNS). Chronic DDC treatment resulted in elevations of LHRH-Gly like immunoreactivity in the preoptic area (POA) and the medial basal hypothalamus (MBH), as well as elevations in SP-Gly like immunoreactivity in all areas of the CNS examined. Castration altered the ratios of SP-G-like/SP-like immunoreactivity in the pons, and LHRH-Gly like immunoreactivity in the MBH. Met-enkephalin concentrations were significantly elevated in the pons and medulla of intact DDC-treated animals, and in the POA of both intact- and castrated DDC-treated animals. Results demonstrate that it is possible to detect basal levels of unamidated LHRH and SP in many areas of the CNS, with ratios of unamidated/amidated peptides representing a unique and sensitive method for determining altered posttranslational processing of these transmitters, especially under altered endocrine states such as castration. Pharmacological blockade of terminal enzymatic processing of these peptides may be useful in studying upstream regulatory events in peptidergic neurons.

Amides↗

PubMed1994

Dextromethorphan inhibits ischemia-induced c-fos expression and delayed neuronal death in hippocampal neurons.

BACKGROUND: Dextromethorphan (DM), a widely used antitussive agent, has been shown to possess both anticonvulsant and neuroprotective properties functionally related to its inhibitory effects on glutamate-induced neurotoxicity. The current study was designed to determine whether DM administration prevents delayed neuronal degeneration in central nervous system areas after global forebrain ischemia and whether this correlates with inhibition of induction of the immediate early gene c-fos. METHODS: Mongolian gerbils, anesthetized with 2% halothane in air at 37 degrees C, received either 0.9% sodium chloride (vehicle, n = 9) or 50 mg/kg DM in vehicle (n = 9) by intraperitoneal injection before bilateral carotid artery occlusion. After 1 h of reperfusion under anesthesia, the animals were killed and the brains removed. Immunohistochemistry was used to detect neurons expressing Fos protein. Computer-assisted image analysis quantified changes in the number of labeled neurons as a function of drug treatment. To determine the extent of delayed neuronal degeneration within the hippocampus, other animals were treated with either DM (n = 7) or vehicle (n = 6) before carotid artery occlusion and allowed to survive for 1 week. RESULTS: Global forebrain ischemia produced consistent patterns of Fos-like immunoreactivity in the hippocampus and neocortex of vehicle-treated animals. DM inhibited the induction of c-fos from 65% to 91%. DM also protected against delayed neuronal degeneration in the CA1 region of the hippocampus (P < 0.001). CONCLUSIONS: The induction of nuclear-associated Fos protein represents a sensitive marker of cellular responses to ischemia and a method to assay the effectiveness of pharmacologic interventions. DM markedly inhibited ischemia-induced Fos expression and prevented cell death in CA1. DM given before conditions of ischemia or decreased central nervous system perfusion may be highly beneficial.

Animals↗

PubMed1994

Expression of substance P and its precursor forms in vagal, tracheal, and lung tissues of the guinea pig.

Steady-state levels of the prototypic tachykinin neuropeptide substance P (SP) and its major precursor form substance P-glycine (SP-G) were detected and authenticated in guinea pig vagal and respiratory tissues by radioimmunoassay (RIA), combined high-performance liquid chromatography (HPLC)/RIA analyses, and immunohistochemistry. Four antisera were employed: anti-SP that recognizes the amidated COOH-terminal of SP and is specific for the mature peptide, anti-SP4-10 that recognizes the midportion 4-10 amino acid sequence of SP and is highly specific for both mature SP and extended precursor forms of SP, anti-SP-G that is highly specific for the unamidated COOH-terminal of SP-G, and affinity-purified anti-SP-G-K that is capable of detecting SP-G and minor forms of SP precursor in immunohistochemical analyses. In all examined areas, the content of substance P4-10-like immunoreactivity (SP4-10-LI) quantified by RIA with the use of anti-SP4-10 was greater than that quantified by RIA with the use of anti-SP serum, thereby providing biochemical evidence of steady-state expression of extended precursor forms of SP. Immunohistochemical analyses demonstrated labeled axonal profiles indicating the presence of immunoreactive SP as well as immunoreactive forms of SP precursor within lung hilum and in small fibers in the parenchyma, with no evidence of labeled neuronal cell bodies in these same areas.

Amino Acid Sequence↗

PubMed1993

Distribution of tachykinin- and opioid-expressing neurons in the hamster solitary nucleus: an immuno- and in situ hybridization histochemical study.

In several sensory systems, tachykinin- and opioid-expressing neurons functionally interact and influence the processing of afferent information. To determine whether a similar relationship exists for the processing of general and special (gustatory) visceral afferent information, the present study mapped the distributions of these two neuronal phenotypes within the nucleus of the solitary tract (NST) of the hamster by employing a combination of immuno- and in situ hybridization histochemistry (ISHH). The hamster was chosen because it is frequently used as a model in taste studies, yet there is a relative dearth of data about peptide expression or the classical neurotransmitters in the brainstem of this animal. The immunohistochemical analyses employed 2 highly selective antisera directed towards the prototypical tachykinin and opioid peptides, i.e. substance P (SP) and methionine enkephalin (ENK), respectively. Intense staining of fibers and preterminal/terminal puncta was concentrated in the rostral pole or gustatory zone of the NST. SP-, but not ENK-like immunoreactivity was also observed in long courses of axon bundles traversing the brainstem enroute to the NST. Local application of colchicine engendered the appearance of a moderate number of SP-positive somata that were mostly clustered in the medial, central and intermediate subnuclei, as well as being scattered throughout the remainder of the NST, including the gustatory zone. A low number of isolated ENK-positive somata were also observed throughout the NST. The somal areas of the SP- and ENK-positive somata averaged 86.3 and 81.8 microns 2, respectively. The ISHH studies were performed using 2 selective oligodeoxynucleotide probes with complementary sequences to mRNAs encoding gamma-preprotachykinin (PPT) and preproenkephalin (PPE) molecules. Overall, the cellular expression of PPT mRNA within the NST corresponded both in distribution and in number to those identified by immunohistochemical analyses using anti-SP serum. In contrast, ISHH analyses monitored a significantly greater number of PPE-expressing somata in the medial, central, intermediate and ventrolateral nuclei than were ENK immunoreactive. These findings indicate that tachykinin and opioid peptide phenotypes are represented in neurons throughout the hamster NST and suggest a functional role for PPT- and PPE-related peptide forms in the modulation of afferent general visceral and gustatory information.

Animals↗

PubMed1993

Substance P markedly potentiates the antinociceptive effects of morphine sulfate administered at the spinal level.

The undecapeptide substance P and the alkaloid morphine sulfate are two agents previously thought to have opposite roles in the mediation of spinal nociceptive processes. The present report, however, demonstrates that low doses of substance P when coadministered with marginally effective doses of morphine sulfate into the rat subarachnoid space produce a markedly enhanced analgesic response, as monitored by the tail-flick test. This pharmacological effect is blocked by prior treatment with the opioid antagonist naloxone, indicating that the potentiated analgesic response is mediated by opioid-responsive neurons. In addition, the putative immediate precursor form of substance P (i.e., substance P-glycine) may substitute for the mature compound in the potentiated pharmacological effect. Moreover, the described synergism is unaffected by transection of the spinal cord, demonstrating the lack of supraspinal modulation of the observed phenomenon. Based on these observations, we are now able to dissociate opioid-potentiating and analgesic properties of substance P from traditional hyperalgesic effects realized at significantly higher concentrations. Consistent with previous biochemical data, a likely mechanism underlying the peptide-mediated enhancement of opioid analgesia may center on the ability of substance P to release endogenous opioid peptides within the local spinal cord environment. Finally, the pharmacological relationship of coadministered substance P and morphine sulfate established here supports the hypothesis that spinal tachykinin and opioid systems have a direct functional interaction in the modulation of local nociceptive responses.

Analgesia↗