-
The Journal of Neuroscience : the... Mar 2009The role of the nucleus retroambiguus (NRA) in the context of respiration control has been subject of debate for considerable time. To solve this problem, we chemically...
The role of the nucleus retroambiguus (NRA) in the context of respiration control has been subject of debate for considerable time. To solve this problem, we chemically (using d, l-homocysteic acid) stimulated the NRA in unanesthetized precollicularly decerebrated cats and studied the respiratory effect via simultaneous measurement of tracheal pressure and electromyograms of diaphragm, internal intercostal (IIC), cricothyroid (CT), and external oblique abdominal (EO) muscles. NRA-stimulation 0-1 mm caudal to the obex resulted in recruitment of IIC muscle and reduction in respiratory frequency. NRA-stimulation 1-3 mm caudal to the obex produced vocalization along with CT activation and slight increase in tracheal pressure, but no change in respiratory frequency. NRA-stimulation 3-5 mm caudal to the obex produced CT muscle activation and an increase in respiratory frequency, but no vocalization. NRA-stimulation 5-8 mm caudal to the obex produced EO muscle activation and reduction in respiratory frequency. A change to the inspiratory effort was never observed, regardless of which NRA part was stimulated. The results demonstrate that NRA does not control eupneic inspiration but consists of topographically separate groups of premotor interneurons each producing detailed motor actions. These motor activities have in common that they require changes to eupneic breathing. Different combination of activation of these premotor neurons determines the final outcome, e.g., vocalization, vomiting, coughing, sneezing, mating posture, or child delivery. Higher brainstem regions such as the midbrain periaqueductal gray (PAG) decides which combination of NRA neurons are excited. In simple terms, the NRA is the piano, the PAG one of the piano players.
Topics: Abdominal Muscles; Animals; Cats; Decerebrate State; Diaphragm; Electromyography; Homocysteine; Inhalation; Intercostal Muscles; Laryngeal Muscles; Medulla Oblongata; Microinjections; Periaqueductal Gray; Pressure; Respiration; Trachea; Vocalization, Animal
PubMed: 19321779
DOI: 10.1523/JNEUROSCI.0607-09.2009 -
Journal of Clinical Microbiology May 2009The examination of rectoanal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens for the diagnosis of transmissible spongiform encephalopathies has been...
Validation of use of rectoanal mucosa-associated lymphoid tissue for immunohistochemical diagnosis of chronic wasting disease in white-tailed deer (Odocoileus virginianus).
The examination of rectoanal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens for the diagnosis of transmissible spongiform encephalopathies has been described in sheep, elk, and small numbers of mule and white-tailed deer. Previous sample numbers have been too small to validate examination of this type of tissue as a viable antemortem diagnostic test. In this study, we examined RAMALT collected postmortem from 76 white-tailed deer removed from a farm in Wisconsin known to be affected by chronic wasting disease (CWD) and from 210 free-ranging white-tailed deer harvested from an area in Wisconsin where the overall prevalence of CWD among the deer was approximately 4 to 6%. The results of immunohistochemical (IHC) staining of the RAMALT sections were compared to the results of IHC staining of sections from the brain stem at the convergence of the dorsal motor nucleus of the vagus nerve, sections of the medial retropharyngeal lymph nodes (RLNs), and sections of tonsil (sections of tonsil only from captive animals were tested). The sensitivities of the IHC staining test with RAMALT sections were 81% for the captive animals and 91% for the free-ranging animals. False-negative results were usually associated with early infection, indicated by a low intensity of immunostaining in the obex and/or a polymorphism at PRNP codon 96. While the RLN remains the tissue of choice for use for the diagnosis of CWD in white-tailed deer, the results of the present study further support the use of RAMALTs collected antemortem as an adjunct to testing of tonsil biopsy specimens and surveillance by necropsy for the screening of farmed deer which have been put at risk through environmental exposure or exposure to deer with CWD.
Topics: Animals; Brain; Deer; False Negative Reactions; Immunohistochemistry; Intestinal Mucosa; Lymphoid Tissue; Rectum; Sensitivity and Specificity; Wasting Disease, Chronic; Wisconsin
PubMed: 19261781
DOI: 10.1128/JCM.02209-08 -
American Journal of Physiology.... Mar 2008Neurons in the medullary reticular formation (MRF) of the rat receive a vast array of urogenital inputs. Using select acute and chronic spinal cord lesions to identify...
Neurons in the medullary reticular formation (MRF) of the rat receive a vast array of urogenital inputs. Using select acute and chronic spinal cord lesions to identify the location of the ascending neural circuitries providing either direct or indirect inputs to MRF from the penis, our previous studies demonstrated that the dorsal columns and dorsal half of the lateral funiculus convey low- and high-threshold inputs, respectively. In the present study, the gracile nucleus was targeted as one of the likely sources of low-threshold information from the penis to MRF. Both electrophysiological recordings and neuroanatomical tracing [injection of cholera toxin B subunit (CTB) into a dorsal nerve of the penis] were used. After discrimination of a single neuron responding to penile stimulation, testing for somatovisceral convergence was done (mechanical stimulation of the distal colon and the skin over the entire hindquarters). In 12 rats, a limited number of neurons (43 in total) responded to penile stimulation. Many of these neurons also responded to scrotal stimulation (53.5%, dorsal and/or ventral scrotum) and/or prepuce stimulation (46.5%). Histological reconstruction of the electrode tracks showed that the majority of neurons responding to penile stimulation were located ventrally within the medial one-third of the gracile nucleus surrounding obex. This location corresponded to sparse innervation by CTB-immunoreactive primary afferent terminals. These results indicate that neurons in the gracile nucleus are likely part of the pathway that provides low-threshold penile inputs to MRF, a region known to play an important role in mating processes.
Topics: Animals; Cholera Toxin; Electrophysiology; Immunohistochemistry; Male; Medulla Oblongata; Microelectrodes; Microscopy, Confocal; Neural Pathways; Neurons, Afferent; Penis; Physical Stimulation; Presynaptic Terminals; Rats; Rats, Wistar
PubMed: 18171689
DOI: 10.1152/ajpregu.00656.2007 -
The Journal of Physiology Oct 2006The climbing fibre projection from the motor cortex to the cerebellar cortical C1 zone in the posterior lobe of the rat cerebellum was investigated using a combination...
The climbing fibre projection from the motor cortex to the cerebellar cortical C1 zone in the posterior lobe of the rat cerebellum was investigated using a combination of physiological, anatomical and neuropharmacological techniques. Electrical stimulation of the ipsilateral fore- or hindimbs or somatotopically corresponding parts of the contralateral motor cortex evoked climbing fibre field potentials at the same cerebellar recording sites. Forelimb-related responses were located in the C1 zone in the paramedian lobule or lobulus simplex and hindlimb-related responses were located in the C1 zone in the copula pyramidis. Microinjections of anterograde axonal tracer (Fluoro-Ruby or Fluoro-Emerald) were made into the fore- or hindlimb parts of the motor cortex where stimulation evoked the largest cerebellar responses. After a survival period of 7-10 days, the neuraxis was examined for anterograde labelling. No terminal labelling was ever found in the inferior olive, but labelled terminals were consistently found in a well-localized site in the dorso-medial medulla, ventral to the gracile nucleus, termed the matrix region. Pharmacological inactivation of the matrix region (2 mm caudal to the obex) selectively reduced transmission in descending (cerebro-olivocerebellar) but not ascending (spino-olivocerebellar) paths targeting fore- or hindlimb-receiving parts of the C1 zone. Transmission in spino-olivocerebellar paths was either unaffected, or in some cases increased. The identification of a novel pre-olivary relay in cerebro-olivocerebellar paths originating from fore- and hindlimb motor cortex has implications for the regulation of transmission in climbing fibre pathways during voluntary movements and motor learning.
Topics: Action Potentials; Animals; Cerebral Cortex; Electric Stimulation; Electrophysiology; Male; Medulla Oblongata; Motor Activity; Motor Cortex; Nerve Fibers; Psychomotor Performance; Rats; Rats, Wistar; Signal Transduction; Spinal Cord; Synaptic Transmission
PubMed: 16887878
DOI: 10.1113/jphysiol.2006.114215 -
Canadian Journal of Veterinary Research... Jul 2005The purpose of this study was to enhance the sensitivity of the Western blot (WB) test for use as an alternative and confirmatory method for the diagnosis of scrapie and... (Comparative Study)
Comparative Study
The purpose of this study was to enhance the sensitivity of the Western blot (WB) test for use as an alternative and confirmatory method for the diagnosis of scrapie and chronic wasting disease (CWD) in Canada by comparing 2 sample preparation procedures: an abnormal prion protein (PrPSc) concentration procedure using sodium phosphotungstic acid (PTA) precipitation and a procedure using crude sample without precipitation. A total of 100 cerebrum samples (52 sheep and 48 elk), including 66 negative (31 sheep, 35 elk) and 34 positive (21 scrapie and 13 CWD positive) samples diagnosed by using immunohistochemistry (IHC) on retropharyngeal lymph node (RPLN) and medulla oblongata at obex, were tested by using WB with the 2 sample preparation procedures. The WB using non-PTA enriched sample (crude extract) detected, on average, only 71.7% (9 of 15, 60.0% for scrapie, 5 of 6, 83.3% for CWD) of the samples that tested positive by using WB with PTA enriched samples. No case was positive by WB using crude extract but negative by WB using PTA enriched sample. No false positive was found. Serial dilution of PTA precipitated samples demonstrated that the technique increases the detection limit approximately 100 fold. Additionally, the comparison of the WB and IHC on cerebrum from all the positive cases demonstrated that WB following PTA precipitation and IHC had 100% agreement by detecting 6 positive for CWD on cerebrum; while IHC detected scrapie in only 14 out of 15 positive cerebrum samples by using WB following PTA precipitation. Phosphotungstic acid precipitation is therefore a useful adjunct to WB analysis of scrapie and CWD and tissues.
Topics: Animals; Animals, Wild; Blotting, Western; Canada; Chemical Precipitation; Deer; Immunohistochemistry; Phosphotungstic Acid; PrPSc Proteins; Prions; Scrapie; Sensitivity and Specificity; Sheep; Wasting Disease, Chronic
PubMed: 16187549
DOI: No ID Found -
Journal of Neurophysiology Feb 2005Responses of separate regions of rat cerebellar cortex (Cb) to inferior olive (IO) stimulation occur with the same latency despite large differences in climbing fiber... (Comparative Study)
Comparative Study
Responses of separate regions of rat cerebellar cortex (Cb) to inferior olive (IO) stimulation occur with the same latency despite large differences in climbing fiber (CF) lengths. Here, the olivocerebellar path of turtle was studied because its Cb is an unfoliated sheet on which measurements of latency and CF length can be made directly across its entire surface in vitro. During extracellular DC recordings at a given Cb position below the molecular layer, IO stimulation evoked a large negative field potential with a half-width duration of approximately 6.5 ms. On this response were smaller oscillations similar to complex spikes. The stimulating electrode was moved to map the IO and the CF path from the brain stem to the Cb. The contralateral brain stem region that evoked these responses was tightly circumscribed within the medulla, lateral and deep to the obex. This response remained when the brain stem was bathed in solutions that blocked synaptic transmission. The Cb response to IO stimulation had a peak latency of approximately 10 ms that was not dependent on the position of the recording electrode across the entire 8-mm rostrocaudal length of the Cb. However, for a constant Cb recording position, moving the stimulation across the midline to the ipsilateral brain stem and along the lateral wall of the fourth ventricle toward the peduncle did shorten the response latency. Therefore a synchronous Cb response to CF stimulation seems to be caused by changes in its conduction velocity within the entire cerebellar cortex but not within the brain stem.
Topics: Action Potentials; Afferent Pathways; Animals; Brain Stem; Cerebellar Cortex; Nerve Fibers; Reaction Time; Turtles
PubMed: 15456808
DOI: 10.1152/jn.00132.2004 -
American Journal of Physiology.... Sep 2003The aim of this study was to investigate the efficacy, receptor specificity, and site of action of Delta9-tetrahydrocannabinol (THC) as an antiemetic in the ferret. THC...
The aim of this study was to investigate the efficacy, receptor specificity, and site of action of Delta9-tetrahydrocannabinol (THC) as an antiemetic in the ferret. THC (0.05-1 mg/kg ip) dose-dependently inhibited the emetic actions of cisplatin. The ED50 for retching was approximately 0.1 mg/kg and for vomiting was 0.05 mg/kg. A specific cannabinoid (CB)1 receptor antagonist SR-141716A (5 mg/kg ip) reversed the effect of THC, whereas the CB2 receptor antagonist SR-144528 (5 mg/kg ip) was ineffective. THC applied to the surface of the brain stem was sufficient to inhibit emesis induced by intragastric hypertonic saline. The site of action of THC in the brain stem was further assessed using Fos immunohistochemistry. Fos expression induced by cisplatin in the dorsal motor nucleus of the vagus (DMNX) and the medial subnucleus of the nucleus of the solitary tract (NTS), but not other subnuclei of the NTS, was significantly reduced by THC rostral to obex. At the level of the obex, THC reduced Fos expression in the area postrema and the dorsal subnucleus of the NTS. The highest density of CB1 receptor immunoreactivity was found in the DMNX and the medial subnucleus of the NTS. Lower densities were observed in the area postrema and dorsal subnucleus of the NTS. Caudal to obex, there was moderate density of staining in the commissural subnucleus of the NTS. These results show that THC selectively acts at CB1 receptors to reduce neuronal activation in response to emetic stimuli in specific regions of the dorsal vagal complex.
Topics: Animals; Antiemetics; Area Postrema; Cisplatin; Dronabinol; Ferrets; Medulla Oblongata; Proto-Oncogene Proteins c-fos; Receptors, Cannabinoid; Receptors, Drug; Tissue Distribution; Vagus Nerve; Vomiting
PubMed: 12791597
DOI: 10.1152/ajpgi.00113.2003 -
The Journal of Physiology Dec 2002We report that after spontaneous breathing movements are stopped by administration of opioids (opioid-induced apnoea) in neonatal rats, abdominal muscles continue to...
We report that after spontaneous breathing movements are stopped by administration of opioids (opioid-induced apnoea) in neonatal rats, abdominal muscles continue to contract at a rate similar to that observed during periods of ventilation. Correspondingly, in vitro bath application of a mu opioid receptor agonist suppresses the activity of the fourth cervical root (C4) supplying the diaphragm, but not the rhythmic activity of the first lumbar root (L1) innervating the abdominal muscles. This indicates the existence of opioid-resistant rhythmogenic neurones and a neuronal pathway transmitting their activity to the abdominal motoneurones. We have investigated this pathway by using a brainstem-spinal cord preparation of the neonatal rat. We identified bulbospinal neurones with a firing pattern identical to that of the L1 root. These neurones were located caudal to the obex in the vicinity of the nucleus retroambiguus. Resting potentials ranged from -49 to -40 mV (mean +/- S.D. -44.0 +/- 4.3 mV). The mean input resistance was 315.5 +/- 54.8 MOmega. The mean antidromic latency from the L1 level was 42.8 +/- 4.4 ms. Axons crossed the midline at the level of the cell body. The activity pattern of the bulbospinal neurones and the L1 root consisted of two bursts per respiratory cycle with a silent period during inspiration. This pattern is characteristic of preinspiratory neurones. We found that 11 % of the preinspiratory neurones projected to the area where the bulbospinal neurones were located. These preinspiratory neurones were found in the rostral ventrolateral medulla close (200-350 microm) to the ventral surface at the level of the rostral half of the nucleus retrofacialis. Our data suggest the operation of a disynaptic pathway from the preinspiratory neurones to the L1 motoneurones in the in vitro preparation. We propose that the same pathway is responsible for rhythmic activation of the abdominal muscles during opioid-induced apnoea in the newborn rat.
Topics: Abdominal Muscles; Animals; Animals, Newborn; Drug Resistance; Electromyography; Electrophysiology; Fentanyl; In Vitro Techniques; Inhalation; Lumbosacral Region; Medulla Oblongata; Narcotics; Neck; Neural Pathways; Neurons; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, Opioid, mu; Respiratory System; Spinal Cord; Spinal Nerve Roots
PubMed: 12482904
DOI: 10.1113/jphysiol.2002.023408 -
The Journal of Veterinary Medical... Sep 2002A seven-year-old male elk (Cervus elaphus nelsoni) was euthanized and necropsied after having a 3-week history of body weight loss, emaciation, excessive salivation,...
A seven-year-old male elk (Cervus elaphus nelsoni) was euthanized and necropsied after having a 3-week history of body weight loss, emaciation, excessive salivation, teeth grinding, fever, anorexia, and respiratory distress. The elk was imported into Korea from Canada on March 9, 1997. Gross pathologic findings were restricted to a diffuse fibrinous pneumonia. Microscopic lesions included mild neuronal vacuolation and spongiform change in the neuropil of selected brain stem nuclei and generalized astrocytosis. Immunohistochemistry for protease-resistant prion protein (PrP(res)) was positive in all brain sections but more pronounced in the section of the obex of the medulla. And the PrP(res) was also detected by western immunoblotting in the brain and spinal cord. All the remaining elk and deer that had been in contact with this elk were destroyed and negative for chronic wasting disease (CWD). To our knowledge, this is the first case of CWD occurring outside of the U.S.A. and Canada.
Topics: Animals; Blotting, Western; Canada; Central Nervous System; Deer; Emigration and Immigration; Korea; Male; Prions; Wasting Disease, Chronic
PubMed: 12399615
DOI: 10.1292/jvms.64.855 -
The Journal of Physiology Oct 2002We have measured the release of adenosine and inosine from the dorsal surface of the brainstem and from within the nucleus tractus solitarii (NTS) during the defence...
We have measured the release of adenosine and inosine from the dorsal surface of the brainstem and from within the nucleus tractus solitarii (NTS) during the defence response evoked by hypothalamic stimulation in the anaesthetised rat. At the surface of the brainstem, only release of inosine was detected on hypothalamic defence area stimulation. This inosine signal was greatly reduced by addition of the ecto-5'-nucleotidase inhibitor alpha,beta-methylene ADP (200 microM), suggesting that the inosine arose from adenosine that was produced in the extracellular space by the prior release of ATP. By placing a microelectrode biosensor into the NTS under stereotaxic control we have recorded release of adenosine within this nucleus. By contrast to the brainstem surface, a fast increase in adenosine, accompanied only by a much smaller change in inosine levels, was seen following stimulation of the hypothalamic defence area. The release of adenosine following hypothalamic stimulation was mainly confined to a narrow region of the NTS some 500 microm in length around the level of the obex. Interestingly the release of adenosine was depletable: when the defence reaction was evoked at short time intervals, much less adenosine was released on the second stimulus. Our novel techniques have given unprecedented real-time measurement and localisation of adenosine release in vivo and demonstrate that adenosine is released at the right time and in sufficient quantities to contribute to the cardiovascular components of the defence reaction.
Topics: Adenosine; Adenosine Diphosphate; Animals; Biosensing Techniques; Brain Stem; Computer Systems; Electric Stimulation; Enzyme Inhibitors; Escape Reaction; Hypothalamus; Inosine; Microelectrodes; Rats; Rats, Sprague-Dawley; Solitary Nucleus; Time Factors
PubMed: 12356888
DOI: 10.1113/jphysiol.2002.024158