dizocilpine-maleate and Paralysis

The aims of this study were to investigate the occurrence of apoptotic cell death in the dorsal horn of the adult rat spinal cord following chronic constriction injury (CCI) to the sciatic nerve and to correlate this with behavioural responses. Six groups of six rats were used as follows: 1) CCI, 2) CCI, 3) MK801 + CCI, 4) axotomy, 5) sham, and 6) naive. Group 1 animals were behaviourally tested for thermal hyperalgesia 8 days following surgery and sacrificed and the spinal cords removed and frozen. The rest of the groups underwent the same procedure 14 days following surgery. The lumbar region of the spinal cord was cryosectioned and the incidence of apoptotic cells investigated using the TUNEL technique plus Hoechst double labelling. By 8 days post-CCI, hyperalgesia had developed in the ipsilateral paw, which was still present 14 days after the injury compared to the contralateral paw and naive and sham animals. Preemptive MK-801 prevented the onset of hyperalgesia. Significant numbers of apoptotic cells were present in the ipsilateral dorsal horn of the spinal cord 8 and 14 days following CCI compared to the contralateral side and to naive and sham animals. Preemptive treatment with MK-801 reduced the extent of apoptosis resulting from CCI to the level seen in control animals. This study demonstrates that cells undergo apoptosis as a result of CCI simultaneous with the occurrence of hyperalgesia. Furthermore, MK-801 prevents the onset of hyperalgesia and reduces the extent of apoptotic cell death, suggesting, perhaps, that apoptosis contributes to the initiation/maintenance of hyperalgesia.

Topics: Animals; Apoptosis; Causalgia; Constriction; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Ganglia, Spinal; Hot Temperature; Hyperalgesia; In Situ Nick-End Labeling; Male; Models, Neurological; N-Methylaspartate; Paralysis; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Reaction Time; Sciatic Nerve

The aims of this study were to clarify the histological and histochemical changes associated with cell death in the spinal cord after acute traumatic injury and to examine the role of excitatory amino acid release mediated by N-methyl-D-aspartate (NMDA) receptors.. Following laminectomy, the spinal cord in 70 rats was injured at the T-9 level by applying extradural static weight-compression, in which a cylindrical compressor was used to induce complete and irreversible transverse spinal cord injury (SCI) with paralysis of the lower extremities. The injured rats were killed between 30 minutes and 14 days after injury, and the injured cord was removed en bloc. Rats that received NMDA receptor antagonist (MK-801) were killed at the same time points as those that received saline. The specimens were stained with hematoxylin and eosin, Nissl, and Klüver-Barrera Luxol fast blue and subjected to in situ nick-end labeling, a specific in situ method used to allow visualization of apoptosis. Thirty minutes post-SCI, a large hematoma was observed at the compressed segment. Six hours after injury, large numbers of dead cells that were not stained by in situ nick-end labeling were observed. Between 12 hours and 14 days postinjury, nuclei stained by using the in situ nick-end labeling technique were observed not only at the injury site but also in adjoining segments that had not undergone mechanical compression, suggesting that the delayed cell death was due to apoptosis. The number of cells stained by in situ nick-end labeling was maximum at 3 days postinjury. The results of electron microscopic examination were also consistent with apoptosis. In the MK-801-treated rats, the number of cells stained by in situ nick-end labeling was smaller than in nontreated rats at both 24 hours and 7 days after injury.. These findings suggest that NMDA-receptor activation promotes delayed neuronal and glial cell death due to apoptosis.

Topics: Animals; Apoptosis; Cell Count; Cell Death; Cell Nucleus; Coloring Agents; Demyelinating Diseases; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Fluorescent Dyes; Hematoma; In Situ Nick-End Labeling; Laminectomy; Male; Microscopy, Electron; N-Methylaspartate; Nerve Fibers, Myelinated; Neurons; Neuroprotective Agents; Paralysis; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Spinal Cord Compression; Spinal Cord Injuries

1. In the vagotomized cat, blockade of NMDA receptors by dizocilpine (MK-801) produces an apneustic pattern of respiration characterized by a large increase in the duration of inspiration. 2. To identify dizocilpine-induced disfacilitations and disinhibitions in respiratory neurones generating the respiratory rhythm, membrane potential and input resistance of augmenting inspiratory (I; n = 11) and post-inspiratory (PI; n = 9) neurones were examined in the ventral respiratory group area, before and after administration of dizocilpine (0.1-0.3 mg kg-1 i.v.) in decerebrate, vagotomized, paralysed and artificially ventilated cats. 3. In I neurones, dizocilpine decreased the ramp depolarization and an 82% increase in input resistance was observed during inspiration. The inspiratory phase was prolonged, leading to a sustained level of depolarization during apneusis. The amplitude of stage 1 expiratory hyperpolarization decreased and its decay, which is normally slow, was faster. Throughout the remainder of expiration (stage 2) the membrane potential levelled off and the input resistance increased slightly (by 15%). 4. In PI neurones, dizocilpine depressed depolarization and suppressed firing in eight out of nine cells during the stage 1 expiratory phase. This was associated with a large (91%) increase of input resistance. The membrane potential switched quickly to stage 2 expiratory repolarization, during which a slight (19%) increase in input resistance occurred. 5. The hyperpolarization of PI neurones during early inspiration was reduced in amplitude by dizocilpine and input resistance was increased by 75% during inspiration, indicating that dizocilpine reduced the activity of the presynaptic inhibitory early-inspiratory (eI) neurones. 6. We conclude that NMDA receptor blockade in the respiratory network disfacilitates eI, I and PI neurones during their active phase. Decreased inhibitory processes during the inspiratory phase probably play a major role in the prolongation of inspiration.

Topics: Animals; Cats; Decerebrate State; Dizocilpine Maleate; Membrane Potentials; Neurons; Paralysis; Receptors, N-Methyl-D-Aspartate; Respiratory Mechanics; Respiratory Physiological Phenomena; Respiratory System; Vagotomy; Vagus Nerve

Paralysis of the soleus muscle in newborn rats causes a large proportion of motoneurons to die by 10 weeks of age. However, all of these neurons are still present at three to four weeks of age. We have previously shown that although nerve injury at five days does not result in any motoneuron death, it does render these neurons susceptible to the toxic effects of the glutamate agonist N-methyl-D-aspartate. Using retrograde labelling of soleus motoneurons, in this study we show that an increased susceptibility to glutamate also plays a role in the eventual death of those motoneurons which survive for three weeks after interruption of neuromuscular transmission at birth but die by 10 weeks. Treatment with dizocilpine maleate an antagonist of the N-methyl-D-aspartate receptor increased the survival of motoneurons to alpha-bungarotoxin-treated soleus muscles. By 10 weeks of age the size of motoneurons to alpha-bungarotoxin-treated soleus muscles is smaller than that of controls, but after treatment with dizocilpine maleate the sizes of motoneurons to control and treated muscles are similar. Moreover, only 55 +/- 2.7% of motoneurons to the soleus muscle paralysed at birth with alpha-bungarotoxin survive for three weeks after a single injection of N-methyl-D-aspartate at 12 days of age. This motoneuron death is due to the application of N-methyl-D-aspartate since treatment with alpha-bungarotoxin alone causes no loss of neurons at this age.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Dizocilpine Maleate; Humans; Infant, Newborn; Motor Neurons; Muscle, Skeletal; Muscles; N-Methylaspartate; Paralysis; Rats; Rats, Wistar; Spinal Cord

Selective antagonists of N-methyl-D-aspartate (NMDA) excitatory amino acid (EAA) receptors have been shown to protect against dynorphin-A (DYN)-induced paralysis and neurotoxicity in the spinal cord. To test the hypothesis that either DYN-induced paralysis or neurotoxicity involves an enhanced release of EAAs, we used microdialysis to monitor aspartate (Asp) and glutamate (Glu) release in both the lumbar spinal cord extracellular fluid (ECF) and the spinal cord cerebral spinal fluid (CSF) of conscious rats in response to DYN (1-13). Injection of 5 nmol of DYN produced temporary paralysis in 8 of 10 animals, but did not significantly change Asp or Glu release in either the ECF or the CSF. Injection of 20 nmol of DYN caused permanent paralysis and neuronal cell loss in all animals tested as well as a significant increase of Asp and Glu in both the ECF and the CSF, and a decrease in glutamine (Gln) release only in the ECF. Pretreatment with 1 mg/kg of the NMDA antagonist MK-801 blocked both paralysis and amino acid changes in the ECF. Pretreatment of animals with 5 mg/kg naloxone inhibited glutamate release in the ECF, but did not block paralysis, Asp release or inhibition of Gln release. As MK-801 sensitive paralysis by DYN was not mediated through enhanced EAA release, we examined whether DYN could act through postsynaptic facilitation of NMDA receptors by testing the ability of DYN to alter the magnitude of a behavioral response produced by intrathecal injection of NMDA in mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Aspartic Acid; Behavior, Animal; Cell Death; Dizocilpine Maleate; Dynorphins; Glutamates; Glutamic Acid; Male; N-Methylaspartate; Neurons; Paralysis; Rats; Rats, Inbred Strains; Spinal Cord

The role of N-methyl-D-aspartate (NMDA) receptor-channel activation in the production of respiratory pattern was studied by administration of the NMDA receptor-channel blocker (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801, 1-3 mg/kg, i.v.) to anesthetized adult rats. This dose of MK-801 blocked the excitatory effects of NMDA (applied iontophoretically) on brainstem respiratory neurons. The predominant respiratory response to systemic MK-801 administration was an increase in inspiratory duration and a decrease in amplitude of diaphragm electromyogram and phrenic nerve discharge. Effects on inspiratory timing and amplitude were most pronounced when the rats were vagotomized. Significant changes in arterial blood gases and pH after systemic MK-801 administration in spontaneously breathing rats (vagi intact or cut) indicated that ventilation was depressed by NMDA receptor-channel antagonism. Respiratory timing changes in response to systemic MK-801 administration differed between two rat strains studied. Breathing patterns resembling apneusis, i.e., with irregular inspiratory durations prolonged 2- to 30-fold, occurred in 60% of the vagotomized, spontaneously breathing Sprague-Dawley rats and none of the Wistar rats. Thus, the breathing pattern in Sprague-Dawley rats is more sensitive to interference with NMDA-mediated mechanisms. We propose that respiratory pattern generation and transmission of rhythmic respiratory drive are mediated by synergistic activation of NMDA and non-NMDA receptors at brainstem and spinal cord sites.

Topics: Anesthesia; Animals; Dizocilpine Maleate; Electromyography; Male; Oxygen; Paralysis; Pentobarbital; Rats; Rats, Sprague-Dawley; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; Respiration; Respiration Disorders; Respiration, Artificial; Vagotomy