Effects of Halothane and Isoflurane on Hyperexcitability of Spinal Dorsal Horn Neurons after Incision in the Rat

2005 ◽  
Vol 102 (1) ◽  
pp. 165-174 ◽  
Author(s):  
Mikito Kawamata ◽  
Eichi Narimatsu ◽  
Yuji Kozuka ◽  
Toshiyuki Takahashi ◽  
Shigekazu Sugino ◽  
...  
Keyword(s):  
Spontaneous Activity ◽  
Dorsal Horn ◽  
Neuronal Activity ◽  
Spinal Dorsal Horn ◽  
Dynamic Range ◽  
Field Size ◽  
Control Group ◽  
Sprague Dawley ◽  
Dorsal Horn Neurons ◽  
Spinal Dorsal

Background The aim of this study was to determine whether halothane and isoflurane used during and after surgical injury attenuate subsequent hyperexcitability of spinal dorsal horn (SDH) neurons by preventing development of central sensitization. Methods Activity of a wide-dynamic-range neuron of the SDH was isolated in decerebrate-spinal Sprague-Dawley rats, and neuronal activity (receptive field size and responses to nonnoxious and noxious stimuli) was recorded. A 1-cm-long incision was made through the skin, fascia, and muscle under anesthesia with halothane (1.1% or 2.2%) and isoflurane (1.4% or 2.8%). Anesthesia was discontinued just after the incision had been made or was continued until 30 min after the incision, and activity of the SDH neurons was measured for up to 2 h after the incision. In a control group, the incision was made without anesthesia. Results In the control group, the incision resulted in maximum excitation in the SDH neurons during surgery; spontaneous activity significantly increased for up to 30 min after the incision (P < 0.05) but did not significantly increase thereafter, returning to the preincision value. Halothane and isoflurane suppressed excitation of the neurons during the incision in a concentration-related manner. Administration of 2.2% halothane and 2.8% isoflurane during the incision and for up to 30 min after the incision almost abolished activity of the neurons for 30 min after the incision. The magnitude of neuronal activity 2 h after the incision was not significantly different among all groups, including the control group. Conclusions The results demonstrate that administration of halothane and isoflurane does not attenuate development of hyperexcitability of SDH neurons despite the fact that excitation and spontaneous activity during and after the incision were greatly suppressed by administration of halothane and isoflurane.

Changes in Properties of Spinal Dorsal Horn Neurons and Their Sensitivity to Morphine after Spinal Cord Injury in the Rat

2005 ◽  
Vol 102 (1) ◽  
pp. 152-164 ◽  
Author(s):  
Jungang Wang ◽  
Mikito Kawamata ◽  
Akiyoshi Namiki
Keyword(s):  
Spinal Cord ◽  
Spontaneous Activity ◽  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
High Threshold ◽  
Dorsal Horn Neurons ◽  
Spinal Dorsal ◽  
Cord Injury ◽  
Spinal Dorsal Horn Neurons ◽  
Wdr Neurons

Background To gain a better understanding of spinal cord injury (SCI)-induced central neuropathic pain, the authors investigated changes in properties of spinal dorsal horn neurons located rostrally and caudally to the lesion and their sensitivity to morphine in rats after SCI. Methods The right spinal cord of Sprague-Dawley rats was hemisected at the level of L2. At 10 to 14 days after the SCI, when mechanical hyperalgesia/allodynia had fully developed, spontaneous activity and evoked responses to mechanical stimuli of wide-dynamic-range (WDR) and high-threshold neurons rostral and caudal to the lesion were recorded. Effects of cumulative doses of systemic (0.1-3 mg/kg) and spinal (0.1-5 microg) administration of morphine on spontaneous activity and evoked responses to the stimuli of the neurons were evaluated. Results Spontaneous activity significantly increased in WDR neurons both rostral and caudal to the SCI site, but high-frequency background discharges with burst patterns were only observed in neurons rostral to the SCI site. Significant increases in responses to the mechanical stimuli were seen both in WDR and high-threshold neurons located both rostrally and caudally to the lesion. The responses to nonnoxious and noxious stimuli were significantly greater in caudal WDR neurons than in rostral WDR neurons. In contrast, the responses to pinch stimuli were significantly higher in rostral high-threshold neurons than those in caudal high-threshold neurons. Systemically administered morphine had a greater effect on responses to nonnoxious and noxious stimuli of rostral WDR neurons than those of caudal WDR neurons. Spinally administered morphine significantly suppressed responses of WDR neurons in SCI animals to nonnoxious stimuli compared with those in sham-operated control animals. Conclusions The findings suggest that changes in properties of spinal dorsal horn neurons after SCI are caused by different mechanisms, depending on the classification of the neurons and their segmental locations.

Antagonism of substance P induced facilitation of central neuronal activity by 2,4-dinitrophenol and depressant agents

1978 ◽  
Vol 56 (3) ◽  
pp. 527-530 ◽  
Author(s):  
Bhagavatula R. Sastry
Keyword(s):  
Nitrous Oxide ◽  
Substance P ◽  
Dorsal Horn ◽  
Neuronal Activity ◽  
Spinal Dorsal Horn ◽  
Cortical Cells ◽  
Dorsal Horn Neurons ◽  
Spinal Dorsal ◽  
Central Neurons ◽  
Spinal Dorsal Horn Neurons

2,4-Dinitrophenol, pentobarbital, thiopental, methoxyflurane, and halothane more often antagonized the facilitatory effects of substance P than of acetylcholine on the activity of spinal dorsal horn neurons (of unanaesthetized decerebrated and spinalized cats) as well as interpeduncular and cerebral cortical cells (of either rats anaesthetized with methoxyflurane, nitrous oxide, and oxygen or 'cerveau isolé' rats). The results of the studies indicate that the excitatory effects of substance P on central neurons are extremely sensitive to anaesthesia.

Plastic Changes in Nociceptive Transmission of the Rat Spinal Cord With Advancing Age

2002 ◽  
Vol 87 (2) ◽  
pp. 1086-1093 ◽  
Author(s):  
Koichi Iwata ◽  
Tetsuo Fukuoka ◽  
Eji Kondo ◽  
Yoshiyuki Tsuboi ◽  
Akimasa Tashiro ◽  
...  
Keyword(s):  
Dorsal Horn ◽  
Neuronal Activity ◽  
Spinal Dorsal Horn ◽  
Dynamic Range ◽  
High Threshold ◽  
Aged Rats ◽  
Adult Rats ◽  
Nociceptive Neurons ◽  
Spinal Dorsal ◽  
Age Related

To understand characteristics of the pain system in the elderly, we investigated the electrophysiological properties of nociceptive neurons in the lumbar spinal dorsal horn of aged (29–34-mo old) and adult (7–13-mo old) rats. The responses of nociceptive neurons to noxious thermal stimulation, as well as the spontaneous firing rate, were significantly higher in the aged as compared with adult rats. Furthermore, the size of the high-threshold receptive field area of wide dynamic range neurons was larger ( P < 0.01) and that of the low-threshold area was smaller ( P< 0.05) in aged rats than in adult rats. The increased nociceptive neuronal activity in the aged rats correlated with the finding that the paw withdrawal latency was significantly shorter in the aged rats than those of the adult rats following heat stimulation of the hind paw ( P < 0.05). Reversible local anesthetic block of descending pathways resulted in a dramatic increase in neuronal activity in adult rats but had little effect in aged rats. There was also a significant loss of serotoninergic and noradrenergic fibers in the spinal dorsal horn of the aged rats. These results demonstrate an age-related plasticity in spinal nociceptive processing that is related to impairment of descending modulatory pathways.

Responses of Rat Spinal Dorsal Horn Neurons to Intracutaneous Microinjection of Histamine, Capsaicin, and Other Irritants

1997 ◽  
Vol 77 (5) ◽  
pp. 2499-2514 ◽  
Author(s):  
E. Carstens
Keyword(s):  
Dorsal Horn ◽  
Spinal Dorsal Horn ◽  
Dynamic Range ◽  
Mustard Oil ◽  
High Threshold ◽  
Dorsal Horn Neurons ◽  
Spinal Dorsal ◽  
Range Type ◽  
The Mean ◽  
Spinal Dorsal Horn Neurons

Carstens, E. Responses of rat spinal dorsal horn neurons to intracutaneous microinjection of histamine, capsaicin, and other irritants. J. Neurophysiol. 77: 2499–2514, 1997. To investigate the spinal processing of cutaneous pruritic and algesic stimuli, single-unit recordings were made from wide-dynamic-range-type lumbar spinal dorsal horn neurons in pentobarbital-sodium-anesthetized rats. Neuronal responses were recorded to mechanical and noxious thermal stimuli, as well as to microinjection (1 μl) of histamine (0.01–10% = 9 × 10−1–9 × 10−4 M), capsaicin (0.1% = 3.3 × 10−3 M), or other algesic chemicals into skin within the receptive field via intracutaneously placed needles. Most (84%) of the 89 neurons responded to intracutaneous (ic) microinjection of histamine with a brief phasic discharge followed by an afterdischarge of variable (s to min) duration. Ten minutes after ic microinjection of histamine (but not NaCl), there was a significant increase in the mean area of the low-threshold (but not high-threshold) portion of unit mechanical receptive fields. However, responses to graded pressure stimuli were not significantly affected after histamine. Responses did not exhibit significant tachyphylaxis when histamine microinjections were repeated at 5- or 10-min intervals. Unit responses significantly increased in a dose-related manner to microinjection of histamine at concentrations ranging across 4 orders of magnitude. Within 30 s after ic microinjection of the H1 antagonist cetirizine, unit responses to ic histamine delivered at the same skin site were significantly attenuated. Unit responses to histamine, as well as to noxious thermal stimulation, were significantly reduced after systemic administration of morphine (3.5 mg/kg ip) in a naloxone-reversible manner. Application of a mechanical rub, scratch, or a noxious heat stimulus during the unit's ongoing response to ic histamine produced a brief and marked excitation, often followed by a period of reduced ongoing discharge. Unit responses to histamine were markedly suppressed by electrical stimulation in the midbrain periaqueductal gray. Most (79%) histamine-responsive units tested also responded to ic microinjection of capsaicin. After the initial microinjection of capsaicin, subsequent responses to histamine and capsaicin microinjections were significantly reduced. Units also responded to ic ethanol (capsaicin vehicle) in a dose-related manner, and showed tachyphylaxis to repeated ic ethanol at 80% but not at 8%. The mean response to 80% ethanol was significantly smaller than to 0.1% capsaicin. All units tested also responded to topical application of mustard oil (50%) and ic serotonin (30 μg). The results are discussed in terms of theories that attempt to reconcile psychophysical and clinical observations of pain and itch sensation.

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