Neuroscience letters
-
Neuroscience letters · May 1999
Mechanical sensitization of cutaneous C-fiber nociceptors by prostaglandin E2 in the rat.
While it is generally assumed that nociceptor sensitization underlies peripheral hyperalgesia, there is disagreement regarding the ability of inflammatory mediators to sensitize nociceptors to mechanical stimuli. In this in vivo electrophysiological study, mechanical threshold and response to sustained threshold and sustained suprathreshold mechanical stimuli were measured before and after intradermal administration of prostaglandin E2 (PGE2) into the receptive field of cutaneous C-fiber nociceptors in the rat. PGE2 produced a decrease in mechanical threshold and an increase in response to sustained threshold but not sustained suprathreshold mechanical stimulation. These data suggest that while inflammatory mediators produce a decrease in mechanical threshold and/or an increase in number of action potentials to sustained threshold stimuli, they do not increase the maximal response to mechanical stimuli in C-fiber nociceptors.
-
Neuroscience letters · Apr 1999
Clinical TrialSensory threshold changes without initial pain or alterations in cutaneous blood flow, in the area of secondary hyperalgesia caused by topical application of capsaicin in humans.
Changes in von Frey hair perception, pricking pain, and vibration thresholds were examined in six healthy human adults, in the zone of secondary hyperalgesia, 45 min following the topical application of capsaicin at concentrations of 0.05 and 0.1 mg/ml. In two of these subjects, cutaneous blood flow was monitored at 10-min intervals, before, during and after capsaicin application, using laser Doppler perfusion imaging. ⋯ However, there was no visible skin flare, and no change in cutaneous blood flow at these doses of capsaicin. The effects on von Frey perception threshold and vibration threshold have not been demonstrated previously, and may be indicative of central changes, initiated by afferent fibres (presumably C fibres) that are not vasoactive.
-
Neuroscience letters · Apr 1999
N-methyl-D-asparate receptor antagonists abolish the maintenance phase of self-sustaining status epilepticus in rat.
We examined the effects of blockers of N-methyl-D-asparate (NMDA) and +/- -alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate receptors on the maintenance of self-sustaining status epilepticus (SSSE) induced in rats by brief intermittent electrical stimulation of the perforant path (PPS). Blocking of NMDA receptor at the PCP site by MK-801 (0.5 mg/kg, i.p.) or ketamine (10 mg/kg, i.p.) as well as at the glycine allosteric site by intrahippocampal 5,7-dichlorokynurenic acid (5,7-DCK, 10 nmol), rapidly and irreversibly aborted both behavioral and electrographic manifestation of SSS. Intrahippocampal injection of the AMPA/kainate receptor blocker 6-cyano7-nitroquinixaline-3-dione (CNQX, 10 nmol) transiently suppressed seizures, which reappeared 4-5 h later. We suggest that the maintenance phase of SSSE depends on activation of NMDA receptors and that NMDA receptor blockers may be a promising class of compounds for the treatment of status epilepticus.
-
Neuroscience letters · Mar 1999
Erectile function in male rats after lesions in the lateral paragigantocellular nucleus.
In previous research on rats, lesions of the lateral paragigantocellular nucleus (LPGi) in the medulla have facilitated the display of reflexive erection and ejaculation. The present research sought to replicate and extend these findings by determining whether LPGi lesions would also promote erection during copulation and during exposure of the male to inaccessible females, i.e. non-contact erections (NCEs). ⋯ However, the lesions did not change the copulatory intromission ratio, a partial measure of erectile function, nor did they change the incidence, latency, or number of NCEs displayed. More direct measures of erection will be necessary to determine whether the inhibitory role of LPGi on sexual reflexes is absent in some erectile contexts, or whether its role in some contexts is too small to be evident in behavioral measures.
-
Neuroscience letters · Mar 1999
Gabapentin prevents hyperalgesia during the formalin test in diabetic rats.
The anticonvulsant agent gabapentin exhibits antihyperalgesic properties in animal models of neuropathic pain. Diabetic rats display increased nocifensive behavior during the formalin test of persistent chemical irritation to the paw, suggesting the presence of abnormal pain processing mechanisms. We therefore, investigated the efficacy of gabapentin on formalin-evoked behavior in diabetic rats. ⋯ When 0.5% formalin was used, diabetic rats exhibited increased flinching during both the quiescent phase and phase 2. Gabapentin was without effect in controls but suppressed (P < 0.01) the increased flinching in diabetic rats. Gabapentin displays efficacy against abnormal sensory processing in diabetic rats and may be of benefit for treating painful diabetic neuropathy.