Neuroscience letters
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Neuroscience letters · Jan 1993
Evidence for endogenous inhibition of autotomy by galanin in the rat after sciatic nerve section: demonstrated by chronic intrathecal infusion of a high affinity galanin receptor antagonist.
We have studied the effect of M-35 [Galanin(1-12)-Pro-bradykinin(2-9)-amide], a newly developed high affinity antagonist for galanin receptors, on self-mutilation (autotomy) behavior of the deafferented limb in rats after unilateral section of sciatic nerves. M-35 (1.3 micrograms/microliters) or saline was applied to the lumbar spinal cord through a chronically implanted intrathecal catheter at a rate of 0.5 microliter/h for 10 days post axotomy via an osmotic minipump. ⋯ M-35 did not noticeably influence either the galanin mRNA level in corresponding dorsal root ganglia and dorsal horn region or the percent of lumbar sensory neurons expressing detectable levels of mRNA for galanin. It is suggested that galanin can endogenously suppress autotomy behavior in rats after nerve injury and thus may play an important role in the control of the development of neuropathic pain.
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Neuroscience letters · Dec 1992
Comparative StudyComparison of binding at strychnine-sensitive (inhibitory glycine receptor) and strychnine-insensitive (N-methyl-D-aspartate receptor) glycine binding sites.
We compared, for a number of ligands to the two receptors, the displacement of [3H]strychnine binding to the glycine-gated chloride channel of spinal cord and brainstem synaptic membranes to the displacement of [3H]glycine binding to the NMDA receptor complex of hippocampal and cortex synaptic membranes. Glycine and beta-alanine are recognized by both receptors. ⋯ Of the compounds tested, only strychnine, brucine, taurine and (S)-HA-966 were more potent displacers of [3H]strychnine than of glycine binding. Generally, the two glycine recognition sites appear to have remarkably different structural requirements.
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Neuroscience letters · Sep 1992
The long-acting cholinesterase inhibitor heptyl-physostigmine attenuates the scopolamine-induced learning impairment of rats in a 14-unit T-maze.
Heptyl-physostigmine (heptyl-Phy), a new carbamate derivative of physostigmine (Phy), has been assessed for potential clinical value by evaluating its in vitro activity against human erythrocyte acetylcholinesterase (AChE) and plasma butyrylcholinesterase (BChE), its duration of in vivo activity against rat plasma AChE, and its effects on attenuating a scopolamine-induced impairment in learning performance of young rats in a 14-unit T-maze. Heptyl-Phy demonstrated potent cholinesterase inhibition, with activity similar to that of Phy against AChE, IC50 values 21.7 +/- 2.0 nM and 27.9 +/- 2.4 nM, respectively, and significantly greater than that of Phy against BChE, IC50 values 5.0 +/- 0.1 nM and 16.0 +/- 2.9 nM, respectively. Heptyl-Phy achieved maximum AChE inhibition of 92.5% at 60 min and maintained a high and relatively constant inhibition for more than 8 h. ⋯ Only a 2.0 mg/kg dose of heptyl-Phy significantly reduced the number of errors in scopolamine-treated rats. The other doses did not improve any aspect of maze performance. Although the therapeutic window of heptyl-Phy did not appear wide enough for clinical use, the longer duration of action of heptyl-Phy would appear beneficial.
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Neuroscience letters · Aug 1992
Oral naloxone reduces constipation but not antinociception from oral morphine in the rat.
Oral administration of naloxone (10 mg/kg) antagonized the slowing of the intestinal transit caused by oral morphine (1, 2.5 and 5 mg/kg) in rats. Oral administration of naloxone (10 mg/kg) did not prevent the antinociceptive effect of orally administered morphine (2.5 mg/kg) in the tail-flick test carried out on rats. It is concluded that oral naloxone locally blocks the constipating effect of morphine, while it fails to reduce the central action of morphine due to extensive metabolization after oral administration.