Abstract
The effects on dorsal root potentials of applying dopamine to the perfusing fluid were investigated in experiments on a segment isolated from the spinal cord of 13- to 18-day-old rats. Dopamine induced slow, dose-dependent depolarization in motoneurons in 28 trials out of 32, retained in the solution blocking synaptic transmission. Threshold concentration of dopamine in the normal perfusing fluid measured 1·10−6 M and 1·10−5 M in a calcium-free perfusate containing magnesium or manganese ions. Depolarization was accompanied by an increased rate of motor discharges recorded from the ventral root. Segmental reflex response produced by dorsal root stimulation was depressed following depolarization. Hyperpolarization in response to dopamine was observed in 4 out of 32 experiments. Dopamine-induced electrotonic dorsal root potentials were suppressed by prior haloperidol application to the brain.
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Literature cited
I. I. Abramets and I. V. Komissarov, "Pharmacological evidence for the existence of dopaminergic interneurons in the rat spinal cord," Neirofiziologiya,28, No. 2, 170–174 (1982).
I. V. Komissarov and I. I. Abramets, "Effects of monoamines on motoneurons isolated from rat spinal cord," Neirofiziologiya,12, No. 4, 391–396 (1980).
N. I. Konenko, "Ionic mechanisms of transmembrane current produced by injecting cyclic adenosine monophosphate into identified neurons of Helix pomatia," Neirofiziologiya,12, No. 5, 526–532 (1980).
N. I. Kononenko and S. L. Mironov, "Effects of intracellular injection of cyclic adenosine monophosphate on electrical parameters of identified Helix pomatia neurons," Neirofiziologiya12, No. 5, 517–525 (1980).
V. N. Oksamitnyi and Z. A. Tamarova, "Inhibitory action of dopamine on excitatory transmission in isolated rat spinal cord," Neirofiziologiya,18, No. 5, 616–621 (1986).
B. Ault and R. H. Evans, "The action of catecholamines on the isolated hemisected spinal cord of the immature rat," J. Physiol.,278, 41–42 (1978).
S. Barasi and M. H. T. Roberts, "Responses of motoneurones to electrophoretically applied dopamine," Br. J. Pharmacol.,60, No. 1, 29–34 (1977).
G. Blinn, G. Heins, and J. Jurna, "Effects of substantia nigra stimulation on suralisevoked spinal reflex activity: comparison with the effects of morphine and stimulation in the periaqueductal gray matter," Neuropharmacology,19, No. 1, 75–85 (1980).
J. W. Commissiong, S. Gentleman, and N. H. Neff, "Spinal cord dopaminergic neurons: evidence for an uncrossed nigro-spinal pathway," Neuropharmacology,18, No. 6, 565–568 (1979).
I. Engberg, J. A. Flatman, and K. Kadzielawa, "The hyperpolarization of motoneurons by electrophoretically applied amines and other agents," Acta Physiol. Scand.,91, No. 3, 3A-4A (1974).
I. Engberg, J. A. Flatman, and K. Kadzielawa, "Lack of specificity of motoneurone responses in microiontophoretically applied phenolic amines," Acta Physiol. Scand.,96, No. 1, 137–139 (1976).
M. Kondo, H. Fujuwara, and C. Tanaka, "Autoradiographic evidence for dopaminergic innervation in guinea pig spinal cord," Jpn. J. Pharmacol.,38, No. 4, 442–444 (1985).
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A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 735–741, November–December, 1987.
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Oksamitnyi, V.N., Tamarova, Z.A. Depolarizing effects of dopamine on motoneurons from a segment of spinal cord isolated from newborn rats. Neurophysiology 19, 529–534 (1987). https://doi.org/10.1007/BF01056917
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DOI: https://doi.org/10.1007/BF01056917