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. 1991 Jul;103(3):1769–1775. doi: 10.1111/j.1476-5381.1991.tb09861.x

Inhibition of reflex responses of neonate rat lumbar spinal cord by 5-hydroxytryptamine.

H Crick 1, D I Wallis 1
PMCID: PMC1907807  PMID: 1933139

Abstract

1. Monosynaptic (MSR) and polysynaptic (PSR) segmental reflex responses were recorded from a ventral root of the neonate rat hemisected spinal cord. Amplitudes of the two components were monitored with a peak height detector. 2. 5-Hydroxytryptamine (5-HT) depressed the MSR and PSR in a concentration-dependent manner. The IC50 for MSR depression was 9.5 +/- 3.2 microM and for PSR depression was 9.0 +/- 4.8 microM. 3. Blockade of neuronal uptake of 5-HT by citalopram (0.1 microM) greatly increased sensitivity to 5-HT. In the presence of citalopram, the IC50 for MSR depression was 30 +/- 18 nM and for PSR depression was 89 +/- 23 nM. 4. 5-HT did not depress the MSR or the PSR by releasing glycine since strychnine (1 microM) did not prevent these actions of 5-HT. 5. 5-Carboxamidotryptamine (5-CT), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), RU 24969, 1-[3-(trifluoromethyl)phenyl]-piperazine (TFMPP) and methysergide were full agonists for depression of the MSR. The IC50 for 5-CT was 3.6 +/- 0.5 nM, for 8-OH-DPAT was 0.4 +/- 0.04 microM, for TFMPP was 0.93 +/- 0.3 microM and for methysergide was 21.8 +/- 3.0 nM. The order of potency was 5-CT greater than methysergide greater than 5-HT greater than 8-OH-DPAT greater than TFMPP. 6. 8-OH-DPAT, RU 24969, TFMPP and methysergide had either no or only a minor action in reducing the PSR. 5-CT caused a 50% depression at the highest concentration tested (30 nM).(ABSTRACT TRUNCATED AT 250 WORDS)

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Selected References

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