[Effect of monoamine neurotransmitters, enkephalin and morphine on substance P contents of several brain regions and pain threshold in rats].
The present work was carried out to observe the effect of intra-cerebroventricular (icv) injection of monoamine neurotransmitters, enkephalin and morphine on immunoreactive substance P(Ir-SP) contents in hypothalamus, striatum, hippocampus and pain threshold. The results were as follows: (1) After icv or intra-DR (dorsal raphe nucleus) injection of 5-HTP, the content of Ir-SP in hypothalamus significantly decreased and pain threshold markedly increased; After depletion of the 5-HT content in brain by pCPA or destruction of DR, the contents of Ir-SP were remarkably elevated in three brain regions by the former and in hypothalamus, striatum by the later. (2) The Ir-SP levels in the three brain regions and the pain threshold were not affected by the icv injection of NE, however, icv injection of DA caused a increase of Ir-SP concentration in striatum which was reversed by the DA receptor antagonist haloperidol, but without any change of the pain threshold. 7th day after icv injection of 6-OHDA, the content of Ir-SP in striatum significantly reduced. (3) Icv injection of met-enkephalin (MEK) or morphine could increase the Ir-SP levels in hypothalamus, striatum and the pain threshold, and above-mentioned effect of morphine could be prevented by the opioid receptor antagonist naloxone. Icv injection of leu-enkephalin (LEK) had no effects both on Ir-SP contents in three brain regions and the pain threshold.
Department of Physiology, Third Military Medical College, Chongqing.
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D000818:Animals; D015306:Biogenic Monoamines / Q000494:pharmacology; D001921:Brain / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D004745:Enkephalins / Q000494:pharmacology*; D006624:Hippocampus / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D009020:Morphine / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D051381:Rats; D011919:Rats, Inbred Strains; D012684:Sensory Thresholds / Q000187:drug effects; D013373:Substance P / Q000378:metabolism*
D015306:Biogenic Monoamines; D004745:Enkephalins; D018377:Neurotransmitter Agents; D013373:Substance P; D009020:Morphine