Neuropeptidergic inhibitory regulation of Met-enkephalin immunoreactive material release from rat spinal cord in vitro.
The release of Met-enkephalin immunoreactive material (ME-IR) from rat spinal slices was measured in vitro. This release increased about 4 fold in response to the addition of K+ ions. K+-evoked release of ME-IR was Ca++ dependent. Veratridine, a depolarizing agent, also stimulated the release of ME-IR. Veratridine-induced ME-IR release was completely prevented by tetrodotoxin (TTX), a Na+ channel blocker. Somatostatin (SRIF) inhibited both basal and K+-evoked release of ME-IR at 10(-7) M. Substance P had a similar effect although higher concentrations were needed. gamma-Aminobutyric acid (GABA) and neurotensin (NT) did not affect the basal release but slightly decreased K+-evoked release at 10(-5) M. Serotonin (5-HT) and noradrenaline (NA), did not affect ME-IR release. These results suggest that some of the neuropeptides present in the spinal cord, especially SP and SRIF, may be potent modulators of ME-IR release at the spinal level.
D000818:Animals; D004744:Enkephalin, Methionine / Q000378:metabolism*; D008297:Male; D009496:Neurotensin / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology; D013004:Somatostatin / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*; D013373:Substance P / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018377:Neurotransmitter Agents; D012701:Serotonin; D013373:Substance P; D009496:Neurotensin; D013779:Tetrodotoxin; D013004:Somatostatin; D005680:gamma-Aminobutyric Acid; D004744:Enkephalin, Methionine; D014701:Veratridine; D011188:Potassium; D009638:Norepinephrine