ici-154129 and normorphine

Electrical stimulation (3 Hz, 2 msec duration, 5-12 V for 2 min every 20 min) of cortical slices from the rat, previously incubated with [3H]noradrenaline, evoked a release of tritium which was inhibited by morphine, normorphine, Tyr-D-Ala-Gly-MePhe-NH(CH2) 2OH ( RX783006 ) and D-Ala2-D-Leu5-enkephalin ( pIC30 5.90, 6.32, 7.45 and 6.74 respectively). Naloxone did not affect the release of tritium when given alone but antagonised the actions of the opioids, giving a Ke value of about 3 nM irrespective of the particular agonist used, which suggests an action at mu receptors. The delta opioid receptor blocker, ICI154129 , antagonised the opioids only in large concentrations (Ke 21300 nM). In slices previously incubated with [3H]5-hydroxytryptamine, electrical stimulation increased overflow of tritium but neither naloxone nor the opioid agonists affected evoked overflow of tritium at concentrations which were effective in slices incubated with [3H]noradrenaline. It is concluded that stimulation of mu opioid receptors may inhibit release of noradrenaline from central noradrenergic neurones and that these receptors are not present in significant numbers on neurones releasing 5-hydroxytryptamine in the cortex.

Topics: Animals; beta-Lipotropin; Cerebral Cortex; Clomipramine; Edetic Acid; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Estradiol; In Vitro Techniques; Male; Morphine; Morphine Derivatives; Naloxone; Narcotics; Neurotransmitter Agents; Norepinephrine; Peptide Fragments; Rats; Rats, Inbred Strains; Receptors, Opioid; Serotonin