Regional Distribution of Methionine‐Enkephalin‐Arg⁶‐Phe⁷ in the Rat Brain: Comparative Study with the Distribution of Other Opioid Peptides

Abstract

The distribution of the opioid peptide methionine-enkephalin-arginine6-phenylalanine7 (M-Enk-Arg6-Phe7) has been investigated in various structures of the rat brain by using a highly specific radioimmunoassay (RIA). Immunoreactive M-Enk-Arg6-Phe7 has been further characterized by high performance liquid chromatography. The levels of M-Enk-Arg6-Phe7 in various structures of the rat brain were compared with the levels of several other opioid peptides, including methionine-enkephalin (M-Enk), leucine-enkephalin (L-Enk), dynorphin 1-13, and alpha-neoendorphin, which were also measured by RIA. There was a close relationship between the distribution of M-Enk-Arg6-Phe7 immunoreactive material (ir), M-Enk ir, and L-Enk ir. The distribution of dynorphin 1-13 ir and alpha-neoendorphin ir appeared to be distinct from that of the enkephalin group. These results are in agreement with recent reports on the cloning and sequencing of the c-DNA coding for the prohormones, in which it has been hypothesized that M-Enk-Arg6-Phe7 and M-Enk are synthesized by the same precursor, called proenkephalin, and that dynorphin-related peptides and alpha-neoendorphin arise from a separate precursor, prodynorphin.

Relaxin increases the firing rate of supraoptic neurones and increases oxytocin secretion in the rat

“…However, the neural lobe also contains consider¬ able amounts of Met-enkephalin (Giraud, Castañas, Patey et al 1983). Met-enkephalin itself is inactive at opioid receptors, the sole opioid receptor type in the neural lobe (Herkenham, Rice, Jacobson & Rothman, 1986), but one extended form of Metenkephalin which is present in the neural lobe does have high affinity for opioid receptors (Castañas, Bourhim, Giraud et al 1985;Bicknell, 1991).…”

Preventive and alleviative effects of the dual enkephalinase inhibitor (Denki) PL265 in a murine model of neuropathic pain

“…It has been previously demonstrated that MOP activation is mainly involved in acute pain relief (Matthes et al, 1996) while DOP activation was shown to decrease chronic pain (Gaveriaux-Ruff et al, 2011). The physiological ligands of MOP and DOP are beta-endorphin, endomorphin-1 and -2 as well as the most abundant pentapeptides Met and Leuenkephalins (Giraud et al, 1983). We decided to test in models of neuropathic pain the efficacy of these latter pentapeptides which are locally released under nocifensive stimuli (Yaksh et al, 1981;Bourgoin et al, 1986;Schreiter et al, 2012).…”

Co‐release of enkephalins and precursors with catecholamines from the perfused cat adrenal gland in situ.

“…The column was pre-equilibrated with 0-25 M-triethylammonium formate, pH 3 1, and eluted with a discontinuous gradient from 0 to 50% acetonitrile in buffer with a flow rate of 1 ml/min. Synthetic peptides were used as calibration standards (see Giraud, Castanas, Patey, Oliver & Rossier, 1983, for details). Fractions of 1 ml were evaporated in a Speed-Vac concentrator (Savant Instrument, Hicksville, NY) and resuspended in 50 mM-Tris HCl buffer, pH 8-4, containing 2 mM-CaCl2.…”