Immunocytochemical distribution of met‐enkephalin‐Arg⁶‐Gly⁷‐Leu⁸ in the rat lower brainstem

Abstract

The distribution of methionine-enkephalin-Arg6-Gly7-Leu8, a unique peptide derived from proenkephalin A in the rat brainstem, was studied immunocytochemically by using a highly specific antiserum to this octapeptide sequence. Immunoreactive perikarya with various shapes and sizes were detected in many regions of the rat brainstem. Dense accumulation of immunoreactive perikarya and fibers was seen in the nuclei associated with special sensory and visceral functions, such as the interpeduncular nucleus, the parabrachial nucleus, the nucleus of the solitary tract, and the nucleus of the spinal tract of the trigeminal nerve. Clusters of methionine-enkephalin-Arg6-Gly7-Leu8-like immunoreactive perikarya and fibers were observed in certain areas considered to play a role in nociception and analgesia, such as the central gray of the midbrain central gray and the raphe magnus nucleus. Some methionine-enkephalin-Arg6-Gly7-Leu8-like immunoreactive perikarya were distributed in the lateral reticular nucleus, the nucleus of the solitary tract, and the raphe magnus nucleus, where monoaminergic neurons were also detected. In addition to the previously reported enkephalinergic cells, we found many methionine-enkephalin-Arg6-Gly7-Leu8 containing neurons; the rostral and caudal linear nucleus of raphe, the median raphe nucleus, entire length of the raphe magnus nucleus, the medial longitudinal fasciculus, the cuneate nucleus, the external cuneate nucleus, the gracile nucleus, and the area postrema. The wide distribution of this octapeptide-like immunoreactivity reflected neurons expressing the preproenkephalin A gene distributed more widely than previously reported and that innervated many regions.

Endometriosis Is Associated With a Shift in MU Opioid and NMDA Receptor Expression in the Brain Periaqueductal Gray

“…Ventrolateral immunolabeling was similar to a previous report. 50 In some brains, well-defined somata-like structures were easily identified with punctae staining around them. However, semiquantitative assessment of immunostaining revealed no difference between the groups ( Figure 5B; sham: 19.59 + 1.91; endo: 20.20 + 2.38).…”

The μ-opioid receptor agonist DAMGO presynaptically suppresses solitary tract-evoked input to neurons in the rostral solitary nucleus

“…Opioids modulate a wide range of visceral and autonomic processes in the brain stem. In the rNST, varicose fibers containing endogenous ligands for MORs are plentiful, including the enkephalins, which activate ␦-opioid receptors as well as MORs (Raynor et al 1994), and the endomorphins, which are specific MOR agonists (Zadina et al 1997 (Davis and Kream 1993;Fallon and Leslie 1986;Murakami et al 1987;Stornetta et al 2001), but endomorphinergic soma are located only in the cNST at the level of area postrema and the hypothalamus near and in the dorsomedial and arcuate nuclei (Martin-Schild et al 1999;Pierce and Wessendorf 2000).…”

Immunocytochemical distribution of Met-enkephalin-Arg6-Gly7-Leu8 (Met-8) in the auditory system of the rat

“…This means that the presence of Met 8 is a selective marker for the pro-enkephalin system (Abe et al, 1987;Murakami et al, 1987). Met 8 acts as a neurotransmitter or neuromodulator and has been implicated in pain, cardiovascular and motor mechanisms (Akil et al, 1984;Basbaum and Fields, 1984;Pasternak, 1987;Douglas and Kitchan, 1992).…”

“…The distribution of Met 8 has been studied using immunocytochemical, radioim-0378-5955 / 03 / $^see front matter ß 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0378-5955(03)00333-2 munoassay or in situ hybridization techniques in the rat (Pittius et al, 1984;Zamir et al, 1985;Fallon and Leslie, 1986;Merchenthaler et al, 1986;Murakami et al, 1987Murakami et al, , 1989Ho¡man et al, 1993;Tanaka et al, 1993;Wynne et al, 1995;Robertson and Mulders, 2000), cat (Belda et al, 2003), monkey (Ibuki et al, 1986) and human (Pittius et al, 1984;Iadarola et al, 1991) central nervous system.…”