Neurons containing beta-endorphin in rat brain exist separately from those containing enkephalin: immunocytochemical studies.

Abstract

Well-characterized antisera to porcine #l-endorphin were used to localize immunoreactive sites in cryostat sections of formaldehyde-fixed rat brain by indirect immunohistochemistry. Specificity was established by absorption of immune sera with synthetic peptide fragments. Specific immunoreactivity was localized to neuronal perikarya in the basal tuberal hypothalamus, and to varicose nerve fibers which were distributed to midline nuclear areas throughout the diencephalon and anterior pons. These patterns of reactivity were unaffected by preabsorption of the immune sera with millimolar concentrations of f3-Endorphin was isolated and purified from extracts of ovine and procine pituitary (3, 4) as was a-endorphin [, (6)] and y-endorphin (7)]. Specific COOH-terminally directed antisera raised against synthetic fl-endorphin and a-endorphin have permitted selective radioimmunoassays for these peptides, which do not read enkephalin pentapeptides (12, 13). These immune antisera have already been used to reveal the immunocytochemical location of a-endorphin-and f3-endorphin-reactive cells in the rat intermediate lobe andBy radioimmunoassay, rat brain contains significant amounts of ,B-endorphin (15), and these levels are unchanged at 6-9 months after hypophysectomy (15). The regional distribution of f,-endorphin in rat brain shows no fixed relationship to radioimmunoassayable enkephalins (15), and many areas reported to be rich in enkephalin immunoreactivity (16)(17)(18)(19)(20)(21)(22) are devoid of detectable f3-endorphin. We now report that immunocytochemical localization studies reveal f3-endorphincontaining neuronal perikarya and fiber tracts throughout the diencephalon that can be clearly distinguished cytologically and immunologically from those cells and fibers observed by us and reported by others (16-23) to be enkephalin-containing neurons.The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. 1591MATERIALS AND METHODS Antiserum Preparation and Characterization. As described in greater detail elsewhere (12, 13) antisera were raised in rabbits to synthetic f-endorphin that had been coupled to bovine serum albumin with bis-diazotized benzidine. The antisera used here for cellular localization of ,B-endorphin immunoreactivity were those used by us for the radioimmunoassay procedures already described (12,13,15). The majority of immunocytochemical results reported here were obtained with antiserum RB 100-10/27; this antiserum recognizes a segment of the COOH-terminal portion of p3-endorphin between asparagine-20 and histidine-27 (12). RB 100-10/27 does not recognize either enkephalin pentapeptide or a-or y-endorphin, but it shows parallel competition for binding of ovine f,-LPH and f3-endorphin. Similarly, this antiserum also shows parallel displacement for binding of ,B-endorphin with the purified 31,000 molecular weight precursor peptide...

Expression of c-Fos in arcuate nucleus induced by electroacupuncture: Relations to neurons containing opioids and glutamate

“…Neurons containing β-endorphin were located bilaterally in the ARC. This observation was consistent with earlier findings (Bloom et al, 1978;Finley et al, 1981). We did not detect a difference in the average number of neurons containing β-endorphin in the ARC between EA-treated and the control groups ( Table 1).…”

“…Separate neurons contain each of these peptides (Bloom et al, 1978). Pan et al (1996) suggested that activated neurons containing β-endorphin in the ARC may be involved in analgesia induced by EA at Zusanli acupoints.…”

“…Perikarya in the ARC contain either β-endorphin or enkephalin, but not both peptides (Bloom et al, 1978;Lantos, et al, 1995). Stimulation of proopiomelanocortin (β-endorphin precursor)-containing neurons in the ARC causes opioid-mediated hypotension (Li et al, 1996).…”

Alterations in Endogenous Brain β-Endorphin Release by Adrenal Medullary Transplants in the Spinal Cord

“…In order to assess changes in endogenous brain ␤-endorphin secretion, a local microdialysis method was utilized which has recently been shown to accurately indicate CNS responses to noxious stimuli such as formalin (Zangen et al 1998). The microdialysis site selected, the hypothalamic arcuate nucleus, is the primary, nearly exclusive, source of ␤-endorphin in the CNS, and ramifies extensively throughout the brain, with particularly dense innervation in pain modulatory regions of the periaqueductal gray and brainstem, and along the walls of the adjacent third ventricle (Bach 1997;Bloom et al 1978;Zakarian and Smyth 1982).…”

“…In order to assess changes in endogenous brain ␤-endorphin secretion, a local microdialysis method was utilized which has recently been shown to accurately indicate CNS responses to noxious stimuli such as formalin (Zangen et al 1998). The microdialysis site selected, the hypothalamic arcuate nucleus, is the primary, nearly exclusive, source of ␤-endorphin in the CNS, and ramifies extensively throughout the brain, with particularly dense innervation in pain modulatory regions of the periaqueductal gray and brainstem, and along the walls of the adjacent third ventricle (Bach 1997;Bloom et al 1978;Zakarian and Smyth 1982).Previous studies in our and other laboratories have demonstrated that transplants of adrenal medullary chromaffin cells into the subarachnoid space of the spinal cord can attenuate pain responses in a variety of animal models and offers a promising avenue for clinical pain management (Brewer and Yezierski 1998;Buchser et al 1996;Burgess et al 1996;Décosterd et al 1998;Hains et al 1998;Hama and Sagen 1993;Lazorthes et al 1995;Ortega-Alvaro et al 1997;Sagen et al 1990;Siegan and Sagen 1997;Vaquero et al 1991;Winnie et al 1993;Yu et al 1998). Although the transplanted cells appear to produce some of their antinociceptive effects via local release of pain-reducing analgesic agents, including catecholamines and opioid peptides, into the host spinal CSF (Sagen and Kemmler 1989;Sagen et al 1991), recent studies have indicated that these transplants can also produce neuroplastic changes in the pain processing circuitry of the spinal cord, including restoration of spinal inhibitory neurons and decreased c-fos activation in response to persistent pain (Ibuki et al 1997;Sagen and Wang 1995).…”