The potent effects of morphine, a plant alkaloid, have long led to the assumption that the brain produces endogenous opioids. Several peptides with opioid properties and varying degrees of selectivity for the delta and kappa receptors have been discovers, whereas endogenous ligands with a clear selectivity for the mu receptor have remained elusive. We have recently isolated from brain two novel peptides, endomorphin-1 and -2, that have high affinity and selectivity for the mu opiate receptor (nature 386:499, 1997). We proposed to characterize the neurobiology of these newly discovered peptides. To determine whether they are produced endogenously from precursor proteins, we will clone and sequence the prohormone precursor(s) of these peptides and analyze the upstream region to identify key regulatory elements. Antibodies directed against each of the peptides have been generated and will be used to determine the distribution of the peptides within the nervous system, a crucial step toward understanding physiological functions of these peptides. Once the sequence of the gene(s) for the peptide is identified, riboprobes for in situ hybridization will be made and used to localize cells expressings the endomorphin genes. The possibility of a unique cell signaling profile will be tested with GTP gamma-S binding to measure capacity to activate G-proteins. Finally, the potential for abuse for the peptides will be tested in behavioral studies of opiate dependence and place preference. We take as our formal hypothesis that endomorphin-1 and -2 are endogenous, selective ligands for the mu receptor.
Our specific aims are: 1. Isolate and sequence the gene(s) for endomorphin-1 and -2. 2. Demonstrate cellular localization of endomorphin protein and mRNA. 3. Determine the cellular signaling profile of the endomorphins. 4. Determine tolerance, dependence, and rewarding properties of endomorphins.

National Institute of Health (NIH)
National Institute on Drug Abuse (NIDA)
Research Project (R01)
Project #
Application #
Study Section
Human Development Research Subcommittee (NIDA)
Program Officer
Rapaka, Rao
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Tulane University
Internal Medicine/Medicine
Schools of Medicine
New Orleans
United States
Zip Code
Horner, Kristen A; Zadina, James E (2004) Internalization and down-regulation of mu opioid receptors by endomorphins and morphine in SH-SY5Y human neuroblastoma cells. Brain Res 1028:121-32
Aicher, Sue A; Mitchell, Jennifer L; Swanson, Kristin C et al. (2003) Endomorphin-2 axon terminals contact mu-opioid receptor-containing dendrites in trigeminal dorsal horn. Brain Res 977:190-8
Abbadie, C; Rossi, G C; Orciuolo, A et al. (2002) Anatomical and functional correlation of the endomorphins with mu opioid receptor splice variants. Eur J Neurosci 16:1075-82
Zadina, James E (2002) Isolation and distribution of endomorphins in the central nervous system. Jpn J Pharmacol 89:203-8
Greenwell, Thomas N; Zangen, Abraham; Martin-Schild, Sheryl et al. (2002) Endomorphin-1 and -2 immunoreactive cells in the hypothalamus are labeled by fluoro-gold injections to the ventral tegmental area. J Comp Neurol 454:320-8
Smith, R R; Martin-Schild, S; Kastin, A J et al. (2001) Decreases in endomorphin-2-like immunoreactivity concomitant with chronic pain after nerve injury. Neuroscience 105:773-8
Wilson, A M; Soignier, R D; Zadina, J E et al. (2000) Dissociation of analgesic and rewarding effects of endomorphin-1 in rats. Peptides 21:1871-4
Soignier, R D; Vaccarino, A L; Brennan, A M et al. (2000) Analgesic effects of endomorphin-1 and endomorphin-2 in the formalin test in mice. Life Sci 67:907-12
Czapla, M A; Gozal, D; Alea, O A et al. (2000) Differential cardiorespiratory effects of endomorphin 1, endomorphin 2, DAMGO, and morphine. Am J Respir Crit Care Med 162:994-9
Martin-Schild, S; Gerall, A A; Kastin, A J et al. (1999) Differential distribution of endomorphin 1- and endomorphin 2-like immunoreactivities in the CNS of the rodent. J Comp Neurol 405:450-71

Showing the most recent 10 out of 12 publications