Review Endogenous opiates and behavior: 2005 Richard J. Bodnar *, Gad E. Klein Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, United States peptides 27 (2006) 3391–3478 article info Article history: Received 17 July 2006 Accepted 19 July 2006 Published on line 12 September 2006 Keywords: Opioids mu Receptor kappa Receptor delta Receptor Enkephalins Endomorphins Dynorphin beta-Endorphin Abbreviations: Ach, acetylcholine ACTH, adrenocorticotrophic hormone AGRP, agouti gene related peptide AMSH, alpha-melanocyte- stimulating hormone AS, antisense ATP, adenosine triphosphate BDNF, brain-derived neurotrophic factor BEND, beta-endorphin BFNA, beta-funaltrexamine BNST, bed nucleus of the stria terminalis Ca(2+), calcium cAMP, cyclic adenomonophosphate CART, cocaine and amphetamine- regulated transcript abstract This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It sum- marizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointest- inal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respira- tion and thermoregulation (Section 16); immunological responses (Section 17). # 2006 Elsevier Inc. All rights reserved. * Corresponding author. Tel.: +1 718 997 3543; fax: +1 178 997 3257. E-mail address: richard_bodnar@qc.edu (R.J. Bodnar). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/peptides 0196-9781/$ – see front matter # 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.peptides.2006.07.011