Endorphins: profound behavioral effects in rats suggest new etiological factors in mental illness.
The endogenous morphinomimetic brain peptides Met5-enkephalin and alpha-, beta-, and gamma-endorphins have been evaluated in rats after intracerebrospinal fluid injection. beta-Endorphin produces marked, prolonged muscular rigidity and immobility similar to a catatonic state, counteracted by the opiate antagonist naloxone; this effect occurs at molar doses 1/100 to 1/400 that at which the other peptides or morphine block the response to painful stimuli. All peptides evoked dose-related, naloxone-reversible, wet-dog shakes in rats that had not been exposed to drugs. beta-Endorphin produced hypothermia, whereas gamma-endorphin produced hyperthermia. Such potent and divergent responses to naturally occurring subtances suggest that alterations in their homeostatic regulation could have etiological significance in mental illness.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001831:Body Temperature / Q000187:drug effects; D002389:Catatonia / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D006801:Humans; D009270:Naloxone / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D009842:Oligopeptides / Q000494:pharmacology; D010455:Peptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011957:Receptors, Opioid; D012018:Reflex / Q000187:drug effects; D013329:Structure-Activity Relationship
D009419:Nerve Tissue Proteins; D009842:Oligopeptides; D010455:Peptides; D011957:Receptors, Opioid; D009270:Naloxone