Gender and Age Influences on Human Brain Mu-Opioid Receptor Binding Measured by PET

• Published in: The American journal of psychiatry Vol. 156; no. 6; pp. 842 - 848
• Main Authors: Zubieta, Jon-Kar, Dannals, Robert F., Frost, J. James
• Format: Journal Article
• Language: English
• Published: Washington, DC American Psychiatric Publishing 01.06.1999; American Psychiatric Association
• Subjects: Adult; Age Factors; Aged; Aging; Amygdala - diagnostic imaging; Amygdala - metabolism; Analgesics, Opioid; Biochemistry; Biological and medical sciences; Brain; Brain - diagnostic imaging; Brain - metabolism; Carbon Radioisotopes; Development. Senescence. Regeneration. Transplantation; Differential and comparative psychology; Female; Fentanyl - analogs & derivatives; Fundamental and applied biological sciences. Psychology; Humans; Male; Middle Aged; Neocortex - diagnostic imaging; Neocortex - metabolism; Neurology; Postmenopause - metabolism; Postmenopause - physiology; Prospective Studies; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Putamen - diagnostic imaging; Putamen - metabolism; Receptors, Opioid, mu - analysis; Receptors, Opioid, mu - metabolism; Reproduction - physiology; Retrospective Studies; Sex Factors; Sexes; Thalamus - diagnostic imaging; Thalamus - metabolism; Tomography, Emission-Computed; Vertebrates: nervous system and sense organs; Radionuclide study; Human; Senescence; Healthy subject; μ Opioid receptor; Sex; Central nervous system; Biological fixation; Age; Comparative study; Neurotransmission; Brain (vertebrata); Positron; Emission tomography
• ISSN: 0002-953X; 1535-7228
• DOI: 10.1176/ajp.156.6.842

OBJECTIVE: Both age and gender are being increasingly recognized as important factors influencing CNS structure and function. However, there are relatively few data on actual neurochemical differences between the sexes in human subjects or on their interaction with age. One of the central neurotransmitter systems for which sex differences have been suggested by animal models and clinical human data is the opioid. In this study the authors examined age- and gender-associated variations in mu-opioid receptor binding with positron emission tomography (PET). METHOD: Healthy human subjects were studied with PET and the radiotracer [11C]carfentanil, a selective mu-opioid agonist. Two separate subject groups were examined: one group of 24 men and 12 women was studied in a retrospective analysis of data, and a second group of 12 men and 18 women was recruited prospectively and studied with a higher-resolution scanner. RESULTS: Mu-opioid receptor binding potential (Bmax Kd) was found to increase with age in neocortical areas and the putamen. Sex differences, with higher mu-opioid binding in women, were observed in a number of cortical and subcortical areas. Gender-by-age interactions were observed in the thalamus and the amygdala; in vivo mu-opioid binding declined in postmenopausal women to levels below those of men. CONCLUSIONS: These data imply that both age and gender are important variables to consider in the interpretation of investigations of human function in which the opioid system plays a role. Also, women's reproductive status (reproductive age versus postmenopausal) may influence the function of CNS opioid systems.