Expression of the mu-opioid receptor in the anterior pituitary gland is influenced by age and sex.
To analyze whether opioids are able to modulate endocrine regulation by acting directly on rat pituitary cells, an immunohistochemical study of micro-opioid receptor expression in these cells was performed, with attention given to the analysis of potential age- and sex-related variations in receptor expression patterns. In both sexes, the micro-opioid receptor was detected in the pituitary pars distalis. However, significant age-related differences were observed. Both in male and female rats, the percentage of micro-opioid receptor-expressing cells decreased significantly from postnatal week one through the 24 months of our study. Interestingly, pituitary cells containing the micro-opioid receptor were significantly more numerous in male than in female, with exception of the pre-pubertal phase and old rats. According to two-way analysis of variance, the gender-related differences in micro-receptor expression were independent of age-related variations. Thus, without excluding hypothalamic actions, our results suggest that opioids may exert their endocrine function by acting directly on pituitary cells.
Carretero
J
J
Department of Human Anatomy and Histology, Lab. Neuroendocrinología experimental y Diabetes, InCyL, Faculty of Medicine, University of Salamanca, Avda. Alfonso X el Sabio, s/n, E-37007, Spain. jcar@gugu.usal.es
Bodego
P
P
Rodríguez
R E
RE
Rubio
M
M
Blanco
E
E
Burks
D J
DJ
D000367:Age Factors; D000818:Animals; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017450:Receptors, Opioid, mu / Q000096:biosynthesis*; D012737:Sex Factors
D017450:Receptors, Opioid, mu