Study of the density of opioid receptors in the male mouse brain at different stages of sexual maturation

Abstract

The binding of opiate receptors was evaluated in male Swiss CD1 mice in different stages of maturation, i.e., prepubertal (7 and 20 days old), pubertal (40 days old) and postpubertal (60 days old). The opiate receptors were labeled with [3H]-diprenorphine and the KD and Bmax were measured. A similar KD (0.35-0.42 nM) value was obtained in all age groups tested indicating no changes in opiate affinity with sexual maturation. The maximal opiate binding capacity, Bmax was similar in 20- and 40-day-old mice as compared to 60-day-old mice while lower values were obtained in 7-day-old mice. These data indicate that sexual maturation does not affect the number of opiate receptors. Since different testosterone plasma levels have been described in males of this strain at the different ages included in our study, our results support previous findings showing that testosterone does not influence opiate binding sites in rodents.