Abstract
The anteroventral periventricular nucleus of the preoptic area (AVPvN) is significantly larger in females than in males. In the present experiment, the changes in the volume of the AVPvN were examined at various stages of development in males and females.
The volume of the AVPvN was measured in rats at the age of 15, 20, 30, 45, 90days. A significant increase was noted during the peripubetal and postpubertal period, while the males showed no significant increase throughout their life. The difference in females was clear after the age of 45 days but was not seen before the age of 30 days. Rats were injected with 20 IU of pregnant mare serum gonadotropin (PMSG) at 27 days of age and the others were injected for 3 days with estradiol benzoate after castration at the age of 27 days, these females were killed 3 days later. The volume of the AVPvN in both groups was significantly larger than that in the control group, being almost the same as that at the age of 45 days.
The rats castrated at the age of 27 days and injected with 20 IU of PMSG showed no significant difference in size of the AVPvN 3 days later, compared to control group.
These results show that a male-female difference in the AVPvN size in rats becomes evident around the onset of puberty and its expression is facilitated by increased levels of estrogen in the pubertal females.
