Pulsatile gonadotropin-releasing hormone (GnRH) secretion is an inherent function of GnRH neurons, as revealed by the culture of medial olfactory placode obtained from embryonic rats

Abstract

To determine whether gonadotropin-releasing hormone (GnRH) neurons in culture without the hypothalamus secrete GnRH in a pulsatile fashion, the nasal placode (NAP) was obtained at day 13.5 of gestation and cultured by a roller tube method. If the GnRH release occurs in a pulsatile fashion, it can be said that the pulse generator of GnRH exists inherently in each cell or community of cells in the culture. The concentration of GnRH in the NAP culture medium collected at 8-min intervals for 160 min after 2- to 4-week cultures showed that GnRH release occurred in a pulsatile fashion with a mean interpulse interval of 29.8 +/- 2.3 min (n = 9). When the NAP was cultured with tissues of the forebrain vesicle (n = 3) or the hypothalamus (n = 4), GnRH was also released in a pulsatile fashion with similar intervals (27.3 +/- 1.0 min for the NAP+forebrain vesicle culture and 36.0 +/- 6.3 min for the NAP+hypothalamus culture) as those in cultures without brain tissues. It is concluded that pulsatile GnRH release is an inherent function of GnRH neurons.