20Kisspeptin within the arcuate nucleus of the hypothalamus is a critical neuropeptide in the 21 regulation of reproduction. Together with neurokinin B and dynorphin A, arcuate kisspeptin 22 provides the oscillatory activity that drives the pulsatile secretion of GnRH, and therefore LH 23 pulses, and is believed to be a central component of the GnRH pulse generator. It is well 24 established that the amygdala also exerts an influence over gonadotrophic hormone secretion 25 and reproductive physiology. The discovery of kisspeptin and its receptor within the 26 posterodorsal medial amygdala (MePD), and our recent finding showing that intra-MePD 27 administration of kisspeptin or a kisspeptin receptor antagonist results in increased LH 28 secretion and decreased LH pulse frequency, respectively, suggests an important role for 29 amygdala kisspeptin signalling in the regulation of the GnRH pulse generator. To further 30 investigate the function of amygdala kisspeptin, the present study used an optogenetic 31 approach to selectively stimulate MePD kisspeptin neurones and examine the effect on 32 pulsatile LH secretion. MePD kisspeptin neurones in conscious Kiss1-CRE mice were virally 33 infected to express a channelrhodopsin protein and selectively stimulated by light via a 34 chronically implanted fibre optic cannula. Continuous stimulation using 5 Hz resulted in an 35increased LH pulse frequency, which was not observed at the lower stimulation frequencies 36 of 0.5 and 2 Hz. In wild-type animals, continuous stimulation at 5 Hz did not affect LH pulse 37 frequency. These results demonstrate that selective activation of MePD Kiss1 neurons can 38 modulate hypothalamic GnRH pulse generator frequency. 39