Spontaneous and flash‐induced multiple unit activity in the hypothalamic gonadotropic areas: Effects of photoperiod and of optic nerve section in quail

Abstract

The present study was devoted to recording of spontaneous and flash‐evoked multiple unit discharges in the gonadotropic areas of the quail hypothalamus and to investigate the influence of the length of the day and of bilateral optic nerve section. Blinding resulted in a marked decrease of MUA in the tuberal region which was much less important in the dorsal part of the nuclear infundibular complex. Burst and continuous patterns of discharges subsisted in tuberal and dorsal areas of blinded quail but responses to flash were completely suppressed. Lengthening the photofraction led to a very strong reduction of firing rates in both tuberal and dorsal hypothalamic regions. Furthermore, flash stimulation was no longer effective in intact photostimulated quail (18L‐6D). Flash‐evoked modification of MUA in gonadotropic regions were differentiated in a clear‐cut fashion from specific responses which were obtained in the visual system.