Pineal multiunit activity in conscious quail: effects of light, blinding, ganglionectomy

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Abstract
Multiunit activity (MUA) was recorded from the pineal gland in unanesthetized male Japanese quail. The influence of light regimen on spontaneous and flash-evoked firing patterns of pineal cells was investigated. Shortening the day length from 18 to 6 h/24 h resulted in a marked increase in pineal MUA. Pineal firing rate was higher during the dark than during the light fraction of the photoperiod. Flashlight stimulation always led to a marked inhibition of the pineal MUA. Cutting the optic nerves bilaterally resulted in a marked increase in the level of MUA. None of the experimental conditions altered the elevated MUA in blinded birds. Photoperiod and light stimulation appeared to be important for pineal activity; however, no direct photosensitivity of the epiphysis could be demonstrated since all responses were suppressed in blinded quail. Superior cervical ganglionectomy resulted in slightly increased spontaneous MUA but did not inhibit pineal responses to flashlight stimulations.