The effect of brief light pulses on the photoperiodic reaction in the Djungarian hamsterPhodopus sungorus

Abstract

The effects of brief light pulses on photoperiodic reaction were examined in male Djungarian hamsters (Phodopus sungorus). Half of the animals came from long photoperiods and, accordingly, were in physiological summer state with large and functional testes. The other half had lived in short natural photoperiods before and was in physiological winter condition with involuted testes. These animals were exposed to long (LD 16∶8) or to short (LD 8∶16) photoperiods, or to short photoperiods in which the 16 h of darktime were interrupted by 1 min of light each night, either 4, 8 or 12 h after light off.