In vitro electrical activity in the suprachiasmatic nucleus following splitting and masking of wheel-running behavior.
Djungarian hamsters (Phodopus sungorus sungorus) were chronically exposed to constant light (60 lux) in order to generate a split rhythm of wheel-running behavior. The animals were killed and coronal hypothalamic slices prepared for extracellular recording from the left and right suprachiasmatic nuclei (SCN). Nine hamsters which exhibited a split in overt behavior also had bimodal peaks (280 cells) of SCN firing frequency (5.4 +/- 1.1 and 5.8 +/- 0.7 Hz); these peaks were about 180 degrees antiphase. Two troughs in firing frequency were also apparent (1.8 +/- 0.4 and 2.4 +/- 0.5 Hz) and coincided with the projected time of wheel-running activity. Differences in circadian pattern of electrical activity between the right and left SCN were not observed. When wheel-running activity in 5 hamsters was suppressed with high intensity (500 lux) constant light, the SCN firing profile (154 cells) failed to exhibit a daily rhythm. Firing frequency was consistently high (5.8 +/- 1.4 Hz) throughout the 24-h period. These results indicate that in vitro electrical activity of the SCN is related to overt behavior in Djungarian hamsters, in that high electrical activity occurs when locomotor activity is minimal.
Zlomanczuk
P
P
Department of Biology, Wesleyan University, Middletown, CT 06459-01700.
Margraf
R R
RR
Lynch
G R
GR
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D004594:Electrophysiology; D066298:In Vitro Techniques; D008027:Light; D009043:Motor Activity / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000502:physiology*