Electrophysiological properties of rat pinealocytes: evidence for circadian and ultradian rhythms.
Extracellular single-unit recordings were made during day- and night-time in the pineal gland of urethane-anesthetized adult male Sprague-Dawley rats. All cells exhibiting spontaneous electrical activity had firing frequencies from less than 1 Hz to about 100 Hz, and their discharge patterns were characterized as regular, irregular or bursting. While most of the spontaneously active cells (n = 163) showed a uniform activity level throughout the recording period (30-120 min), a group of 9 cells exhibited oscillatory rhythms with periods of 4-8 min. In addition, long-term recordings across day- and night-time from five cells revealed increasing activity during night-time in three cells, while the remaining two units showed constant activity throughout the recording time (8-20 h). Comparison of day- and night-data in general indicated an overall higher level of activity at night.
D000200:Action Potentials; D000818:Animals; D002940:Circadian Rhythm; D007031:Hypothalamus / Q000502:physiology; D008027:Light; D008297:Male; D009434:Neural Pathways / Q000502:physiology; D010870:Pineal Gland / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012160:Retina / Q000502:physiology