Single unit response of neurons within the hamster suprachiasmatic nucleus to GABA and low chloride perfusate during the day and night

• Published in: Brain research bulletin Vol. 25; no. 1; p. 93
• Main Authors: Liou, S Y, Albers, H E
• Format: Journal Article
• Language: English
• Published: United States 01.07.1990
• Subjects: Animals; Chlorides - pharmacology; Circadian Rhythm; Cricetinae; Electric Stimulation; gamma-Aminobutyric Acid - pharmacology; Neurons - drug effects; Neurons - physiology; Suprachiasmatic Nucleus - cytology; Suprachiasmatic Nucleus - drug effects; Suprachiasmatic Nucleus - physiology
• ISSN: 0361-9230; 1873-2747
• DOI: 10.1016/0361-9230(90)90257-Z

Using the in vitro hamster hypothalamic slice preparation, the effects of GABA and 80% chloride (Cl-) reduced medium on the single unit activity of SCN neurons was investigated. GABA 10(-4) M produced inhibitory responses in 55% of the 69 SCN neurons examined. No statistically significant day-night difference was observed in either the percentage of SCN units responding to GABA, or in their threshold response. During the day 80% Cl- reduced medium had an excitatory effect on SCN neurons; however, following the return to normal Cl- concentrations a transient, but significant inhibition was observed. During the night, 80% Cl- reduced medium produced an excitatory response similar to that observed during the day, but no inhibition following return to the medium containing normal Cl- concentrations. Only during the night was Cl- reduced medium found to initiate activity in a dose-dependent manner in some silent cells. No significant day-night difference in response to 80% Cl- reduced medium occurred in neurons of the paraventricular nucleus of the hypothalamus. These results indicate that SCN neurons whose activity is mediated by Cl- may be involved in the control of circadian rhythms.