Article

GABA in the mammalian suprachiasmatic nucleus and its role in diurnal rhythmicity.

Department of Neurobiology, Institute of Life Sciences, Hebrew University, Jerusalem, Israel.
Nature (impact factor: 36.28). 07/1997; 387(6633):598-603. DOI:10.1038/42468 pp.598-603
Source: PubMed

ABSTRACT Mammals manifest circadian behaviour timed by an endogenous clock in the hypothalamic suprachiasmatic nucleus (SCN). Considerable progress has been made in identifying the molecular basis of the circadian clock, but the mechanisms by which it is translated into cyclic firing activity, high during the day and low at night, are still poorly understood. GABA (gamma-aminobutyric acid), a common inhibitory neurotransmitter in the central nervous system, is particularly densely distributed within the SCN, where it is located in the majority of neuronal somata and synaptic terminals. Using an in vitro brain-slice technique, we have now studied the effect of bath-applied GABA on adult SCN neurons at various times of the day. We find that GABA acts as an inhibitory neurotransmitter at night, decreasing the firing frequency; but during the day GABA acts as an excitatory neurotransmitter, increasing the firing frequency. We show that this dual effect, which is mediated by GABA(A) receptors, may be attributed to an oscillation in intracellular chloride concentration. A likely explanation is that the amplitude of the oscillation in firing rate, displayed by individual neurons, is amplified by the dual effect of GABA in the SCN's GABAergic network.

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Keywords

bath-applied GABA
 
circadian clock
 
common inhibitory neurotransmitter
 
Considerable progress
 
cyclic
 
day GABA acts
 
dual effect
 
excitatory neurotransmitter
 
firing frequency
 
GABA
 
GABA acts
 
gamma-aminobutyric acid
 
hypothalamic suprachiasmatic nucleus
 
inhibitory neurotransmitter
 
intracellular chloride concentration
 
likely explanation
 
Mammals manifest circadian behaviour timed
 
molecular basis
 
neuronal somata
 
SCN's GABAergic network
 

S Wagner