. Author manuscript; available in PMC: 2018 Jan 1.

Published in final edited form as: Front Neuroendocrinol. 2016 Nov 25;44:35–82. doi: 10.1016/j.yfrne.2016.11.003

Table 4.

Cellular effects of GABA agonists on SCN neurons.

Paper	LD cycle	Technique	Preparation	GABA agonists	Effects on SCN neurons
Liou et al. (1990) PMID 1976421	12:12	Extracellular single unit recording	Slice preparation; rats	Baclofen, muscimol, (bath application)	During the day, muscimol produced excitation followed by inhibition (N = 5); baclofen produced exclusively inhibition (N = 4)
Liou and Albers (1990) PMID 2207720	14:10	Extracellular single unit recording	Slice preparation; hamsters	Baclofen (bath application)	Baclofen produced exclusively inhibition
Kawahara et al. (1993) PMID 8247331	Not noted	Whole-cell voltage-clamp	Dissociated culture of SCN neurons; PD21 rats	Muscimol, baclofen (bath application)	Muscimol elicited large inward currents in all neurons tested at a holding potential of −60 mV; baclofen had no effect on current
Tominaga et al. (1994) PMID 8190363	12:12	Extracellular single unit recording	Slice preparation; rats	Muscimol (bath application)	Muscimol produced an inhibitory response in 70% of neurons at 10 µM and in 100% at 100 µM when administered between CT 2–10
Jiang et al. (1995) PMID 7715789	12:12	Whole cell patch clamp	Slice preparation prepared during the light period; rats	Baclofen (bath application)	Baclofen reduced amplitude of EPSCs evoked by optic nerve stimulation by a presynaptic action; in a subpopulation of SCN neurons baclofen induced an outward current by postsynaptic action; baclofen had no effect on spontaneous or induced IPSCs with a holding potential of −60 mV
Obrietan and van den Pol (1996) PMID 8627385	Not noted	Fura-2 Ca²⁺ imaging	Dissociated culture of SCN neurons; organotypic SCN cultures; ED19–21 rats	Baclofen (bath application)	GABA, but not baclofen, elevated Ca²⁺ in embryonic SCN neurons maintained in dissociated and organotypic cultures
Chen and van den Pol (1998) PMID 9465016	Not noted	Whole cell patch clamp	Dissociated culture of SCN neurons; PD1 and PD2	Baclofen (bath application)	Baclofen induced large, dose-dependent inhibition of evoked IPSCs at a holding potential of −60 mV; baclofen reduced the frequency of spontaneous IPSCs but had little effect on miniature IPSCs in the presence of TTX; GABA_B receptor activation produced a strong presynaptic inhibition of GABA release from SCN neurons
Gribkoff et al. (1999) PMID 10194649	12:12	Multiple unit recordings	Slice preparation; rats	Muscimol (bath application or pressure applied with a Picospritzer)	Muscimol inhibited firing during the day and night
Colwell (2000) PMID 10861563	12:12	Whole cell recordings with biocytin-filled patch electrodes	Slice preparation; P10– 14 rats	Muscimol (bath application)	Muscimol decreased dye coupling during the day and the number of cells in a coupled cluster
Liu and Reppert (2000) PMID 10707977	12:12	Extracellular single unit recordings	Dissociated culture of SCN neurons; PD0–3 mice	Baclofen, muscimol (bath application)	Muscimol given between CT 8 and 14 inhibited firing and produced phase delays; baclofen inhibited firing but did not produce phase delays
Shinohara et al. (2000) PMID 10717439	14:10	Optical imaging of voltage sensitive dye; application of Lucifer Yellow, to detect gap junctions	Cultured organotypic SCN slices prepared from PD6 rats	Muscimol (bath application)	Muscimol decreased the spread of SCN depolarization following electrical stimulation; muscimol reduced the spread of the gap junction-permeable dye
Gribkoff et al. (2003) PMID 12750413	12:12	Multiple unit recordings	Slice preparation; rats	Baclofen, muscimol (bath application)	Muscimol produced exclusively inhibitory responses with no differences between day and night. Baclofen inhibited neurons during the day and night but with greater potency at night
Ikeda et al. (2003) PMID 12534969	12:12	Fura-2 Ca²⁺ imaging	Slice preparation; PD6– 16 mice	Muscimol hydrobromide (bath application)	Muscimol increased Ca²⁺ in PD6–8 mice; Ca²⁺ was reduced in PD9–10 mice preferentially at night
Moldavan et al. (2006) PMID 16709723	12:12	Whole cell patch clamp; Fura- 2 Ca²⁺ imaging	Slice preparation prepared during the light period; rats	Baclofen (bath application)	Baclofen inhibited evoked EPSCs in a dose-dependent manner during day and night; GABA_B receptors acted presynaptically to reduce glutamate release
Irwin and Allen (2009) PMID 19821838	12:12	Fura-2 Ca²⁺ imaging	Slice preparation; PD28–42 rats	Baclofen; muscimol (bath application)	Baclofen reduced Ca²⁺ levels in neurons where GABA reduced Ca²⁺ and in neurons where GABA increased Ca²⁺
Moldavan and Allen (2013) PMID 23401614	12:12	Whole cell patch clamp	Slice preparation prepared during the light period; rats	Baclofen (bath application)	55% of RHT inputs on SCN neurons were tonically inhibited during the day and 33% were tonically inhibited at night by baclofen

Circadian time (CT), excitatory postsynaptic current (EPSC); see other notes in Table 1.