Regulation of Burst Activity through Presynaptic and Postsynaptic GABA_BReceptors in Mouse Superior Colliculus

GABAergic mechanisms for shaping transient visual responses in the mouse superior colliculus

“…A previous study demonstrated the different roles of GABA A and GABA B receptors on visual information processing, but did not precisely examine the effects of GABA receptor blockade on the nature of transient ON activity (Binns and Salt, 1997). Our previous study in slice preparations demonstrated that GABAergic sSC interneurons regulate the duration of discharges through a mechanism of feed-forward inhibition mediated by both GABA A and GABA B receptors in non-GABAergic and GABAergic sSC neurons (Kaneda et al, 2008), suggesting that GABAergic neurons contribute to transient activity. However, whether the same mechanism is at work in vivo has not been examined.…”

“…With the use of juxtacellular labeling, we revealed that the ON + Pause + OFF responses were observed in a variety of morphological types of sSC neurons. These include WFV and NFV cells, which are reported to be excitatory neurons (Isa et al, 1998;Saito and Isa, 2005;Kaneda et al, 2008), and stellate, piriform, multipolar, and horizontal cells that are considered to be inhibitory GABAergic neurons (Mize, 1992;Endo et al, 2003;Kaneda et al, 2008). Three marginal cells, which are projection neurons (Mooney et al, 1988) and have not been characterized as GABAergic (Mize, 1992), also exhibited the ON + Pause + OFF responses.…”

“…The sSC consists of several cell types, including excitatory and inhibitory neurons (Mize, 1992;Endo et al, 2003Endo et al, , 2005May, 2006;Kaneda et al, 2008). Previous intracellular recording and labeling studies elucidated that some sSC neurons responded to moving or static visual stimuli with short bursts of spike discharges (Mooney et al, 1985(Mooney et al, , 1988.…”

“…Three marginal cells, which are projection neurons (Mooney et al, 1988) and have not been characterized as GABAergic (Mize, 1992), also exhibited the ON + Pause + OFF responses. These findings are of particular importance because both excitatory and inhibitory neurons exhibited the same response pattern, although their functions must be different from each other: as 20 excitatory sSC neurons are projection neurons (Mooney et al, 1988;Isa et al, 1998;Özen et al, 2000;Kaneda et al, 2008), they send visual information to nuclei outside the sSC. On the other hand, given that the majority of GABAergic neurons are interneurons with some exceptions (Mooney et al, 1988), their primary role is most likely to inhibit excitatory and inhibitory neurons within the sSC.…”

“…sSC neurons exhibit transient spike discharges, called ON responses, immediately after the appearance of a visual stimulus (Schiller and Koerner, 1971; Cynader, 1972, 1975;Cynader and Berman, 1972;Goldberg and Wurtz, 1972;Dräger and Hubel, 1975;Rhoades and Chalupa, 1977;Marrocco and Li, 1977;Moors and Vendrik, 1979;Wang et al, 2010), implying that the sSC could detect the appearance of the object. Indeed, lesions or inactivation of the SC cause a detection deficit of visual stimuli (Butter et al, 1978;Overton and Dean, 1988;Fitzmaurice et al, 2003).The sSC consists of several cell types, including excitatory and inhibitory neurons (Mize, 1992;Endo et al, 2003Endo et al, , 2005May, 2006;Kaneda et al, 2008). Previous intracellular recording and labeling studies elucidated that some sSC neurons responded to moving or static visual stimuli with short bursts of spike discharges (Mooney et al, 1985(Mooney et al, , 1988.…”