Developmental Changes in the Neurotransmitter Regulation of Correlated Spontaneous Retinal Activity

Abstract

Synchronized spontaneous rhythmic activity is a feature common to many parts of the developing nervous system. In the early visual system, before vision, developing circuits in the retina generate synchronized patterns of bursting activity that contain information useful for patterning connections between retinal ganglion cells and their central targets. However, how developing retinal circuits generate and regulate these spontaneous activity patterns is still incompletely understood. Here we show that in developing retinal circuits, the nature of excitatory neurotransmission driving correlated bursting activity in ganglion cells is not fixed but undergoes a developmental shift from cholinergic to glutamatergic transmission. In addition, we show that this shift occurs as presynaptic glutamatergic bipolar cells form functional connections onto the ganglion cells, implicating the role of bipolar cells in providing endogenous drive to bursting activity later in development. This transition coincides with the period when subsets of ganglion cells (On and Off cells) develop distinct activity patterns that are thought to underlie the refinement of their connectivity with their central targets. Here, our results suggest that the differences in activity patterns of On and Off ganglion cells may be conferred by differential synaptic drive from On and Off bipolar cells, respectively. Taken together, our results suggest that the regulation of patterned spontaneous activity by neurotransmitters undergoes systematic change as new cellular elements are added to developing circuits and also that these new elements can help specify distinct activity patterns appropriate for shaping connectivity patterns at later ages.Key words: retinal development; ferret retina; spontaneous activity; retinal waves; activity dependent; APB; glutamate Electrical activity in the developing nervous system is characterized by spontaneous periodic bursts of action potentials that are synchronized among neighboring cells (Feller, 1999;O'Donovan, 1999;Wong, 1999). Such activity occurs in the immature nervous systems of different species (Masland, 1977;Galli and Maffei, 1988;Meister et al., 1991;Gummer and Mark, 1994; Sernagor and Grzywacz, 1996;Wong et al., 1998;Z hou, 1998) and has been implicated in the development and refinement of neuronal connectivity (Katz and Shatz, 1996;Wong, 1999). Because of this functional importance, recent work has focused on how coordinated network oscillations are produced and regulated across development.Spontaneous rhythmic activity in structures from the spinal cord to the hippocampus and retina often requires excitatory neurotransmission (O'Donovan, 1999). Intriguingly, spontaneous rhythmic activity occurs before and throughout the period when synaptic networks are assembled (Wong et al., 1993;Spitzer et al., 1995; C atsicas et al., 1998;Milner and Landmesser, 1999), raising the question of whether unique or even transient mechanisms are required for its production. Additionally, as new synaptic elements are incorp...

Melanopsin Is Highly Resistant to Light and Chemical Bleaching in Vivo

“…The temperature of both the perfusate and the tissue chamber was maintained at 33.0°C. For ipRGC recordings from wild-type P8 -10 mouse retinas, spontaneous retinal waves (14) (as well as any input from rod and cone photoreceptors) were suppressed by using glutamatergic (50 mM d(2)-2-amino-5-phosphonopentanoic acid, 20 mM d(Ϫ)-2-amino-4-phosphonobutyric acid, 10 mM 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and cholinergic (5 nM epibatidine) inhibitors (Tocris Biosciences, Ellisville, MO). For ipRGC recordings from wild-type P13-16 mouse retinas, only glutamatergic blockade was used (100 mM d(2)-2-amino-5-phosphonopentanoic acid, 50 mM d(Ϫ)-2-amino-4-phosphonobutyric acid, 40 mM CNQX).…”

Developmental loss of miniature N -methyl- d -aspartate receptor currents in NR2A knockout mice

“…considered synaptic if they had rise times Ͻ8-9 ms and peak amplitudes at least two times baseline to peak noise (1.5 pA). Spontaneous events (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) were averaged by using MINIANALY-SIS software (SynaptoSoft). When AMPA as well as GABA A receptors were blocked, the frequency of spontaneous NMDARcs dropped significantly.…”

“…Because this pathway uses glutamate as its primary transmitter (25,26), photoreceptor-elicited activity in retinal ganglion cells was blocked by antagonizing glutamate receptors in the eye (see Methods). Animals were killed on P11, and synaptoneurosomes from the sSC contra-and ipsilateral to the blocked eyes were prepared separately.…”

Disruption and Recovery of Patterned Retinal Activity in the Absence of Acetylcholine

“…A third possibility is that GABAergic and glycinergic drive, which are depolarizing in the neonatal retina and modulate waves, could have increased to enable wave propagation in the KO region (Fischer et al, 1998;Wong et al, 1998Wong et al, , 2000Myhr et al, 2001;Zhou, 2001). Such GABAergic and glycinergic synaptic upregulation is seen in the developing spinal cord in response to cholinergic and glutamatergic blockade .…”

“…Pharmacological studies show that the circuitry underlying synchronized activity alters systematically with development. Before synaptogenesis, gap junctions are responsible (Peinado et al, 1993;Catsicas et al, 1998;Wong et al, 1998;Roerig and Feller, 2000;Syed et al, 2004b), but after synapse formation, chemical neurotransmission drives correlated activity (Leinekugel et al, 1997;O'Donovan et al, 1998;O'Donovan, 1999;Bansal et al, 2000;Wong et al, 2000;Zhou and Zhao, 2000;Syed et al, 2004b). In the spinal cord and retina, synchronized activity is first dependent on cholinergic transmission and thereafter on glutamatergic transmission.…”