The Journal of Neuroscience, April 15, 2003, 23(8):3130
BRIEF COMMUNICATION
Presynaptic Modulation of the Retinogeniculate Synapse
Chinfei
Chen2 and
Wade
G.
Regehr1
1 Department of Neurobiology, Harvard Medical School,
Boston, Massachusetts 02115, and 2 Division of
Neuroscience, Children's Hospital, Boston, Massachusetts 02115
Modulatory projections from brainstem nuclei and intrinsic thalamic
interneurons play a significant role in modifying sensory information
as it is relayed from the thalamus to the cortex. In the lateral
geniculate nucleus (LGN), neurotransmitters released from these
modulatory inputs can affect the intrinsic conductances of
thalamocortical relay neurons, thus altering their firing properties. Here, we show that in addition to postsynaptic effects, neuromodulators such as serotonin (5-HT) and GABA can act presynaptically to regulate neurotransmitter release at the synapse between retinal ganglion cells
(RGCs) and relay neurons in the LGN, the retinogeniculate synapse.
Activation of 5HT1 and GABAB receptors
significantly decreased EPSC amplitude. This inhibition was accompanied
by a decrease in the extent of paired-pulse depression, suggesting that
it is presynaptic in origin. In addition, fluorometric calcium measurements from retinal axon terminals labeled with Calcium Green-1
dextran revealed that 5HT1 and GABAB receptor
agonists decreased presynaptic calcium influx. Taken together, our data indicate that serotonin and GABA can act presynaptically to decrease calcium influx at the retinogeniculate synapse and modify transmission of visual information in the LGN.
Key words:
GABAB receptors; serotonin receptors; thalamus; visual system; presynaptic modulation; brainstem inputs
Copyright © 2003 Society for Neuroscience 0270-6474/03/2383130-06$05.00/0