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Dorsal root and dorsal column mediated synaptic inputs to reticulospinal neurons in lampreys: Involvement of glutamatergic, glycinergic, and GABaergic transmission
Author(s) -
Dubuc Réjean,
Bongianni Fulvia,
Ohta Yoshihiro,
Grillner Sten
Publication year - 1993
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903270207
Subject(s) - inhibitory postsynaptic potential , neuroscience , excitatory postsynaptic potential , glutamatergic , neurotransmission , biology , brainstem , spinal cord , glycine receptor , kynurenic acid , strychnine , dorsal column nuclei , glutamate receptor , postsynaptic potential , anatomy , glycine , receptor , biochemistry , amino acid
Abstract This study was aimed at characterizing the inputs from dorsal roots and dorsal columns to reticulospinal neurons within the posterior rhombencephalic reticular nucleus in the lamprey. The in vitro isolated brainstem and spinal cord preparation was used. Microstimulation of dorsal roots and columns on both sides induced, in identified reticulospinal neurons, synaptic responses which consisted of large IPSPs mixed with excitation, particularly from stimulation on the ipsilateral side. When the spinal cord was selectively exposed to kynurenic acid or to Ca 2+ , synaptic responses to stimulation of dorsal roots and columns were not modified, whereas the same responses were abolished when the brainstem was exposed selectively to kynurenic acid, thus suggesting that the responses were carried by long fibres ascending directly to the brainstem. The excitatory and inhibitory synaptic responses are relayed by interneurons located in the brainstem. The ascending excitatory inputs to inhibitory interneurons and, most likely, also to excitatory interneurons, use excitatory amino acid transmission. Inhibitory responses were abolished by adding the glycinergic antagonist strychnine (5 μM) to the physiological solution, thus suggesting that inhibitory interneurons use glycine transmission. The synaptic transmission was depressed by (−)‐baclofen, a GABA u agonist, probably acting at a presynaptic site. Taken together, the present results suggest that dorsal root and dorsal column stimulations give rise to disynaptic inhibition and excitation of reticulospinal neurons mediated by excitatory and inhibitory amino acid transmission via brainstem interneurons. © 1993 Wiley‐Liss, Inc.