Effects of a depressant/convulsant pair of glutarimides on neuronal activity in the isolated spinal cord of the immature rat.

The effect of depressant/convulsant pair of glutarimides on the isolated spinal cord of the immature rat was examined using extracellular recording. At concentrations of 300 microM the depressant beta-butyl-beta-methyl glutarimide enhanced the response of motoneurones and dorsal root fibres to gamma-aminobutyric acid (GABA) while the convulsant bemegride (beta-ethyl-beta-methyl glutarimide) decreased both responses to GABA. At this concentration both the convulsant and depressant reduced mono- and polysynaptic reflex activity. Neither the convulsant or depressant had prominent direct actions, with only a small hyperpolarization being produced by both glutarimides on dorsal root fibres. The overall depressant or convulsant properties of these glutarimides may be due in part therefore to a differential effect on the postsynaptic action of the inhibitory transmitter GABA. Furthermore, the depressant glutarimide reduced the excitatory effects of L-glutamate and the convulsant reduced the inhibitory effects of glycine on spinal neurones; thus, actions on these transmitters may also contribute to the overall effects of these glutarimides.