[Changes in the reflex discharges and electrotonic potentials of spinal nerve roots in the rat upon exposure to biologically active substances].

The ionic nature of neuronal postsynaptic responses to monoamines, aminoacids and the substance P was studied in the newborn rat isolated spinal cord. The responses of motoneurons to GABA, glycine, noradrenaline and dopamine appeared to be Cl-dependent. The depolarization of motoneurons induced by L-glutamate and 5-hydroxytryptamine was Na-dependent whereas the same response to the substance P was Cl-dependent. Primary afferent depolarization with GABA is Cl-dependent whereas if induced by glycine and 5-hydroxytryptamine it is Na-dependent. Neurochemical and ionic profiles of mono- and polysynaptic ventral and dorsal root potentials are discussed.