[Effect of lithium gamma-hydroxybutyrate on evoked potentials in the caudal trigeminal nucleus and somatosensory cortex in rats with trigeminal neuropathy].

Lithium gamma-hydroxybutyrate (20 mg/kg, i.e.) was studied for effects on the evoked potentials (EP) in the caudal trigeminal nucleus (CTN) and somatosensory cortex (SSC) in acute tests on rats with trigeminal neuropathy induced by incomplete compression of the infraorbital nerve. Before drug administration, EPs in CTN on the side of nerve compression were characterized by the increased amplitude of presynaptic R1N1 and late postsynaptic P3N3-P4N4 components and by the reduction in the early postsynaptic P2N2 component. In the contralateral CTN, EP had higher amplitudes. Spontaneous epileptoid activity was recorded in CTN in a third of the animals and in SSC in a half. These changes are regarded as a result of A-delta-C-afferent entry due to attenuation of afferentation along A-beta fibers. After administration of the drug, there was suppression of EP in SSC, while in CTN there was a decrease in the amplitude of the EP presynaptic component with increases in the postsynaptic components. There was suppression of abnormally enhanced spontaneous activity in CT and SSC. The findings are under discussion in terms of the cortical action of the drug resulting in the suppression of the abnormally enhanced activity developed in the brain projectional regions in nerve compression lesion.