Effects of a GABA C Receptor Blocker on the Formation of Evoked Potentials in Neuronal Columns in the Rat Somatosensory Cortex

Microelectrode studies of the evoked activity of neuronal columns in the barrel cortex in rats showed that the GABA_C receptor blocker 1,2,5,6-tetrahydropyridin-4-ylmethylphosphonic acid (TPMPA) had an activatory effect on the secondary components of evoked potentials (EP) mainly of the upper afferent modules of columns as compared with the lower efferent layers. This is evidence that GABA_C receptors are located on the presynaptic terminals of thalamocortical glutamatergic afferents and ascending apical dendrites of pyramidal cells. Blockade of GABA_C influences with TPMPA led to dose-dependent depolarization of afferents with development of presynaptic inhibition and suppression of the primary responses (PR) of EP. The different effects of the GABA_C receptor blocker on the secondary components of EP in the upper layers of the cortex are due to the development of afterhyperpolarization of neurons after high-amplitude PR and afterdepolarization after low-amplitude responses, with subsequent activation of different voltage-gated channels and the formation of different gradients in the direct current (DC) potential of the cortex.

http://ift.tt/2hS07iv