TY - JOUR
T1 - Bicuculline-induced alterations in neuronal responses to controlled tactile stimuli in the second somatosensory cortex of the cat
T2 - A microiontophoretic study
AU - Alloway, K. D.
AU - Burton, H.
PY - 1985
Y1 - 1985
N2 - Single-neuron activity (n = 29) was recorded from the second somatosensory cortex of cats, and the effect of glutamate, γ-amino-butyric acid (GABA), and bicuculline methiodide (BMI) on spontaneous and stimulus-induced responses were analyzed. Iontophoresis of glutamate produced dose-dependent increases in spontaneous activity, whereas GABA suppressed both spontaneous and glutamate-induced activity. Neuronal responses elicited by cutaneous stimuli were also inhibited by GABA in a dose-dependent fashion; current levels needed to produce at least a 25-50% decrease in stimulus-evoked activity ranged from 5 to 100 nA, with a mean of about 45 nA. Iontophoresis of BMI (10-75 nA) effectively antagonized GABA-induced inhibition of stimulus-evoked responses without altering spontaneous activity. Furthermore, BMI increased the magnitude of responses produced by ramp stimuli and caused a several-fold increase in receptive field size. For neurons responsive to sinusoidal stimulation, BMI caused an increase in the frequency-following probability at preferred frequencies, but failed to alter the response to nonpreferred frequencies. These results suggest that GABA-ergic circuits may limit response magnitude but not the submodality properties of somatosensory cortical neurons.
AB - Single-neuron activity (n = 29) was recorded from the second somatosensory cortex of cats, and the effect of glutamate, γ-amino-butyric acid (GABA), and bicuculline methiodide (BMI) on spontaneous and stimulus-induced responses were analyzed. Iontophoresis of glutamate produced dose-dependent increases in spontaneous activity, whereas GABA suppressed both spontaneous and glutamate-induced activity. Neuronal responses elicited by cutaneous stimuli were also inhibited by GABA in a dose-dependent fashion; current levels needed to produce at least a 25-50% decrease in stimulus-evoked activity ranged from 5 to 100 nA, with a mean of about 45 nA. Iontophoresis of BMI (10-75 nA) effectively antagonized GABA-induced inhibition of stimulus-evoked responses without altering spontaneous activity. Furthermore, BMI increased the magnitude of responses produced by ramp stimuli and caused a several-fold increase in receptive field size. For neurons responsive to sinusoidal stimulation, BMI caused an increase in the frequency-following probability at preferred frequencies, but failed to alter the response to nonpreferred frequencies. These results suggest that GABA-ergic circuits may limit response magnitude but not the submodality properties of somatosensory cortical neurons.
UR - http://www.scopus.com/inward/record.url?scp=0022230254&partnerID=8YFLogxK
M3 - Article
C2 - 2875510
AN - SCOPUS:84907140476
SN - 0736-7244
VL - 3
SP - 197
EP - 211
JO - Somatosensory Research
JF - Somatosensory Research
IS - 3
ER -