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C L Faingold

Publications and source records attributed to C L Faingold.

At least 73 records · Page 4Linked to original sources
PubMed1984

Effects of iontophoretic application of convulsants on the sensory responses of neurons in the brain-stem reticular formation.

Iontophoretic or pneumatic application of convulsants produced enhancement of the sensory responses of brain-stem reticular formation (RF) neurons in cat and rat. Enhanced sensory responsiveness is observed with visual, auditory, somatosensory and vibrissa manipulation following application of strychnine, bicuculline or pentylenetetrazol. The effect was not transmitter-specific, since it could be produced by sequential application of bicuculline and strychnine which are thought to affect different neurotransmitters. Intravenous administration of convulsant also enhanced the responsiveness of RF neurons which had previously been affected by application of a different convulsant. Both systemic and iontophoretic effects could be antagonized by application of GABA and glycine. These data, coupled with previous findings in primary sensory pathways, indicate that sensory response enhancement in the RF induced by intravenous administration of these convulsants is in large part due to actions on synaptic elements of reticular formation neurons.

Animals↗
PubMed1984

Baclofen reduces tone-evoked activity of cochlear nucleus neurons.

Recent evidence suggests that an excitant amino acid may be a neurotransmitter at acoustic nerve synapses in cochlear nucleus (CN). Release of excitant amino acids is reportedly reduced by baclofen, a lipophilic GABA-mimetic used to treat the spasticity of multiple sclerosis and spinal injury. Microiontophoresis of (-)baclofen suppressed spontaneous and tone-evoked activity in CN neurons. GABA inhibited the responses of most neurons responsive to (-)baclofen. However, iontophoresis of these two substances onto the same CN neuron resulted in dramatic differences in time course to maximum effect and to recovery. Onset and offset of (-)baclofen-induced firing reduction were gradual at all doses (currents), but even the highest doses rarely caused total suppression of firing. Inhibition of firing by GABA was abrupt, and total suppression was frequently observed over the range of doses used. GABA desensitization (fading) commonly occurred while the (-)baclofen response never faded. The same CN neurons were also suppressed by D-alpha-aminoadipate, which blocks certain excitatory amino acid receptors, while the GABA antagonist bicuculline had no effect on the (-)baclofen response. These findings support the hypothesis that an excitant amino acid may be a transmitter at acoustic nerve synapses in CN.

2-Aminoadipic Acid↗
PubMed1983

Bicuculline-induced enhancement of sensory responses and cross-correlations between reticular formation and cortical neurons.

The visual, auditory and somatosensory responses of neurons in the brain stem reticular formation (RF) and pericruciate cortex of the cat are enhanced by intravenous administration of subconvulsant doses of bicuculline. The degree of enhancement in RF neurons is somewhat greater in magnitude and occurs in a greater percentage of RF neurons. The latency of response is shorter in the RF than in the cortex in 70% of cases. A large percentage of simultaneously recorded RF and cortical neurons which became responsive to the same stimulus exhibited consistent convulsant-induced cross-correlations of firing which were not present before drug treatment. The latency and correlation data are consistent with the possibility that the RF may subserve the cortical enhancement. Auditory response thresholds in RF neurons are reduced by bicuculline administration. Enhancement of RF neuronal responsiveness has previously been observed with several other convulsant drugs which are thought to act on different neurotransmitters suggesting that it may reflect a general action of these agents beyond the effects on specific neurotransmitters. The bicuculline-induced correlation of firing of RF and pericruciate neurons may be involved in the mechanism of initiation of convulsant-mediated seizure generalization induced by sensory stimuli.

Animals↗
PubMed1983

Effects of acetylcholine on cochlear nucleus neurons.

Iontophoretic application of acetylcholine (ACh) onto neurons in the dorsal cochlear nucleus (DCN) resulted in an inhibition of the tone-evoked responses of 85% of neurons which were affected. That effect in the DCN contrasts with the predominance of excitatory effects of ACh seen in ventral cochlear nucleus (VCN) neurons. The ACh-induced inhibition in the DCN had a considerably slower onset and time course of recovery than that seen with glycine-induced inhibition. The degree of ACh effects was constant with increasing intensity or attained a maximum effect at 20 to 30 dB above best-frequency threshold in contrast to glycine, which had effects that were relatively greater at low intensities. These findings suggested a modulatory role for ACh at DCN and VCN synapses.

Acetylcholine↗
PubMed1983

On the site of pentylenetetrazol-induced enhancement of auditory responses of the reticular formation: localized cooling and electrical stimulation studies.

Pentylenetetrazol (PTZ), administered systemically, enhanced the auditory responses of neurons of the mesencephalic reticular formation (MRF). Responses evoked in the mesencephalic reticular formation by electrical stimuli in several primary auditory nuclei (cochlear nucleus, superior olivary complex and lateral lemniscus, but not inferior colliculus) were also enhanced by pentylenetetrazol in the majority of cases. Bilateral cryoprobe cooling in the lateral lemniscal tract substantially reduced the auditory-evoked field potentials (EPs) in the mesencephalic reticular formation before and after administration of pentylenetetrazol. Cooling in the inferior colliculus (IC) produced a small reduction in auditory-evoked field potentials in the mesencephalic reticular formation before drug but a more substantial degree of reduction after administration of pentylenetetrazol. A relatively small degree of pentylenetetrazol-induced enhancement of the response was seen in neurons of the inferior colliculus (158% of control) as compared to that of neurons in the mesencephalic reticular formation (410%). These findings would be consistent with the reported ability of pentylenetetrazol to block presynaptic inhibition if the input from the inferior colliculus to the mesencephalic reticular formation has inhibitory as well as excitatory components. These data along with the present authors' recent finding of enhancement of response with microapplication of convulsants strongly suggest that enhancement of responses of neurons of the mesencephalic reticular formation, induced by systemically administered convulsants such as pentylenetetrazol is exerted, to a large extent, by direct actions on synaptic elements of the reticular formation.

Animals↗
PubMed1981

Effects of bemegride on the sensory responses of neurons in the hippocampus and brain stem reticular formation.

Administration of subconvulsant doses of bemegride results in extensive enhancement of sensory responsiveness to auditory, visual, somatosensory and vibrissa stimulation of neurons in the medullary and mesencephalic reticular formation (RF). This effect is not altered by cord transection. Most neurons in the dorsal hippocampus do not show enhanced sensory responsiveness. In the minority of hippocampal neurons which do show enhancement the effect is much less extensive than that seen in the RF despite larger doses of bemegride. The enhancement of RF neuronal response may involve the reversal of repetition induced response attenuation ('habituation') and reductions in response threshold. During EEG seizures the firing of neurons in RF and hippocampus are temporally correlated with the spikes in the cortical EEG. The effects of bemegride on RF neurons are similar to those previously reported for strychnine and pentylenetetrazol and preliminary studies with physostigmine and bicuculline. These findings further extend the concept that a relatively selective enhancement of the sensory responses of brain stem reticular formation neurons may be indicative of a general neuronal effect of convulsants which may play an important role in the initiation of sensory-induced seizures.

Animals↗
PubMed1981

Glutamate and aspartate: alteration of thresholds and response patterns of auditory neurons.

Iontophoretic application of the excitant amino acids glutamate and aspartate onto neurons in the chinchilla cochlear nucleus results in a lowering of the threshold of response to auditory stimuli. Neurons that display 'on'-type phasic responses to toneburst stimuli may become tonic, sustained responders with iontophoretic application of glutamate or aspartate. The ability of either glutamate or aspartate to effect changes in thresholds and response patterns of cochlear nucleus neurons is further evidence that one of these amino acids may be the afferent transmitter of the auditory nerve. The effects seen with these excitant amino acids may also provide insight into the underlying synaptic events involved in the generation of a particular response pattern.

Animals↗
PubMed1980

Strychnine effects on the sensory response patterns of reticular formation neurons.

Strychnine (ST) administration results in enhanced responses of reticular formation neurons of the cat to visual, auditory, or somatosensory stimuli. Neurons in the bulbar reticular formation (BRF) also exhibited ST-induced spike-bursting which coincides with the onset of 10--20 Hz high amplitude rhythmic discharge in the lower brain stem often obscuring sensory response enhancement. Mesencephalic reticular formation (MRF) neurons showed enhanced sensory responsiveness at higher doses of ST but rarely showed spike-bursting. The rhythmic discharge in the EEG of BRF and spike-bursting in BRF neurons was not observed in animals with spinal cord transection suggesting that this bursting activity is due to the action of ST on the spinal cord. The enhancement of sensory responses may be due in part to reversal of repetition-induced response attenuation (habituation) mechanisms in RF neurons. The ST-induced enhancement of RF neuronal responses to sensory stimuli is similar to that reported previously with pentylenetetrazol. These findings extend the concept that enhancement of RF responses to sensory stimuli may be indicative of a general neuronal action of convulsant agents which may be important in sensory-induced seizures.

Animals↗
PubMed1980

Comparative effects of pentylenetetrazol on the sensory responsiveness of lateral geniculate and reticular formation neurons.

The responses of bulbar and mesencephalic reticular formation (MRF) neurons to visual, auditory and/or somatosensory stimuli were considerably enhanced after subconvulsant doses of pentylenetetrazol (PTZ) in a similar fashion suggesting a general action of PTZ on reticular formation (RF) neurons. PTZ enhanced MRF responses evoked by electrical stimuli in the lateral geniculate nucleus (LGN) or cochlear nucleus but only modestly enhanced LGN neuronal responses. These findings indicate that the effects of this convulsant on the first brain sensory 'relay' nuclei and primary sensory receptors do not appear to be sufficient to account for the extensive PTZ-induced enhancement of RF neuronal responses, and direct effects of PTZ on the reticular formation may play a major role in this enhancement.

Animals↗
PubMed1979

Frequency-following responses in primary auditory and reticular formation structures.

The responses of the cat brain to tonal stimuli were recorded from the inferior colliculus, medial geniculate, reticular formation and the far field. The response consisted of an onset component and a frequency-following response (FFR) component in the inferior colliculus (IC) and the far field. In contrast to previous work, the FFR was also observed in the reticular formation. The response in the reticular formation was abolished at lower doses of pentobarbital and at lower relative intensities of masking than that in the IC and far field. The amplitude of the FFR increased and the latency decreased with progressive ventral movement of the electrode through the IC. The onset component of the response in IC was more easily masked than the FFR component, while the FFR component was depressed to a somewhat greater extent by pentobarbital administration. These findings suggest that the different components of the response to tonal stimuli are generated by different mechanisms.

Acoustic Stimulation↗