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At least 937 records · Page 52Linked to original sources
PubMed1981

Reticular influences on primary and augmenting responses in the somatosensory cortex.

The effects of brief, conditioning trains of high-frequency pulses to the midbrain reticular formation (RF) on primary and augmenting responses of somatosensory (SI) cortex were investigated. Testing stimulation was applied to the ventrobasal (VB) thalamus or to the white matter (WM) beneath SI in VB-lesioned animals. The RF-elicited EEG activation was associated with increased firing rates of SI neurons, enhanced probability of early synaptic discharges to VB or WM stimuli, and significantly reduced duration of the suppressed firing period following an afferent VB or WM volley. The diminished latency of the postinhibitory rebound under RF stimulation had the consequence that, within 10/sec shock-train, the second stimulus was delivered following completion of the rebound component and, instead of an augmented potential, generated a field response of primary-type. The dependence of the RF-induced change in augmenting potentials upon the sharpening effect exerted on the preceding inhibitory-rebound sequence was corroborated by analyzing the RF influence on neurons with different time-course of recovery from inhibition. The replacement of augmenting potentials by primary responses under RF stimulation is advanced as the mechanism behind the obliteration of spontaneously developing 'type I' spindle-waves during EEG arousal. The demonstration of RF influences on SI responses to WM stimulation in VB-lesioned animals points out the cortical level of the effects. The reticulo-thalamo-cortical pathways underlying these influences are discussed.

Animals↗
PubMed1984

Site-specific enhancement and suppression of desynchronized sleep signs following cholinergic stimulation of three brainstem regions.

The behavioral effects of carbachol microinjection into the pontine, midbrain and medullary reticular formation (RF) have been studied. Enhancement of electrographic desynchronized (D) sleep signs and D sleep-like behavior was specific to the pons; these parameters were contrastingly suppressed following cholinergic stimulation of the midbrain and medullary RF. Polygraphically defined wakefulness (W) was increased from the midbrain and medulla and was characterized by stereotyped motor activity, whereas slow wave (S) sleep was reduced or eliminated when carbachol was administered into all 3 brainstem regions. In addition, as a function of the site of carbachol administration within the pons, some qualitative electrographic differences between carbachol-induced D sleep and the physiological D sleep state were observed. These results are consistent with the hypotheses that the pontine RF is involved in the cholinergic initiation and/or maintenance of D sleep and that the midbrain RF mediates arousal via cholinoceptive reticular cells. The hypothesis that the medullary RF plays a major role in the generation of S sleep and the atonia of D sleep is not supported by these data, but non-cholinergic mechanisms of these proposed roles remain to be investigated. Preliminary reports of these data have been published.

Animals↗
PubMed1986

Cutting rostral trigeminal nuclear complex projections preferentially affects perioral nociception in the rat.

Sagittal knife cuts were made medial to rostral trigeminal brainstem nuclei in 11 rats. These cuts resulted in significant group deficits in facial thermal nociception at only two of the 5 ipsilateral sites tested. The affected sites were close to the vibrissa and oral cavity, suggesting that rostral trigeminal projections signal anterior rather than more caudal facial nociception. Three rats were also tested for EEG arousal responsiveness to innocuous air puffs before and after the cuts at the same facial sites. Only one of the rats demonstrated a significant deficit at one of the 5 sites tested, suggesting that the rostral projections interrupted in this study are not necessary for innocuous facial sensation.

Animals↗
PubMed1987

An analysis of the responses of rat striatal neurones to scrotal skin temperature.

The responses of neurones in the caudate-putamen complex of anaesthetised rats to different scrotal skin temperatures were examined, together with the electroencephalogram (EEG). Caudate neuronal firing patterns did not change independently of rate, unlike the thermo-responsive cells of the hypothalamus previously reported. The scrotal skin temperature threshold for the caudate neuronal response corresponds precisely with the temperature which provokes desynchronisation of the EEG.

Action Potentials↗