Cortical visual areas process intestinal information during slow-wave sleep.

BACKGROUND: Previously we have shown that, during sleep, electrical and magnetic stimulation of areas of the stomach and small intestine evoked neuronal and EEG responses in various cortical areas. In this study we wanted to correlate natural myoelectrical activity of the duodenum with cortical neuronal activity, and to investigate whether there is a causal link between them during periods of slow-wave sleep. METHODS: We have recorded the myoelectrical activity from the wall of the duodenum and activity of single neurons from three cortical visual areas in naturally sleeping cats and investigated causal interrelationship between these structures during slow-wave sleep. KEY RESULTS: About 30% of the cortical neurons studied changed their firing rate dependent on the phases of the peristaltic cycle and demonstrated selectivity to particular pattern of duodenal myoelectrical activity during slow-wave sleep. This interrelationship was never seen when awake. CONCLUSIONS & INFERENCES: This observation supports the hypothesis that, during sleep, the cerebral cortex switches from processing of exteroceptive and proprioceptive information to processing of interoceptive information.

[Structural organization of neurons of spinal ganglia innervating the colon].

The localization and morphological features of viscerosensory neurons of sacral spinal ganglia (SSG), innervating the colon, were investigated. In urethane anaesthetized cats, the solution of horseradish peroxidase was injected under the serosa of ascending and descending parts of the colon as well as of the rectum. After 48 hours animals were repeatedly anesthetized and transcardially perfused. Sections of SSG were stained according to Mezulam protocol (1978). All the regions of the colon studied were shown to receive afferent innervation from neurons of SSG SI, SII and SIII. Maximum number of the labeled cells was detected in SSG SII. The intensity of afferent innervation of the colon by the neurons of SSG was found to increase along its length in cranio-caudal direction.

Muscarinic modulation of nitrergic neurotransmission in guinea-pig gastric fundus.

Muscarinic receptor activation by (4-Hydroxy-2-butynyl)-1-trimethylammonium-m-chlorocarbanilate chloride (McN-A-343) was investigated both on NADPH-d staining and on electrically induced responses in guinea-pig gastric fundus. McN-A-343 (10 micromol L(-1)) significantly increased the optical density of NADPH-d positive neurones, while blockade of nitric oxide synthase with N(omega)-nitro-L-arginine (L-NA) decreased it, suggesting facilitation of nitric oxide (NO) production. Electrical field stimulation (EFS; 2 Hz, 0.2 ms, supramaximal current intensity, 10 s train duration) elicited on-contraction followed by off-relaxation in the circular muscle strips. McN-A-343 (10 micromol L(-1)) transformed the EFS-evoked response from on-contraction into on-relaxation, which was neurogenic, tetrodotoxin-sensitive and hexamethonium-resistant. L-NA partly reduced the EFS-evoked relaxation, revealing two components: a nitrergic and a non-nitrergic one. The effect of McN-A-343 on the amplitude of the EFS-evoked relaxation was not changed by the M(3) receptor antagonist para-fluoro-hexahydro-sila-difenidol hydrochloride, but was significantly enhanced by M(1) receptor blockade with telenzepine. In the presence of telenzepine, the L-NA-dependent nitrergic component of the EFS-induced relaxation predominates. We suggest that cholinergic receptor activation has a dual effect on nitrergic neurotransmission: (i) stimulation of NOS by muscarinic receptor(s) different from M(1) and M(3) subtype, (ii) prejunctional inhibition of NO-mediated relaxation via M(1) receptors. In addition, M(1) receptors may facilitate the non-nitrergic relaxation.

Identification of a respiratory related area in the rat insular cortex.

The aim of this study was to map areas within the rat insular cortex from which respiratory responses originate and compare those sites with gastrointestinal control regions. The insular cortex was systematically microstimulated and histological location of responsive sites determined. Increased inspiratory airflow and decreased respiratory cycle duration were considered to be respiratory excitatory responses. The responses were localized in dysgranular and agranular insular cortex at levels caudal to the joining of the anterior commissure. More rostrally, respiratory inhibitory responses were elicited: these were manifested as a decrease in inspiratory airflow without a significant alteration in respiratory cycle duration. Respiratory inhibitory responses were usually accompanied by changes in gastric motility. These results suggest that the respiratory area in the rat insular cortex consist of two distinct zones which overlap a region modulating the gastrointestinal activity.

[Visceral field of the rat insular cortex]. / Vitseral'noe pole insuliarnoi oblasti kory mozga krys.

Structural-functional organisation of the cortical insular area relating to processes of the visceral functions control, was analysed. Representation of gastrointestinal, respiratory, and cardiovascular systems in the area, is given. Sites of respective neuronal groups and specifics of their spatial organisation within the area, were found. The data obtained suggest a scheme of the rat insular cortex's visceral field.

[The neurons of the medial vestibular nucleus initiating the relaxation of the rat's stomach wall]. / Neirony medial'nogo vestibuliarnogo iadra, initsiiruiushchie relaksatsiiu stenki zheludka u krys.

In acute rat experiments the technique of retrograde axonal transport of horseradish peroxidase in the medial vestibular nucleus allowed to identify a group of neurones sending axons to the "stomach" region of a single tract nucleus. These neurones and, accordingly, the descending vestibular/solitary links can be viewed as the morphologic basis for vestibular influences on the gastric motor activity. As was shown, local irritation of the neurones initiates relaxation of the stomach wall. Activation of the anterior limbic cortex modulates the vestibular/autonomous responses of the intragastric pressure reduction. Irritation of the infralimbic cortex of the rat's brain may have a preventive effect on the stomach wall relaxation stimulated by the vestibular neurones projecting on the "stomach" region of single tract nucleus.

Gastric related neurons in the rat medial vestibular nucleus.

Some structural and functional peculiarities of the rat vestibular nuclei neurones involved in realisation of vestibular-gastrointestinal reflectory reactions were studied. After microinjection of a horseradish peroxidase solution in the 'gastric' area of the nucleus tractus solitarius, retrogradely-labelled cell bodies were found in caudal part of the medial vestibular nucleus. Electrical stimulation of these neurons resulted in the decrease of gastric tone. The respiratory arrest was registered simultaneously. The results suggest that activation of the identified vestibular neurons can induce coordinated changes in visceral systems which are peculiar to a vomiting reaction.

[Possible mechanisms of the anterior limbic cortex influence on the neuron activity of the vago-solitary complex]. / Analiz vozmozhnykh mekhanizmov limbicheskoi kory na aktivnost' neironov vago-solitarnogo kompleksa.

In ananesthetized cats, neurons of the nucleus of the tractus solitarius (NTS) and the dorsal motor nucleus of the vagus nerve (DMNV) revealed phasic excitatory responses to separate single vagal and cortical stimuli. Stimulation of the anterior limbic cortex combined with vagal stimulation resulted in inhibitory or excitatory modification of the vagal induced responses of the NTS and DMNV neurons. The data obtained suggest that complete inhibitory effects are related to general cortical mechanisms of control of the functional state of the brain stem visceral neurons. Selective inhibition of the vagal induced responses by limbic cortex stimulation is due to particular cortical mechanisms of the visceral sensory transmission control via the NTS neurons.

[The dorsal motor nucleus of the vagus nerve and its role in innervating the digestive tract]. / Dorsal'noe motornoe iadro bluzhdaiushchego nerva i ego rol' v innervatsii pishchevaritel'nogo trakta.

Findings on topography of dorsal motor vagal nucleus neurons from which axons towards functionally different regions of digestive tract extend were analysed. Based on that and on the data available in literature main peculiarities of these cells topical organization were formulated. It is noted that "gastrointestinal" neurons are localised in dorsal motor nucleus as narrow stripes oriented caudo-rostrad. Stripes (or columns) of neurons from axons towards the digestive trace different parts arise do not cross. Digestive tract oral parts receive parasympathetic efferent inputs from neurons of medial and dorsomedial parts of the nucleus and caudal--from ventromedial cells of dorsal motor nucleus. Sites of maximal accumulation of initial "gastrointestinal" neurons that occupy an area within +0.5-(+)2.0 mm of functionally different regions of stomach and gut were demonstrated in cat and rat.

Identification of gastric related neurones in the rat insular cortex.

Location peculiarities of insular neurones implicated in the regulation of gastrointestinal motility have been studied in acute experiments on rats. After microinjection of a horseradish peroxidase solution in a part of the dorsal vagal complex that receive gastric afferent inputs, retrogradely labelled cell bodies are observed in a certain area of the agranular and disgranular insular cortex. Electrical stimulation of the insular cortex area had no significant effect on heart and respiration rate but had evoked gastric tone changes. These results suggest that the insular cortex contains a specific cell group that provides direct output to the bulbar 'gastric' centre and takes part in regulation of gastrointestinal functions.

[The afferent link in the system of the bulbar regulation of gastric motor function]. / Afferentnoe zveno v sisteme bul'barnoi reguliatsii motornoi funktsii zheludka.

The data obtained suggest a possible participation of neurons of the tractus solitarius' nucleus in mechanisms of the stomach motility control. These neurons seem to be involved in an afferent link of the bulbar "gastric" centre participating in regulation of the stomach motor activity.

Limbic cortical influences to the vagal input neurones of the solitary tract nucleus.

In acute experiments on cats, electrical stimulation of the anterior limbic cortex was shown to modulate activity of vagal input neurones of the nucleus of the tractus solitarius. In the majority of the solitary tract nucleus neurones the responses induced by electrical stimulation of the vagus were depressed by the stimulation of anterior limbic cortex. Under these conditions the patterns of responses or their latency were changed. Our results are discussed with respect to possible mechanisms for cortical control of sensory transmission in the nucleus of the tractus solitarius.

[The morphological characteristics of the parasympathetic innervation of the pyloric sphincter in the cat]. / Morfologicheskie osobennosti parasimpaticheskoi innervatsii piloricheskogo sfinktera u koshki.

The method of axonal transport of horse-radish peroxidase was used to detect the localization of neurons in the dorsal motor nucleus of the vagus nerve sending the axons to the pyloric sphincter. The investigation was carried out in cats. Under study were also morphological features of the nodular ganglion responsible for afferent innervation of the sphincter. The maximum amount of the corresponding cells are found in the dorsomedial part of the dorsal motor nucleus in the area from +1.0 to +2.0 mm (with respect to obex). The afferent neurons to which information comes from interoceptors of the sphincter zone along the vagus nerve fibers, are distributed in the left and right nodular ganglia almost evenly. The major part of these cells have the area of 300-800 mkm2.

Localization of neurons innervating the upper portion of the duodenum in the motor nucleus of the vagus nerve.

Using the method of the retrograde axonal transport of horseradish peroxidase and a microelectrode technique, a population of neurons sending axons to the upper portion of the duodenum was identified in the dorsal motor nucleus of the vagus nerve. It was established that the maximal number of such neurons was located 1.0-2.5 mm rostral to the obex. The effects of their stimulation on the electrical activity of the smooth muscles of the duodenum was studied.

[The localization of neurons in the nodose ganglion of the cat that innervate the rostral portion of the duodenum]. / Lokalizatsiia neironov uzlovatogo gangliia koshki, innerviruiushchikh rostral'nuiu chast' dvenadtsatiperstnoi kishki.

The method of axonal transport of horseradish peroxidase was used for studying the sites of localization and morphological features of sensory neurons of the vagus nerve in the left and right ganglion nodosum innervating the rostral part of the duodenum. Animals under nembutal narcosis were given 90-100 mcl of 33% solution of horseradish peroxidase ("Olaine", Riga RZ 2.7) injected into a limited area (1 x 1 sm) of the muscular layer of the duodenum. Horseradish peroxidase labelled neurons were found bilaterally in the both ganglia. The number of neurons in the left ganglion was 91 +/- 23, in the right one--115 +/- 24. The sensory cells are mainly of the ellipsoid form and of different sizes. Areas of sections of the neurons vary from 100 to 1300 mkm2, most on them having the area from 300 to 700 mkm2. The distribution of neurons according to the sizes of their areas have no substantial differences in the left and right ganglia. It was found that 65% of neurons in the right ganglion and 67% in the left one are localized in its caudal half.

[Extra-organ sources of parasympathetic innervation of small intestine in the region of ligament of Treitz]. / Ekstraorgannye istochniki parasimpaticheskoi innervatsii tonkoi kishki v oblasti sviazki treittsa.

Localization sites of neurons in the dorsal motor nucleus of cat vagus innervating the duodenal-jejunal region and upper part of the jejunum were investigated using the technique of the retrograde axonal transport of horseradish peroxidase. Most part of the neurons was located within the ventrolateral area of the nucleus from +1.0 to +2.7 mm (according to obex). Morphological features of the ganglion nodosum neurons which organize afferent innervation of the intestine were analyzed. It has been shown that the maximal amount of such neurons is concentrated in the medium and caudal parts of the ganglion.