Search PubMed⌕ Search

PubMed · 7374852

[Tegmento-thalamic interrelationships in turtles].

Abstract

In immobilized, weakly anesthetized with chloralose turtles Emys orbicularis the focus of evoked potentials and the largest number of single unit responses to the stimulation of the mesencephalic tegmentum were revealed in the ventral thalamic region (a heterosensory zone with dominating somatic modality). An incomplete separation of latero- and mediotegmental projections was observed in dorsal and ventral subdivisions of the ventral thalamic region, respectively. The tegmental stimulation coinciding or preceding the electrical stimulation of the limb skin or light flash produced mainly a suppressing effect on somatic reactions of single units, the influence on visual reactions being much less significant. A possibility to compare tegmento-thalamic systems in reptiles and mammals is discussed.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M G Belekhova. 1980. [Tegmento-thalamic interrelationships in turtles].. https://pubmed.ncbi.nlm.nih.gov/7374852/

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Effect of neonatal spinal transection and dorsal rhizotomy on hindlimb muscles.

The purpose of this study was to elucidate the effect of deafferentation on spinal motoneurons. We studied the effects of spinal cord transection and/or dorsal rhizotomy upon the contractile properties of EDL and soleus muscle, as well as on the number of motoneurons corresponding to these muscles. Neonatal Wistar rats were randomly divided into four groups in which spinal midthoracic section (T8-T10), unilateral dorsal lumbar rhizotomy (L3-S2) or both procedures were performed on the second postnatal day (PND2). Another group served as unoperated control. At 2 months of age, the animals were evaluated for the contractile properties of a fast (EDL) and a slow (soleus) muscle. Isometric tension recordings were elicited by way of sciatic nerve branches stimulation. In addition, the incremental method was applied for the determination of the number of motor units supplying the two muscles, which was also verified by using the horseradish peroxidase (HRP) method of reverse labeling of motoneurons. Muscle alterations were confirmed by the usual biochemical staining. Our results, in agreement with the data from other researchers, show that significant muscle atrophy takes place after all experimental procedures. Additionally, spinal cord section alters the development of the dynamic properties of soleus muscle, which attains a fast profile. Following transection, the number of motor units remained unaltered, while rhizotomy affected only the soleus by reducing its motor units. The combined procedure affected both muscles, indicating that adequate synaptic input is essential for motoneuron survival.

Afferent Pathways↗

Descending projections of the hamster intergeniculate leaflet: relationship to the sleep/arousal and visuomotor systems.

The intergeniculate leaflet (IGL), homolog of the primate pregeniculate nucleus, modulates circadian rhythms. However, its extensive anatomical connections suggest that it may regulate other systems, particularly those for visuomotor function and sleep/arousal. Here, descending IGL-efferent pathways are identified with the anterograde tracer, Phaseolus vulgaris leucoagglutinin, with projections to over 50 brain stem nuclei. Projections of the ventral lateral geniculate are similar, but more limited. Many of the nuclei with IGL afferents contribute to circuitry governing visuomotor function. These include the oculomotor, trochlear, anterior pretectal, Edinger-Westphal, and the terminal nuclei; all layers of the superior colliculus, interstitial nucleus of the medial longitudinal fasciculus, supraoculomotor periaqueductal gray, nucleus of the optic tract, the inferior olive, and raphe interpositus. Other target nuclei are known to be involved in the regulation of sleep, including the lateral dorsal and pedunculopontine tegmentum. The dorsal raphe also receives projections from the IGL and may contribute to both sleep/arousal and visuomotor function. However, the locus coeruleus and medial vestibular nucleus, which contribute to sleep and eye movement regulation and which send projections to the IGL, do not receive reciprocal projections from it. The potential involvement of the IGL with the sleep/arousal system is further buttressed by existing evidence showing IGL-efferent projections to the ventrolateral preoptic area, dorsomedial, and medial tuberal hypothalamus. In addition, the great majority of all regions receiving IGL projections also receive input from the orexin/hypocretin system, suggesting that this system contributes not only to the regulation of sleep, but to eye movement control as well.

Afferent Pathways↗

Expression of the vanilloid receptor TRPV1 in rat dorsal root ganglion neurons supports different roles of the receptor in visceral and cutaneous afferents.

A combination of tracing and multiple color immunofluorescence revealed that 69% of rat dorsal root ganglion (DRG) neurons innervating the urinary bladder expressed the vanilloid receptor TRPV1. In contrast, only 32% of DRG neurons innervating the skin of the L6 dermatome expressed TRPV1. However, a similar fraction of visceral (60-62%) and of cutaneous (59-60%) TRPV1-positive DRG neurons expressed the peptidergic markers substance P and calcitonin gene-related peptide, while the fraction of TRPV1-positive neurons that was labeled by the non-peptidergic marker Isolectin B4 was 58% for cutaneous and only 24% for visceral afferents. These results underscore differences of expression of functional markers in visceral and cutaneous afferents and support different mechanisms of activation of TRPV1 in viscera and in skin.

Afferent Pathways↗