Browsing by Author "TORREALBA, F"

Now showing 1 - 9 of 9
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    BLOCKADE OF DOPAMINE-INDUCED CHEMOSENSORY INHIBITION BY DOMPERIDONE
    (1984) ZAPATA, P; TORREALBA, F
    The sensory discharges from the carotid body chemoreceptors of the cat are transiently inhibited by dopamine (DA) injections. This chemosensory inhibition was effectively blocked by domperidone, a selective antagonist of D2 dopaminoceptors. The basal frequency of spontaneous chemosensory impulses was immediately and sustainly increased after domperidone, suggesting the withdrawal of a tonic inhibition of chemosensory discharges by endogenous DA released from glomus cells. The peripheral dopaminergic modulation of chemoreflexes may be separately blocked by domperidone, a drug unable to cross the blood-brain barrier.
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    CALCITONIN GENE-RELATED PEPTIDE IMMUNOREACTIVITY IN THE NUCLEUS OF THE TRACTUS-SOLITARIUS AND THE CAROTID RECEPTORS OF THE CAT ORIGINATES FROM PERIPHERAL AFFERENTS
    (1992) TORREALBA, F
    The presence and distribution of the calcitonin gene-related peptide was studied, using immunohistochemical techniques, in carotid receptors, in the nodose and glossopharyngeal ganglia and in the nucleus tractus solitarii of the cat. Seventy-seven per cent of the petrosal and 42% of the nodose ganglion cells were labeled. Fine, sparsely branched immunoreactive terminal axonal arborizations were found in the carotid body; they disappeared after petrosal ganglionectomy. The intense immunoreactivity present in fibers in the commissural, medial, interstitial, gelatinosus, dorsal, intermediate and rostral gustatory subnuclei of the nucleus tractus solitarius was drastically reduced after removal of the ipsilateral nodose and petrosal ganglia.
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    COMPARATIVE-STUDY OF VISUAL INTER AND INTRAHEMISPHERIC CORTICO-CORTICAL CONNECTIONS IN 5 NATIVE CHILEAN RODENTS
    (1990) BRAVO, H; OLAVARRIA, J; TORREALBA, F
    Previous studies of the visual cortical organization in the rat and other rodent species have raised the possibility that the visual cortical plan in the rat is common to a large number of species within the order. We have tested this idea by comparing the visual plan in the rat to cortical subdivision schemes obtained from five native Chilean rodent species, including members of the Cricetidae family within the Miomorph group, as well as from the Octodontidae family within the Caviomorph group. Cortical subdivision schemes were inferred from the analysis of the patterns of callosal connections revealed following multiple injections of HRP contralaterally, as well as from ipsilateral cortico-cortical connections observed after small injections of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) into striate cortex. As in the rat, callosal connections in the native rodents concentrate at the border between cytoarchitectonic areas 17 and 18a, and along the borders of discrete, sparsely callosal islands of cortex in lateral peristriate cortex. Furthermore, single injections of WGA-HRP into striate cortex produce multiple, separate fields of labelled cells and terminations in cortex surrounding are 17. Together, our data supports the idea of a common plan of visual cortical organization among rodents by providing evidence that the visual cortex in the native species is subdivided into multiple visual areas in a manner that resembles the rat cortical plan.
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    CYTOCHROME-OXIDASE ACTIVITY IN THE NUCLEUS OF THE TRACTUS-SOLITARIUS OF THE CAT
    (1992) TORREALBA, F; MUNOZ, M
    We studied the cytochrome oxidase (CO) activity in the nucleus of the tractus solitarius (NTS) of normal cats and in animals subjected to unilateral removal of vagal and glossopharyngeal afferents. In normal cats CO activity was higher in the ventrolateral, dorsolateral, interstitial and ventral NTS subnuclei. The dorsal, medial, commissural and gelatinosus subdivisions showed lower levels of CO activity. The peripheral deafferentation up to 47 days did not reduce the CO activity, suggesting an important role for the central inputs in deter-mining the neural activity of the NTS.
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    SEGREGATION OF COARSE AND FINE GLOSSOPHARYNGEAL AXONS IN THE VISCERAL NUCLEUS OF THE TRACTUS SOLITARIUS OF THE CAT
    (1989) CLAPS, A; TORREALBA, F; CALDERON, F
    The projections of coarse and fine axons of the glossopharyngeal (IX) nerve upon the caudal two thirds of the nucleus of the tractus solitarius (NTS) were studied in the cat. These afferents convey the chemo- and baroreceptor activities from the carotid receptors. We applied the Fink-Heimer method on brainstem sections, at different survival times, after a petrosal ganglionectomy. A segregation of fine and coarse fibered components was observed. Degeneration of coarse axons was mostly found in the lateral NTS, while fine fiber degeneration was predominant in regions of the medial and commissural NTS. The injection of WGA-HRP in the different NTS divisions demonstrated that the lateral NTS was mainly innervated by the set of largest neurons of the petrosal ganglion and that the medial and the commissural NTS were innervated by the set of smaller neurons of the ganglia. These results were discussed in relation to cytoarchitecture, myeloarchitecture, distribution of normal axons, and known central connectivity of the different NTS divisions. We concluded that coarse and fine visceral afferents of the IX nerve, which includes the afferents of the carotid body and the carotid sinus, represent different afferent populations that project to particular divisions of the NTS and connect to different central pathways.
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    THE CAROTID-BODY CONNECTIONS - A WGA-HRP STUDY IN THE CAT
    (1988) CLAPS, A; TORREALBA, F
    Previous neuroanatomical studies described the central representation of the carotid sinus nerve, but did not differentiate the projections of the baroreceptors from the chemoreceptors present in the carotid bifurcation. In this research we investigated the individual territories occupied by the primary afferents from the carotid body in the brainstem of the cat. We also studied the distribution of afferent and efferent neurons to the carotid body. We injected into the carotid body lectin coupled to horseradish peroxidase. We found labeled axons only in the nucleus of the tractus solitarius; in particular, we found strong projections to the following ipsilateral subnuclei:dorsal, interstitial, and medial part of the commissural subnucleus. Moderate labeling was found in the ipsilateral medial and intermediate subnuclei and in the contralateral dorsal subnucleus and the medial region of the commissural subnucleus. We found a mean of 256 .+-. 79 (S.E.M.) labeled afferent ganglion cells in the petrosal ganglia, and no evidence of efferent neurons in the brainstrem that innervate the carotid body; conversely, about 4000 efferent neurons of the superior cervical ganglion send terminals to the ipsilateral carotid body.
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    THE CAROTID-SINUS CONNECTIONS - A WGA-HRP STUDY IN THE CAT
    (1988) TORREALBA, F; CLAPS, A
    The neural connections of the carotid sinus were studied by administration of horseradish peroxidase or a lectin conjugate to the adventitia of the carotid sinus of cats. The carotid sinus afferents project exclusively to the nucleus of the tractus solitarius (NTS). Rostral to the obex the projection is mainly ipsilateral with a strong contralateral component caudal to the obex. The carotid sinus projects to several NTS territories that do not receive afferents from the carotid body chemoreceptors; they are: the dorsolateral, the lateral extension of the commissural, the caudal intermediate, the ventrolateral and the gelatinosus subnuclei. In addition the carotid sinus central representation includes territories occupied also by carotid body terminals; dorsal, interstitial, rostral intermediate, medial and the medial part of commissural subnuclei (see previous paper). Labeled cell bodies were found in the petrosal (216 .+-. 37, mean .+-. S.E.M.) nodose (825 .+-. 434) and superior cervical ganglia (3583 .+-. 1227) demonstrating the sympathetic efferent innervation of the carotid sinus and a dual sensory innervation via both the glossopharyngeal and vagus nerves.
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    THE VAGAL CONNECTION OF THE CAROTID-SINUS
    (1988) TORREALBA, F; CLAPS, A
    We applied wheat germ agglutinin-horseradish peroxidase (WGA-HRP) to the adventitia of the left carotid sinus of cats after tying the glossopharyngeal and the carotid sinus nerves. Forty-five to 255 neurons were labeled in the rostral pole of the nodose ganglion, through the pharyngeal branch of the vagus nerve. Transganglionic label was present only in the ipsilateral dorsal and medial subnuclei of the nucleus tractus solitarii at levels nearly rostral to the area postrema. These findings show the existence of a novel pathway from the carotid sinus, projecting via the vagus nerve, to the nucleus tractus solitarii.
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    ULTRASTRUCTURE OF CALCITONIN-GENE-RELATED PEPTIDE-IMMUNOREACTIVE, UNMYELINATED AFFERENTS TO THE CAT CAROTID-BODY - A CASE OF VOLUME TRANSMISSION
    (1995) TORREALBA, F; CORREA, R
    To relate the ultrastructure of unmyelinated afferents to the cat carotid body with the known electrophysiological properties of cat chemosensory C-fibers, we took advantage of the fact that the calcitonin gene-related peptide is exclusively present in a population of sparsely branched afferents to the carotid body. They have a morphology identical to the afferents originating from carotid sinus nerve unmyelinated axons. Immunoreactive axons were stained using pre-embedding protocols and horseradish peroxidase-labeled secondary antibody. Labeling was present only in unmyelinated axons and boutons distributed in the interstitial and parenchymal tissue. The varicosities had an average diameter of 0.7 mu m, and contained both small, clear vesicles and larger dense-core vesicles. No labeled axons were ever seen to contact glomus cells, but could be observed as close as 0.2 mu m to a glomus cell, always with an interposed glial process. With a very sensitive protocol, that used tungstate-stabilized tetramethylbenzidine as the chromogen, amorphous deposits of reaction product were often detected in the extracellular space around a labeled bouton.