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R Guevara-Aguilar

Publications and source records attributed to R Guevara-Aguilar.

At least 19 recordsLinked to original sources
PubMed1989

Fetal brain grafts induce recovery of learning deficits and connectivity in rats with gustatory neocortex lesion.

Three groups of rats showing disrupted taste aversion due to gustatory neocortex lesions, were studied. One group received a transplant of homotopic cortical tissue, another of heterotopic tectal tissue, obtained from 17-day-old fetuses. The third group remained without transplant as a lesioned control group. Comparisons of the taste aversion scores before and after graft, revealed that cortical grafted animals significantly improved the taste aversion, whereas those which received tectal grafts, and the cortical-lesioned controls did not. Moreover, results with horseradish peroxidase (HRP) histochemistry revealed that the homotopic, but not the heterotopic, brain transplants were able to re-establish connections with amygdala and with the ventromedial nucleus of the thalamus areas who normally kept connectivity with the gustatory neocortex. These results support the hypothesis that fetal brain transplants can reestablish cognitive functions, as well as connectivity with its host tissue.

Amygdala↗
PubMed1988

Olfactory and visceral projections to the nucleus of the solitary tract.

Electrophysiological studies were performed to determine if neurons of the nucleus of the solitary tract (NTS) which receive inputs from the stomach via vagal afferents also respond to olfactory bulb (OB) stimulation. The frequency of neuronal activity of the rostral ventral portion of the NTS was increased by gastric distension (GD). The evoked potentials in the same site due to vagal stimulation displayed short latencies; whereas, the evoked potentials in the dorsomedial part of the NTS due to vagal stimulation had considerably longer latencies. Gastric distension decreased neuronal activity in the dorsomedial NTS. Evoked potentials and increases in neuronal activity were also observed in the dorsomedial NTS due to electrical stimulation. In the dorsomedial NTS, OB stimulation enhanced the decrease in neuronal activity due to GD. Olfactory and visceral functions apparently interact in the NTS in modulating taste mechanisms involved in food selection and ingestion.

Afferent Pathways↗
PubMed1988

Olfactory and visceral projections to the paraventricular nucleus.

Electrophysiological studies were performed to determine if neurons of the paraventricular nucleus (PVN) which receive inputs from the stomach via vagal afferents also respond to nucleus of the solitary tract (NTS) and olfactory bulb (OB) stimulation. We found that the NTS, OB stimulation, and gastric distension depress the firing frequency of PVN neurons. The pathway from the NTS to the PVN contains larger fibers than the projection from the PVN to the NTS.

Action Potentials↗
PubMed1987

Effect of locus coeruleus and periventricular gray substance lesions on suprachiasmatic damage-induced persistent estrous.

To assess the relation between the suprachiasmatic nucleus and the locus coeruleus, persistent estrous was induced in female rats by damage of the suprachiasmatic nucleus followed with electrolytic damage of the locus coeruleus. Locus coeruleus lesions resulted in a transient loss of persistent estrous indicated by sustained diestrous aspect of the vaginal smears. There was a direct correlation between duration of estrous loss and the amount of locus coeruleus damage. Simultaneous damage to the periventricular gray substance, adjacent to the locus coeruleus, prevented the suppression effects of locus coeruleus damage upon persistent estrous. These results suggest a physiological role of the locus coeruleus and periventricular gray substance in the modulation of the neuroendocrine control of ovarian function due to suprachiasmatic nucleus activity.

Animals↗
PubMed1986

Effect of locus coeruleus and periventricular gray substance lesions on bright light-induced persistent estrous.

To assess the relation between the suprachiasmatic nucleus and the locus coeruleus, persistent estrous was induced in female rats by exposure to constant bright light followed with electrolytic damage of the locus coeruleus. Locus coeruleus lesions resulted in a transient loss of persistent estrous indicated by sustained diestrous aspect of the vaginal smears. There was a direct correlation between duration of estrous loss and the amount of locus coeruleus damage. Simultaneous damage to the periventricular gray substance adjacent to the locus coeruleus prevented the suppression effects of locus coeruleus damage upon persistent estrous. These results suggest a physiological role of the locus coeruleus and periventricular gray substance in the modulation of the neuroendocrine control of ovarian function due to suprachiasmatic nucleus activity.

Animals↗
PubMed1985

Olfactory bulb neurons respond to gastric distension.

Single unit discharges in the olfactory bulb (OB) were recorded extracellularly in anesthetized rats during controlled gastric distension. The activity of 37 neurons in the periglomerular layer of the OB modulated by gastric distension was analyzed. Twelve of the 37 cells decreased, eight decreased and then increased in frequency, and 17 displayed more complex effects due to gastric distension. Generally, the latency of the responses to gastric distension was less than one second. All those cells which responded to gastric distension also responded to vagus nerve stimulation. This effect was abolished or attenuated by cutting the vagus nerve at the cervical level. The threshold volume by which the stomach was infused for the initial decrease in OB neuronal discharge frequency was 3.0 ml. When more than 8 ml were infused, increases in firing frequencies were always observed. The results of the present experiments indicate that the discharge frequency of the periglomerular OB neurons are modulated by visceral afferents.

Action Potentials↗
PubMed1985

Effects of dopamine and norepinephrine on neuronal activity of the olfactory tubercle.

The effects of iontophoretic administration of norepinephrine (NE) and dopamine (DA) on olfactory tubercle (OT) neurons that respond to lateral hypothalamus (LH) or locus coeruleus (LC) electrical stimulation were studied. NE and DA decreased the frequency of OT neurons which were increased or decreased by the LH stimulation. An increased firing of OT neurons following NE or DA administration was less frequently observed. NE administration decreased the firing of OT neurons that responded to LC stimulation. These results suggest that the LC fibers which reach the OT use NE as a neurotransmitter. DA administration also suppressed the unitary discharge of OT neurons responding to LC stimulation. The increase in frequency of OT neurons observed following LH stimulation cannot be attributed to DA. The possibility that other suspected neural transmitters are involved in this effect is discussed.

Animals↗
PubMed1985

Convergence of influences from hypothalamus and locus coeruleus upon the olfactory tubercle.

The interaction of locus coeruleus (LC) and lateral hypothalamus (LH) stimulation upon the evoked potentials and unitary activity in the olfactory tubercle (OT) were studied. The difference in latency of the evoked potentials in the OT by LC or by LH stimulation seems to indicate that thin fibers compose the LC-OT pathway and that thick fibers compose the LH-OT pathway. The most common pattern of OT neuronal discharge was in bursts. The train stimulation of the LC decreased the OT neuronal discharge. The LH stimulation produced an increase of the OT neuronal discharge. These results suggest a convergence of LH fibers and LC fibers upon the OT. The nature of the neurotransmitters involved in both pathways is suggested: norepinephrine for the LC-OT projection and dopamine for the LH-OT projection.

Animals↗
PubMed1984

Vagus nerve stimulation modifies the electrical activity of the olfactory bulb.

Evoked potential and unit activity recording techniques were used to study the effects of the vagus nerve stimulation on the olfactory bulb. A biphasic potential was evoked in the olfactory bulb by a single pulse delivered to the vagus nerve. Half of the neurons studied decreased discharge frequency after single pulse or train stimulation. The interval during which neurons ceased activity corresponded to the duration of the negative wave of the evoked potential. Responsive neurons were marked with horseradish peroxidase applied iontophoretically. Responsive neurons were located in the periglomerular layer of the olfactory bulb. These results suggest the existence of a vagus nerve-olfactory bulb pathway. The functional significance of this pathway is discussed.

Afferent Pathways↗
PubMed1983

Limbic connections to the lateral preoptic area: a horseradish peroxidase study in the rat.

Horseradish peroxidase, 13% Sigma Type VI, was administered iontophoretically to the lateral preoptic area (LPA) of male hooded rats. Animals were perfused intracardially on the following day and brains were removed and sliced in the coronal plane into 50 microns sections. Alternate sections were processed with DAB and BDH for the brown and blue reaction products and later examined by bright and dark field microscopy for the presence and location of retrogradely labeled neurons. Results indicate that there are a significant number of limbic efferent connections to the LPA. Afferents to the LPA originate in the prefrontal corex, nucleus accumbens, diagonal band and olfactory structures, lateral and medial septum, stria hypothalamic tract and stria terminalis, the magnocellular and medial preoptic nuclei, along the extent of the medial forebrain bundle in the LPA and LH, anterior and basolateral amygdala, ventromedial caudate-putamen, stria medullaris and lateral habenula, the stellatocellular-periventricular, ventromedial, arcuate and anterior hypothalamic nuclei, the perifornical area, zona incerta, ventral medial thalamic area, ventral tegmental area of Tsai, interpeduncular nucleus, reticular zone of the substantia nigra, mesencephalic periaqueductal gray and reticular formation, all aspects of the raphe nuclei and the locus coeruleus. Results are discussed in terms of known anatomical and neurophysiological data and the similar limbic inputs observed for lateral hypothalamic neurons which are found along the extent of the medial forebrain bundle.

Animals↗
PubMed1982

Transient cessation of female rat sexual cycle after electrolytic damage of locus coeruleus.

In order to evaluate the possible participation of the locus coeruleus (LC) in the regulation of estrous cyclicity, bilateral LC electrolytic lesions were made in intact female rats. Vaginal smears were sampled daily and the estrous cyclicity was established. LC lesions resulted in a transient loss of cyclicity characterized by a sustained diestrous period. The delay in recovery was dependent on the percentage of LC destroyed. The cyclicity of sham operated rats and of nonoperated rats showed no change. Results are discussed within the context of the LC as a generalized influencing system.

Animals↗
PubMed1982

Differential projections from locus coeruleus to olfactory bulb and olfactory tubercle: an HRP study.

The microiontophoretic administration of horseradish peroxidase (HRP) to the olfactory bulb (OB) or olfactory tubercle (OT) in cats and rats yielded similar results in both species. After an OB HRP-injection ipsilateral and contralateral labelled neurons were seen in the piriform cortex, polymorphic layer of OT, magnocellular preoptic region, lateral hypothalamus, ventromedial hypothalamic nucleus and locus coeruleus (LC). In both species more labelled structures were found after an OT HRP-injection than after an OB HRP-injection. The substantia nigra in rats was more abundantly labelled after an OT injection than after an OB one. In cats the dorsal and the ventral raphe were also labelled. In either species, OT HRP-injections resulted in a higher frequency of LC labelled neurons than after OB injections. These results favor the hypothesis that the OT plays an important role as a relay station for efferent inflow from the brain stem en route to the OB.

Animals↗
PubMed1981

Afferent connections to the lateral hypothalamus: a horseradish peroxidase study in the rat.

Horseradish peroxidase, 13% Sigma Type VI, was administered iontophoretically to the mid lateral hypothalamus (LH) of male hooded rats. Animals were perfused intracardially on the following day and brains were removed and sliced in the coronal or sagittal planes into 30-50 micrometer sections. Sections were processed with DAB and BDH for the brown and blue reaction products and later examined by bright and dark field microscopy for the presence and location of retrogradely labeled neurons. Results indicate that a significant number of afferent connections to the LH originate in the olfactory and accumbens nuclei, pyriform cortex, olfactory tracts, magnocellular and medial preoptic and anterior hypothalamic regions, stria terminalis, stria hypothalamic tract, diagonal tract of Broca, caudate-putamen and globus pallidus, internal capsule, lateral septal nuclei, lateral preoptic area and anterior medial forebrain bundle, the various amygdaloid nuclei, zona incerta, perifornical region, dorsal and ventral medial hypothalamic areas, supraoptic, paraventricular and periventricular nuclei, posterior hypothalamus and medial forebrain bundle, ventral thalamic nuclei, the fields of Forel, arcuate and mammillary nuclei, adjacent to the fasciculus retroflexus, in the ventral tegmental area of Tsai, interpeduncular nucleus, substantia nigra, mesencephalic reticular formation, periaqueductal gray, locus coeruleus and parabrachial region. Results are discussed in terms of previous anatomical and neurophysiological data, probable pathways, and the function of LH neurons.

Afferent Pathways↗
PubMed1981

Olfactory tubercle's different neural elements activated by locus coeruleus.

Olfactory tubercle (OT) evoked potentials were recorded following single pulse stimulation of the locus coeruleus (LC) in cats. Also, OT unit responses were recorded extracellularly following LC repetitive stimulation in rats. In order to characterize the properties of OT evoked potentials, these responses were evaluated following repetitive stimulation, paired shock, animal asphyxiation and damage to the recording site. Longer latency potential changes were more labile to repetitive stimulation, paired shock and asphyxiation than short latency changes. The time course of the effects following experimental procedures was not equal for the potentials of different latencies. Most of the individual OT neurons studied were not affected by repetitive LC stimulation. However, a small percentage were enhanced and the remainder decreased discharge frequency. Hypertensive effects were ruled out as a cause of the OT unit responses following LC stimulation because the temporal course of both events were not similar. Results of both electrophysiological techniques suggest that the LC influences different neural elements and/or neural populations within the OT. These responses appear to be independent of one another.

Animals↗