Luis Pastor Solano-Flores

Vagus nerve afferent and efferent innervation of the rat uterus : an electrophysiological and HRP study

To determine a possible brainstem connection with the uterus, a study with electrophysiological techniques and horseradish peroxidase (HRP) tracing was performed in the rat. Neurons of the nucleus of the tractus solitarius decreased in discharge frequency during cervicovaginal distension. HRP injections into the uterine walls resulted in the appearance of labelled cells in the nodose ganglion and in the dorsal motor nucleus of the vagus nerve. The results demonstrate a direct bidirectional vagal complex-uterus connection via the vagus nerve. Results are discussed in terms of a complex uterus control system in which the paraventricular nucleus might play an integrative role.

Electrophysiological evidences of a bidirectional communication between the locus coeruleus and the suprachiasmatic nucleus

To assess a possible relation between the suprachiasmatic nucleus (SCN) and the locus coeruleus (LC), a study with evoked potentials was performed in the rat. An evoked potential was recorded in the SCN area after electrical stimulation of the LC. Also, an evoked potential was recorded in the LC after electrical stimulation of the SCN area. The results indicate specificity of the projecting regions and of the activated regions, suggesting the existence of a possible bidirectional communication between the LC and the SCN. The pathways possibly involved are discussed.

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.

Locus coeruleus influences upon the olfactory tubercle

Locus coeruleus (LC) influences upon the olfactory tubercle (OT) were studied. Evoked potentials and unit activity recording techniques were used as well as the horseradish peroxidase (HRP) labelling method. A biphasic potential was recorded in cats OT following a single pulse delivered to the LC. Latencies were 35 msec and 80 msec for the first positive and second negative component respectively. The largest potentials were recorded between the superficial part of the pyramidal layer and the polymorphic layer. This potential was tested in order to determine whether it was an OT generated potential caused by LC stimulation. Contralateral recordings were made. Extracellularly recorded OT neurons decreased their discharge frequency upon repetitive LC stimulation in rats. The decreases endured longer when the stimulus frequency or train duration were increased. Neurons from which unit data were used in the analysis were verified to be in the OT polymorphic layer. Labelled neurons were seen in the LC after HRP application to the OT in rats and cats. Results support the presence of LC fibers which influence OT neurons. The relation between the LC as a general arousal system and the OT as an important olfactory information processing structure is discussed.

Recovery of vestibular function in young guinea pigs after streptomycin treatment: Glutamate decarboxylase activity and nystagmus response assessment

Fifty‐day streptomycin (STP) treatment in guinea pigs causes specific vestibular hair cell (VHC) types I and II (HCI; HCII) degeneration, depletion of glutamate decarboxylase (GAD) and a gradual disappearance of postrotatory nystagmus response (PRNR), which is a sign of vestibular function alteration. In order to look for a possible spontaneous reversibility and its time course guinea pigs receiving 300 mg/kg STP daily were monitored for PRNR and vestibular GAD loss. Once PRNR was lost, STP was interrupted and the animal was allowed to recover; at the time that PRNR was completely reestablished, vestibular GAD was measured.

Nucleus of the tractus solitarius projections to the olfactory tubercle: An HRP study ☆

Labelled cells were found in the nucleus of the tractus solitarius (NTS) after horseradish peroxidase injections in the olfactory tubercle (OT) of the rat. These results suggest a direct pathway from the NTS to the OT. The importance of this pathway in a neural circuit related to autonomic functions is discussed.

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.

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.

Role of the paraventricular nucleus in the projection from the nucleus of the solitary tract to the olfactory bulb

Electrophysiological experiments were performed on anesthetized rats to determine the effects of lesions of the paraventricular nucleus on the amplitude of evoked potentials recorded in the periglomerular layer of the olfactory bulb after nucleus of the solitary tract electrical stimulation. Lesions of the paraventricular nucleus enhance the amplitude of both the positive and negative components of the evoked potential in the olfactory bulb. The pathway from the paraventricular nucleus to the olfactory bulb seems to exert a suppressive influence over the projection from the nucleus of the solitary tract to the olfactory bulb under these conditions.

Olfactory bulb neurons respond to cervicovaginal distension

Mitral cell layer neuronal activity in the olfactory bulb (OB) of the anesthetized rat is modulated by cervicovaginal distension. Data are reported on 22 cells that decreased and 6 that increased in response to the distension. These results provide support for the existence of a functional interaction between the reproductive tract and the olfactory system.