Dominique Rose

c-fos-like immunoreactivity in the cat's neuraxis following moderate hypoxia or hypercapnia

The overall pattern of c-fos immunoreactivity was studied in the brainstem and spinal cord of cats subjected to moderate hypoxia or hypercapnia. In control cats (normoxic, normocapnic), c-fos was expressed mainly in pontine and periaqueductal grey but not in brainstem structures engaged in respiratory control nor in the spinal cord. Both hypoxia and hypercapnia induced c-fos expression in the parabrachial area (pneumotaxic center). In the retrotrapezoid nucleus, a structure involved in respiratory rhythmogenesis and chemoreception, immunoreactivity was detected in hypoxic but not in hypercapnic cats. Neurons in the nucleus raphe pallidus preferentially expressed c-fos in response to hypercapnia. Labelled neurons were concentrated in the dorsal and gelatinosus subnuclei of the solitary tract following hypoxia and hypercapnia, respectively. Our data suggest that some neurons that express c-fos in hypoxic or hypercapnic cats may be involved in coordination of cardiovascular and respiratory function.

Spinal localization of the intercostal motoneurones innervating the upper thoracic spaces

At the rostral level of the thorax, the intercostal muscles participate both in postural and respiratory functions to a variable degree depending upon the considered muscle: external intercostal, intercartilaginous, internal intercostal, and triangularis sterni. In order to determine if these physiological properties are related to a special organization at the spinal cord level, we have used the retrograde transport of horseradish peroxidase as a tool for studying the spinal distribution of intercostal motor cells in the adult cat. Results suggest that the intercostal motoneurones could be distributed, in the ventral grey horn, among two areas according to the respiratory or postural muscle specialization.

A comparative HRP study of the neuronal supply to the inferior and superior nasal meatus in the cat.

Neurons supplying the nasal mucosa in the cat were retrogradely labelled with horseradish peroxidase. Sensory trigeminal neurons to the inferior and superior nasal meati are somatotopically organized, according to the ophthalmic or maxillary origin of the afferents studied. Whatever their relative location, the cell bodies from nasal afferents were, on average, smaller than the overall cell population in the ganglion, in keeping with the high proportion of nasal receptors innervated by thin fibers. Postganglionic neurons from parasympathetic origin could be labelled in the sphenopalatine ganglion. These neurons probably supply mucosal secretory glands. They are in the same size range as the bulk of neurons in the same ganglia.

Identification of phrenic afferents in the dorsal columns: A fluorescent double-labeling study in the cat

In this study in the cat, the tracer combination of the anterogradely transported Fast Blue and the retrogradely transported Nuclear Yellow was used to label dorsal root ganglion cells related to phrenic afferents running up through the ipsilateral dorsal column. These afferents are few; some of them leave the dorsal column near their segment of entry. Their localization in the dorsal column suggests that they are related to tendon and muscle receptors, which confirms previous electrophysiological studies.

The sneeze: maturation of the reflex in kittens.

This is the first study to compare the influence of nasal afferent stimulation on inspiratory and expiratory muscle activity during sneezing, in kittens and adult cats. In kittens, we demonstrate that nasal afferent stimulation does not reinforce inspiratory activity prior to the expiratory thrust as it normally does in adult cats. These stimulations evoke an active expiration similar to but weaker than the expiratory thrusts observed under the same conditions during sneezing in adult cats. Sneezing can be elicited from three weeks of life. Among the different hypotheses discussed, the most likely explanation appears to be the immaturity of medullary respiratory connections.

Morphometrical study of the cat thoracic dorsal root ganglion cells in relation to muscular and cutaneous afferent innervation.

The sizes of neuronal somata in cat dorsal root ganglia were determined at the different thoracic segmental levels (T1-T13). The intersegmental variations in the average value and class distribution of diameters were analysed. The maximal and minimal average mean cell diameters were 51.1 and 43.3 microns at the T1 and T2 levels, respectively. Caudally, this value gradually increased from T2 to T8 (47.8 microns) and thereafter decreased progressively to T12 (44.7 microns). At T1, large cells (greater than 50 microns in diameter) were 3.3-fold in excess compared to small ones (less than 35 microns in diameter). The proportion of large to small cells strongly decreased to a 0.9 ratio from T1 to T2, then increased again from T2 (0.9) to T8 (2.3). The size distributions of the overall cell populations were compared to those of neurones supplying muscular targets via the external intercostal nerves or cutaneous targets via the lateral branch of the internal intercostal nerves, identified following the retrograde transport of horseradish peroxidase. The size distribution of cells serving cutaneous nerves was similar to that exhibited by the overall population of ganglion cells. In contrast, the size distributions of cells giving rise to muscle afferents tended towards smaller values. In the thoracic dorsal root ganglia, the cell body sizes of the muscular primary afferents were close to those previously reported for the visceral primary afferents.

Identification of phrenic afferents to the external cuneate nucleus: A fluorescent double-labeling study in the cat

In the cat, C5-C6 dorsal root ganglion cells related to phrenic afferents projecting directly to the ipsilateral external cuneate nucleus (ECN) were submitted to a double-labeling procedure using anterogradely transported Fast Blue and retrogradely transported Nuclear yellow. These afferents, certainly related to muscle spindles and/or Golgi tendon organs, are very few and terminate preferentially in the intermediate and rostral parts of the ECN. Our results confirm previous electrophysiological and histological studies on the participation of phrenic afferents to the spino-cuneo-cerebellar pathway ascending through the dorsal columns.

Postnatal development of small and large dorsal root ganglion neurons in the cat. A study on cervical levels (C5-C6) and on phrenic afferents.

During feline postnatal development, the size of phrenic afferent neurons labelled by horseradish peroxidase was evaluated in comparison to that of the bulk of counterstained neurons located in the same cervical dorsal root ganglia (DRG) (C5-C6). From age 1 week to maturity, small and large cell components were individualized from experimental size distributions using a mathematical approach. The analysis of data in adult indicated a close correspondence between small cells and unmyelinated afferents and between large cells and myelinated afferents, respectively. From age 1 week to adulthood, mean increases in cell diameter ranged between 10 microns (small cells from phrenic afferents) and 29.5 microns (large counterstained cells). In each population, the ratio of small/large cells remained constant during growth. In contrast to data in adults, at 1 week, large phrenic neurons were bigger than the counterstained ones. At 19 weeks, the cat DRG cells had not yet reached their adult size.

Valeur pronostique des anomalies EEG observées au cours du sommeil dans l'épilepsie à paroxysmes rolandiques (EPR).

Summary The aim of this study is the quantitative analysis of the interictal discharges during nocturnal sleep in 6 children with rolandic spikes on the awake EEG, before and during treatment. During treatment, whatever it may be, these interictal discharges (diffuse spike and wave complexes and rolandic spikes) have no prognostic value and only the generalized paroxysmal ones, which are observed solely in sleep, decrease. Moreover, if the number of spikes of a slow irritative focus secondary to an organic cerebral lesion keeps steady during wakefulness and all sleep stages, the number of rolandic spikes is modulated by the type of sleep (REM or NREM). This modulation may be in favour of the benignity of this childhood epilepsy. Finally, in spite of the great number of interictal discharges during the whole night, sleep organization is not disturbed and only the advent of an epileptic seizure can interfere with sleep rhythms, depleting the REM phase.

The cat cervical dorsal root ganglia: general cell-size characteristics and comparative study of neck muscle, neck cutaneous and phrenic afferents

Sizes of neuronal somata in the cat cervical dorsal root ganglia were determined at different levels (C1-C8). The average value and class distribution of mean cell diameter were analyzed. The ganglia from C1 to C5 could be clearly distinguished from those at levels of brachial plexus afferents (C6-C8) with respect to cell size range, distribution and average. The size distribution, most often limited to 70 microns from C1 to C5, skewed to more than 90 microns from C6 to C8. Cells in the 35-50 microns range of diameter constituted the main portion of the cell population (49-52%) at the C1-C5 levels, whereas from C6 to C8 51-77% of the ganglion cell bodies were more than 50 microns in diameter. The cell size distribution of afferents projecting from C1 to C5 and supplying different muscle or cutaneous targets was studied following retrograde labeling with horseradish peroxidase conjugated to wheatgerm agglutinin. Sizes of cell bodies of biventer cervicis (postural muscle), phrenic (purely respiratory muscle) and cutaneous afferents were all similar. The labelled cell bodies were in the majority (51-64%) less than 35 microns in diameter and ranged towards smaller diameters than counterstained cells in the corresponding ganglia. In spite of similarities in cell size distribution it was estimated from the fiber caliber spectra of the labelled afferents that both unmyelinated and myelinated cutaneous afferents originate from larger cell bodies than muscle afferents in the same diameter range.