Biomedical subjects

N Koshiya

Publications and source records attributed to N Koshiya.

21 records · Page 2Linked to original sources

PubMed1987

Central respiratory drive-related activity in sympathetic nerves of the rat: the regional differences.

In halothane-anaesthetized, vagotomized, SA-denervated rats, the activity of various sympathetic nerves has been analyzed with respect to phrenic nerve discharge (an indicator of central respiratory drive (CRD)). The cervical and lumbar sympathetic nerves had maximal activity following, and were least active during phrenic nerve discharge. In contrast, the splanchnic, cardiac, renal and adrenal nerves exhibited their activity peak during phrenic nerve discharge (i.e. inspiration). Similar activity profiles were observed after ganglion blockade in the mixed pre- and postganglionic fibre preparations. These observations indicate that it is the subpopulations of preganglionic neurones and the proportional contribution of each to whole-nerve activity which give rise to the differences in CRD-related activity profiles between nerves.

Action Potentials↗

PubMed1987

Morphological and physiological properties of caudal medullary expiratory neurons of the cat.

The activity of respiratory neurons in the caudal part of the nucleus retroambigualis (NRA) was recorded intracellularly in decerebrated, spontaneously breathing cats. Spinal projections of these neurons were determined by antidromic stimulation at the C3 segment. A high concentration of bulbospinal expiratory (BS-E) neurons was identified in the caudal NRA, whereas the inspiratory (I) neurons, not activated antidromically, were also found to be intermingled in the same region. The BS-E neurons had ramp-like depolarizing potentials during expiration, and repolarized rapidly at the onset of phrenic nerve discharge. The I neurons depolarized abruptly in the early I phase, and repolarized gradually thereafter, namely, they were early-I neurons. Intracellular current injections revealed postsynaptic inhibition of the BS-E neurons during inspiration, as evidenced by inhibitory postsynaptic potential reversal. Using the technique of intracellular labeling with horseradish peroxidase, seven well-stained expiratory cells located in the caudal NRA revealed detailed information about axonal morphology: the axon projected rostrally and dorsomedially for the first 2 mm after emerging from the soma, then turned caudally and ventrally along two different courses, and crossed the midline of the medulla almost at the same rostrocaudal level as the soma. No axon collaterals were observed along the length of the stained portion, indicating that the BS-E neurons cannot influence other respiratory neurons in the brainstem. It has been concluded that the NRA expiratory neurons are involved only in spinal action, and that they receive a postsynaptic inhibition during inspiration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

Working model of the sympathetic chemoreflex in rats.

This review examines the neural network responsible for activation of the sympathetic vasomotor system during stimulation of carotid chemoreceptors (CC) in anesthetized vagotomized rats (sympathetic chemoreflex, SChR). Based on unit recording studies and experiments designed to impair synaptic transmission within selected lower brainstem nuclei or subregions, a model of the SChR is proposed with the essential features: i) key role of the nucleus of the solitary tract (NTS), rostral ventrolateral medulla (RVL) and ventrolateral pons (A5 area), ii) no role for caudal ventrolateral medulla (CVL), iii) modulatory role of dorsolateral pons and pre-Botzinger area, iv) dual control of bulbospinal presympathetic (preS) cells by CC inputs, one via the central respiratory network and the other through a direct excitatory pathway independent of the activity of this network, and v) independent medullary pathways for SChR and baroreflex until the preS neuronal stage in RVL.

Animals↗