The effects of the mediodorsal nucleus of the thalamus on respiratory neurons of the medulla oblongata and respiration in rats in conditions of hypoxia

Abstract

The effects of the associated mediodorsal nucleus of the thalamus on spike activity of respiratory neurons in the medulla oblongata and on respiration were studied in normal conditions and in oxygen insufficiency. At normal atmospheric pressure, before animals were elevated to low pressures, electrical stimulation of the mediodorsal nucleus of the thalamus had predominantly inhibitory effects. At the initial phase of hypoxia, at a "height" of 4,000-5,000 m, hypoxic activation of neuron discharge frequency occurred. with an increase in the frequency of respiration. In these conditions, the inhibitory effect of stimulation of the mediodorsal nucleus of the thalamus was less marked than in normoxic conditions. The opposite effect occurred at the second phase of hypoxia (7,500-8,000 m)-inhibition of activity in the medulla oblongata and thalamic center. In severe hypoxia, there was inhibition of neuron spike activity and a decrease in the frequency of respiration, which became superficial; in these conditions, the inhibitory effect of the thalamus was insignificant.

Sub-cortical and brainstem sites associated with chemo-stimulated increases in ventilation in humans

“…The concurrent activation of motor regions of the thalamus, a target of striatal projections, is consistent with engagement of a specific cortico-striato-thalamo-cortical functional circuit dedicated to adaptive respiratory control (Chen et al, 1992;Evans et al, 2002;Fink et al, 1995;Ramsay et al, 1993), in a manner similar to that implicated in skeletomotor control (Middleton and Strick, 1997). The link to respiratory control during chemo-stimulation is further highlighted by animal studies reporting that electrical stimulation of the mediodorsal thalamus directly inhibits phasic respiratory neurons in the medulla during hypoxic conditions (Akopyan et al, 2000), while lesions of the posteromedial thalamus eliminates respiratory responses to hypoxia and adenosine during fetal development (Koos et al, 2000). In the present study, activity changes within the thalamus were maximal bilaterally within the ventrolateral nucleus, a region anatomically connected with the deep cerebellar nuclei and the ventral respiratory group in the medulla (Gaytan and Pasaro, 1998).…”

Cerebrovascular reactivity among native-raised high altitude residents: an fMRI study

“…The motor cortex controls respiratory muscles in human [25,28]. The thalamus has projections to the medulla in the brainstem which controls respiration cycle [29], and in particular, under hypoxia conditions the thalamus had inhibitory effects on the respiratory neurons of the medulla and reduces the frequency of respiration [30]. The caudate was previously reported to be associated with voluntary control of breathing [31].…”

Gray Matter Concentration Abnormality in Brains of Narcolepsy Patients

“…The anterior thalamic nucleus belongs to the Papez circuit, the neural circuit of emotion. The median thalamic nucleus has been implicated in the wake-sleep cycle (24). A decrease in metabolism and regional cerebral blood flow in the thalamus of the narcoleptic brain, have been demonstrated by previous neuroimaging studies (16, 17).…”