Activation of neurons of zone A5 of the rat brain upon hypoxic and thermonociceptive stimulation and switching off of the central respiratory generator

Abstract

We recorded spike activity of noradrenergic neurons of zone A5 (n = 89) in the brain of anesthetized rats under conditions of hypoxic stimulation (breathing with pure N 2 , 10 sec), thermonociceptive stimulation (tail-flick test), and reversible hypothermal blocking of the central respiratory activity. Hypoxic stimulation of peripheral О 2 -sensitive chemoreceptors considerably increased the discharge frequency in all the examined neurons and induced tachypnea and a hypotensive reaction. Sixty-nine (77.5%) neurons of the studied group were tested using nociceptive stimulation (thermal stimulation of the tail); such stimulation resulted in a multifold increase in their discharge frequency. This was accompanied by tachypnea and a hypertensive response. Thus, we first demonstrated the role of nociception in the control of activity of noradrenergic neurons in zone A5 and the role of nociceptive afferent signals in the modulation of functions of the respiratory and cardiovascular systems mediated by neurons of the above zone. Under conditions of blocking of the central respiratory activity, we examined 36 (40.4%) neurons of zone A5 and first observed the effect of strong activation of a significant proportion of these cells upon switching off of respiration. This fact shows that there is an activating "respiratory" drive on neurons of zone A5 (probably, from the side of an expiratory neuronal population of the respiratory center) and allows us to hypothesize on the genesis of "respiratory" modulation of these cells. The activity of 16 (18.0%) cells was recorded under conditions of consecutive applications of the above stimuli; all the neurons were activated by the respective afferent influences. The simultaneously induced effects of hypoxic and nociceptive stimulations on the activity of neurons of zone A5 were additive. Thus, we first obtained proofs in favor of the multimodality of noradrenergic neurons of the above zone. This feature is a significant factor providing integrative interaction between the respiratory and cardiovascular systems and the system of nociception.

Activity of neurons of the cerebral A5 zone of rat induced by adequate stimulation of muscle afferents: On the control of arterial pressure and respiration during muscle activity

“…); spontaneous respiration was preserved. Surgery procedures providing access to the ventral surface of the brainstem and also the technique of recording of the arterial pressure and activity from the phrenic nerve were described in detail in our previous publications [14,15].…”

“…The frequency of APs and duration of impulse neuronal reactions to the stimuli were considered analyzed parameters. The technique of recording of the activity of A5 neurons was described earlier [15].…”

Integrative function of proprioceptive system in the acute effects of whole body vibration on the movement performance in young adults

“…The integrative properties of the proprioceptive system at the CNS segmental level are manifested by the tonic vibration reflex ( 16 , 17 ) and tendon reflexes ( 6 , 18 ) with recruitment of the maximum number of motor units of skeletal muscles ( 16 , 19 ). At the stem level, proprioceptive interneurons integrate vegetative functions (blood circulation, respiration) ( 20 – 22 ), nociception ( 9 ) and balance ( 23 ) during WBV. The integrative properties of the proprioceptive system at the level of the hypothalamus elicits neuroendocrine responses, and at the level of sensorimotor cortical areas (M1) ( 15 , 24 ) participates in the control of motor activity, improves cognitive function and psychological well-being such as mood ( 25 , 26 ).…”