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1.
Front Neurosci ; 13: 1355, 2019.
Article in English | MEDLINE | ID: mdl-31920514

ABSTRACT

Tongue exercise programs are used clinically for dysphagia in aged individuals and have been shown to improve lingual strength. However, the neural mechanisms of age-related decline in swallowing function and its association with lingual strength are not well understood. Using an established rat model of aging and tongue exercise, we hypothesized that the motor cortex of aged rats would have a smaller lingual motor map area than young adult rats and would increase in size as a function of tongue exercise. Over 8 weeks, rats either underwent a progressive resistance tongue exercise program (TE), learned the task but did not exercise (trained controls, TC), or were naïve untrained controls (UC). Cortical motor map areas for tongue and jaw were determined using intracortical microstimulation (ICMS). Rats in the TE and TC groups had a significantly larger motor cortex region for the tongue than the UC group. Lingual cortical motor area was not correlated with protrusive tongue force gains and did not differ significantly with age. These results suggest that learning a novel tongue force skill was sufficient to induce plasticity of the lingual motor cortex yet increasing tongue strength with progressive resistance exercise did not significantly expand the lingual motor area beyond the gains that occurred through the skilled learning component.

2.
Respir Physiol Neurobiol ; 180(1): 79-87, 2012 Jan 15.
Article in English | MEDLINE | ID: mdl-22067556

ABSTRACT

There is evidence for a "sensitive period" in respiratory development in rats around postnatal age (P) 12-13d. Little is known about sex differences during that time. The purpose of this study was to assess the effect of sex on breathing development, specifically around the "sensitive period". We used whole-body plethysmography to study breathing in normoxic, hypoxic and hypercapnic gases in non-anesthetized male and female neonatal rats from P10 to P15, juvenile (P30) and young adult (P90) rats. Compared to other neonatal ages, P12-13 male rats had significantly lower ventilation during normoxia, hypoxia, and hypercapnia. Compared to age-matched females, P12-13 male rats had lower ventilation in normoxia and hypoxia and a lower O(2) saturation during hypoxia. Circulating estradiol was greater in P12-13 male vs. female rats. Estradiol and ventilatory responses to hypoxia and hypercapnia were negatively correlated in neonatal male, but not female rats. Our results suggest that P10-15 includes a critical developmental period in male but not female rats.


Subject(s)
Hypercapnia , Hypoxia , Pulmonary Ventilation/physiology , Respiration , Respiratory System/growth & development , Age Factors , Animals , Animals, Newborn , Consciousness , Female , Male , Plethysmography , Rats , Rats, Sprague-Dawley , Sex Factors
3.
Respir Physiol Neurobiol ; 164(1-2): 213-21, 2008 Dec 10.
Article in English | MEDLINE | ID: mdl-18599386

ABSTRACT

There is a growing public awareness that sex hormones can have an impact on a variety of physiological processes. Yet, despite almost a century of research, we still do not have a clear picture as to the effects of sex hormones on the regulation of breathing. Considerable data has accumulated showing that estrogen, progesterone and testosterone can influence respiratory function in animals and humans. Several disorders of breathing such as obstructive sleep apnea (OSA) and sudden infant death syndrome (SIDS) show clear sex differences in their prevalence, lending weight to the importance of sex hormones in respiratory control. This review focuses on questions such as: how early do sex hormones influence breathing? Which is the most effective? Where do sex hormones exert their effects? What mechanisms are involved? Are there age-associated changes? A clearer understanding of how sex hormones influence the control of breathing could enable sex- and age-specific therapeutic interventions for diseases of the respiratory control system.


Subject(s)
Gonadal Steroid Hormones/metabolism , Respiratory Physiological Phenomena , Respiratory System/metabolism , Sex Characteristics , Animals , Humans
4.
Respir Physiol Neurobiol ; 160(3): 301-12, 2008 Feb 29.
Article in English | MEDLINE | ID: mdl-18069076

ABSTRACT

Perinatal hyperoxia attenuates the hypoxic ventilatory response in rats by altering development of the carotid body and its chemoafferent neurons. In this study, we tested the hypothesis that hyperoxia elicits this plasticity through the increased production of reactive oxygen species (ROS). Rats were born and raised in 60% O(2) for the first two postnatal weeks while treated with one of two antioxidants: vitamin E (via milk from mothers whose diet was enriched with 1000 IU vitamin E kg(-1)) or a superoxide dismutase mimetic, manganese(III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP; via daily intraperitoneal injection of 5-10 mg kg(-1)); rats were subsequently raised in room air until studied as adults. Peripheral chemoreflexes, assessed by carotid sinus nerve responses to cyanide, asphyxia, anoxia and isocapnic hypoxia (vitamin E experiments) or by hypoxic ventilatory responses (MnTMPyP experiments), were reduced after perinatal hyperoxia compared to those of normoxia-reared controls (all P<0.01); antioxidant treatment had no effect on these responses. Similarly, the carotid bodies of hyperoxia-reared rats were only one-third the volume of carotid bodies from normoxia-reared controls (P <0.001), regardless of antioxidant treatment. Protein carbonyl concentrations in the blood plasma, measured as an indicator of oxidative stress, were not increased in neonatal rats (2 and 8 days of age) exposed to 60% O(2) from birth. Collectively, these data do not support the hypothesis that perinatal hyperoxia impairs peripheral chemoreceptor development through ROS-mediated oxygen toxicity.


Subject(s)
Antioxidants/administration & dosage , Carotid Sinus/drug effects , Hyperoxia/pathology , Hyperoxia/prevention & control , Metalloporphyrins/administration & dosage , Analysis of Variance , Animals , Animals, Newborn , Anorexia/physiopathology , Anorexia/prevention & control , Asphyxia/physiopathology , Asphyxia/prevention & control , Dose-Response Relationship, Drug , Drug Interactions , Phrenic Nerve/drug effects , Phrenic Nerve/physiopathology , Protein Carbonylation/drug effects , Rats , Rats, Sprague-Dawley , Sodium Cyanide/pharmacology , Vitamin E/administration & dosage
5.
Respir Physiol Neurobiol ; 150(2-3): 155-64, 2006 Feb 28.
Article in English | MEDLINE | ID: mdl-15978876

ABSTRACT

Adult rats have decreased carotid body volume and reduced carotid sinus nerve, phrenic nerve, and ventilatory responses to acute hypoxic stimulation after exposure to postnatal hyperoxia (60% O2, PNH) during the first 4 weeks of life. Moreover, sustained hypoxic exposure (12%, 7 days) partially reverses functional impairment of the acute hypoxic phrenic nerve response in these rats. Similarly, 2 weeks of PNH results in the same phenomena as above except that ventilatory responses to acute hypoxia have not been measured in awake rats. Thus, we hypothesized that 2-week PNH-treated rats would also exhibit blunted chemoafferent responses to acute hypoxia, but would exhibit ventilatory acclimatization to sustained hypoxia. Rats were born into, and exposed to PNH for 2 weeks, followed by chronic room-air exposure. At 3-4 months of age, two studies were performed to assess: (1) carotid sinus nerve responses to asphyxia and sodium cyanide in anesthetized rats and (2) ventilatory and blood gas responses in awake rats before (d0), during (d1 and d7), and 1 day following (d8) sustained hypoxia. Carotid sinus nerve responses to i.v. NaCN and asphyxia (10 s) were significantly reduced in PNH-treated versus control rats; however, neither the acute hypoxic ventilatory response nor the time course or magnitude of ventilatory acclimatization differed between PNH and control rats despite similar levels of PaO2 . Although carotid body volume was reduced in PNH rats, carotid body volumes increased during sustained hypoxia in both PNH and control rats. We conclude that normal acute and chronic ventilatory responses are related to retained (though impaired) carotid body chemoafferent function combined with central neural mechanisms which may include brainstem hypoxia-sensitive neurons and/or brainstem integrative plasticity relating both central and peripheral inputs.


Subject(s)
Acclimatization/physiology , Carotid Sinus/physiopathology , Hyperoxia/physiopathology , Hypoxia/physiopathology , Phrenic Nerve/physiopathology , Pulmonary Ventilation/physiology , Animals , Animals, Newborn , Asphyxia/physiopathology , Blood Gas Analysis/methods , Enzyme Inhibitors/pharmacology , Female , Male , Partial Pressure , Phrenic Nerve/drug effects , Pregnancy , Rats , Rats, Sprague-Dawley , Sodium Cyanide/pharmacology , Time Factors
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