The effect of a 22.5 week training program on the fuel-hormone response to prolonged (1 h) high intensity (85% maximal aerobic power, MAP) of six male subjects was studied. The training program consisted of pedalling 1 h per day, four days a week, a bicycle ergometer at 80% of their MAP. It resulted in a 14.3% increase in Vo2 max (P less than 0.01). Training did not significantly alter the RQ neither the blood glucose and lipid values measured at the end of a 1 h exercise requiring 85% of Vo2 max. At the end of the exercise blood level of norepinephrine was unchanged; in contrast, that of epinephrine was significantly (35%; P less than 0.01) reduced at the end of training. These results lead to the conclusion that during high intensity submaximal exercise there is no consistent relationship between the epinephrine blood level and mobilization or metabolic utilization of energy substrates in trained subjects.

Adult↗

PubMedDate not supplied

Effect of hemilabyrinthectomy on monoamine metabolism in the medial vestibular nucleus, locus coeruleus, and other brainstem nuclei of albino and pigmented rats.

We compared in albino and pigmented rats the early effect of unilateral labyrinthectomy (UL) on the concentrations of monoamines (norepinephrine, dopamine, serotonin) and their respective metabolites--3-methoxy,4-hydroxyphenylglycol (MHPG), 3,4-dihydroxy-phenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5HIAA)--in medial vestibular nuclei (MVN), locus coeruleus, raphe dorsalis, and cochlear nuclei. The study was conducted 6 hours after UL in both strains, differing by the functional optokinetic responses of their central vestibular neurons and the time-course of their vestibular compensation. The results show that the monoaminergic changes are different in the two rat strains. In the MVN of albino rats, there was a bilateral increase of MHPG and an ipsilateral increase of dopamine suggesting activation of norepinephrine synthesis and metabolism, whereas no such changes were observed in the MVN of pigmented rats. On the other hand, the simultaneous increase of norepinephrine and DOPAC observed in the contralateral locus coeruleus of albino rats suggested enhanced norepinephrine synthesis, whereas in pigmented rats the decreased norepinephrine content found in the ipsilateral locus coeruleus might reflect an earlier strong stimulation of NE release. These biochemical results confirm the relevant role of locus coeruleus noradrenergic innervation in vestibular compensation and also point out the involvement of norepinephrine of the MVN in the early stages of this process. The different strain-related noradrenergic responses observed on the 6th hour suggest that the involvement of central norepinephrine, particularly from locus coeruleus innervation, may be more crucial and more sustained in the albino than in pigmented rats. No serotonin and 5HIAA changes were found in either brainstem nuclei of albino rats. In contrast, the increase of the ratio 5HIAA/5HT observed in raphe dorsalis, in ipsilateral locus coeruleus, and in both sides of MVN of pigmented rats suggested that UL induced an extended and enhanced utilization of 5HT in this strain.

Albinism↗