Evidence for Direct Neural Regulation of the Mammalian Anterior Pituitary

Ju, Gong

doi:10.1046/j.1440-1681.1999.03128.x

Cited by 17 publications

(6 citation statements)

References 17 publications

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“…One possibility is that the greater external load used during accentuated eccentric loading elicited greater motor unit activation during the eccentric phase (Ojasto and Häkkinen ). This greater activation has been shown to stimulate a greater hormone release from the pituitary gland (Ju ). In the context of the present study, it could be hypothesized that the greater muscle activation in AEL allowed for a continued GH response in the last 5 weeks of training (Ojasto and Häkkinen ), which may partly explain the greater increase in MVC (weeks 6–10) and larger GH response at week 9 when compared to ISO.…”

Section: Discussionmentioning

confidence: 99%

Acute elevations in serum hormones are attenuated after chronic training with traditional isoinertial but not accentuated eccentric loads in strength-trained men

et al. 2017

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It has been proposed that the maintenance of acute hormonal responses reveal an efficacy of a training stimulus to evoke ongoing increases in strength and muscle mass. We previously observed that maximum strength continued to improve throughout a 10‐week period in an accentuated eccentric loading group (AEL) but not a traditional isoinertial loading (ISO) group. Therefore, this study investigated whether the magnitude of acute hormonal responses was greater (i.e., maintained) in AEL compared to ISO at the end of the training period. Subjects in AEL (eccentric load = concentric load + 40%) and ISO performed experimental loading tests (three sets of 10 repetitions in the leg press and knee extension exercises) during weeks 2 and 9 of the training period. Blood samples collected during these experimental loadings were analyzed for serum testosterone, growth hormone and cortisol concentrations. Maximum isometric knee extension torque (MVC) and lower‐limb lean mass were assessed before and after 5 and 10 weeks of training. Acute testosterone, growth hormone and cortisol responses to traditional isoinertial loading were reduced at the end of the training period but were not reduced after accentuated eccentric load training (P < 0.05‒0.1 between‐groups). Increases in MVC and lower‐limb lean mass over weeks 6‒10 were greater in AEL compared to ISO (MVC: 7.3 ± 5.4 vs. −0.4 ± 7.2%, P = 0.026 for between‐group difference; lower‐limb lean mass: 1.6 ± 2.2 vs. −0.2 ± 1.4%, P = 0.063 for between‐group difference). The maintenance of acute hormonal responses and continued strength gain in AEL but not ISO are consistent with the hypothesis that maintained acute responses indicate an efficacy of a training stimulus to evoke ongoing adaptation. However, since relationships between hormonal responses and training‐induced adaptations were not statistically significant, the data suggest that tracking of acute hormonal responses on an individual level may not provide a sensitive enough guide for decisions regarding program design and periodization.

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Section: Discussionmentioning

confidence: 99%

Acute elevations in serum hormones are attenuated after chronic training with traditional isoinertial but not accentuated eccentric loads in strength-trained men

et al. 2017

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“…This reduced metabolic stress may partly have caused the lower hGH responses in the elderly. Whether or not other factors that may stimulate hGH secretion with resistance exercise (i. e., direct stimulation from higher brain centers or through muscle afferent activity [20,30]) are altered with aging, requires further study.…”

Section: Discussionmentioning

confidence: 99%

Hormonal Responses after a Strength Endurance Resistance Exercise Protocol in Young and Elderly Males

et al. 2007

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This study examined testosterone, cortisol and growth hormone responses in elderly and young men after a strength endurance protocol. Eight elderly (age: 69 +/- 5 yrs) and nine young (age: 23 +/- 1 yrs) males with recreational experience in resistance training performed a strength endurance protocol, which included six exercises. At each exercise, the subjects performed 3 sets of 15 reps at 60 % of 1-RM with a 90 s rest interval between sets. The subjects also participated in a control session. Hormonal and blood lactate concentrations were measured before exercise, immediately after exercise and 15 min after the end of exercise. Blood lactate increased (p<0.05) with resistance exercise in both age groups with the highest increases observed in the young males. Testosterone and cortisol concentrations were higher (p<0.05) immediately and 15 min after exercise as compared to the respective control session values in both young and elderly subjects, whereas no differences were observed between groups (p>0.05). Growth hormone concentration increased (p<0.05) after resistance exercise compared to the control session in both age groups. This increase was higher (p<0.05) in the young as compared to the elderly group. The above results show that a moderate intensity - high repetition resistance exercise protocol for the improvement of strength endurance, seems to be a sufficient stimulus that increases testosterone, growth hormone and cortisol concentrations in elderly males. These hormonal responses may create an optimal metabolic environment, which improves muscular function after a strength endurance program although the elderly subjects present an attenuated growth hormone response compared to younger ones.

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“…The highly variable nature of plasma concentrations of norepinephrine in sheep may have accounted for the lack of a significant rise in norepinephrine during stress in the current study. Neural modulation of secretory cells of the pituitary may also be a mechanism by which short-term changes in pituitary responsiveness can be regulated; synapses between nerve fibres and secretory cells of the anterior pituitary have been identified on gonadotropes in the rat [27].…”

Section: Discussionmentioning

confidence: 99%

Seasonal Differences in the Effect of Isolation and Restraint Stress on the Luteinizing Hormone Response to Gonadotropin-Releasing Hormone in Hypothalamopituitary Disconnected, Gonadectomized Rams and Ewes

Stackpole

Turner

Clarke

et al. 2003

Biology of Reproduction

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Stress responses are thought to act within the hypothalamopituitary unit to impair the reproductive system, and the sites of action may differ between sexes. The effect of isolation and restraint stress on pituitary responsiveness to GnRH in sheep was investigated, with emphasis on possible sex differences. Experiments were conducted during the breeding season and the nonbreeding season. In both experiments, 125 ng of GnRH was injected i.v. every 2 h into hypothalamopituitary disconnected, gonadectomized rams and ewes on 3 experimental days, with each day divided into two periods. During the second period on Day 2, isolation and restraint stress was imposed for 5.5 h. Plasma concentrations of LH and cortisol were measured in samples of blood collected from the jugular vein. In the second experiment (nonbreeding season), plasma concentrations of epinephrine, norepinephrine, 3,4-dihydroxyphenylalanine, and 3,4-dihydroxyphenylglycol were also measured. In both experiments, there was no effect of isolation and restraint stress on plasma concentrations of cortisol in either sex. During the breeding season, there was no effect of isolation and restraint stress on plasma concentrations of LH in either sex. During the nonbreeding season, the amplitude of the first LH pulse after the commencement of stress was significantly reduced (P < 0.05) in rams and ewes. In the second experiment, during stress there was a significant increase (P < 0.05) in plasma concentrations of epinephrine in rams and ewes and significantly higher (P < 0.05) basal concentrations of norepinephrine in ewes than in rams. These results suggest that in sheep stress reduces responsiveness of the pituitary gland to exogenous GnRH during the nonbreeding season but not during the breeding season, possibly because of mediators of the stress response other than those of the hypothalamus-pituitary-adrenal gland axis.

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Evidence for Direct Neural Regulation of the Mammalian Anterior Pituitary

Cited by 17 publications

References 17 publications

Acute elevations in serum hormones are attenuated after chronic training with traditional isoinertial but not accentuated eccentric loads in strength-trained men

Acute elevations in serum hormones are attenuated after chronic training with traditional isoinertial but not accentuated eccentric loads in strength-trained men

Hormonal Responses after a Strength Endurance Resistance Exercise Protocol in Young and Elderly Males

Seasonal Differences in the Effect of Isolation and Restraint Stress on the Luteinizing Hormone Response to Gonadotropin-Releasing Hormone in Hypothalamopituitary Disconnected, Gonadectomized Rams and Ewes

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