Endurance and resistance exercise training programs elicit specific effects on sciatic nerve regeneration after experimental traumatic lesion in rats.

OBJECTIVE: To evaluate the effects of endurance, resistance, and a combination of both types of exercise training on hindlimb motor function recovery and nerve regeneration after experimental sciatic nerve lesion in rats. METHODS: Sciatic nerve crush was performed on adult male rats, and after 2 weeks of the nerve lesion, the animals were submitted to endurance, resistance, and a combination of endurance-resistance training programs for 5 weeks. Over the training period, functional recovery was monitored weekly using the Sciatic Functional Index (SFI) and histological and morphometric nerve analyses were used to assess the nerve regeneration at the end of the trainings. RESULTS: The SFI values of the endurance-trained group reached the control values from the first posttraining week and were significantly better than both the resistance-trained group at the first, second, and third posttraining weeks and the concurrent training group at the first posttraining week. At the distal portion of the regenerating sciatic nerve, the endurance-trained group showed a greater degree of the myelinated fiber maturation than the sedentary, resistance-trained, and concurrent training groups. Furthermore, the endurance-trained group showed a smaller percentage area of endoneurial connective tissue and a greater percentage area of myelinated fibers than the sedentary group. CONCLUSION: These data provide evidence that endurance training improves sciatic nerve regeneration after an experimental traumatic injury and that resistance training or the combination of 2 strategies may delay functional recovery and do not alter sciatic nerve fiber regeneration.

Neuronal somatic volume of posteroventral medial amygdala cells from males and across the estrous cycle of female rats.

The posteroventral medial amygdala (MePV) is a brain area where gonadal hormones have neurotrophic effects in rats. The aim of the present study was to estimate the MePV neuronal somatic volume from males and diestrus, proestrus and estrus female Wistar rats (n=5 in each group) in an attempt to identify a possible sexual dimorphism in this parameter. The effect of laterality was also evaluated. The brains of adult animals were sectioned (1 microm), stained with 1% toluidine blue and serial-section reconstructions of each neuronal cell body were obtained. Images from both left and right MePV were studied and the somatic volume was estimated using the Cavalieri method in combination with the point counting technique. Results were compared according to sex and phase of the estrous cycle using a two-way ANOVA for repeated measures followed by the least significance difference test. Mean neuronal somatic volume showed a statistical difference among groups and the post hoc comparisons revealed that males present higher values than females in proestrus and estrus (p<0.05). On the other hand, neither a laterality effect (p=0.6) nor an interaction between groups and laterality (p=0.4) were found. Our results indicate that cell body volume in the MePV is distinct when comparing males to females in the different phases of the estrous cycle. Through dynamic changes modulated by sex steroids, it is likely that this morphological plasticity within the MePV may be affecting the functioning of local neurons and their integrated roles in neural circuits relevant for neuroendocrine control and reproductive behaviors.

Gonadal hormone regulation of glial fibrillary acidic protein immunoreactivity in the medial amygdala subnuclei across the estrous cycle and in castrated and treated female rats.

The medial amygdala (MeA) is a sexually dimorphic area that modulates neuroendocrine and behavioral activities and where gonadal hormones play an important role in neuron-glial and synaptic plasticity. Immunohistochemistry was used to identify the astrocytic marker glial fibrillary acidic protein (GFAP) in the different MeA subnuclei--anterodorsal (MeAD), posterodorsal (MePD) and posteroventral (MePV)--of intact female rats in the different phases of the estrous cycle and in ovariectomized females treated with hormonal substitutive therapy. Data semi-quantified by optical densitometry showed that, in the proestrus phase, the GFAP immunoreactivity (GFAP-ir) was higher when compared to the other phases of the estrous cycle (P < 0.02). GFAP-ir was also higher in the MePD than in the MeAD or in the MePV (P < 0. 02). In ovariectomized females, injections of estradiol alone or estradiol plus progesterone increased GFAP-ir in the MePD and in the MePV (P < 0.001), but not in the MeAD (P > 0.3), when compared to control data. These findings suggest that astrocytic GFAP in the MeA subnuclei can be affected either by physiological levels or by hormonal manipulation of the ovarian steroids, which may contribute to the plasticity of local and integrated functional activities of these brain areas in female rats.

Influence of sex and estrous cycle, but not laterality, on the neuronal somatic volume of the posterodorsal medial amygdala of rats.

The aim of the present study was to measure the cell body volume of neurons from the posterodorsal subnucleus of the medial amygdala (MePD) of adult male (n=5) and diestrus, proestrus and estrus female (n=4-5 in each group) rats to reveal a possible sexual dimorphism, estrous cycle variations and laterality in this morphological parameter. The brains of adult Wistar rats were sectioned (1 microm), stained with 1% toluidine blue and the stereological estimation of neuronal soma volume of both sides of MePD was realized using the Cavalieri method and the technique of point counting. Data were compared by a two-way ANOVA for repeated measures and the least significance difference post hoc test. In the MePD, mean neuronal somatic volume showed a statistical difference among groups (p=0.005), but neither an effect of laterality (p=0.33) nor interactions between groups and laterality (p=0.78) were found. Post hoc test showed that males (mean+/-S.E.M., 2075.67+/-135.79 microm(3)) have larger mean neuronal somatic volume compared to females in proestrus (1503.30+/-44.46 microm(3)) and in estrus (1616.69+/-71.49 microm(3), p<0.05 in both cases), but not in diestrus (1940.78+/-129.68 microm(3), p>0.05). Moreover, diestrus females displayed larger mean neuronal somatic volume than proestrus female rats (p<0.05). It is suggested that neuronal somatic volume is another sexually dimorphic finding in the MePD, for which it is relevant to set apart the different phases of the estrous cycle to reveal the presence of gonadal hormones effects in the rat MePD neurons.

Influence of substitutive ovarian steroids in the nuclear and cell body volumes of neurons in the posterodorsal medial amygdala of adult ovariectomized female rats.

The volumes of the neuronal nucleus and the cell body in the left posterodorsal medial amygdala (MePD) of adult ovariectomized (OVX) female rats submitted to different hormonal therapies were studied here, aiming to reveal possible influence of substitutive sex steroids in these morphological parameters. One week following ovariectomy and at the end of treatments, brains were cut to semi-thin sections (1 microm) and stained with 1% toluidine blue for stereological estimations, carried out using the Cavalieri method and the technique of point counting. Both the volume of the neuronal nucleus and the soma showed a statistically significant difference when comparing the data among OVX females treated with vehicle (V), estradiol (EB) alone, EB plus progesterone (EB+P) or P alone [n=5 rats in each group; one-way ANOVA test, P<0.01 in both cases]. The Tukey test showed that OVX and EB+P treated females had higher mean neuronal nucleus and somatic volumes when compared to V (P<0.01) or EB alone (P<0.01). Also, OVX females treated with P alone showed larger mean neuronal nucleus and somatic volumes when compared to V (P<0.05). These results suggest that the neuronal nucleus and the somatic volumes can be modulated by substitutive ovarian hormones administered to OVX females, for which P can lead to higher results. These findings reveal additional epigenetic actions of the sex steroids in the MePD and new neuronal morphological features in adult female rats.

Treadmill training increases the size of A cells from the L5 dorsal root ganglia in diabetic rats.

The aim of this study was to evaluate the effects of physical training on the L5 dorsal root ganglion (DRG) cells in streptozotocin diabetic rats. Male adult rats were divided into 3 groups: (control, diabetic and trained diabetic). Treadmill training was performed for 10 weeks (5 days/week, twice a day). Blood glucose concentrations and body weight were evaluated 48h after diabetes induction and every 30 days thereafter. Then, animals were killed and the right L5 DRG removed. Histological and morphometric analysis consisted of evaluating nuclear and cellular volumes and areas in A and B cells at light and ultrastructural levels. Blood glucose concentrations were higher in both diabetic groups vs controls at all periods. Body weights were lower in all diabetics vs controls at all periods after diabetes induction, with a significant time vs group interaction. In A cells, the cellular and nuclear volumes were lower than control animals only in the diabetic group; control and trained diabetic animals did not differ; in B cells the cellular and nuclear volumes were lower in diabetic and trained diabetic rats. The cellular areas of A cells were smaller in diabetic rats than in control and trained diabetic rats, while the cellular areas of B cells were smaller in the diabetic and trained groups. In conclusion, treadmill training was able to increase the size of A cells from the DRG in diabetic rats and improved the morphological features of these cells.