Dehydroepiandrosterone increases the number and dendrite maturation of doublecortin cells in the dentate gyrus of middle age male Wistar rats exposed to chronic mild stress

Dehydroepiandrosterone Attenuates Astroglial Activation, Neuronal Loss and Dendritic Degeneration in Iron-Induced Post-Traumatic Epilepsy

Iron-induced experimental epilepsy in rodents reproduces features of post-traumatic epilepsy (PTE) in humans. The neural network of the brain seems to be highly affected during the course of epileptogenesis and determines the occurrence of sudden and recurrent seizures. The aim of the current study was to evaluate astroglial and neuronal response as well as dendritic arborization, and the spine density of pyramidal neurons in the cortex and hippocampus of epileptic rats. We also evaluated the effect of exogenous administration of a neuroactive steroid, dehydroepiandrosterone (DHEA), in epileptic rats. To induce epilepsy, male Wistar rats were given an intracortical injection of 100 mM solution (5 µL) of iron chloride (FeCl3). After 20 days, DHEA was administered intraperitoneally for 21 consecutive days. Results showed epileptic seizures and hippocampal Mossy Fibers (MFs) sprouting in epileptic rats, while DHEA treatment significantly reduced the MFs’ sprouting. Astroglial activation and neuronal loss were subdued in rats that received DHEA compared to epileptic rats. Dendritic arborization and spine density of pyramidal neurons was diminished in epileptic rats, while DHEA treatment partially restored their normal morphology in the cortex and hippocampus regions of the brain. Overall, these findings suggest that DHEA’s antiepileptic effects may contribute to alleviating astroglial activation and neuronal loss along with enhancing dendritic arborization and spine density in PTE.

Androgens and Adult Neurogenesis in the Hippocampus

Adult neurogenesis in the hippocampus is modulated by steroid hormones, including androgens, in male rodents. In this review, we summarize research showing that chronic exposure to androgens, such as testosterone and dihydrotestosterone, enhances the survival of new neurons in the dentate gyrus of male, but not female, rodents, via the androgen receptor. However, the neurogenesis promoting the effect of androgens in the dentate gyrus may be limited to younger adulthood as it is not evident in middle-aged male rodents. Although direct exposure to androgens in adult or middle age does not significantly influence neurogenesis in female rodents, the aromatase inhibitor letrozole enhances neurogenesis in the hippocampus of middle-aged female mice. Unlike other androgens, androgenic anabolic steroids reduce neurogenesis in the hippocampus of male rodents. Collectively, the research indicates that the ability of androgens to enhance hippocampal neurogenesis in adult rodents is dependent on dose, androgen type, sex, duration, and age. We discuss these findings and how androgens may be influencing neuroprotection, via neurogenesis in the hippocampus, in the context of health and disease.

Antidepressant-like effects of acupuncture via modulation of corticosterone, sex hormones, and hippocampal BDNF expression in male rats

BACKGROUND

Post-weaning social isolated rodents exhibit pathophysiological changes associated with depression including adrenal axis hyperactivity, gonadal hormone level disturbances, molecular alterations in hippocampus, and immobility behavior in the forced swimming test (FST). Although acupuncture by absorbable thread implantation (acu-catgut, AC) elicits antidepressant-like effects in social isolated rats, AC effects on neuroendocrine and hippocampal molecular alterations have been less characterized.

OBJECTIVE

To investigate the participation of gonadal hormones, corticosterone, and brain-derived neurotrophic factor (BDNF) hippocampal expression, on the AC antidepressant-like effects in social isolated male rats.

METHODS

Sprague-Dawley male rats were raised in social isolation (SI) or standard conditions, for 11 weeks. AC (on Baihui (Du20), Yintang (E X-HN3), Shenshu (BL 23), Pishu (BL 20), Ganshu (BL 18), Xinshu (BL 15) and Guanyuan (Ren 4)), or Sham-AC (puncturing of acupoints without embedding the thread), was applied during the last three weeks of isolation period. Rats were evaluated in the FST; hormones plasmatic levels and hippocampal BDNF content were quantified by ELISA and Western blotting, respectively.

RESULTS

Social isolated rats showed more immobility in the FST and had lower testosterone and estradiol levels, higher corticosterone levels, and reduced hippocampal BDNF content than controls. BDNF level in hippocampus inversely correlated to depression-like behavior. AC but not sham-AC normalized immobility behavior, steroid hormone levels, and BDNF content, as in rats raised in a social environment.

CONCLUSIONS

AC antidepressant effect could be related to an improvement of hippocampal BDNF protein expression, as well as corticosterone and sex hormones disturbances associated with prolonged exposure to stress caused by social isolation. Present findings have implications for depression treatment in individuals early exposed to stress.