This study was conducted to investigate the possible protective role of thymoquinone (TQ) and l-cysteine on the reproductive toxicity of male rats induced by cadmium chloride (CdCl2). Forty rats were divided into four even groups. The first group served as untreated control. The second, third and fourth groups received CdCl2, CdCl2 and TQ, and CdCl2 and l-cysteine, respectively for 56 days. Cd exposure caused spermatological damage (decrease sperm count and motility and increased the rates of sperm abnormalities), decrease serum testosterone level and increased oxidative stress. Histological alterations were also observed in the form of vascular and cellular changes in CdCl2 treated rats. The vascular changes were congestion of the blood vessels with interstitial edema in the testes, epididymis, seminal vesicle and prostate. The cellular changes were in the form of degenerative changes with presence of multinucleated giant cells in the lumen of seminiferous tubules, vacuolation and sloughing of the lining epithelium of the epididymis, seminal vesiculitis and prostatitis. Co-administration of TQ and l-cysteine with CdCl2 increased glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and testosterone and reduced lipid peroxidation (LPO) activity. In conclusion, our results showed that TQ and l-cysteine can ameliorate the deleterious effects of CdCl2 probably by activating testicular endocrine and antioxidant systems.

Thyroid hormones and omega-3 are essential for normal brain functions. Recent studies have suggested that omega-3 may protect against the risk of dementia. The aim of this study was to investigate the effect of hypothyroidism on spatial learning and memory in adult male rats, the underlying mechanisms and the possible therapeutic value of omega-3 supplementation. Thirty male rats were divided into three groups; control, hypothyroid and omega-3 treated. Hypothyroidism induced significant deficits in working and reference memories in radial arm maze, retention deficits in passive avoidance test and impaired intermediate and long-term memories in novel object recognition test. Serum total antioxidant capacity (TAC) and hippocampal serotonin and γ-aminobutyric acid (GABA) levels were decreased in the hypothyroid group as compared to the control group. Moreover, the hippocampus of hypothyroid rats showed marked structural changes as diffuse vacuolar degeneration and distortion of the pyramidal cells. Immunohistochemistry showed that the expression of Cav1.2 (the voltage dependent LTCC alpha 1c subunit) protein was increased in the hypothyroid group as compared to the control group. Omega-3 supplementation ameliorated memory deficits, increased TAC, decreased the structural changes and decreased the expression of Cav1.2 protein. In conclusion omega-3 could be useful as a neuroprotective agent against hypothyroidism-induced cognitive impairment.Keywords: hypothyroidism, cognition, omega-3, Cav1.2, GABA and serotonin Thyroid hormones play an important role in the development and the normal function of CNS by different mechanisms. They regulate synaptic transmission (15), modulate the synthesis and turnover of neurotransmitters and modify the sensitivity of their receptors (42, 51). They modulate signal transduction pathways in the CNS through Ca 2+ channels. L-type voltagesensitive Ca 2+ (Cav) channel (L-VSCC) mediates long lasting Ca 2+ currents (55) that play important roles in neurotransmitters release, second messenger cascades and gene regulation (28). L-VSCCs localize prominently on neuronal cell bodies and proximal dendrites (24). They consist of five subunits: α1, α2, β, γ and δ (40); α1 subunit is the ion-conducting pore and contains the binding sites for dihydropyridine (9). There are two different L-VSCC α1 subunits: α1C (Cav1.2) and α1D (Cav1.3) (47). Growing evidence has suggested that excessive Ca 2+ influx through L-VSCCs may be detrimental to memory (55). Moreover, L-VSCC currents were reported to be increased in the hippocampus of aged rats and rabbits and thus, had been implicated in aged-related memory deficits (50). Omega-3 polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are major components of neuronal membranes and have a wide range of functions including neural growth (18), neuroprotection and modulation of

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