Behavioral Assessment of Genetic Mouse Models of Huntington’s Disease

Recuperative effect of estrogen on rotenone-induced experimental model of Parkinson's disease in rats

Parkinson's disease (PD) is described as the loss of dopaminergic neurons located in the substantia nigra (SN) region of the brain and a progressive motor failure. Increased frequency of PD in women, especially after menopause, suggests the effect of estrogen. This view has been supported with empirical studies. Therefore, the effect of estrogen in an experimental model of Parkinson's disease induced by rotenone was investigated. A total of 32 female Wistar Albino rats were randomly assigned to four groups (control group, ovariectomy group, Parkinson's group, Parkinson's + estrogen group). The Parkinson's group received rotenone subcutanously at the dose of 2.5 mg/kg bw, on the 1st, 2nd, 3rd 4th, 6th, 9th, 12th, 15th, 18th, and 21st days animals in the Parkinson's + estrogen group received retonon as in the Parkinson's group and was additionally subcutaneously given estrogen (implant containing 0.5 mg 17 β-estradiol lasting for 21 days). The rats were subjected to rotarod, pole, and swimming tests at the end of the experiment for comparison of their motor activities, and then, histopathological and biochemical analyses were performed on the tissues that were extracted. The rotarod results revealed that Parkinson's group had the shortest time (32.33 ± 3.98 sn) than the groups of control (92.50 ± 12.60 s) ovariectomy (71.42 ± 10.58 s), and Parkinson's + estrogen (71.37 ± 9.26 s). The results of pole disclosed that return and landing time prolonged for Parkinson's group when compared with other groups (return time for control 2.98 ± 0.38 s, ovariectomy 3.02 ± 0.75 s, Parkinson 5.91 ± 0.33 s, Parkinson's + estrogen 3.48 ± 0.42 s and landing time for control 5.30 ± 0.59 s, ovariectomy 5.45 ± 0.73 s, Parkinson 9.80 ± 0.90 s, Parkinson's + estrogen 5.37 ± 1.02 s). Parkinson's group had longest (90.71 ± 12.56 s) swimming time to reach the target when compared with control (33.16 ± 8.68 s), ovariectomy (47.37 ± 12.19 s), and Parkinson's + estrogen (49.82 ± 5.78 s). Histopathological examination indicated a significant difference in tyrosine hydroxylase-stained cells (dopaminergic neurons and dopamine) between the Parkinson's + estrogen group and the Parkinson's group. The biochemical analyses of Caspas-3 activation in SN and striatum (STR) was significantly different between the Parkinson's + estrogen group and the Parkinson's group, but this difference was not observed in STR while evaluating Bcl-2. The results of this study suggested that estrogen may have a recuperative effect on PD.

Sensorimotor tests unmask a phenotype in the DYT1 knock-in mouse model of dystonia

Hereditary generalized dystonia is often caused by a GAG deletion in TOR1A (DYT1) that encodes for the protein torsinA. Although mutation carriers show alterations in neuronal connectivity and sensorimotor deficits, only 30% develop dystonia. Uncovering the factors triggering the dystonic symptoms and underlying pathophysiology would greatly benefit the development of more effective therapies. In DYT1 knock-in (KI) mice, the expression of torsinA mutant alters the connectivity of neurons and the function of striatal cholinergic interneurons. We aimed to determine if heterozygous DYT1 KI mice exhibit deficits in behavioural tests that explore the connectivity of the sensory and motor system. DYT1 KI mice were tested in cognitive tests and challenging motor paradigms, followed by the adhesive removal test and the adaptive rotating beam test which both require sensorimotor integration. DYT1 KI mice did not exhibit cognitive deficits and were able to perform similarly to wild type mice even in challenging motor tests with relatively stable sensory input. Conversely, DYT1 KI mice spent more time on sensing and removing an adhesive sticker from the back of the nose; they exhibited difficulty to traverse rotating rods, especially if the surface was smooth and the diameter small. Our observations further support a role of sensorimotor integration in manifestation of this movement disorder. Future studies in DYT1 KI mice will explore the involved neurocircuitry and underlying molecular mechanisms.