Evidence of thalamic dysfunction in Huntington disease by proton magnetic resonance spectroscopy.

Our objective was to investigate thalamic neuronal dysfunction in patients with Huntington disease (HD). We performed localized single-voxel proton magnetic resonance spectroscopy (MRS) of the thalamus in 22 HD patients and 25 healthy individuals. The mean age of patients was 48.5 years (ranging from 32 to 71 years). Age at onset varied between 20 and 66 years (mean 38.9 years). The expanded CAG repeat ranged from 40 to 52 (mean 45.2) CAGs. The mean age of control group was 35.4 years, ranging from 19 to 67 years. N-acetylaspartate (NAA) relative to creatine (NAA/Cr) values in the thalamus of HD patients were decreased when compared with controls (P = 0.0001). The spectroscopic findings were not correlated with motor impairment. However, there was a positive correlation between duration of disease and motor impairment (P = 0.02, r = 0.48), and a tendency for positive correlation between duration of disease and NAA/Cr (P = 0.059, r = 0.4). We found decreased NAA/Cr values in the thalamus of patients with HD, indicating neuronal loss or dysfunction. This is in agreement with previous studies that indicated the involvement of mitochondrial dysfunction in the neurodegenerative process of HD.

Hypothalamic response to experimental allergic encephalomyelitis: role of substance P.

Adjuvant-induced arthritis (AA) is thought to be a model for experimental chronic stress that has as main features decreased adrenocorticotropin hormone (ACTH) plasma levels and a rise in median eminence content of arginine vasopressin (AVP) due to the activity of substance P. In experimental allergic encephalomyelitis (EAE), another chronic stress model, the role of substance P action is not clear. In this paper we tried to clarify the role of substance P in Lewis rats, which are susceptible to this disease. EAE was induced using myelin basic protein plus complete Freund's adjuvant injected into the hind limbs. One day later injections of an antagonist to substance P (RP 67580), saline, and substance P were administered daily for 12-14 days through a stainless steel cannula into the lateral ventricle of the brain, and then the rats were killed. The rats were divided into groups of controls, sham, diseased controls (no intracerebroventricular injections) and EAE (injected intracerebroventricularly). Plasma was used for the quantification of ACTH and corticosterone but not AVP which was assayed in hypothalamic median eminence extracts. In noninjected diseased rats the plasma levels of ACTH and corticosterone were significantly higher than in noninjected control rats, whereas the AVP concentrations in the median eminence were unchanged. The substance P antagonist did not affect the levels of these hormones in plasma or the median eminence. Substance P decreased the plasma levels of ACTH and corticosterone but did not increase the median eminence content of vasopressin. Administration of the antagonist 30 min before an equivalent dose of substance P increased the plasma levels of the two hormones, but did not change the content of AVP. Based on the lack of response to the antagonist RP 67580 we suggest that the substance P has different roles in EAE and AA at least in the later stages of EAE (after 11 days of immunization).