Metabolic abnormalities caused by 3-acetylpyridine in the cerebral motor regions of rats: partial recovery by thyrotropin-releasing hormone

Thyrotropin-releasing hormone (TRH) in the cerebellum

Thyrotropin-releasing hormone (TRH) was originally isolated from the hypothalamus. Besides controlling the secretion of TSH from the anterior pituitary, this tripeptide is widely distributed in the central nervous system and regarded as a neurotransmitter or modulator of neuronal activities in extrahypothalamic regions, including the cerebellum. TRH has an important role in the regulation of energy homeostasis, feeding behavior, thermogenesis, and autonomic regulation. TRH controls energy homeostasis mainly through its hypophysiotropic actions to regulate circulating thyroid hormone levels. Recent investigations have revealed that TRH production is regulated directly at the transcriptional level by leptin, one of the adipocytokines that plays a critical role in feeding and energy expenditure. The improvement of ataxic gait is one of the important pharmacological properties of TRH. In the cerebellum, cyclic GMP has been shown to be involved in the effects of TRH. TRH knockout mice show characteristic phenotypes of tertiary hypothyroidism, but no morphological changes in their cerebellum. Further analysis of TRH-deficient mice revealed that the expression of PFTAIRE protein kinase1 (PFTK1), a cdc2-related kinase, in the cerebellum was induced by TRH through the NO-cGMP pathway. The antiataxic effect of TRH and TRH analogs has been investigated in rolling mouse Nagoya (RMN) or 3-acetylpyridine treated rats, which are regarded as a model of human cerebellar degenerative disease. TRH and TRH analogs are promising clinical therapeutic agents for inducing arousal effects, amelioration of mental depression, and improvement of cerebellar ataxia.

Taltirelin improves motor ataxia independently of monoamine levels in rolling mouse nagoya, a model of spinocerebellar atrophy

To examine the relationship between motor ataxia and monoamine levels in the central nervous system, the contents and concentrations of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in the cerebellum, brain stem and spinal cord were measured in rolling mouse Nagoya (RMN), a murine model of spinocerebellar atrophy. The tissue weight of the cerebellum and spinal cord, but not that of the brain stem was significantly lower in RMN than in the control group. In RMN, the NA content of the brain stem and spinal cord, but not the cerebellum were decreased relative to the control, and the concentration of NA in the spinal cord was also lower, but not significant. The DA and 5-HT contents in each tissue did not differ from those of the control, but the concentrations of monoamines, except for DA, were elevated in the brain stem and spinal cord in RMN. In particular, the concentrations of NA, DA and 5-HT in the cerebellum were significantly increased in RMN. Repeated administration of tartilerin hydrate, an analog of thyrotropin-releasing hormone, improved the ataxia of RMN, and elicited no obvious changes in either monoamine content or concentration of cerebellum, brain stem and spinal cord. These results indicate that the concentration of DA, as well as NA and 5-HT, increased in the RMN cerebellum, and that tartilerin improves the motor function of these mice via mechanisms other than changes in the levels of NA, DA and 5-HT in the central nervous system.