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SummaryWe identified major ion channels influencing the resting membrane potential of nociceptive sensory neurons and demonstrated that changes of somatic/perisomatic membrane potential of these neurons can strongly influence peripheral nociceptive transmission.

Spastin and P60-katanin are two distinct microtubule-severing proteins. Autosomal dominant mutations in the SPG4 locus corresponding to spastin are the most common cause of hereditary spastic paraplegia (HSP), a neurodegenerative disease that afflicts the adult corticospinal tracts. Here we sought to evaluate whether SPG4-based HSP is best understood as a "loss-of-function" disease. Using various rat tissues, we found that P60-katanin levels are much higher than spastin levels during development. In the adult, P60-katanin levels plunge dramatically but spastin levels decline only slightly. Quantitative data of spastin expression in specific regions of the nervous system failed to reveal any obvious explanation for the selective sensitivity of adult corticospinal tracts to loss of spastin activity. An alternative explanation relates to the fact that the mammalian spastin gene has two start codons, resulting in a 616 amino acid protein called M1 and a slightly shorter protein called M85. We found that M1 is almost absent from developing neurons and most adult neurons but comprises 20 -25% of the spastin in the adult spinal cord, the location of the axons that degenerate during HSP. Experimental expression in cultured neurons of a short dysfunctional M1 polypeptide (but not a short dysfunctional M85 peptide) is deleterious to normal axonal growth. In squid axoplasm, the M1 peptide dramatically inhibits fast axonal transport, whereas the M85 peptide does not. These results are consistent with a "gain-of-function" mechanism underlying HSP wherein spastin mutations produce a cytotoxic protein in the case of M1 but not M85.

Abstract-There is increasing evidence that all-trans retinoic acid (atRA) influences gene expression of components of renin-angiotensin system (RAS), which plays a pivotal role in the pathophysiology of essential hypertension. To further validate effects of atRA on the RAS and to assess the possibility that atRA affects the activity of angiotensin-converting enzyme 2 (ACE2), gene, and protein expression of ACE2 have been examined by real-time polymerase chain reaction and Western blot methods in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Rats were treated with atRA (10 or 20 mg ⅐ kg Ϫ1 ⅐ day Ϫ1 ) or placebo given as daily intraperitoneal injection for 1 month. ACE2 expression was markedly decreased in placebo-treated SHR when compared with WKY rats. However, in atRA-treated SHR, a significant upregulation of ACE2 expression was observed in heart and kidney. In conclusion, chronic atRA treatment increases gene and protein expressions of ACE2, resulting in the reduction of blood pressure and the attenuation of myocardial damage in SHR, which suggests that atRA may be an attractive candidate for the potential prevention and treatment of human essential hypertension. Key Words:hypertension, essential Ⅲ angiotensin-converting enzyme Ⅲ renin-angiotensin system Ⅲ rats I t is well-recognized that essential hypertension is a genetically complex metabolic and cardiovascular disorder controlled by both genetic and environmental factors. 1 The ideal aim of modern antihypertensive therapy is not only a reduction of blood pressure but also the prevention or amelioration of its complications, such as myocardial remodeling at the molecular genetic level. 2,3 Research advances on the key transcription factors and nuclear hormone receptors provide insight into the development of novel transcriptionmodulating antihypertensive drugs, among which is all-trans retinoic acid (atRA), a biologically active metabolite of vitamin A. 2 atRA modulates gene transcription and exerts its other effects by binding the retinoic acid receptor (RAR) and retinoid X receptor (RXR) 4,5 and interfering with some key transcription factors such as the activated protein-1. 6,7 Studies have demonstrated that atRA influences the activities of genes responsible for the pathogenesis of hypertension and its complications. 2,3,6,8 Dechow et al 6 reported that atRA reduced blood pressure in the renal damage model. Spontaneously hypertensive rats (SHR) are recognized as genetically hypertensive rats, which resemble, in many aspects, humans with essential hypertension. 9 Chronic atRA treatment prevented medial thickening of intramyocardial and intrarenal arteries and ventricular fibrosis in SHR. 3 However, whether atRA reduces arterial pressure and attenuates myocardial damage in SHR deserves further study.atRA has been shown to regulate the gene expression of components of renin-angiotensin system (RAS), including renin, angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and its type 1 (AT 1 ) receptor. 6,7,10 RAS is critically inv...

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