Koba S, Watanabe R, Kano N, Watanabe T. Oxidative stress exaggerates skeletal muscle contraction-evoked reflex sympathoexcitation in rats with hypertension induced by angiotensin II. Am J Physiol Heart Circ Physiol 304: H142-H153, 2013. First published October 19, 2012 doi:10.1152/ajpheart.00423.2012.-Muscle contraction stimulates thin fiber muscle afferents and evokes reflex sympathoexcitation. In hypertension, this reflex is exaggerated. ANG II, which is elevated in hypertension, has been reported to trigger the production of superoxide and other reactive oxygen species. In the present study, we tested the hypothesis that increased ANG II in hypertension exaggerates skeletal muscle contraction-evoked reflex sympathoexcitation by inducing oxidative stress in the muscle. In rats, subcutaneous infusion of ANG II at 450 ng·kg Ϫ1 ·min Ϫ1 for 14 days significantly (P Ͻ 0.05) elevated blood pressure compared with shamoperated (sham) rats. Electrically induced 30-s hindlimb muscle contraction in decerebrate rats with hypertension evoked larger renal sympathoexcitatory and pressor responses [ϩ1,173 Ϯ 212 arbitrary units (AU) and ϩ35 Ϯ 5 mmHg, n ϭ 10] compared with sham normotensive rats (ϩ419 Ϯ 103 AU and ϩ13 Ϯ 2 mmHg, n ϭ 11). Tempol, a SOD mimetic, injected intra-arterially into the hindlimb circulation significantly reduced responses in hypertensive rats, whereas this compound had no effect on responses in sham rats. Tiron, another SOD mimetic, also significantly reduced reflex renal sympathetic and pressor responses in a subset of hypertensive rats (n ϭ 10). Generation of muscle superoxide, as evaluated by dihydroethidium staining, was increased in hypertensive rats. RT-PCR and immunoblot experiments showed that mRNA and protein for gp91 phox , a NADPH oxidase subunit, in skeletal muscle tissue were upregulated in hypertensive rats. Taken together, hese results suggest that increased ANG II in hypertension induces oxidative stress in skeletal muscle, thereby exaggerating the muscle reflex. muscle contraction; angiotensin II; oxidative stress; sympathetic nerve activity HYPERTENSION is associated with an increased risk of cardiovascular disease (50). Antihypertensive treatments include increased physical activity or exercise (8, 23). It has been noted that in hypertension, the sympathoexcitation and elevation of blood pressure seen during exercise are excessive (10,39). This cardiovascular hyperexcitability is potentially dangerous because it can elevate risks for adverse cardiac events such as acute myocardial ischemia, myocardial infarction, left ventricular hypertrophy, or arrhythmia as well as stroke after a bout of exercise (23,36). Determining the causes underlying the hyperexcitability in this pathological condition is clinically important.A reflex originating in exercising skeletal muscle is activated as thin fiber muscle afferents (groups III and IV) are stimulated by mechanical deformation of the afferents' receptive fields as well as by metabolic byproducts during contraction (9, 33). In turn, afferent e...

The optic gland, which is analogous to the anterior pituitary in the context of gonadal maturation, is found on the upper posterior edge of the optic tract of the octopus Octopus vulgaris. In mature octopus, the optic glands enlarge and secrete a gonadotrophic hormone. A peptide with structural features similar to that of vertebrate gonadotophin‐releasing hormone (GnRH) was isolated from the brain of octopus and was named oct‐GnRH. Oct‐GnRH showed luteinising hormone‐releasing activity in the anterior pituitary cells of the Japanese quail Coturnix coturnix. Oct‐GnRH immunoreactive signals were observed in the glandular cells of the mature optic gland. Oct‐GnRH stimulated the synthesis and release of sex steroids from the ovary and testis, and elicited contractions of the oviduct. Oct‐GnRH receptor was expressed in the gonads and accessory organs, such as the oviduct and oviducal gland. These results suggest that oct‐GnRH induces the gonadal maturation and oviposition by regulating sex steroidogenesis and a series of egg‐laying behaviours via the oct‐GnRH receptor. The distribution and expression of oct‐GnRH in the central and peripheral nervous systems suggest that oct‐GnRH acts as a multifunctional modulatory factor in feeding, memory processing, sensory, movement and autonomic functions.