Mamoru Tanida

Auditory stimulation affects renal sympathetic nerve activity and blood pressure in rats

Here, we examined the effects of auditory stimulation at 50 dB with white noise (WN) or music (Traeumerei [TM] by Schumann or Etude by Chopin) on renal sympathetic nerve activity (RSNA) and BP in urethane-anesthetized rats. Auditory stimulation with TM, but not with WN or the Etude, significantly decreased RSNA and BP. Complete bilateral destruction of the cochleae and bilateral lesions of the auditory cortex (AuC) eliminated the effects of TM stimulation on RSNA and BP, but bilateral lesions of primary somatosensory cortex (S1C) had no effect. Bilateral lesions of the hypothalamic suprachiasmatic nucleus (SCN) or intracerebral administration of thioperamide, a histaminergic H3 receptor antagonist, also abolished TM-induced decreases in RSNA and BP. These findings suggest that exposure to music can decrease RSNA and BP through the auditory pathway, histaminergic neurons, and the SCN.

Involvement of the histaminergic system in renal sympathetic and cardiovascular responses to leptin and ghrelin.

Previous studies have demonstrated that histamine affects blood pressure (BP) in anesthetized rats. Here, we examined the effects of lateral cerebral ventricular (LCV) injection of various doses of histamine on renal sympathetic nerve activity (RSNA) and BP in anesthetized rats. LCV injection of a low dose of histamine (0.0001nmol) suppressed RSNA and BP. Conversely, a high dose of histamine (100nmol) elevated both RSNA and BP. Moreover, inhibiting effects of a low dose of histamine were eliminated by LCV pre-injection of thioperamide, an antagonist of histaminergic H3-receptor, and accelerating effects of a high dose of histamine were abolished by LCV pre-injection of diphenhydramine, an antagonist of histaminergic H1-receptor. Thus, these evidences suggest that central histamine affects RSNA and BP via histaminergic receptors. In addition, we examined a role for histaminergic system in cardiovascular modulators such as leptin and ghrelin. The LCV pre-injection of thioperamide clearly blocked suppressing effects of ghrelin on RSNA and BP. The LCV pre-injection of diphenhydramine also blocked elevating effects of leptin. Therefore, these results suggest that leptin and ghrelin might affect RSNA and BP by mediating central histaminegic H1- and H3-receptors, respectively.

CHAPTER 13:Carnosine and the Control of Blood Glucose

Imidazole dipeptides such as carnosine (β-alanyl-l-histidine) and anserine (β-alanyl-N-π-methyl-l-histidine) are naturally occurring dipeptides present at high concentrations in the muscles and the brain in vertebrates. In addition to various functions proposed so far, central and peripheral administration of carnosine have been shown to regulate blood-glucose levels of rats with hyperglycemia induced by 2-deoxy-d-glucose. This effect was likely to be due to regulation of insulin and glucagon secretions by the autonomic nervous system. Carnosine also induces changes in physiological events that are regulated by the autonomic nervous system, e.g. lipolysis and thermogenesis in the white and brown adipose tissues, respectively. The autonomic nervous system is under the control of specific regions in the hypothalamus and the brain stem. The carnosine action on the autonomic nerves is suggested to involve histaminergic neurons located in the tuberomammillary nucleus and the master circadian clock in the suprachiasmatic nucleus of the hypothalamus. These findings indicate that carnosine regulates the blood glucose and other peripheral physiological events by affecting the central regulation of the autonomic nervous system.