Lifetime prolongation in voluntary alcohol-consuming rats (SHR) treated with clofibrate

Age related decreases in neural sensitivity to NaCl in SHR-SP

To determine whether neurophysiological taste responses of young and old rats are different, recordings were made from the whole chorda tympani nerve which innervates taste buds on the anterior tongue. SHR-SP (Stroke-Prone Spontaneously Hypertensive Rats) in two age groups were studied. Chemical stimuli included single concentrations of 250 mM NH(4)Cl, 100 mM NaCl, 100 mM KCl, 500 mM sucrose, 20 mM quinine-hydrochloride, 10 mM HCl, 10 mM monosodium glutamate (MSG), 10 mM L- glutamic acid (L-Glu) and an NaCl concentration series. The magnitude of the neural response (response ratio) was calculated by dividing the amplitude of the integrated response by the amplitude of the spontaneous activity that preceded it. Substantial neural responses to all chemicals were obtained at both ages. The responses to KCl, sucrose, quinine-hydrochloride, HCl, monosodium glutamate (MSG) and glutamic acid (Glu) did not change with age, but the response to NaCl did decrease significantly. The profile of the response/concentration function for NaCl differed with age. In particular, the responses to solutions more concentrated than 100 mM NaCl were significantly weaker in aged than in young SHR-SPs. We also observed that recovery from amiloride treatment on the tongue of SHR-SPs was faster in aged rats than in young ones, suggesting that there is some functional difference in the sodium-specific channels on the taste cell. These results suggest that aged SHR-SP may be less able than young SHR-SPs to discriminate among higher concentrations of NaCl solutions.

Bicuculline sensitive depressor response to ethanol infusion into the lateral hypothalamus

Decreased GABA function in the hypothalamus increases mean arterial pressure (MAP) and heart rate (HR). Since ethanol acts on GABA-A receptors, blocking GABA-A receptors can prevent a decrease of MAP and HR by ethanol in the lateral hypothalamus (LH). Ethanol at 5-30 mM, with or without 25 ng/microl bicuculline, was infused into the LH, and the activity of the site was validated with 100 nmoles of serotonin. Male rats were anesthetized with pentobarbital, and the femoral artery was catheterized to measure MAP and HR. Microinfusion was performed with a 28-gauge cannula placed into the LH. Serotonin increased MAP and HR within 15 sec. Ethanol decreased the MAP by -21.15 +/- 3.92 mmHg and HR by -53.61 +/- 14.95 BPM, at 15 min, which recovered by 15 min after the infusion was terminated. These maximum decreases were produced by 20 mM ethanol giving a U-shaped dose response. The aCSF vehicle had no effect. Bicuculline prevented ethanol-induced changes and had no effect when administered alone. Both serotonin and ethanol have direct effects on LH neurons with cardiovascular function. Ethanol produces this effect through GABA-A receptors.

Influence of chronic ethanol consumption on arterial tone in young and aged rats

The aim of this work was to evaluate the effects of long-term ethanol consumption on arterial responses in vitro in young and aged rats. Therefore, Wistar rats (ages 3 and 29 mo, respectively) were allocated to six groups: control-young, sucrose-young, ethanol-young, control-aged, sucrose-aged, and ethanol-aged. The ethanol-fed groups were given 25% ethanol by intragastric gavage three times a day 4 days a week. Responses of mesenteric arterial rings were examined in standard organ chambers after 5 treatment weeks. In norepinephrine-precontracted arterial rings, endothelium-dependent relaxations to acetylcholine, as well as endothelium-independent relaxations to isoproterenol, were attenuated in aged rats when compared with young controls. Relaxation responses to isoproterenol, but not to acetylcholine and nitroprusside, were clearly improved by ethanol treatment in both young and aged rats. The cyclooxygenase inhibitor diclofenac, which reduces the synthesis of dilating and constricting prostanoids, enhanced the relaxation to acetylcholine in all three aged rat groups but was without significant effect in the young rats. In the presence of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester the relaxation to acetylcholine in control and sucrose-fed aged rats was markedly reduced compared with control rats, whereas in the young controls and in both young and aged ethanol-exposed groups, distinct relaxations to higher concentrations of acetylcholine were still present. The endothelium-independent relaxations to cromakalim, a hyperpolarizing vasodilator acting via ATP-sensitive potassium channels, were also markedly augmented by ethanol feeding in both young and aged rats. In conclusion, ethanol consumption in both young and aged rats was associated with markedly improved arterial relaxations to isoproterenol and cromakalim, as well as clearly augmented relaxation to acetylcholine during inhibition of cyclooxygenase and nitric oxide synthase. These findings suggest that especially the potassium channel-related component of arterial relaxation was augmented by long-term ethanol exposure.