Harbans Lal

Oxidative damage, mitochondrial oxidant generation and antioxidant defenses during aging and in response to food restriction in the mouse

This study was conducted in order to test the concept that oxidative damage is associated with aging and may be a factor in the modulation of life span in response to variations in caloric intake. Mice fed a diet that was 40% lower in calories (DR) than the ad libitum fed (AL) animals exhibited a 43% extension in average life span and a 61% prolongation in mortality rate doubling time. A comparison of AL and DR mice at 9, 17 and 23 months of age indicated that the protein carbonyl content in the brain, heart and kidney increased with age and was significantly greater in the AL than DR group in each organ at each of the three ages. Mitochondrial state 4 or resting respiratory rate increased with age in the AL, but not the DR group, and was also relatively higher in the former. The rates of mitochondrial superoxide and hydrogen peroxide generation increased with age and were higher in the AL than DR mice in all the three organs at each age. In contrast, there was no clear-cut overall pattern of age-related or dietary-related changes in antioxidant defenses provided by superoxide dismutase, catalase and glutathione peroxidase. Results suggest that mechanisms of aging and life span shortening by enhanced caloric intake are associated with oxidative damage arising from corresponding changes in mitochondrial oxidant production. Protein carbonyl content, and mitochondrial O2.- and H2O2 generation may act as indices of aging.

Effect of age and caloric restriction on DNA oxidative damage in different tissues of C57BL/6 mice

The objective of this study was to explore the role of molecular oxidative damage and caloric intake in the aging process. The concentration of 8-hydroxydeoxyguanosine (8-OHdG), a product of DNA oxidation, was compared in five different tissues of mice (skeletal muscle, brain, heart, liver and kidney) as a function of age and in response to dietary restriction. A comparison of 8- and 27-month-old mice indicated that the age-related increase in 8-OHdG concentration was greater in skeletal muscle, brain and heart, which are primarily composed of long-lived, post-mitotic cells, than in liver and kidney, which consist of slow-dividing cells. Dietary restricted (DR) mice kept on 60% caloric intake as compared to the ad libitum-fed (AL) mice showed a lower concentration in 8-OHdG content in all the tissues compared to AL mice. The DR-related amelioration of DNA oxidative damage was greater in the post-mitotic tissues compared to those undergoing slow mitoses. Results support the hypothesis that oxidative damage to long-lived post-mitotic cells may be a key factor in the aging process.

The discriminative stimulus effects of pentylenetetrazol as a model of anxiety: recent developments.

Pentylenetetrazol (PTZ), a GABA(A) receptor antagonist and prototypical anxiogenic drug, has been extensively utilized in animal models of anxiety. PTZ produces a reliable discriminative stimulus which is largely mediated by the GABA(A) receptor. Several classes of compounds can modulate the PTZ discriminative stimulus including 5-HT(1A), 5-HT(3), NMDA, glycine, and L-type calcium channel ligands. Spontaneous PTZ-lever responding is seen in trained rats during withdrawal from GABA(A) receptor compounds such as chlordiazepoxide and diazepam, and also ethanol, morphine, nicotine, cocaine, haloperidol, and phencyclidine. This effect is largely mediated by the GABA(A) receptor, which suggests that anxiety may be part of a generalized withdrawal syndrome mediated by the GABA(A) receptor. There are also important hormonal influences on PTZ. Corticosterone plays some role in mediation of its anxiogenic effects. There is a marked sex difference in response to the discriminative stimulus effects of PTZ, and estrogens appear to protect against its anxiogenic effects. Further work with the PTZ drug discrimination is warranted for characterization of anxiety during withdrawal, and the hormonal mechanisms of anxiety.

Effects of NMDA Antagonists on Ethanol-Withdrawal Induced “Anxiety” in the Elevated Plus Maze

The anxiolytic effects of NMDA antagonists during ethanol withdrawal were assessed in Long-Evans rats. Anxiety was measured by the elevated plus maze. Male rats were exposed to ethanol (6.5%) in a liquid diet for 10 days. Behavioral testing took place 12 h after withdrawal of ethanol. The competitive NMDA antagonists, AP-7 (0.02-0.32 mg/kg) and CGP-37849 (0.64-10 mg/kg), at least partially reversed the anxiety-like effects induced by withdrawal from ethanol. Both drugs produced a small increase in total arm entries, and a much larger increase in the percentage of open arm entries. AP-7, but not CGP-37849, also increased the percentage of open arm time. In contrast, the NMDA channel blocker, dizocilpine (MK-801; 0.08-0.32 mg/kg), produced only a small increase in the percentage of open arm entries and of open arm time. HA-966, a glycine-site antagonist, also failed to produce changes in ethanol withdrawal induced changes in anxiety at the doses tested. These results suggest that competitive NMDA antagonists may be useful for reduction of signs of anxiety during ethanol withdrawal.

Abecarnil and alprazolam reverse anxiety-like behaviors induced by ethanol withdrawal

This study investigated the effects of a benzodiazepine partial agonist, abecarnil, and a full agonist, alprazolam, on ethanol withdrawal-induced anxiety-like behaviors in rats. Anxiety was assessed in two models: elevated plus maze and pentylenetetrazol (GABA(A) antagonist) discrimination assay. Male rats received an ethanol-containing (4.5%) liquid diet for 7 to 10 days and were tested for withdrawal symptoms 12 h after termination of the diet. In the elevated plus maze, ethanol-withdrawn rats displayed less open arm activity and total arm entries than pair-fed rats. Abecarnil (0.08-0.32 mg/kg, IP) and alprazolam (0.08-1.25 mg/kg, IP) each produced a dose-dependent, full reversal of ethanol withdrawal-induced reduction of open arm activity, but only alprazolam increased the total arm entries. In the pentylenetetrazol assay, ethanol-withdrawn rats selected the pentylenetetrazol lever (100%) over the salin-lever. Abecarnil (0.04-0.32 mg/kg, IP) and alprazolam (0.08-0.32 mg/kg, IP) dose dependently reduced pentylenetetrazol-lever responding to control levels (10-20%). Alprazolam was more potent than abecarnil in reversing ethanol withdrawal-induced decrease in open arm activities, but showed comparable potency and efficacy to abecarnil in blocking the pentylenetetrazol-like ethanol withdrawal stimulus. These results suggest that abecarnil and alprazolam may have therapeutic potential for treatment of ethanol withdrawal-induced anxiety-like symptoms.

A discrimmative stimulus produced by l-(3-Chlorophenyl)-piperazine (mCPP) as a putative animal model of anxiety

1. This study compares behavioral responses to serotonergic (5HT) agonists and pentylenetetrazol (PTZ) in two behavioral paradigms used as animal models of anxiety. PTZ and mCPP were compared for behavioral effects in elevated plus-maze and interoceptive discriminative stimuli they produce. 2. PTZ is a known anxiogenic drug. The discriminative stimuli of mCPP were selected for comparison because this drug produces anxiety in human subjects and anxiety-like behaviors in rats, and is a potent agonist at 5HT1B/2C receptors and a partial agonist at 5HT2A receptors. 3. In rats trained to discriminate mCPP (1.4 mg/kg, training dose) from saline, PTZ substituted for the mCPP suggesting the anxiety-like properties of the mCPP stimulus. The mCPP stimulus was blocked in a dose-related manner by methysergide, a 5HT2A/2C antagonist but not by the anxiolytic diazepam. TFMPP (a 5HT agonist) and DOI (a 5HT2A/2C agonist) substituted for mCPP, but 1-NP (a 5HT1 agonist and 5HT2C/2A antagonist) did not. 4. In animals trained to discriminate PTZ (16 mg/kg) from saline, mCPP and DOI substituted for PTZ, while TFMPP and 1-NP do not. 5. In the elevated plus maze, time spent on the open arms was reduced by mCPP, DOI and PTZ but there was no significant dose effect of TFMPP, or 1-NP. 6. Methysergide blocked the anxiety-like behavior in the EPM. 7. These data suggest that the discriminative stimuli produced by mCPP are based upon its selective actions on 5HT receptors and their use in behavioral pharmacology may offer another tool in studying pharmacology of 5HT based anxiogenic and anxiolytic drugs.

Estimating age-related changes in psychomotor function: influence of practice and of level of caloric intake in different genotypes.

This article presents a discussion of some key considerations in the measurement of age-related changes in psychomotor function of mice. We illustrate that standard measures of psychomotor performance, such as running speed on a rotorod task, are highly sensitive to practice effects. Examples are cited in which failure to assess practice effects can influence conclusions regarding the magnitude and rate of change in psychomotor capacity as a function of age. A second set of examples is focused on estimating the effect of an experimental intervention, caloric restriction, on age-related changes in psychomotor performance. These examples show that psychomotor performance at a given age may vary directly, and reversibly, with the level of caloric intake. Independent of such reversible effects, the level of caloric intake can also modulate the rate of change in capacity as a function of age. It is concluded that reversible, short-term effects must be considered in estimating the effect of an experimental intervention on the rate of age-associated change in psychomotor function.

Effects of ritanserin on ethanol withdrawal–induced anxiety in rats

This study investigated the ability of ritanserin, a 5-HT2 antagonist, to modify ethanol withdrawal (EW) symptoms in two animal models of anxiety: the elevated plus-maze (EPM) and the pentylenetetrazol (PTZ) discrimination assay. Long-Evans hooded rats were given a nutritionally balanced liquid diet containing 4.5% ethanol for 10 days. Twelve hours after removal of the ethanol diet, rats were tested in the EPM. A significant reduction in the open-arm activity and the number of total arm entries was observed, which is indicative of EW. Acute ritanserin (0.16-0.64 mg/kg, i.p., 60 min) had no effect on EW-induced anxiety-like behavior on the EPM. Ritanserin (0.08-0.64 mg/kg, i.p., b.i.d. 12 h) administered concurrently with the last 5 days of ethanol diet produced an increase in the time spent on the open arms of the EPM and reversed the EW-induced reduction in total arm entries. Rats trained to discriminate between saline and PTZ (an anxiogenic drug), selected the PTZ lever during EW. Chronic ritanserin (0.32 mg/kg, i.p., b.i.d. ) did not block PTZ lever responding during EW. On the rotorod, ritanserin (0.32 mg/kg, i.p.) increased the motor incoordination induced by ethanol. In conclusion, coadministration of ritanserin with ethanol prevented the development of EW-induced anxiety as measured by the EPM, but not in the PTZ drug discrimination.

Pharmacological treatment of alcoholism

1. Pharmacological treatments are effective as part of a treatment plan that includes substantial education, psychological therapy and social support. This paper reviews recent literature on animal models of and treatment for alcohol abuse under seven categories: agents to block craving or reduce alcohol intake, agents to induce aversion to alcohol, agents to treat acute alcohol withdrawal, agents to treat protracted alcohol withdrawal, agents to diminish drinking by treating associated psychiatric pathology, agents to decrease drinking by treating associated drug abuse, and agents to induce sobriety in intoxicated individuals. 2. The benzodiazepines provide safe and effective treatment for detoxification, although current research focuses on finding drugs with a smaller likelihood of dependence. As yet, there are no drugs that effectively reverse the intoxicating effects of alcohol. 3. Currently, only two major groups of drugs that are relatively safe have shown any effect at reducing alcohol consumption: aversives such as disulfiram, and opioid antagonists such as naltrexone. 4. Finally, it is important to customize therapy for each patient rather than putting everyone through a standard treatment plan, especially in regards to the use of antidepressant or antipsychotic medications. Tailoring the program to the patients needs dramatically improves the outcome of therapy and reduces the risk of adverse effects.

The Effects of Adenosine Ligands R-PIA and CPT on Ethanol Withdrawal

The potential anxiogenic or anxiolytic effects of R(-)-N6-(2-phenylisopropyl)adenosine (R-PIA), an adenosine agonist, and 8-cyclopentyl-1,3,dimethylxanthine (CPT), an adenosine antagonist, were tested during chronic exposure to ethanol and to ethanol-induced withdrawal in rats. Effects on anxiety were measured by the elevated plus maze and dark-light box. Ethanol consumption and preference was tested in an additional experiment. In testing of elevated plus maze performance during withdrawal from ethanol, R-PIA produced no change in the anxiety-related behaviors of total arm entries and percent open arm entries, but produced a significant decrease in percent open arm time. CPT produced at least partial recovery from the anxiogenic effects of ethanol withdrawal on all three measures of elevated plus maze performance, although peak effects were seen at the intermediate dose of CPT (0.08 mg/kg) for total arm entries and percent open arm time. CPT also showed anxiolytic effects at low to intermediate doses (0.04, 0.08 mg/kg) in the dark-light box. CPT did not reduce the preference for ethanol over water or the total consumption of ethanol over a range of ethanol doses. In summary, the adenosine agonist, R-PIA, exacerbated the effects of ethanol withdrawal, whereas the adenosine antagonist, CPT, at least partially blocked the anxiogenic effects produced by ethanol withdrawal. These results suggest that adenosine antagonists, at least at some doses, may be useful for ameliorating the anxiogenic effects produced by ethanol withdrawal, although it does not appear useful for reducing consumption.