Calcium and sedative-hypnotic drug actions

Similar effects of nifedipine and hydralazine on anaesthesia and hypermotility induced by pentobarbitone in mice

Nifedipine, a dihydropyridine calcium channel blocker, and hydralazine, a non-calcium channel antagonist vasodilatator, enhanced pentobarbitone-induced sleeping time and reversed locomotor hyperactivity induced by a subhypnotic dose of the barbiturate in mice. The similarity of the behavioural effects, exerted by nifedipine and hydralazine, suggest that haemodynamic factors may play an important role in the interaction of calcium channel antagonists with barbiturates.

Anxiolytic-like actions of melatonin, 5-metoxytryptophol, 5-hydroxytryptophol and benzodiazepines on a conflict procedure

Male Wistar rats (120-230 g) were used in these experiments. Some rats were deprived of water for 48 h before testing in a conflict procedure. Then, after 20 licks from a water bottle with a metal drinking tube, the animal received an electric shock (0.5 mA/500 msec). The effects of two classical anxiolytic drugs, DIAZ (1.0, 2.0 and 4.0 mg/Kg b.wt), and CDP (5.0 and 10.0 mg/Kg b.wt) were compared to those produced by MEL (0.1, 0.2, 0.5, 1.0 and 2.0 mg/Kg b.wt), 5-MTOPHOL (1.0 and 2.0 mg/Kg b.wt), 5-HTOPHOL (1.0 and 2.0 mg/Kg b.wt) and vehicle solution. Anxiolytic drugs as well as MEL produced a dose-dependent increase in the number of shocks received. The results suggest that the three pineal indoles are involved in the modulation of the stress responses. MEL showed a higher potency than the other indoles.

Diltiazem alters some withdrawal signs in pentobarbital-dependent rats

Male, Sprague-Dawley rats were made dependent on pentobarbital sodium (PB) by continuous, IP infusion of PB for 13 days. On Day 14, a 72-hour PB-free period began during which body weight, 24-hour water consumption and withdrawal scores were noted. In Study 1, rats were placed into one of four treatment groups at the start of the PB-free period. Groups included saline-infused control rats with twice daily administration of either vehicle or diltiazem and PB-dependent rats treated twice daily with either diltiazem or vehicle. In Study 2, rats were placed into one of the four treatment groups at the start of the 13-day PB-infusion period. In Study 1, PB-dependent rats treated with diltiazem exhibited approximately 10% loss of body weight at both 12 and 48 hours of the PB-free period while PB-dependent rats treated with vehicle exhibited only about a 5% loss of body weight. PB-dependent rats treated with either diltiazem or vehicle both exhibited about a 40% decline in water consumption and were noted to have significant increases in withdrawal scores by the fifth hour of the PB-free period. As compared to the scores of PB-dependent rats treated with vehicle, diltiazem did not significantly alter the withdrawal scores of PB-dependent rats at any time point during the PB-free period. In Study 2, the chronic administration of diltiazem to PB-infused rats produced both a significant decrease in water consumption at 48 and 72 hours and a significant increase in withdrawal scores from 3-48 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Time-dependency for the bimodal effect of melatonin on calcium uptake in rat hypothalamus. Short communication

The activity of 0.01-1 microM of melatonin on depolarization-induced 45Ca2+ influx by hypothalamic synaptosomes of rats killed at late evening (2000 h) depended on melatonin preincubation time, exhibiting an early (10 min) stimulation of uptake and an inhibition after 30 min of incubation. Both stimulatory and inhibitory effects were maximal at 2000 h and tended to a minimum at 2400 h, exhibiting intermediate values at 400 h. At 1000 h, only inhibitory effects of melatonin (1 microM) on Ca2+ uptake were found.

The molecular biology of addictive drugs

The additive drugs alcohol, morphine, cocaine, and amphetamine are each associated with the development of tolerance and physical dependence. Changes in gene expression occur in cell culture and in vivo with the administration of these centrally-acting drugs. This article reviews those experiments that have studied drug-induced alterations in gene transcription. Ethanol has diverse effects on the amounts of messenger RNA molecules within the central nervous system. Ion channels, neuropeptides, membrane receptors, and immediate early genes represent several regulated mRNAs. The effects are selective, however, as many other specific products are not altered. Evidence for a genetic predisposition to ethanol use reinforces the importance of the genotype. Opioids, cocaine, and amphetamine also affect gene transcription. Messenger RNAs studied have included many of those demonstrated to be altered by alcohol use. Interestingly, use of any of these drugs alters the expression of immediate early genes. These genes may represent an initial step in the pathway that leads to drug addiction. The composite of drug-induced changes in gene expression results in the cellular responses of tolerance and dependence. The characterization of these changes should provide a better understanding of the molecular mechanisms of drug addiction.

Changes in benzodiazepine receptors of rat brain after long-term treatment with the Ca(2+)-antagonists nifedipine, verapamil, flunarizine and with the calmodulin antagonist trifluoperazine

1. The binding of [3H]flunitrazepam to benzodiazepine receptors in the cerebral cortex and hippocampus (membrane fraction P2) was studied after 13-day oral treatment of male Wistar rats with the Ca(2+)-antagonists nifedipine (20 mg/kg), verapamil (50 mg/kg), flunarizine (10 mg/kg) and with the calmodulin (CaM)-antagonist trifluoperazine (TFP) (3 mg/kg). 2. The changes in the binding characteristics of the benzodiazepine receptors in the frontal cortex were studied in vitro after the addition of nifedipine (10(-6) and 10(-5) M) and verapamil (10(-6) and 10(-5) M). 3. A significant decrease of the binding capacity (Bmax) of [3H]flunitrazepam was established after in vivo treatment with the three Ca(2+)-antagonists as well as after TFP, the decrease being much more pronounced in the hippocampus. 4. Changes in the affinity values (Kd) of [3H]flunitrazepam binding were found in neither of the groups. 5. No data for a direct interaction of nifedipine and verapamil with the brain benzodiazepine receptors were obtained in in vitro experiments.

Aging and ethanol alter neuronal electric membrane properties

The effect of age of donor mouse and acute ethanol exposure on the electrical membrane properties (EMP) of 825 freshly dissociated dorsal root ganglion (DRG) neurons was investigated. Both age and ethanol exerted a number of significant linear and independent effects. Age effects included a 52% increase in action potential overshoot, a 50% increase in a measure of afterhyperpolarization duration, a 31% increase in action potential duration due to decreased rate of repolarization and depolarization, and decreased electrical excitability. Also, specific membrane resistance increased and specific membrane capacitance decreased while the membrane time constant was not significantly affected by age. These EMP alterations with age for freshly dissociated DRG neurons are consistent with those reported previously for cultured DRG neurons and hence further support the hypothesis that the EMP of neurons in situ change significantly with age. Acute ethanol exposure caused relatively few EMP alterations including decreased electrical excitability, specific membrane capacitance, time constant, and overshoot; specific membrane resistance was increased. These changes are similar to those seen previously and are consistent with a membrane expansion effect of ethanol.