Effects of the Ca2(+)-antagonists nifedipine, verapamil, flunarizine and of the calmodulin antagonist trifluoperazine on muscarinic cholinergic receptors in rat cerebral cortex

Migraine Pharmacological Treatment and Cognitive Impairment: Risks and Benefits

Migraine is a common neurological disorder impairing the quality of life of patients. The condition requires, as an acute or prophylactic line of intervention, the frequent use of drugs acting on the central nervous system (CNS). The long-term impact of these medications on cognition and neurodegeneration has never been consistently assessed. The paper reviews pharmacological migraine treatments and discusses their biological and clinical effects on the CNS. The different anti-migraine drugs show distinct profiles concerning neurodegeneration and the risk of cognitive deficits. These features should be carefully evaluated when prescribing a pharmacological treatment as many migraineurs are of scholar or working age and their performances may be affected by drug misuse. Thus, a reconsideration of therapy guidelines is warranted. Furthermore, since conflicting results have emerged in the relationship between migraine and dementia, future studies must consider present and past pharmacological regimens as potential confounding factors.

Verapamil and Alzheimer's Disease: Past, Present, and Future

Verapamil is a phenylalkylamine class calcium channel blocker that for half a century has been used for the treatment of cardiovascular diseases. Nowadays, verapamil is also considered as a drug option for the treatment of several neurological and psychiatric disorders, such as cluster headache, bipolar disorders, epilepsy, and neurodegenerative diseases. Here, we review insights into the potential preventive and therapeutic role of verapamil on Alzheimer’s disease (AD) based on limited experimental and clinical data. Pharmacological studies have shown that verapamil has a wide therapeutic spectrum, including antihypertensive, anti-inflammatory, and antioxidative effects, regulation of the blood-brain barrier function, due to its effect on P-glycoprotein, as well as adjustment of cellular calcium homeostasis, which may result in the delay of AD onset or ameliorate the symptoms of patients. However, the majority of the AD individuals are on polypharmacotherapy, and the interactions between verapamil and other drugs need to be considered. Therefore, for an appropriate and successful AD treatment, a personalized approach is more than necessary. A well-known narrow pharmacological window of verapamil efficacy may hinder this approach. It is therefore important to note that the verapamil efficacy may be conditioned by different factors. The onset, grade, and brain distribution of AD pathological hallmarks, the time-sequential appearances of AD-related cognitive and behavioral dysfunction, the chronobiologic and gender impact on calcium homeostasis and AD pathogenesis may somehow be influencing that success. In the future, such insights will be crucial for testing the validity of verapamil treatment on animal models of AD and clinical approaches.

The effects of herbal medicine on epilepsy

Traditional herbal medicine plays a significant role in the treatment of epilepsy. Though herbal medicine is widely used in antiepileptic treatment, there is a lack of robust evidence for efficacy and toxicity of most herbs. Besides, the herbal medicine should be subject to evidence-based scrutiny. In this context, we present a review to introduce the effects of herbal medicine on epilepsy. However, hundreds of herbal medicines have been investigated in the available studies. Some commonly used herbal medicines for epilepsy have been listed in our study. The overwhelming majority of these data are based on animal experiments. The lack of clinical data places constraints on the clinical recommendation of herbal medicine. Our study may conduct further studies and provide some insight on the development of anti-epileptic drugs.

Verapamil Blocks Scopolamine Enhancement Effect on Memory Consolidation in Passive Avoidance Task in Rats

Our recent data have indicated that scopolamine, a non-selective muscarinic receptor antagonist, improves memory consolidation, in a passive avoidance task, tested in rats. It has been found that verapamil, a phenylalkylamine class of the L-type voltage-dependent calcium channel antagonist, inhibits [3H] N-methyl scopolamine binding to M1 muscarinic receptors. However, there are no data about the effect of verapamil on memory consolidation in the passive avoidance task, in rats. The purpose of the present study was to examine the effects of verapamil (0.5, 1.0, 2.5, 5.0, 10, or 20 mg/kg i.p.) as well as the interaction between scopolamine and verapamil on memory consolidation in the step-through passive avoidance task, in Wistar rats. Our results showed that verapamil (1.0 and 2.5 mg/kg) administered immediately after the acquisition task significantly increased the latency of the passive avoidance response, on the 48 h retested trial, improving memory consolidation. On the other hand, verapamil in a dose of 5 mg/kg, that per se does not affect memory consolidation, significantly reversed the memory consolidation improvement induced by scopolamine (1 mg/kg, i.p., administered immediately after verapamil treatment) but did not change the passive avoidance response in rats treated by an ineffective dose of scopolamine (30 mg/kg). In conclusion, the present data suggest that (1) the post-training administration of verapamil, dose-dependently, improves the passive avoidance response; (2) verapamil, in ineffective dose, abolished the improvement of memory consolidation effect of scopolamine; and (3) exists interaction between cholinergic muscarinic receptors and calcium homeostasis-related mechanisms in the consolidation of emotional memory.

Ionic and pharmacologic characteristics of epithelial cells in a semi-intact preparation of the rat ventral prostate gland

BACKGROUND

The essential ionic and pharmacologic characteristics of epithelial cells within the ducts of the prostate gland are not well known.

METHODS

Experiments were carried out on segments of ventral prostate glands from adult male rats. By using sharp microelectrodes, intracellular epithelial cell and transepithelial (lumen) potentials were recorded in response to ionic substitution and application of ion channel blockers, hormones, and other pharmacologic agents related to prostatic function.

RESULTS

Membrane permeabilities to K(+), Na(+), and Cl(-) were found to account for approximately 43% of the resting membrane potential, whereas some 39% was likely to be metabolic in origin. The membrane potential also responded to adrenaline, acetylcholine, insulin, prolactin, testosterone, nerve growth factor, and nitric oxide. The lumen potential was found to be particularly sensitive to citrate, prolactin, and testosterone.

CONCLUSION

It was concluded that the basal membrane potential of prostatic epithelial cells is associated with a relatively high Na(+):K(+) permeability ratio and metabolic dependence. The hormonal and pharmacologic sensitivity observed is consistent with the functional characteristics of the prostate gland.

Effects of the calcium antagonists diltiazem, verapamil and nitrendipine on the contractile responses of guinea-pig isolated ileum to electrical stimulation or carbachol

The effects of the organic Ca2+ antagonists nitrendipine, verapamil and diltiazem on the cholinergic contractile responses induced by field electrical stimulation or carbachol (0.1 microM) and on contractions evoked by high concentration KCl (30 mM) were studied in isolated preparations from the guinea-pig ileum. The three Ca2+ antagonists dose-dependently suppressed the contractile responses showing the same order of potency (nitrendipine greater than verapamil greater than diltiazem) with the three different types of stimulation. Comparison of the IC50 values of the Ca2+ antagonists for carbachol-, KCl- and electrically-evoked contractions demonstrated that the carbachol-evoked contractions were most sensitive to the inhibitory action of the antagonists tested. The presynaptic inhibitory effect of (Met)enkephalin (10 nM) on the electrically-evoked cholinergic contractions was only slightly potentiated by high concentrations (1 or 10 microM) of nitrendipine and diltiazem and remained unchanged by verapamil. The results suggest that the Ca2+ antagonists tested block mainly the carbachol-activated L-type Ca2+ channels on the smooth muscle cells, while the effects on the N-type Ca2+ channels are insignificant, except for the high concentrations of nitrendipine and diltiazem.

Psychopharmacological properties of calcium channel inhibitors

The previous decade has witnessed a major expansion of knowledge of the role played by voltage-sensitive calcium channels in the function of the central nervous system. Significant progress in the field has been made possible with the broadening use of organic calcium channel inhibitors (CCIs, Ca2+ antagonists), until recently considered almost exclusively as peripherally active antianginal and antiarrhythmic drugs. CCIs, however, do penetrate the blood-brain barrier from the periphery. Autoradiographic studies have established a highly heterogeneous distribution of CCI recognition sites within the brain. The existing evidence suggests that CCIs have marked psychotropic properties. The profile of their central activity is unique and spans a wide range of effects. Nevertheless, question regarding potentially confounding potent peripheral effects of these drugs remain. This paper reviews the psychopharmacology of CCIs, concentrating on preclinical data, but including supportive clinical and biochemical evidence as well. It focuses on these drugs' antidepressant, antidopaminergic (neuroleptic-like), anxiolytic and anticonvulsant effects. CCIs may also modify the reinforcing properties of some addictive drugs.

Long-term treatment with different calcium- and calmodulin-antagonists induces changes in rat brain alpha-adrenoceptors

1. The binding characteristics (Bmax and Kd) of the alpha-adrenoceptor radioligand [3H] WB4101 in crude membrane fraction (fraction P2) from cerebral cortex were 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-antagonist trifluoperazine (TFP) (3 mg/kg). 2. A significant reduction of the binding sites (Bmax) for [3H] WB4101 was established after the three Ca(2+)-antagonists as well as after TFP treatment. 3. Different changes in the affinity constant (Kd) of brain adrenoceptors were observed depending on the type of the Ca2+ or CaM-antagonist used: nifedipine did not change the Kd value, verapamil and TFP decreased whereas flunarizine increased the Kd value. 4. Relationships between Ca ions and alpha-adrenoceptor functions are suggested.

The long-term treatment with the Ca(2+)-antagonists nifedipine, verapamil, flunarizine and with the calmodulin antagonist trifluoperazine decreases the activity of 5-HT1 receptors in rat cerebral cortex and hippocampus

1. The binding activity of 5-HT1 receptors was studied in membrane fractions from the cerebral cortex and hippocampus of male Wistar rats treated orally for 13 days with the Ca(2+)-antagonists nifedipine (20 mg/kg), verapamil (50 mg/kg) and flunarizine (10 mg/kg) and with the calmodulin antagonist trifluoperazine (3 mg/kg). 2. The binding capacity and affinity of the 5-HT1 receptors in the cerebral cortex were significantly decreased after the treatment with the Ca(2+)-antagonists nifedipine, verapamil and flunarizine. The dissociation constant (Kd) was increased after the treatment with the calmodulin antagonist trifluoperazine. 3. In the hippocampus the 5-HT1 receptor affinity and number of binding sites were significantly reduced after the treatment with all four antagonists tested--nifedipine, verapamil, flunarizine and trifluoperazine, the Kd value being increased insignificantly after the flunarizine treatment. 4. The results obtained afford the suggestion that the reduction of 5-HT1 receptor activity is at least one of the results of the well known Ca(2+)-ions mediated automodulation of 5-HT release. The data confirm the view about the great importance of Ca(2+)-ions for the regulation of membrane neurotransmitter receptor activities.