Antisense knockdown of the Shaker-like Kv1.1 gene abolishes the central stimulatory effects of amphetamines in mice and rats.

Amphetamine (AMPH) is an indirect sympathomimetic compound classified as a substrate-type releaser that distinguishes it from other stimulants that act as uptake 1 blockers, such as cocaine (COC). In mammals, AMPH elicits central stimulation, hypermotility, anorexia, analgesia and analeptic activity, mainly through the increase of extracellular brain dopamine (DA). The inversion of vesicular transporters and/or intravesicular alkalinization is assumed to have a role in AMPH-induced exocytosis. However, the action mechanism of this compound has not yet been completely clarified. Recent evidence on the action of AMPHs indicates potassium channel-blocking properties in peripheral tissues. We investigated the possible involvement of a Shaker-like Kv1.1 channel subtype in the central effects of AMPH, using an antisense oligodeoxyribonucleotide (aODN) that specifically and reversibly inhibits the expression of these channels in the brain. The effect of aODN pretreatments was studied by evaluating the modification of behavioral effects induced in mice through the intracerebroventricular administration of AMPH, COC, or other compounds. The aODN in mice almost completely blocked the stimulatory effects of AMPH and other releasers but was ineffective in reducing the central activity of COC. In aODN-pretreated rats a strong reduction of the AMPH, but not of the COC-stimulated DA efflux from nucleus accumbens was observed. Our results suggest that the stimulant effects of AMPH and chemically related compounds, but not COC, require the presence of functionally active Kv1.1 channels in the brain.     

The Risk of Myocardial Infarction Associated with Antihypertensive Drug Treatment in Persons with Uncomplicated Essential Hypertension

We conducted a case-control study based on computer-recorded information accrued in the United Kingdom General Practice Research Database to assess and compare the relation between different antihypertensive drug therapies and myocardial infarction in patients with no known clinical or laboratory risk factors for myocardial infarction other than hypertension. Cases were treated hypertensive patients with no other known risk factors who developed a first acute myocardial infarction between January 1, 1993, and October 31, 1994. They were ascertained from a review of the clinical record together with a questionnaire filled out by the attending general practitioner. Controls were matched to each case for age, sex, general practice, and index date. Antihypertensive therapy was derived from the computerized patient record. The study consisted of 210 cases and 793 controls. Compared with users of β-blockers alone, the adjusted relative risk (RR) estimates for all other treatment regimens were close to 1.0. A comparison of users of calcium channel blockers alone with users of β-blockers alone yielded a RR estimate of 0.9 (95% CI 0.5, 1.7). We conclude that the risk of acute myocardial infarction in otherwise healthy, treated hypertensive patients is not materially associated with the particular drug they receive.     

dCTP misincorporation in a Chinese hamster mutator phenotype: the role of GGA genetic context

Clone CSA7 is a CHEF18 hamster cell line that shows an increasedintracellular accumulation of dCTP. To localize the mutationsthat accumulate spontaneously in a functional gene of such amutator phenotype, independent CSA7 mutants of the hypoxanthine–guaninephosphoribosyl transferase (hprt) gene were isolated and screenedby a polymerase chain reaction–single strand conformationpolymorphism technique. Sixty-two percent of mutants produceddetectable changes of the strand migration profile and the mutationswere preferentially localized in the exons 3 (31%) and 6 (62%).The sequencing of such exons revealed that the rate of C baseincorporation was the major mutation pathway and that the Abase of a GGA sequence was the preferential site of misincorporation. ³To whom correspondence should be addressed     

Desensitization of AMPA Receptors Limits the Amplitude of EPSPs and the Excitability of Motoneurons of the Rat Isolated Spinal Cord

Intracellular recording was used to study the effect of cyclothiazide, a selective blocker of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor desensitization, on lumbar motoneurons of the rat isolated spinal cord. Cyclothiazide (25 μM) enhanced the responses to AMPA in a tetrodotoxin-insensitive fashion, without affecting those produced by N -methyl-D-aspartate or γ-aminobutyric acid. Excitatory postsynaptic potentials (EPSPs) evoked by dorsal root stimulation were strongly potentiated in amplitude while paired-pulse depression (produced by applying pairs of pulses at 2 s interval) of the EPSP was decreased. In the presence of cyclothiazide the frequency of spontaneous synaptic events was greatly increased and network-driven bursting activity developed with eventual loss of electrical excitability. The present results suggest that pharmacological block of AMPA receptor desensitization led to strong excitation of motoneurons and indicate a physiological role of desensitization in protecting these nerve cells from overactivity.     

Dopamine receptors on human T- and B-lymphocytes

The presence of functional dopamine receptors on differentiated cells of the mammalian immune system is still under discussion. This study has utilized (-)-[³H]sulpride as a ligand to detect the presence of recognition sites of the dopamine D₂ receptor family on human T- and B-lymphocytes. The (-)-[³H]sulpiride binding was of high affinity (K_d 0.9 nM ± 0.2 nM, specific, saturable (B_max 10.2 ± 1.4 fmol/10⁶ cells) and reversible. The pharmacological characterization of the recognition site suggests, similarities mainly with the D₂ and D₄ rather than D₃ subtype of dopamine receptor. Furthermore, dopamine treatment was able to reduce the intracellular cAMP levels of lymphocytes stimulated with forskolin, thus suggesting a potential functional significance of this dopamine receptor in mediating neural-immune interactions.     

An evaluation of Tourette Syndrome and medication use in Canada

Self-report data were gathered from a national sample of over 200 Canadian Tourette Syndrome (TS) patients. Information regarding symptom severity both on and off medication was gathered along with an analysis of different medications in use, and patient ratings of effectiveness of those medications. Patients also rated their own mental health. Results indicated that approximately 60% of TS patients take some form of medication for relief from their symptoms. Of these, over 80% reported that symptoms are less severe when medicated. The most commonly prescribed medications in order of popularity are haloperidol, pimozide, clonidine and benztropine mesylate (Cogentin). Patient ratings of effectiveness of these medications places haloperidol first, pimozide second and clonidine third although all were found to be "somewhat" to "very" effective. Of those TS patients on medications, 50% rated their own mental health as good to excellent and 50% rated it as fair to poor.     

The potential role of lonidamine (LND) in the treatment of malignant glioma

Summary Up-to-date unsatisfactory results obtained in multimodality treatments of malignant glioma have prompted the research of new therapeutic modalities with unconventional modes of action. Lonidamine (LND) is a drug which reduces aerobic glycolytic activity in both human and experimental tumors. This effect mainly depends on the inhibition of mitochondrially-bound hexokinase (HK) which is present in large amounts in malignant cells. A Phase II study was conducted on patients with recurrent glioma; 12 patients were admitted to the study. Clinical side effects were moderate, necessitating a reduction of the dosage in only 1 case. The objective results were evaluated according to the indications of Levin. 2 responders and 3 cases of stable disease were observed out of 10 evaluable patients. The potential value of this new drug is discussed.