Differential effects of an anxiogenic beta-carboline on single unit activity in the locus coeruleus and substantia nigra of the rat brain

Eye movement effects of diazepam in sons of alcoholic fathers and male control subjects

Both animal and human studies suggest that the GABA-benzodiazepine receptor complex may be involved in the acute effects of ethanol, as well as the development of tolerance and dependence with chronic ethanol use. The current study was performed to assess sensitivity to benzodiazepines, and thus the functional sensitivity of the GABA-benzodiazepine receptor system, in subjects at high risk for alcoholism. Sons of alcoholic fathers (SOAs; n = 27) were compared with male controls without a family history of alcoholism (n = 23) in response to diazepam versus placebo. SOAs and controls received four logarithmically increasing doses of intravenous diazepam or placebo in randomized order on 2 days at least 1 week apart. Effects of diazepam were assessed using two eye movement tasks, peak saccadic eye movement velocity, and average smooth pursuit eye movement gain, which provide reliable, quantitative measures of benzodiazepine effects. In addition, memory, self-rated sedation, and pleasurable drug effects were measured. In comparison with control subjects, SOAs displayed significantly less diazepam effects on peak saccade velocity, average smooth pursuit gain, memory, and self-rated sedation, but significantly greater pleasurable drug effects. Differences in response to diazepam between SOAs and male controls may reflect altered functional sensitivity of the central GABA-benzodiazepine receptor system or a more general difference between groups in the effects of CNS active or sedating drugs.

Personality and benzodiazepine sensitivity in anxious patients and control subjects

Cloninger has recently proposed a model of personality variability that is based on three independent heritable traits of harm avoidance, novelty seeking, and reward dependence, each of which is thought to be mediated by a separate neurochemical and neuroanatomic mechanism. The current study tested hypotheses generated on the basis of this theory in anxious patients and control subjects. Eighteen patients with panic disorder, 12 patients with generalized anxiety disorder, and 21 control subjects underwent both personality testing and assessment of their sensitivity to diazepam, as measured by slowing of saccadic eye movement velocity. As expected, anxious patients displayed higher harm avoidance scores than controls. Although an inverse correlation between harm avoidance and benzodiazepine sensitivity was predicted, no relationship between these variables was found in any diagnostic group. However, a significant correlation was found between novelty-seeking scores and sensitivity to diazepam. This finding, although not predicted by Cloninger's theory, is consistent with prior preclinical and human studies.

Benzodiazepines preferentially affect mesolimbic dopamine turnover in rats

Withdrawal of benzodiazepines in man may induce hallucinatory symptoms and can evoke delusional depressions, which can be treated with dopamine-antagonistic drugs. Withdrawal of benzodiazepines in rats induces a strong hyperactivity during daytime, leaving the nighttime activity relatively undisturbed. This hyperactivity may be related to an enhanced dopaminergic activity in the mesolimbic area, especially in the nucleus accumbens. Mesolimbic dopaminergic activity may be specifically involved in the development of benzodiazepine withdrawal. Acute administration of benzodiazepines in otherwise non-treated rats, has been described not to affect the dopamine-turnover in the nucleus accumbens, measured by synthesis inhibition. However, activation by administration of haloperidol (feedback activation) can be suppressed by benzodiazepines effectively. Five different benzodiazepines viz. desmethyldiazepam (DMD), lorazepam (LRZ), brotizolam (BTZ), triazolam (TRZ) and flunitrazepam (FNZ) have been compared with respect to their acute effects. Using a 3-fold increase in dopamine turnover (determined by measuring the DOPAC-concentration), benzodiazepines were capable to reduce this increase maximally for 70-80% in the nucleus accumbens. The results point to a selective effect of benzodiazepines in the nucleus accumbens. The increase induced by haloperidol in the corpus striatum was found to be much less sensitive to benzodiazepines. In contrast to the other compounds lorazepam appeared to have no effect on haloperidol-induced increase in DOPAC concentration. Flunitrazepam and brotizolam did affect not only the haloperidol-induced DOPAC increase but also the basal DOPAC concentrations. Linear dose-response curves could not be obtained for the compounds, but minimal effective doses could be assessed. Flunitrazepam and triazolam appeared to be the most active compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Response to diazepam in sons of alcoholics

Alcohol exerts several of its actions via the chloride channel associated with the central GABA-benzodiazepine receptor complex. To explore a possible role for this receptor complex in risk for alcoholism, and to determine whether risk for alcoholism is associated with risk for benzodiazepine abuse, the authors administered intravenous diazepam to 18 sons of male alcoholics (SOAs) and 18 control subjects. Four logarithmically increasing doses of diazepam and matched volumes of placebo were given in randomized order on separate days about 1 week apart. SOAs were significantly more likely than controls to report euphoric responses to diazepam. At some diazepam doses, SOAs were more likely to report feeling "high" and "intoxicated." SOAs and controls did not differ in feeling "drugged." SOAs and controls may differ in expectations regarding the subjective effects of drugs and/or in the function of the central GABA-benzodiazepine receptor complex. These findings also add further evidence for increased pleasurable effects, and thus possibly increased risk for benzodiazepine abuse, in a subgroup of SOAs.

Behavioral, biochemical, and cardiovascular responses to the benzodiazepine receptor antagonist flumazenil in panic disorder

To evaluate the possibility that abnormal regulation of benzodiazepine receptor (BZR) function may relate to the pathophysiology of anxiety disorders, two doses of the BZR antagonist flumazenil (Ro 15-1788) and placebo were administered to panic disorder patients in a double-blind, randomized, crossover design. All 11 patients received flumazenil (600 mg). Ten of the 11 also received flumazenil (200 mg), and 8 of the 11 were given matching placebo capsules orally on separate test days. Neither dose of flumazenil showed significant anxiolytic effects or significantly altered heart rate, blood pressure, or levels of plasma cortisol or 3-methoxy-4-hydroxyphenylglycol in comparison to placebo. On 200 mg days, anxiety ratings on a visual analog scale significantly increased compared to placebo at 30 min and then returned to baseline levels. Panic attacks occurred on placebo, 200 mg, and 600 mg days in 0/8, 4/10, and 0/11, respectively. Failure to observe anxiolytic effects suggests that flumazenil at these doses does not antagonize a tonic increased interaction of BZRs with an endogenous BZR inverse agonist in panic patients.

Substantia nigra: a site of action of muscle relaxant drugs

Sites of action of centrally active muscle relaxant drugs are not well defined. Clinical experience with such drugs suggests that the spinal cord may be one of the important regions from which pathologically increased muscle tone may be relieved. Supraspinal centers that may also be involved in the expression of muscle relaxant action have not yet been defined. We report here that microinjections of therapeutically relevant muscle relaxants into the midbrain tegmentum of genetically spastic rats decrease muscle tone. The substantia nigra is the region from which midazolam, baclofen, and tizanidine (drugs used clinically in the treatment of spasticity), or gamma-vinyl-GABA, (-)-2-amino-7-phosphonoheptanoate, and [D-pro2-D-phe7-D-trp9]-substance P (experimental drugs active in animal models of spasticity), reduce muscle tone in genetically spastic rats and Hoffmann reflexes in normal rats. The effects of muscle relaxant drugs are topographically restricted to the substantia nigra pars reticulata and are receptor specific. These observations disclose a previously unknown function of the substantia nigra in mediating muscle relaxation.

Tolerance to diazepam and methyl-beta-carboline-3-carboxylate measured in substantia nigra of benzodiazepine tolerant rats

The spontaneous activity of neurons in the pars reticulata of substantia nigra (SNpr) was studied in chloral hydrate anesthetized rats. As a function of dose, intravenous diazepam decreased, and methyl-beta-carboline-3-carboxylate (beta CCM) increased discharge frequency. Two days after terminating a one week treatment with flurazepam (FZP), both diazepam and beta CCM showed decreased ability to alter SNpr neuronal activity. Neither residual FZP nor down-regulation of benzodiazepine receptors can account for these results. In contrast, behavioral testing revealed no change in the ability of i.v. beta CCM to cause convulsions, suggesting that sites other than the SNpr are of prime importance in expressing the convulsant actions of systemically injected beta CCM.