Bernard Beer

A simple and reliable conflict procedure for testing anti-anxiety agents.

The effects of three benzodiazepines (chlordiazepoxide, diazepam, and oxazepam), meprobamate, pentobarbital, d-amphetamine sulfate, magnesium pemoline, and scopolamine hydrobromide were studied with a simple conflict procedure in which thirsty naive rats were periodically administered shocks for licking water. The results indicated that this simple procedure clearly demonstrated “anti-anxiety” (i.e., increases in punished responding) effects with benzodiazepines, meprobamate and pentobarbital. Doses of d-amphetamine sulfate, magnesium pemoline, and scopolamine hydrobromide did not increase responding.

Some properties of brain specific benzodiazepine receptors: New evidence for multiple receptors

Several new lines of evidence suggest the existence of two or more distinct types of benzodiazepine receptors, in contrast to earlier results suggesting the presence of only one class of receptors. Appropriate thermoinactivation experiments indicate two receptors with different thermostabilities. Several triazolopyridazines, with some of the pharmacological properties of anxiolytics have recently been shown to displace 3H-diazepam and 3H-flunitrazepam with Ki values in the 6 to 100 nanomolar range. These new substances are active in conflict tests in rats and monkeys and prevent metrazol induced seizures in vivo, but strikingly lack the ataxia and sedative properties of the benzodiazepines. Hill analyses of dose-response curves for some of these substances yields Hill coefficients in the range of 0.4--0.6, suggesting that these compounds may be able to discriminate between several types of benzodiazepine receptors.

Resolution of two biochemically and pharmacologically distinct benzodiazepine receptors

Brain-specific binding sites have been isolated on synaptosomal membrane fragments which recognize pharmacologically active benzodiazepines (BDZs) and triazolopyridazines (TPZs). While early evidence indicated the existence of a single homogeneous class of BDZ binding sites, more recent biological and pharmacological studies support the notion of BDZ receptor multiplicity. We now propose that two biochemically distinct BDZ receptors exist in brain which are responsible for the mediation of different pharmacological activities. Type I BDZ receptors display a high affinity for both BDZs and TPZs, are not coupled to GABA receptors or to chloride ionophores, and are the sites which mediate anxiolytic actions. Type II BDZ receptors display a high affinity for BDZs, display a low affinity for TPZs, are coupled to GABA receptors and/or chloride ionophores, and are the sites which mediate pharmacological effects other than anxiolytic activity.

A synthetic non-benzodiazepine ligand for benzodiazepine receptors: a probe for investigating neuronal substrates of anxiety.

CL 218,872 is the first non-benzodiazepine to selectively displace brain specific 3H-diazepam binding with a potency comparable to that of the benzodiazepines. Like the benzodiazepines, CL 218,872 increased punished responding in a conflict situation and protected against the convulsions induced by pentylenetetrazole. These three pharmacological properties are highly predictive of anxiolytic activity. Unlike the benzodiazepines, however, CL 218,872 was relatively inactive in tests designed to measure effects on neuronal systems which utilize GABA, glycine and serotonin as transmitters. Furthmore, CL 218,872 was relatively free of the ataxic and depressant side effects commonly associated with the benzodiazepines. Because of this high degree of selectivity, CL 218,872 may represent a new probe for investigating neuronal substrates of anxiety.

Brain cholinergic dysfunction and memory in aged rats

Age related alterations in mnemonic ability and in the functional status of muscarinic receptors were evaluated and compared to biochemical measures of pre and post-synaptic cholinergic functioning. Retention of a single trial passive avoidance task was considerably disturbed as a function of aging. The functional status of muscarinic receptors, as measured by the ability of microiontophoretically applied acetylcholine to stimulate the firing of hippocampal pyramidal cells, was similarly disturbed in aged rats. A small, but significant decrease in muscarinic receptors was detected in the dorsal hippocampi of these same aged rats, while choline acetyltransferase activity did not change. When considered with prior psychopharmacological studies, these data suggest that specific muscarinic receptor impairments may play a critical role in the memory disturbances associated with old age.

Cyclic Adenosine Monophosphate Phosphodiesterase in Brain: Effect on Anxiety

Drugs that reduce anxiety may be mediated by cyclic adenosine monophosphate in the brain because (i) potent anxiety-reducing drugs are also potent inhibitors of brain phosphodiesterase activity; (ii) dibutyryl cyclic adenosine monophosphate has the ability to reduce anxiety; (iii) the methylxanthines show significant anxiety-reducing effects; (iv) theophylline and chlordiazepoxide produce additive anxiety-reducing activity; and (v) there is a significant correlation between the anxiety-reducing property of drugs and their ability to inhibit phosphodiesterase activity in the brain.

Age-related differences in behavior across the life span of the C57BL/6J mouse

C57Bl/6J mice, representing four divergent age groups (ranging from 3 months to 31 months) were each tested on a number of behavioral procedures, selected to sample a wide spectrum of behaviors. The evaluation demonstrated that, as with other mammalian species, not all behaviors in the mouse are affected by old age. Most severely impaired was retention of a single-trial passive avoidance task, most probably reflecting a deficit in memory ability. One tests of motor function, the most demanding tasks revealed the greatest debilitating effects of age, paralleling the effects of task difficulty previously reported in numerous learning studies. Finally, a deficit in the ability to modify preexisting habits in a T-maze learning situation was observed, corroborating reports of increased perseveration in aged humans and nonhuman primates. The similarity of these results across the life span of the C57 mouse with those previously reported for other aged mammalian species demonstrates that certain common types of behaviors seem to be impaired selectively by increased age across mammalian species and raises the possibility that common neurological etiologies may exist for these behavioral deficits.

Human brain receptor alterations in suicide victims

A comparison was made of human postmortem muscarinic-cholinergic, beta-adrenergic and serotonergic (presynaptic) recognition sites in cortical tissues derived from suicide and homicide (control) victims. An elevation of 47% and 35% in the suicide group compared to controls was observed in receptor ligand binding for 3H-quinuclidinyl benzilate (QNB, muscarinic antagonist) and 3H-imipramine (IMI, a presynaptic serotonin marker), respectively. In contrast, no appreciable differences in 3H-dihydroalprenolol (DHA, beta-adrenergic antagonist) binding were observed between the two groups. Additionally, tissues from both groups of subjects were analyzed for tricyclic antidepressive agent (TAD) content. High performance liquid chromatographic (HPLC) tissue analysis revealed no detectable levels of tricyclic agents with an assay sensitivity of 50 picograms/mg tissue. The results presented herein demonstrate neurotransmitter-receptor alterations in suicide subjects compared to homicide (control) victims. The attendant roles of serotonergic and muscarinic-cholinergic processes in the psychobiology of suicide and depression are addressed.

Antidepressant-like actions of DOV 21,947: a ''triple'' reuptake inhibitor

DOV 21,947 [(+)-1-(3,4-dichlorophenyl)-3-azabicyclo-[3.1.0]hexane hydrochloride] inhibits the reuptake of [3H]serotonin, [3H]norepinephrine, and [3H]dopamine in human embryonic kidney (HEK) 293 cells expressing the corresponding human recombinant transporters (IC(50) values of 12, 23, and 96 nM, respectively). This compound also inhibits [125I]RTI 55 (3beta-(4-iodophenyl)tropane-2beta-carboxylic acid methyl ester) binding to the corresponding transporter proteins in membranes prepared from these cells (K(i) values of 99, 262, and 213 nM, respectively). DOV 21,947 reduces the duration of immobility in the forced swim test (using rats) with an oral minimum effective dose of 5 mg/kg. This antidepressant-like effect manifests in the absence of significant increases in motor activity at doses of up to 20 mg/kg. DOV 21,947 also produces a dose-dependent reduction in immobility in the tail suspension test, with a minimum effective oral dose of 5 mg/kg. The ability of DOV 21,947 to inhibit the reuptake of three biogenic amines closely linked to the etiology of depression may result in a therapeutic profile different from antidepressants that inhibit the reuptake of serotonin and/or norepinephrine.

Memory Deficits in Aged Cebus Monkeys and Facilitation With Central Cholinomimetics

Cebus monkeys of 3 different age groups were trained to perform an automated behavioral task (delayed response), intended to measure recent memory ability. In in initial study, the aged monkeys (18 years and older) exhibit prprogressively greater performance impairments (relative to young monkeys) as they were required to remember the location of a visual stimulus for increasingly longer durations (0 to 20 sec). This deficits replicated previously published results from aged Rhesus monkeys and appeared similar to the primary memory deficits reported in elderly humans and demented patients. In subsequent studies, the effects of three different cholinomimetics were evaluated for their ability to improve the aged monkeys performance on this task. Each monkey was tested under several acute doses of the cholinergic precursor, choline, the anticholinesterase, physostigmine, and the cholinergic muscarinic receptor agonist, arecoline. The results revealed clear differences in the ability of these drugs to improve performance on this task. Choline exerted no apparent effects in the aged monkeys at any dose tested. Physostigmine clearly enhanced performance in certain aged monkeys, but the optimal dose varied dramatically between subjects, replicating previously published results with aged Rhesus monkeys and humans. Arecoline produced clear improvement within a restricted dose range, with little variation in optimal dose between subjects. In addition to demonstrating differences in the effects of different cholinomimetics on memory performance in aged primates, these data also suggest a possible rationale for future investigations. Assuming that each of these drugs primarily affected cholinergic function in the manner conventionally attributed, these data suggest that, within the cholinergic system, the more directly one stimulates the receptor, the more one might expect robust and consistent effects on memory performance in aged subjects.