Effects of the amygdalo-hippocampal evoked potential in the cat of four benzodiazepines and some other psychotropic drugs

Effect of antianxiety drugs on fear and stress

This paper, on the use of antianxiety drugs to relieve certain neurotic symptoms, involves decision making at the level of the individual organism. The words "anxiety," "fear," and "stress" are often used interchangeably in everyday English. In medical usage "anxiety" denotes a state caused by an internal danger, while "fear" is a response to an external danger. "Stress" is the sum total of the bodily responses which occur when the organism has to adapt to a change. The antianxiety tranquilizers relieve anxiety and certain other neurotic symptoms, but do not counteract stress, fear, or anxiety caused by schizophrenia and other psychiatric disorders. The antianxiety drugs are now being most frequently prescribed for the relief and prevention of emotional distress that might accompany a physical disorder. Somatic illness can cause stress and fear, but does not usually induce neurotic anxiety. In patients suffering from physical disorders, treatment with antianxiety drugs appears justified only in the presence of an underlying psychoneurotic condition.

Central actions of benzodiazepines: general introduction

After a brief review of the characteristic somatic and psychotropic effects of benzodiazepines evidence is presented which supports a specific facilitatory action of these drugs on GABA ergic synapses within the mammalian central nervous system. Benzodiazepines enhance presynaptic inhibition in the spinal cord and dorsal column nuclei as well as postsynaptic inhibition in dorsal column nuclei, hippocampus, hypothalamus, cerebral cortex, cerebellar cortex, which are all examples of recurrent and collateral inhibition mediated by GABA ergic intrinsic neurones. In addition, the compounds also enhance the inhibitory effect of GABA ergic long projection neurones in the substantia nigra and the lateral vestibular nucleus of Deiters. Several problems remain to be solved, such as the exact site at which benzodiazepines initiate their action (pre-synaptically at GABA ergic nerve endings or postsynaptically at the target cells) and the possible existence of endogenous ligands for the benzodiazepine receptor. Some suspected implications which studies on benzodiazepine binding sites could have for a deeper understanding of the mode of action of these drugs are discussed.

Effects of benzodiazepines and pentobarbital on the evoked potentials in the cat brain

The sites of action of benzodiazepines, diazepam and ID-540 [7-chloro-5-(o-fluorophenyl)-1-methyl-1,3-dihydro-2H-1,4-benzodiazepin-2-one) on the central nervous system were examined and compared with those of pentobarbital using evoked potentials recorded on the limbic system and hypothalamus in the cat brain. Benzodiazepines affected the various neuronal connections of the intra-limbic, limbic-hypothalamic and midbrain-limbic systems; especially the amygdala (AMYG)-, ventromedial hypothalamus (VMH)- and central gray matter (SGC)-hippocampal (HIPP) evoked potentials were attenuated, whereas the AMYG-VMH, VMH-AMYG and the septum (SP)-VMH evoked potentials were facilitated. Pentobarbital selectively attenuated the SGC-, VMH- and AMYG-HIPP evoked potentials, or facilitated the VMH-AMYG and the SP-HIPP evoked potentials. Both benzodiazepines and pentobarbital affected three afferent hippocampal neuronal connections, areas of the reticulo-hypothalamic systems regulating hippocampal activity, while only benzodiazepines affected the neuronal influence of the amygdaloid and septal areas on the hypothalamus.

Changes in excitability of amygdaloid and septal nuclei induced by medazepam hydrochloride

Electrical stimulations of the central and basolateral part of the amygdaloid complex and of the septum in freely moving cats elicit changes in arterial pressure (i.e., an increase in pressure during stimulation of the central part of the amygdala, and a decrease followed by an increase during stimulation of the basolateral part of the amygdala and of the septum). These changes within the cardiovascular system are followed by rage reactions when the central part of the amygdala is stimulated, defense patterns when the basolateral part of the amygdala is stimulated, and pitiful mewing as a result of septal stimulation. Medazepam hydrochloride in a dose of approximately 15 mg/kg i.v. given over a period of 3 h, in order to maintain constant blood levels of the drug, attenuated slightly the cardiovascular reactions and elevated markedly the thresholds for psychomotoric behavior. The latencies between the onset of electrical stimulation and the beginning of the increase in arterial pressure were only slightly increased, whereas the latencies for spychomotoric behavior were markedly prolonged due to drug application. The data support the view that medazepam hydrochloride exerts depressant effects on the limbic-hypothalamic level with respect to psychomotoric responses. The effect was not identical for all nuclei tested. The basolateral part of the amygdala was significantly less sensitive to medazepam hydrochloride than the central part of the amygdala.