Antidepressant and anxiolytic profiles of E-10-hydroxynortriptyline on electrocorticograms of rats

Electrocorticograms of rats were recorded after administration of increasing doses of the major metabolite of nortriptyline (NT), E-10-hydroxynortriptyline (E-10-OH-NT). The results were compared with those of NT administration. In visual as well as computerized evaluations, E-10-OH-NT demonstrated clear antidepressant properties, thus confirming previous experiments in depressed patients. There is some evidence that E-10-OH-NT also has an anxiolytic profile. The results with the parent drug NT were not so pronounced. Since E-10-OH-NT has been shown to be devoid of side effects when previously administered to humans, this substance is clearly to be considered of interest for potential development into a new antidepressant. Whether or not the anxiolytic profile is of clinical interest needs to be investigated further.

Classification of psychotropic drugs based on pharmaco-electrocorticographic studies in vigilance-controlled rats

The effects of a number of psycho-active drugs on electrocorticographic activity (ECoG) of the rat have been studied. Frontoparietal ECoG was recorded during 6-min periods immediately before drug/vehicle administration and starting at 20 and 45 min after administration. For each 6-min recording time, a mean power spectrum was calculated and smoothed. A quotient of the power at 20 and 45 min after and before drug, respectively, was then calculated. These quotients were used as input for an analysis of variance, followed by a t test and a normalization for the degrees of freedom, resulting in so-called n-profiles. Although each drug has its own characteristic n-profile, n-profiles of drugs belonging to the same clinical class have some characteristics in common. An automated classification system of psychotropic drugs, based on parameters extracted from n-profiles by discriminant analysis, is presented. For the antidepressant drug class the success rate of correct classification of antidepressant drugs is between 53 and 88%, for a neuroleptic drug in the neuroleptic drug class the success rate is 87%, for an anxiolytic drug in the anxiolytic drug class 100% and for a psychostimulant drug in the psychostimulant drug class between 86 and 100%. For a reliable classification of a drug about 10 n-profiles of active doses are needed. Using n-profiles, it appeared also possible to discriminate between antidepressant, neuroleptic, anxiolytic and psychostimulant drugs based on visual judgement. Moreover, visual evaluation of the n-profiles enables 4 subclasses to be recognized within the antidepressant class, 2 subclasses within the neuroleptic and 2 subclasses within the anxiolytic class.

Effects of depressant amino acids and antagonists on an in vitro spinal cord preparation from the adult rat

A mature sacrococcygeal in vitro spinal preparation from the rat has been used to demonstrate effects of neutral amino acids and their antagonists. gamma-Aminobutanoate (GABA), glycine and taurine (0.5-5 mM) produced dose-dependent depression of spontaneous paroxysmal activity generated in Mg2+ -free medium. The depressant effect of GABA was antagonised selectively by picrotoxin (25-50 microM) and the depressant effects of glycine and taurine were antagonised selectively by strychnine (0.2 microM). Glycine (0.5-5 mM) had a dose-dependent depolarizing action which was present at the central ends of isolated ventral roots. gamma-Aminobutanoate and taurine, had only weak depolarizing actions on ventral root fibres. Depolarizing responses to glycine showed a marked fading. Reduction in the fading appeared to be responsible for a paradoxical potentiation of glycine-induced depolarizations, which occurred in the presence of strychnine (0.2-2 microM). Strychnine (2-10 microM), picrotoxin (10-50 microM) or bicuculline (10 microM) had little or no effect on the amplitude, duration or latency of the monosynaptic component of ventral root reflexes evoked by supramaximal stimulation of dorsal roots (DR-VRP). However all three antagonists introduced slow, NMDA receptor mediated, components to these ventral root potentials. Picrotoxin and bicuculline, but not strychnine, reversibly depressed the dorsal root potential evoked from an adjacent dorsal root (DR-DRP). The depressant actions of 2-amino-5-phosphonopentanoate (AP5), kynurenate and 3-((+/-)-2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) revealed both NMDA and non-NMDA receptor mediated components in the dorsal root potential.

An in vitro mature spinal cord preparation from the rat

The preparation of an isolated hemisected spinal cord preparation, maintained in vitro, from mature (180-300 g body weight) rats is described. Sacral and coccygeal segments (S2-Co1) gave consistent ventral root reflexes (DR-VRP) from electrical stimulation of dorsal roots. The mean latency and amplitude of the fastest component in the ventral root reflex, at 25 degrees C, were 1.6 msec +/- 0.4 SE mean and 8.2 mV +/- 0.9 SE mean, respectively (28 preparations). This component was resistant to the NMDA antagonist, 2-amino-5-phosphonopentanoate (AP5) but was depressed markedly by kynurenate. A slow component of the ventral root reflex, which was sensitive to AP5 was enhanced and spontaneous AP5-sensitive synaptic potentials sensitive to AP5 appeared in the absence of magnesium ions. The excitant amino acids L-aspartate, L-glutamate, N-methyl-D-aspartate (NMDA), kainate and quisqualate produced dose-dependent depolarizing responses in the ventral roots. The relative depolarizing potencies +/- SE mean (N) of NMDA, kainate and quisqualate, relative to L-glutamate = 1, were 96 +/- 30 (6), 234 +/- 57 (6) and 145 +/- 40 (5), respectively. These properties, apart from reduced latency of synaptic responses, are similar to those described previously for preparations from immature animals. However, it will be easier with the mature preparation to selective activate high and low threshold primary afferents.

Classification of psychotropic drugs by rat EEG analysis: learning set development

EEG recordings from 5 different brain areas of freely moving rats were performed under controlled vigilance stage conditions. Effects of antidepressant and neuroleptic drugs were assessed following their intraperitoneal injection. Quantification of the drug effects was achieved by analysis of variance following on-line fast-Fourier transformation of the EEG signal. This resulted in so-called drug profiles. From the individual antidepressant and neuroleptic drug profiles, an antidepressant and neuroleptic drug class profile was calculated. Using the absolute power for the calculation of the antidepressant and neuroleptic drug class profiles gave a better discrimination between the two drug class profiles than using the relative power. The antidepressant and neuroleptic drug class profiles derived from the n. amygdala and hippocampus did not show significant differences. The antidepressant and neuroleptic drug class profiles showed significant differences (p less than 0.05) in rather small frequency bands from the n. caudatus (16-14 Hz), n. accumbens septum (19-24 and 27-31 Hz) and cortex (10-20 Hz).

Comparison of the (pro)convulsive properties of fluvoxamine and clovoxamine with eight other antidepressants in an animal model

Freely moving rats were implanted with cortical, caudal, thalamic, and reticular electrodes. Drugs were infused intravenously at a constant rate up to a final cumulative dose of 40, 50, or 60 mg/kg. Doses of 10 mg/kg imipramine, viloxazine, desmethylimipramine, mianserin, and maprotiline produced spike-wave complexes, spikes, and increased spindling. General sustained discharges occurred after 20 mg/kg of mianserin, viloxazine, imipramine, desmethylimipramine and amitriptyline, and after 30 mg/kg of maprotiline. An abnormal high-amplitude pattern was evident after mianserin, amitriptyline, imipramine, and desmethylimipramine. On the average, seizures were observed at 40 mg/kg and were seen after desmethylimipramine (50 mg/kg), mianserin (30 mg/kg), amitriptyline (20 mg/kg), imipramine (40 mg/kg), maprotiline (40 mg/kg), and zimelidine (50 mg/kg). Ranking the tested antidepressants in decreasing order in accordance with their relative (pro)convulsive properties gives: amitriptyline greater than mianserin much greater than imipramine greater than desmethylimipramine greater than viloxazine much greater than maprotiline much greater than zimelidine greater than clovoxamine greater than nomifensine = fluvoxamine.

Effects of antidepressants on the EEG of the rat

The aim of the study was to detect whether antidepressants cause specific EEG effects in rats. The results presented are based on quantitative evaluation of a series of 6-min vigilance-controlled EEG recordings in rats under standardized conditions. Standard conditions comprised: a vigilance control, a rigid test procedure in which drugs and rats are divided according to a Greek-Latin square, and the same electrode placement. Computer analyses are based on an analysis of variance for which the averaged power spectral values are used as input. The use of a moving window technique in this type of EEG studies is introduced in comparison to the well-known use of fixed frequency bands. A number of antidepressants have been tested and several common characteristics are found.