Assessment of noradrenaline and 5-hydroxytryptamine uptake in intact rat brain

Role of central serotonin and noradrenaline interactions in the antidepressants' action: Electrophysiological and neurochemical evidence

The development of antidepressant drugs, in the last 6 decades, has been associated with theories based on a deficiency of serotonin (5-HT) and/or noradrenaline (NA) systems. Although the pathophysiology of major depression (MD) is not fully understood, numerous investigations have suggested that treatments with various classes of antidepressant drugs may lead to an enhanced 5-HT and/or adapted NA neurotransmissions. In this review, particular morpho-physiological aspects of these systems are first considered. Second, principal features of central 5-HT/NA interactions are examined. In this regard, the effects of the acute and sustained antidepressant administrations on these systems are discussed. Finally, future directions including novel therapeutic strategies are proposed.

Clomipramine induces the opening of Na+ channels in the frog skin epithelium

This paper studies the effect of clomipramine on the electrical parameters of the frog skin epithelium. We have found that clomipramine induces: 1) an increase in short circuit current that is equivalent to an increase in net Na+ flux, 2) an increase in total transepithelial conductance, 3) a depolarisation of the apical barrier, and 4) a decrease in the fractional resistance of the apical membrane. These results suggest that clomipramine promotes an increase in the sodium permeability of the apical barrier by increasing either the concentration of amiloride-sensitive Na+ channels or by increasing their individual conductance. Using kinetic models, values for the affinity constants for clomipramine and amiloride were estimated (K(Clo)=(18.l +/- l.04) x l0(-6) M; K(Amil) = 56 x 10(-8) M). Identical studies were performed for eel intestinal epithelium and no significant changes on the short circuit current were observed.

Beta 2- but not beta 1-adrenoceptors are involved in desipramine enhancement of aggressive behavior in long-term isolated mice

The effects of several beta-adrenoceptor antagonists on the desipramine-induced increase in aggressive behavior in long-term isolated mice were examined. Desipramine HCl (10 mg/kg, IP) significantly increased the duration of aggressive behavior in isolated mice but did not significantly change the latency to the first attack consistent with our previous reports. Intraperitoneal administration of (+/- )propranolol HCl (2.5-10 mg/kg), a nonselective beta-adrenoceptor antagonist, dose dependently attenuated the desipramine-induced enhancement of aggressive behavior without significantly affecting the basal aggressive responses. ICI118,551 HCl (1.25-5 mg/kg, IP), a selective beta 2-adrenoceptor antagonist, also blocked the desipramine-induced enhancement of aggressive behavior in a dose-dependent manner, whereas metoprolol tartrate (5-20 mg/kg, IP), a selective beta 1-adrenoceptor antagonist, did not affect it. Moreover, clenbuterol HCl (0.1-0.5 mg/kg, IP), a lipophilic beta 2-adrenoceptor agonist, significantly increased the duration of basal aggressive behavior. Taken together with our previous finding that the desipramine-induced enhancement of aggressive behavior can be blocked by yohimbine, an alpha 2-adrenoceptor antagonist, the present results indicate that not only alpha 2- but also beta 2-adrenoceptor stimulation plays important roles in modulation of aggressive behavior in long-term isolated mice.

Biphasic effects of typical antidepressants and mianserin, an atypical antidepressant, on aggressive behavior in socially isolated mice

Effects of several typical antidepressants and of an atypical antidepressant, mianserin, on the aggressive behavior (AGB) in long-term isolated mice were examined. IP administration of maprotiline (2.5 and 5 mg/kg), amitriptyline (5 and 10 mg/kg), clomipramine (2.5 and 5 mg/kg), and mianserin (5 mg/kg) significantly increased the duration of AGB. However, at higher doses (maprotiline, 10 mg/kg; amitriptyline, 20 mg/kg; clomipramine, 10 and 20 mg/kg; mianserin, 10 and 20 mg/kg) these antidepressants either did not affect AGB or inhibited it. Amitriptyline (20 mg/kg) and mianserin (10 mg/kg) but not maprotiline (10 mg/kg) or clomipramine (20 mg/kg) decreased spontaneous motor activity in isolated mice. Yohimbine (0.5 mg/kg, IP), an alpha 2-antagonist, changed the antidepressant-induced enhancement of AGB into inhibition without affecting the basal aggressive responses. Prazosin (0.3 mg/kg, IP), an alpha 1-antagonist, did not affect either maprotiline- or clomipramine-induced enhancement of AGB, but it changed the mianserin-induced enhancement of AGB into inhibition. These results indicate that antidepressants that inhibit noradrenaline uptake and/or stimulate noradrenaline output from nerve terminals have biphasic effects on AGB in isolated mice and that the antidepressant-induced enhancement of AGB is mediated by noradrenergic stimulation of alpha 2-adrenoceptors, whereas the antidepressant-induced inhibition of AGB may be mediated by non-alpha 2-adrenoceptors or by nonadrenergic system(s).

The influence of brain catecholamines on 'drug taking behaviour' relative to oral self-administration of d-amphetamine by rats

Oral administration of 5 mg/kg of d-amphetamine to adult Wistar rats caused brain NE to decrease to approx. 80% of the control level during 4-24 h after acute treatment and slowly further to 65% after 24 days of self-administration via drinking water. The norepinephrine (NE)-reducing effect was first recognized at 1 mg/kg and appeared to peak at 5 mg/kg of d-amphetamine. Brain dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were only shortly affected. Neither iprindole nor desipramine altered the effect of amphetamine on brain NE. DA was decreased by both inhibitors depending on the duration of pre-treatment. Iproniazid and alpha-methyl-p-tyrosine antagonized and potentiated respectively the amphetamine effect on NE- and DA-concentration after 4 days of simultaneous treatment. In the free choice experiment (water vs. 0.005% d-amphetamine solution) rats developed an aversion to amphetamine. The number of rats taking the drug and the consumption by rats still drinking it declined gradually from 100% and approx. 3 mg/kg/day to 50% and approx. 1.5 mg/kg/day, respectively, during 18 days. The time course of the developing aversive reaction to oral amphetamine ran approximately parallel to that of NE-depletion. Iprindole and desipramine intensified, iproniazid and propranolol weakened, while alpha-methyl-p-tyrosine and haloperidol hardly influenced the aversive effect of amphetamine. It is concluded that the development of aversive behaviour in response to oral d-amphetamine is mediated not only through the depleting effect of amphetamine on NE stores but also by its direct stimulation at beta-adrenergic receptors in the CNS.

Deltamethrin-induced changes in synaptosomal transport of 3H-epinephrine in the squid optic lobes

In fresh synaptosomal preparation from the squid optic lobe 3H-epinephrine transport was significantly affected by deltamethrin at greater than 10(-9) M. Under the experimental conditions such an effect of deltamethrin manifested as either a reduction (at nondepolarized state) or an increase (at depolarized state) in the final level of 3H-epinephrine accumulated in the synaptosomes. Only a part of such a deltamethrin effect was due to its effect on the sodium channel. The remainder of the deltamethrin effect was strongly influenced by agents or treatments which are known to influence internal Ca2+ concentration, suggesting a possible involvement of Ca2+ regulatory mechanisms in the process of stimulation of transmitter release by deltamethrin.