Synthesis of pyridylallylamines related to zimelidine and their inhibition of neuronal monoamine uptake.

Analogues of the antidepressant agent zimelidine [6, (Z)-3-(4-bromophenyl)-N,N-dimethyl-3-(3-pyridyl)allylamine], a selective inhibitor of neuronal 5-hydroxytryptamine reuptake, were synthesized by several routes with the aim of obtaining compounds having a cis configuration (with respect to pyridyl and allylamine). Two methods utilized suitably substituted benzoylpyridines as starting materials. In two other routes, the bromine in 6 was either directly displaced (CN) or converted via the corresponding lithio derivative to H, Cl, I, Me, SiMe3, and SMe. The configurations were determined by UV, 1H NMR, and lanthanide-induced shifts in 1H NMR. The compounds were evaluated as uptake inhibitors by measuring the accumulation of [3H]noradrenaline and 5-hydroxy[14C]tryptamine in mouse brain slices (in vitro and in vivo). Para substitution favored 5-hydroxytryptamine activity and ortho substitution favored NA activity in the cis series. The in vitro effect on 5-hydroxytryptamine was rather insensitive to variations in the para substituent, whereas pronounced effects in vivo were observed only with Cl, Br (6), and I.

The pharmacology of zimelidine: a 5-HT selective reuptake inhibitor.

Zimelidine (ZIM) and its main active metabolite norzimelidine (NZIM) have been shown to preferentially inhibit 5-hydroxytryptamine (5-HT) neuronal uptake both in vitro and in vivo while having much less effect on noradrenaline (NA) uptake. ZIM in vivo blocked the 5-HT uptake mechanism in the cerebral cortex, hippocampus, striatum, hypothalamus and spinal cord, thus indicating effects on both the ascending and descending 5-HT pathways. ZIM is devoid of a 5-HT releasing action, MAO-inhibitory properties and effects on dopamine (DA) uptake. ZIM failed to reduce NA turnover even in high doses, but markedly reduced 5-HT turnover in very low doses in the rat. ZIM also enhanced 5-HT mediated behaviours in mice in doses related to the inhibition of 5-HT uptake. In contrast to amitriptyline (AMI) and mianserin (MIAN), ZIM only in extremely high doses displayed a 5-HT receptor blocking action in vitro and failed to block 5-HT mediated behaviour. ZIM was practically devoid of action on histamine H1 and H2 receptors, and had also a neglible action on noradrenergic alpha 1- and alpha 2-receptors, and on beta-receptors. Unlike the tricyclic antidepressants (TAD's) ZIM had a negligible action on muscarinic receptors and failed to affect cholinergic induced activity. Long-term treatment with ZIM did not result in any attenuation of the 5-HT uptake blocking potency or the reduction of 5-HT turnover. This long-term treatment slightly reduced the number of beta-receptors in the brain. However, repeated ZIM-treatment induced a new 5-HT receptor binding site characterized by a low affinity and with a high number of binding sites and decreased the number of high affinity 5-HT receptor binding sites. Unlike the TAD's zimelidine failed to block the action of reserpine. Metabolic and behavioural interactions studies in mice showed that ZIM was devoid of any significant interactions with ethanol, barbiturates and benzodiazepines. It is concluded that ZIM markedly differs from both the TAD's and new antidepressants such as mianserin and nomifensine. ZIM seems preferentially to effect the presynaptic 5-HT reuptake mechanism while having a negligible action on noradrenergic, 5-HT, acetylcholine and histamine receptors in the brain.

Anti-aggressive effect of zimelidine in isolated mice.

The anti-aggressive actions of zimelidine, a 5-HT uptake inhibitor, and p-chloroamphetamine (PCA), a 5-HT releasing compound, were examined in isolated male mice. Both agents blocked the aggressive behaviour in a dose range in which they produced inhibition of the accumulation of 14C-5-HT in brain slices. The time course of the inhibition of both compounds was related to their effects on 5-HT mechanisms (5-HT uptake inhibition or 5-HT release) in the brain. These findings suggest that zimelidine and PCA inhibit aggressive behaviour in mice via enhancement of post-synaptic activity in certain 5-HT neuronal pathways. The possible relationship between the role of 5-HT in the anti-aggressive effect and in anxiolytic effects is discussed.

Inhibitors of neuronal monoamine uptake. 2. Selective inhibition of 5-hydroxytryptamine uptake by alpha-amino acid esters of phenethyl alcohols.

A series of alpha-amino acid esters of substituted phenethyl alcohols was prepared and tested as inhibitors of the neuronal reuptake of noradrenaline and 5-hydroxytryptamine. Some of the compounds are potent and very selective in blocking the 5-hydroxytryptamine uptake, as evidenced by biochemical data and behavioral tests. The most promising agent, alaproclate [2-(4-chlorophenyl)-1,1-dimethylethyl 2-aminopropanoate hydrochloride (I, IV)], was selected for further studies as a potential antidepressant agent. A discussion on structure--activity relationships (SAR) is given. In an attempt to explain the selective action on the mechanism of 5-hydroxytryptamine uptake by the new inhibitors, their structures are compared with those of the two neurotransmitters. From the tentative pharmacophore and conformations of transmitter (5-HT) and inhibitor (alaproclate) derived from SAR, a hypothetic carrier site for 5-HT uptake is deduced in terms of geometry and electronic properties.

Effect of (+)-amphetamine on the retention of 3H-catecholamines in slices of normal and reserpinized rat brain and heart.

The effect of reserpine on the inhibition by (+)-amphetamine and cocaine of the accumulation of 3H-dopamine (DA) in striatal slices and 3H-noradrenaline (NA) in slices of cerebral occipital cortex and heart atrium of rats and the release of 3H-amines from these tissues were examined. Reserpine (5 mg/kg intraperitoneally) was injected 18 hours before the experiments. It was found that reserpine markedly enhanced the in vitro potency of amphetamine in the striatum and heart but only slightly in the cortex. After administration in vivo (+)-amphetamine was about 10 time more potent in reducing the amine accumulation in the cortex as in the striatum. Reserpine enhanced the effect in both regions. The inhibitory potency of cocaine in vitro was unchanged by reserpine in the striatum but was reduced in the cortex and heart. Reserpine did not change the inhibitory potency of desipramine in the cortex and heart. The release of the 3H-amines by (+)-amphetamine was enhanced by reserpine in the striatum and heart but the small release produced in the cortex was not increased. The release produced by cocaine was similarly enhanced by reserpine but cocaine was much less active than (+)-amphetamine. The results indicate that (+)-amphetamine and cocaine inhibit the amine accumulation by different mechanisms.

Antidepressant agents. 9. 3,3-Diphenylcyclobutylamines, a new class of central stimulants.

3,3-Diphenylcyclobutylamine (4), N-methyl-3,3-diphenylcyclobutylamine (6), and N,N-dimethyl-3,3-diphenyl-cyclobutylamine (7) have been prepared and tested as potential antidepressant agents. The secondary (6) and tertiary (7) amines strongly decrease the accumulation of NA and 5-HT in brain slices in vitro and in vivo. The cyclobutylamines also cause motor stimulation. The most potent compound in this respect is the tertiary amine 7. The increase in locomotion is not blocked by pretreatment with phenoxybenzamine, methergoline, or alpha-methyltyrosine. Pretreatment with pimozide or reserpine reduces the hyperactivity induced by 7. This hyperstimulation seems to be caused by a mechanism of action which differs from that of amphetamine. 7 may cause increase in locomotion by release of dopamine from granular stores.

Tricyclic antidepressant agents. I. Comparison of the inhibition of the uptake of 3-H-noradrenaline and 14-C-5-hydroxytryptamine in slices and crude synaptosome preparations of the midbrain-hypothalamus region of the rat brain.

The simultaneous uptake of 3-H-l-noradrenaline (NA) and 14-C-5-hydroxytryptamine (5-HT) in slices from the midbrain-hypothalamus region of the rat brain was compared with the corresponding uptake in crude synaptosome preparations of the same brain region. In both preparations the uptake of the two amines was selective at the concentration used (1 times 10- minus 7 M or lower). The KM values for the amines (NA: 2 times 10- minus 7 M in synaptosomes and 5 times 10- minus 7 M in slices; 5-HT: 8 times 10- minus 8 M in synaptosomes and 6 times 10- minus 7 M in slices) and the inhibitory concentrations (IC50) of the antidepressant agents were lower in the synaptosome experiments than in the slices experiments. Moreover the order of the inhibitory activities differed between the two preparations. In the slices experiments the NA uptake was inhibited most markedly by desipramine followed by imipramine greater than chlorimipramine = nortriptyline greater than or equal to amitriptyline greater than or equal to chlordesipramine whereas in the synaptosome experiments the order was desipramine greater than nortriptyline greater than or equal to chlordesipramine greater than or equal to imipramine greater than amitriptyline greater than or equal to chlorimipramine. For the 5-HT uptake in slices the order of activity was: chlorimipramine greater than imipramine greater than or equal to amitriptyline greater than or equal to chlordesipramine = desipramine greater than or equal to nortriptyline whereas in the synaptosome preparations the order was: chlorimipramine greater than imipramine greater than or equal to amitriptyline greater than or equal to chlordesipramine greater than nortriptyline = desipramine. The role of protein binding and diffusion barriers in the causation of the difference in the results obtained with the two preparations is discussed.

Tricyclic antidepressant agents. II. Effect of oral administration on the uptake of 3-H-noradrenaline and 14-C-5-hydroxytryptamine in slices of the midbrain-hypothalamus region of the rat.

The inhibition of the simultaneous uptake of 3-H-l-noradrenaline (NA) and 14-C-5-hydroxytryptamine (5-HT) in slices of the midbrain-hypothalamus region of the rat brain after oral administration of desipramine, imipramine, nortriptyline, amitriptyline, chlordesipramine and chlorimipramine was determined. All compounds were more active in inhibiting the NA uptake than the 5-HT uptake. This difference was very marked for desipramine, imipramine, nortriptyline and chlordesipramine. Chlorimipramine was almost as active on the 5-HT uptake (ED50 = 35 mg/kg orally) as on the NA uptake (ED50 = 20mg/kg orally) and amitriptyline had low activity on both uptake mechanisms (ED50 greater than 50 mg/kg orally). Desipramine and imipramine were the most active compounds on the NA uptake (ED50 = 8 mg/kg orally for both compounds) and the duration of the action was very long. The ED50 values for nortriptyline and chlordesipramine in inhibiting the NA uptake were about 20 mg/kg orally for both compounds. The inhibition of the 5-HT uptake was less than 50% at 50 mg/kg orally for all compounds except for imipramine (ED50 = 50 mg/kg orally) and for chlorimipramine. The role of the biotransformation for the inhibitory activities of imipramine, chlorimipramine and amitriptyline was investigated in animals pre-treated with SKF 525 A. The inhibitory potency of imipramine was increased by the same factor for both uptake mechanisms probably due to the large increase in the concentration of imipramine in the rat brain, which was demonstrated after the administration of 14-C-imipramine. The inhibitory activity of chlorimipramine was somewhat more increased for the5-HT uptake than for the NA uptake. The low activity of amitriptyline seems to be mainly due to poor resorption, since pretreatment of the animals with SKF 525 A only slightly increased the potency whereas intraperitoneal injection of amitriptyline had a rather marked effect on the NA uptake (ED50 = 11 mg/kg intraperitoneally).