Tricyclic antidepressants with dopamine

Adverse effects are similar to those seen with tricyclic antidepressants. Additionally, dopamine-related effects, such as akathisia, galactorrhea/amenorrhea. and Parkinson-like symptoms are seen. 

Cocaine and desipramine inhibit the reuptake of monoamine neurotransmitters whereas amphetamine, which is a phenylalkylamine - similar in structure to the catecholamines, see Fig. 4 - competes for uptake and more importantly, evokes efflux of the monoamine neurotransmitters. All of them exert antidepressant effects. Cocaine and amphetamine are addictive whereas tricyclic antidepressants and their modern successors are not. The corollaty of the addictive properties is interference with DAT activity. Blockade of DAT by cocaine or efflux elicited by amphetamine produces a psychostimulant effect despite the different mechanisms even the experienced individual can hardly discern their actions. Because of the risk associated with inhibiting DAT mediated dopamine clearance the antidepressant effects of psychostimulants has not been exploited. 

Noradrenaline transporters (NAT) are localized in the presynaptic plasma membrane of adrenergic nerve terminals. They belong to a family of proteins with 12 putative transmembrane proteins which are responsible for recycling of released neurotransmitters (noradrena-line/adrenaline, dopamine, serotonin, amino acid transmitters) back into the presynaptic nerve ending. Noradrenaline transporters can be blocked by a number of different antidepressant drags, including tricyclic antidepressants (e.g. desipramine) and selective noradrenaline reuptake inhibitors (e.g. reboxetine). 

Many neurotransmitters are inactivated by a combination of enzymic and non-enzymic methods. The monoamines - dopamine, noradrenaline and serotonin (5-HT) - are actively transported back from the synaptic cleft into the cytoplasm of the presynaptic neuron. This process utilises specialised proteins called transporters, or carriers. The monoamine binds to the transporter and is then carried across the plasma membrane it is thus transported back into the cellular cytoplasm. A number of psychotropic drugs selectively or non-selectively inhibit this reuptake process. They compete with the monoamines for the available binding sites on the transporter, so slowing the removal of the neurotransmitter from the synaptic cleft. The overall result is prolonged stimulation of the receptor. The tricyclic antidepressant imipramine inhibits the transport of both noradrenaline and 5-HT. While the selective noradrenaline reuptake inhibitor reboxetine and the selective serotonin reuptake inhibitor fluoxetine block the noradrenaline transporter (NAT) and serotonin transporter (SERT), respectively. Cocaine non-selectively blocks both the NAT and dopamine transporter (DAT) whereas the smoking cessation facilitator and antidepressant bupropion is a more selective DAT inhibitor. 

The atypical tricyclic antidepressant amineptine (Survector) is an indirect dopamine agonist, which selectively inhibits dopamine uptake and induces its release, with additional stimulation of the adrenergic system. Its antidepressant effects are similar to those of other tricyclic antidepressant drugs. However, it acts more rapidly, is better... 

Another tricyclic antidepressant, amineptine (104), acting essentially by inhibition of dopamine uptake, differs from the other drugs by its aminohepta-noic side-chain. After oral administration to rat, dog or human, the main metabolites were acids with shortened C5 and C3 side-chains (105, 106), together with the corresponding 10-hydroxylated derivatives, the relative and absolute... 

A growing number of drugs are used that affect the many neurotransmitters in the brain benzodiazepines and others act on GABAergic transmission antidepressants, such as monoamine oxidase inhibitors and tricyclic antidepressants, are thought to increase the concentration of transmitter amines in the brain and so elevate mood—these will also act at peripheral nerve terminals, so interactions with them are a combination of peripheral and central actions. Levodopa (L-dopa) increases central as well as peripheral dopamine, and the newer class of psychoactive drugs, the selective serotonin reuptake inhibitors (SSRIs) of which the ubiquitous fluoxetine (Prozac) is best known, act in a similar way on serotonergic pathways. 

Levodopa or dopamine agonists produce diverse dyskinesias as a dose-related phenomenon in patients with Parkinson s disease dose reduction reverses them. Chorea may also develop in patients receiving phenytoin, carbamazepine, amphetamines, lithium, and oral contraceptives, and it resolves with discontinuance of the offending medication. Dystonia has resulted from administration of dopaminergic agents, lithium, serotonin reuptake inhibitors, carbamazepine, and metoclopramide and postural tremor from theophylline, caffeine, lithium, valproic acid, thyroid hormone, tricyclic antidepressants, and isoproterenol. 

Rasagiline Inhibits MAO-B selectively, higher doses also inhibit MAO-A Increases dopamine stores in neurons may have neuroprotective effects Parkinson s disease adjunctive to levodopa smooths levodopa response Oral Toxicity interactions may cause serotonin syndrome with meperidine, and theoretically also with selective serotonin reuptake inhibitors, tricyclic antidepressants... 

Clomipramine has also aroused interest because of an action on prolactin release, which occurs with major tranquillizers but not with other tricyclic antidepressants (289). This action of clomipramine is related to its chemical structure and reflects a greater effect on dopamine metabolism and serotonin uptake compared with other antidepressants. 

Correct answer = D. MAO inhibitors and aspirin can be taken concurrently. Hypertensive crisis may result from use (concurrently or within 2 weeks) of MAO inhibitors and indirect sympathomimetic amines, such as ephedrine. Concomitant use of MAO inhibitors and tricyclic antidepressants may result in mutual enhancement of effects with the possibility of hyperpyrexia, hypertension, seizures and death. Tyramine-containing foods, such as aged cheeses and beer, may precipitate a hypertensive crisis because of the accumulation and release of stored catecholamines from nerve endings. MAO inhibitors may lead to an exaggerated response to dopamine. 

The neuroleptic malignant syndrome, which is classically associated with antipsychotic drugs and is usually attributed to excessive dopamine D2 receptor blockade, can rarely occur with other medications, including tricyclic antidepressants. 

Amineptine is a tricyclic antidepressant that selectively reduces the dopamine reuptake without affecting the uptake of noradrenaline or serotonin (5-HT) (1). In vivo, it increases striatal homovanillic acid concentrations without affecting the concentrations of other metabolites of dopamine, 3,4,dihydroxyphenylacetic acid (DOPAC) and 3-methoxytyramine. However, high doses of amineptine reduced the extracellular DOPAC concentration in the nucleus accumbens but not in the striatum. Long-term treatment with amineptine causes down-regulation of beta-adrenoceptors. 

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