Different central mediation of the stimulant effects of amphetamine and its p-chloro analogue

p-Chloroamphetamine (PCA) suppresses ingestive behavior in male rats

Ingestive behavior was activated in male rats by intraoral intake and intake from a bottle of 1-M solution of sucrose. Intraperitoneal injection of p-chloroamphetamine (PCA), releasing central 5-hydroxytryptamine (5-HT) from serotonergic nerve terminals, inhibited ingestion of the sucrose solution. Significant inhibition of sucrose intake by PCA was observed at 1.25 and 2.5 mg/kg dose in a bottle intake test, and at 5.0 mg/kg dose in an intraoral intake test. These findings suggested that 1.25 and 5.0 mg/kg of PCA suppressed appetitive ingestive behavior and consummatory ingestive behavior in male rats, respectively.

Suppression of behavioral activity by norfenfluramine and related drugs in rats is not mediated by serotonin release

Fenfluramine, a phenalkylamine with serotonin (5-HT) releasing properties, decreases motor activity in rats. The following studies assessed the contribution of 5-HT release to the behavioral effects of fenfluramine and norfenfluramine using a behavioral pattern monitor that simultaneously assesses locomotor and investigatory behavior. First, both fenfluramine and its active metabolite d-norfenfluramine dose-dependently reduced locomotor and investigatory activity. The norfenfluramine-induced reduction in activity was not antagonized by pretreatment with the 5-HT uptake inhibitor fluoxetine or the 5-HT synthesis inhibitor p-chlorophenylalanine, drugs that reduce drug-induced 5-HT release. Second, the d- and l-enantiomers of norfenfluramine were nearly equipotent at reducing behavioral activity, although d-norfenfluramine is more potent as a 5-HT releasing agent. Third, p-chloroamphetamine, a drug that shares the 5-HT releasing properties of fenfluramine produced locomotor hyperactivity in the same paradigm. Previous studies indicate that other 5-HT releasing phenalkylamines have behavioral effects resembling those of p-chloroamphetamine rather than those of fenfluramine. Finally, a structurally related drug, 4-methoxy-5-methyl-aminoindan (MMAI), produced dose-dependent reductions in behavioral activity that are similar to the effects of fenfluramine. The behavioral effects of MMAI were not antagonized by fluoxetine or by the 5-HT receptor antagonist methiothepin. These data suggest that the decrease in activity induced by fenfluramine, norfenfluramine and the related drug MMAI is not related to 5-HT release.

Evidence for monoaminergic involvement in triadimefon-induced hyperactivity

Triadimefon is a triazole fungicide that produces hyperactivity in both mice and rats similar to that seen following administration of compounds with catecholaminergic activity (e.g., d-amphetamine). To determine whether the triadimefon-induced hyperactivity is due to an action on CNS catecholaminergic systems, we evaluated the effects of combined treatment of triadimefon with either the tyrosine hydroxylase inhibitor d,l-alpha-methyl-p-tyrosine methyl ester HCl (alpha MPT) or the amine depletor reserpine. Adult male Long-Evans hooded rats, approximately 70 days of age were used. Dosage-effect functions were determined for alpha MPT (0-200 mg/kg IP), reserpine (0-2.5 mg/kg IP), d-amphetamine (0-3 mg/kg IP), and methylphenidate (0-40 mg/kg IP). Motor activity was measured as photocell interruptions in figure-eight mazes. The interaction between triadimefon and alpha MPT was determined with the following groups: 1) vehicle control; 2) 200 mg/kg triadimefon PO; 3) 100 mg/kg alpha MPT; and 4) both alpha MPT and triadimefon. A similar design was used to determine the interaction between triadimefon and reserpine (0.62 mg/kg), alpha MPT and d-amphetamine (1.5 mg/kg), and reserpine and methylphenidate (5.0 mg/kg). In the first experiment alpha MPT did not block the increased motor activity produced by triadimefon (i.e., both triadimefon alone and alpha MPT in combination with triadimefon produced significant increases in motor activity). alpha MPT did, however, block d-amphetamine-induced hyperactivity. Since alpha MPT did not antagonize the effect of triadimefon, these data suggest that increased motor activity produced by triadimefon is not mediated through release of newly synthesized catecholamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Ejaculations induced by p-chloroamphetamine in the rat

The ejaculatory response following acute injections of p-chloroamphetamine (PCA) and several other drugs was measured by weighing the compact seminal material accumulated over 2 hr. p-Chloroamphetamine caused a dose-dependent ejaculatory response that was inhibited by the inhibitor of the synthesis of 5-hydroxytryptamine (5-HT), p-chlorophenylalanine (PCPA), neurotoxic doses of PCA, reserpine, DSP 4 a selective noradrenergic neurotoxin given 48 hr before PCA, the inhibitor of synthesis of noradrenaline (NA) FLA 63, the specific inhibitors of uptake of 5-HT, alaproclate, fluoxetine and norzimeldine and the selective inhibitor of the uptake of NA, CPP 199, the E form of norzimeldine. The doses of several receptor antagonists producing a 50% decrease in the weight of seminal material were determined. The non-selective 5-HT receptor antagonists, metitepine and methergoline, the selective alpha 1-adrenoreceptor antagonists, prazosin and phenoxybenzamine and the non-selective alpha-adrenoreceptor antagonist, phentolamine, had strong effects, followed by the selective 5-HT2 antagonists, ketanserin and pirenperone. Yohimbine, an alpha 2-adrenoreceptor antagonist and atropine, a muscarinic receptor antagonist, only produced a partial blockade. The rank order of potency for some dopamine (DA) receptor antagonists was chlorpromazine, domperidone, haloperidol, pimozide. Remoxipride, a selective DA2 receptor antagonist and the selective DA1 antagonist, Sch 23390, had no effect. The following drugs had no effect: propranolol, naloxone, picrotoxin, cimetidine and mepyramine. The 5-HT receptor agonist 5-methoxy-N,N-dimethyltryptamine (5-MeODMT 3 mg/kg, i.p.) produced a small effect on the weight of seminal material, although 72% of the rats ejaculated. d-Amphetamine did not induce ejaculation at 5 mg/kg but had a marked effect at 15 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)

Separation of the associative and non-associative effects of brain serotonin released by p-chloroamphetamine: dissociable serotoninergic involvement in avoidance learning, pain and motor function

p-Chloramphetamine (PCA, 0.63-5 mg/kg IP) injected 30-60 min before testing produced a dose-related impairment of avoidance acquisition, prolonged reaction time in the hot-plate test and increased locomotor activity. Pretreatment with the selective serotonin (5-HT) uptake inhibitor zimeldine (10 mg/kg IP) blocked these behavioral effects. Degeneration of brain 5-HT neurons by a high neurotoxic dose of PCA (2 X 10 mg/kg IP) or inhibition of tryptophan hydroxylase by p-chlorophenylalanine (300 mg/kg IP) also blocked the behavioral effects of PCA. There was a complete blockade of the PCA-induced avoidance deficit following pretreatment with metergoline, a central 5-HT receptor blocking agent. On the other hand, metergoline failed to block the hot-plate analgesia and the increased locomotion caused by PCA. Depletion of brain NA and DA by the tyrosine hydroxylase inhibitor H44/68 did not counteract the PCA effect on avoidance or hot-plate performance, but reduced the locomotor stimulating effect. The selective NA neurotoxin DSP4 (50 mg/kg IP) or the opiate antagonist naloxone (1 mg/kg) failed to affect the PCA-induced modulations of the behaviours studied. In addition, PCA administration in doses that caused avoidance deficits, did not result in motor impairment as assessed by the tread mill test. The above results support the hypothesis that the PCA-induced impairment of active avoidance acquisition does not involve changes in nociception or altered locomotor activity. It is concluded that behavioural processes related to serotonergic neurotransmission can be independently modified, suggesting differences in the underlying 5-HT mechanisms.

Effects of the chronic ingestion of therapeutic doses of chlorimipramine on the behavioral action of agonists and antagonists of serotonin in male rats

Locomotor activity and hole-board exploration (frequency and time spent head-dipping) were impaired in male rats by injecting IP the 5-HT agonists, fluoxetine and 5-HTP. This treatment produced also myoclonus and increased the time spent resting during trials. The chronic ingestion of chlorimipramine (CIM) or the injection of the 5-HT receptor blocker, methysergide (15 mg/kg) prevented the action of the 5-HT agonists on locomotion and resting and blocked the appearance of myoclonus. Both CIM and methysergide prevented to a minor degree the fluoxetine-5-HTP-induced decrease of exploration. The chronic ingestion of CIM clearly potentiated the effects of methysergide on hole-board exploration. Results suggest that the chronic treatment with therapeutic doses of CIM reduces the functional activity of some 5-HT systems in the brain of the rat, probably by blockade of post-synaptic 5-HT receptors. This does not preclude, however, that CIM may also alter some NA systems.

Environmental determinants of parachloroamphetamine toxicity in rats

The present investigation assessed PCA toxicity at 0.0, 5.0, and 10.0 mg/kg, in both social (4 rats per cage) and non-social (acrylic tube-restraint or tube restraint-plus-tail shock) circumstances with 16 rats per drug-environment condition. The results indicated that no dose of PCA alone yielded mortality under individual housing, and similarly no environmental circumstance by itself yielded mortality in the absence of PCA. However, various drug-environment interactions produced a dose-related enhancement of PCA toxicity. For both 5.0 mg/kg and 10 mg/kg parachloroamphetamine dose levels, restraint-plus-shock generated the highest percent mortality, followed by restraint-only, with conspecific aggregation producing a mortality incidence lower still. Further, the mortality displayed under each of these environmental conditions was greater for the 10.0 mg/kg PCA treatment than for the 5.0 mg/kg treatment. The results are discussed in terms of the relative aversiveness of the environmental setting and it is suggested that stress-related drug toxicity may be further analyzed in non-social settings. It is proposed that toxic environment-PCA interactions may result from altered cardiovascular and/or thermoregulatory processes, mediated by enhanced catecholaminergic activity.

Mechanisms of PCA-induced hypothermia, ejaculation, salivation and irritability in rats

Injections of p-chloramphetamine (PCA, 5 mg/kg) induced hypothermia, ejaculation, salivation and irritability in male rats kept at an ambient temperature of 20 +/- 1 degree C. PCA-induced hypothermia was attenuated by pretreatment with the 5-hydroxytryptamine (5-HT) uptake blockers Lundbeck 10-171 (Lu 10-171, 10 mg/kg) and chlorimipramine (CMI, 20 mg/kg) and the 5-HT synthesis inhibitor parachlorophenylalanine (PCPA, 150 mg/kg daily for 3 days); it was potentiated by pretreatment with the noradrenaline uptake blocker Lundbeck 5-003 (Lu 5-003, 10 mg/kg) and the catecholamine synthesis inhibitor alpha-methyl-p-tyrosine (AMPT, 50 mg/kg every 3 hr for 9 hr). PCA- induced ejaculation was attenuated by pretreatment with Lu 10-171 and CMI. PCA-induced salivation was attenuated by pretreatment with Lu 10-171 and CMI and potentiated by pretreatment with Lu 5-003. PCA-induced irritability was potentiated by pretreatment with PCPA. These results suggest that both 5-HT and the catecholamines play a role in PCA-induced hypothermia, ejaculation, and salivation.

Disproportionate increases in locomotor activity in response to hormonal and photic stimuli following regional neurochemical depletions of serotonin

The role of forebrain serotonin in behavior-related energy output was assessed in two locomotor activity tests conducted 3 and 6 months after bilateral, intrahypothalamic microinfusion of the serotonin neurotoxin, 5,7-dihydroxytryptamine (5,7-DHT). The serotonin-depleted animals exhibited a long-lasting and stable increase in energy expenditure as locomotor activity. This increased activity was investigated at the behavioral level by relating the hyperactivity to estrous cycle, photoperiod and body weight. Although the serotonin depletion-induced hyperactivity occurred in all photoperiod and estrous cycle stages, its magnitude was disproportionately increased during light and estrus. This hyperactivity could not be related to decreases in body weight because the serotonin-depleted animals weighed significantly more than the control animals. These animals responded to the weight loss that normally accompanies wheel running by increasing their activity to the same proportion as the other groups. The neuroanatomical and neurochemical substrate of the increased locomotor activity was investigated with a regional neurochemical assay for serotonin, dopamine and norepinephrine. This assay revealed that the toxin had no effect on dopamine or norepinephrine in any structure analyzed; however, serotonin was depleted in the hippocampus, septum and, to a lesser degree, in the hypothalamus. Serotonin levels were negatively correlated with overall activity. The magnitude of the disproportionate increase in activity during light and estrus was negatively correlated with hippocampal serotonin level. These results indicate that forebrain depletions of serotonin differentially affect the control of activity exerted by the phases of the photoperiod and estrous cycle. However, the modulation of activity levels by decreases in body weight remains intact.

Elevation of serum prolactin acutely after administration of p-chloroamphetamine in rats

p-Chloroamphetamine hydrochloride (0.5-10 mg/kg, i.p.) caused a rapid (within 30 minutes), dose-related increase in serum prolactin concentration in male rats. The effect was antagonized by pretreatment with p-chlorophenylalanine, an inhibitor of serotonin synethesis, or by metergoline, a serotonin receptor antagonist. The acute elevation of serum prolactin may have been mediated by the release of serotonin by p-chloroamphetamine.

The effects of putative 5-hydroxytryptamine antagonists on the behaviour produced by administration of tranylcypromine and L-tryptophan or tranylcypromine and L-DOPA to rats

1 The putative 5-hydroxytryptamine (5-HT) receptor blocking drugs methysergide (10 mg/kg) and methergoline (5 mg/kg) were found to abolish some components of the hyperactivity syndrome, including head weaving and forepaw treading, which follow administration to rats of tranylcypromine (20 mg/kg) and L-tryptophan (100 mg/kg). Hyperactivity and hyper-reactivity were potentiated with a resultant increase in automated locomotor activity counts. In contrast (-)-propranolol (20 mg/kg) inhibited all features of the syndrome. The same results were obtained with these drugs when the behaviour was elicited by p-chloroamphetamine (10 mg/kg) or by tranylcypromine and tryptamine (10 mg/kg). 2 Methysergide and methergoline had similar effects on the syndrome produced by tranylcypromine and L-DOPA (50 mg/kg) whereas propranolol was without effect. 3 None of the putative 5-HT receptor antagonists affected brain 5-HT turnover as assessed by rate of accumulation of 5-HT following monoamine oxidase inhibition with tranylcypromine. 4 Microinjections of 5,7-dihydroxytryptamine into the spinal cord resulted in a 70% fall in cord 5-HT concentrations without an effect on brain 5-HT concentrations. The behavioural response to the putative 5-HT receptor agonist, 5-methoxy N,N-dimethyltryptamine (2 mg/kg), was potentiated in these animals suggesting that 5-HT receptors become supersensitive on denervation, and that some components of the behavioural syndrome are mediated by spinal cord 5-HT receptors. 5 Pretreatment with alpha-methyl p-tyrosine (2 X 200 mg/kg) delayed the onset of all components of the behaviour elicited by tranylcypromine/L-tryptophan by 60 min, indicating an involvement of catecholamines in the syndrome. 6 p-Chloroamphetamine-induced 5-HT depletion had no effect on any component of the tranylcypromine-L-DOPA behaviour.

The relationship between amphetamine antagonism and depletion of brain catecholamines by alpha-methyl-p-tyrosine in rats

The time-course and the dose-response relationship for the antagonistic effect of alpha-methyl-p-tyrosine methyl ester HCl H 44/68 (alpha-MT) on d-amphetamine (10.6 mumoles/kg) induced increase in motor activity was studied. The effect of amphetamine was gradually reduced from 30--60 min to a minimum at 1--4 h after the administration of 0.407 mmoles/kg of alpha-MT. From (4--) 8 h the amphetamine response started to reappear and the original response was restored completely at 16 h after alpha-MT. The dose-response curve showed, that between 0.051--0.41 mmoles/kg of alpha-MT, given 1 h before amphetamine, there was a gradual reduction of the amphetamine response; doses above 0.41 mmoles/kg did not cause any further effect. The antiamphetamine action of alpha-MT was compared with its time- and dose-dependent effects of inhibition of synthesis and reduction of stores of brain catecholamines. It was found, that the antiamphetamine action was more closely correlated with the reduction of the levels of brain dopamine, than with the brain noradrenaline levels. Further, the inhibition of catecholamine synthesis per se did not appear to be a sufficient condition for alpha-MT induced antagonism of amphetamine. These findings support the view that amphetamine is dependent on a substantial portion of the brain pool of dopamine and possibly noradrenaline rather than on very small, newly synthesized pools of these neurotransmitters.

Rapid tolerance to the motor effects of p-chloroamphetamine in rats

Studies were designed to test the hypothesis that tolerance to the effect of p-chloroamphetamine (PCA) on motor activity in rats would develop with repeated injections. In related biochemical studies the effects of single or repeated doses of PCA on the in vitro synaptosomal uptake of 3H-NE and 3H-DA and on the in vivo metabolism of intraventricularly administered 3H-NE and 3H-DA were investigated. The administration of 10 mg/kg of PCA induced a complex behavioral syndrome, which was quantified by scoring specific symptoms after direct observation. In agreement with previous data, this syndrome appears to be mediated by a release of 5-HT since pretreatment with PCA prevented its development on subsequent injection of the drug. After the administration of lower doses of PCA, total motor activity as measured in activity cages increased, and tolerance to this effect also developed rapidly. For example, pretreatment with 5 mg/kg of PCA greatly attenuated the stimulant effect of a subsequent dose of 3 or 5 mg/kg of the drug. Moreover, the degree of tolerance was the same if the time between the 2 injections was 1 day or 2 weeks, suggesting that 5-HT release is also involved in the tolerance to the motor effects of lower doses of the drug. Moreover, biochemical studies of the response of catecholaminergic neurons to PCA suggest that tolerance does not develop to the effects on DA and NE neurons on repeated injection of PCA.

Substituted amphetamine derivatives. II. Behavioural effects in mice related to monoaminergic neurones

The effects of the amphetamine derivatives (+/-)-amphetamine (A), 2-, 3- and 4-chloroamphetamine (CA), 4-methylamphetamine (MA) and chlorphentermine (CP) in producing central stimulation (increase in motor activity), antagonism of the reserpine syndrome, potentiation of 1-dopa and 5-hydroxytryptophan (5HTP) responses in mice were investigated. The inhibitors of the membrane amine uptake despramine (DMI) and chlorimipramine (CI) were also included in the study. It was found that the order in central stimulating potency was A greater than 3-CA = 4-CA greater than MA greater than CP. 2-CA, DMI and CI decreased the motor activity. All the compounds potentiated the 1-dopa response with the order of activity: 4-MA greater than A greater than 2-CA = 3-CA = 4-CA = CI greater than or equal to DMI greater than CP. The decrease in motor activity (sedation) produced by reserpine was only reversed by A greater than or equal to 3-CA greater than 2-CA. alpha-Methyltyrosine but not parachlorophenylalanine, antagonized the reversal effect. Three of the compounds (3-CA, 4-CA and MA) produced head-twitches in the reserpinized mice. The 5-HTP syndrome was potentiated in order of potency by MA = 4-CA greater than CI greater than CP greater than 3-CA whereas A, 2-CA and DMI had no effect.

p-Chloroamphetamine: short and long term effects upon shock-elicited aggression

In a series of experiments the effects of p-chloroamphetamine (PCA) on shock-elicited aggression in rats were investigated. 15 min after 5 mg/kg PCA, shock elicited aggression was inhibited. 2 h to 4 weeks after PCA, fighting was facilitated. Both the inhibitory and the excitatory effects of PCA were directly related to the dose of PCA (1.5, 2.5 OR 5 mg/kg) and were blocked by pretreatment with p-chlorophenylalanine but not by alpha-methyl-p-tyrosine. PCA-increased pain thresholds 15 min after injection and then decreased pain thresholds over the next 24 h but not thereafter, even though shock-elicited aggression continued to be facilitated. The results are consistent with the idea that inhibition of shock-elicited aggression is associated with enhanced release of serotonin whereas enhancement of shock-elicited aggression is associated with serotonin depletion.

Evidence concerning the involvement of 5-hydroxytryptamine in the locomotor activity produced by amphetamine or tranylcypromine plus L-DOPA

1 Pretreatment of rats with p-chlorophenylalanine (PCPA; 2 X 200 mg/kg) decreased the concentration of 5-hydroxytryptamine (5-HT) in the brain. It also decreased the locomotor activity produced by tranylcypromine plus L-DOPA administration 24 h after the second dose of PCPA. 2 Pretreatment with p-chloroamphetamine, which produced a similar decrease in brain 5-HT concentrations did not decrease the locomotor response to tranylcypromine and L-DOPA. 3 PCPA pretreatment decreased the rise in the concentration of DOPA and dopamine in the brain following tranylcypromine and L-DOPA, suggesting its effect on the dopamine-induced locomotor activity was the result of this drug diminishing dopamine formation in the brain, probably by inhibiting L-DOPA uptake. 4 The locomotor activity produced by tranylcypromine and L-DOPA was not decreased by pretreatment 6 h earlier with disulfiram (400 mg/kg). This argues against the locomotor activity being due to noradrenergic stimulation. 5 PCPA pretreatment did not alter amphetamine-induced stereotypy or the circling behaviour in unilateral nigro-striatal lesioned rats.

p-Chloroamphetamine (PCA): acute and chronic effects on habituation and sensitization of the acoustic startle response in rats

In a series of 6 experiments the effects of p-chloroamphetamine (PCA) on the acoustic startle response in rats were investigated. 15 min after 5 mg/kg PCA startle amplitude was inhibited, 2-15 hr after PCA startle was facilitated. Rate of habituation however was not altered. Both the inhibitory and excitatory effects of PCA were blocked by pretreatment with p-chlorophenylalanine but not by alpha-methyl-p-tyrosine. 24 hr, 1 week and 4 weeks after PCA, initial startle amplitude was unchanged but PCA increased rate of sensitization over successive tone blocks. Increased sensitization was most pronounced at 10 mg/kg and absent at 2.5 mg/kg. The early inhibitory effect of PCA but not the later facilitatory effect was eliminated by reducing the level of background noise. The results suggest that inhibition of startle sensitization is associated with enhanced release of serotonin (5-HT) whereas enhancement of startle sensitization is associated with 5-HT depletion.

[Effects of diazepam on six drug-induced locomotor hyperactivities in mice (author's transl)]

Experiments were carried out in mice to investigate the influence of diazepam (DZP) on dexamphetamine, parachloro-N-methylamphetamine (pCMA), cocaine, morphine, trihexyphenidyl or (in MAOIs pretreated) reserpine induced motor hyperactivity. The interaction of DZP with these hyperactivities in which probably different biochemical central mechanisms are involved allows to construct a profile of action of DZP and to approach its mechanism of action. The locomotor hyperactivities induced by dexamphetamine, pCMA, morphine, cocaine were not reduced by DZP even by doses which decrease spontaneous locomotor activity; low doses of DZP enhance the hyperactivity induced by these compounds. Those induced by trihexyphenidyle or by reserpine (after MAOI) were reduced by DZP at doses which produce no decrease in spontaneous motor activity. Inasmuch as DZP at low doses potentiates the effects of 4 different substances, the results can hardly be satisfactorily explained neither by an interference of the benzodiazepine on the metabolism of the drugs or by a depression of the anxiogenic action of dexamphetamine. Even though it may be difficult to relate the antagonism of DZP on trihexyphenidyl- or on reserpine- (after MAOI) induced motor hyperactivity to the suggested anticholinergic and dopaminergic actions of DZP, these effects may partly be involved in the increase in locomotor hyperactivity induced by dexamphetamine, morphine, or cocaine. The observed effect of DZP on pCMA induced locomotor hyperactivity does not support a possible antiserotonine action often suggested to explain the effects of benzodiazepines in conflict situations.

Antagonistic effect of cyproheptadine on neuroleptic-induced catalepsy

The influence of cyproheptadine on the neuroleptic-catalepsy in rats was studied. Cyproheptadine antagonized dose-dependently the catalepsy induced by spiroperidol, pimozide, fluphenazine and reserpine. The anticataleptic effect of two antiparkinsonian drugs, L-DOPA or amantadine was potentiated by cyproheptadine.

Blockade of biogenic amine synthesis: its effect on the responses to leptazol and dexamphetamine in rats

1. The convulsive effects of leptazol in the rat are potentiated by prior treatment with dexamphetamine.2. An intact dopamine synthesis is necessary for the potentiation of the convulsive action of leptazol.3. An intact noradrenaline synthesis is not necessary for this action of amphetamine, as long as the dopamine synthesis is intact.4. An intact 5-hydroxytryptamine synthesis is not necessary for the potentiation to be shown.5. Blockade of either noradrenaline, dopamine or 5-hydroxytryptamine synthesis has no direct effect on leptazol convulsions.6. It is possible that it is an intact 3-4 dihydroxyphenylalanine (dopa) synthesis rather than an intact dopamine synthesis that is involved.