M.T. Morgadinho

Toxic Effects of Opioid and Stimulant Drugs on Undifferentiated PC12 Cells

Abstract: Cell death and reactive oxygen species production have been suggested to be involved in neurodegeneration induced by the drugs of abuse. In this study we analyze the toxicity of the following drugs of abuse: heroin, morphine, d‐amphetamine, and cocaine in undifferentiated PC12 cells, used as dopaminergic neuronal models. Our data show that opioid drugs (heroin and morphine) are more toxic than stimulant drugs (d‐amphetamine and cocaine). Toxic effects induced by heroin are associated with a decrease in intracellular dopamine, an increase in DOPAC levels, and the formation of ROS, whereas toxic effects induced by amphetamine are associated with a decrease in intracellular dopamine and in ATP/ADP levels. In contrast with cocaine, both amphetamine and heroin induced features of apoptosis. The data suggest that the death of cultured PC12 cells induced by the drugs of abuse is correlated with a decrease in intracellular dopamine levels, which can be associated with an increased dopamine turnover and oxidative cell injury.

Migraine, Serum Serotonin and Platelet 5–HT2 Receptors

In spite of recent theories about the aetiopathogenesis of migraine, serotonin continues to play a central role, explaining the efficacy of almost all migraine prophylactic drugs. In migraineurs with and without aura we measured (by HPLC-EC) the serum serotonin (5–HT) and 5–hydroxyindoleacetic acid (5–HIAA) levels between as well as during headache attacks. Between attacks of migraine with aura and at the beginning of attacks of both types of migraine the serum 5–HT and 5–HIAA concentration was significantly increased. These results were corroborated by 3H-spiperone binding to platelet membranes: in migraineurs with aura in the attack-free interval, there was a significant decrease in its Bmax, which suggests down-regulation of 5–HT2 receptors. In conclusion, we have verified that migraine with aura differs biochemically from migraine without aura.

Catecholamine and MHPG plasma levels, platelet MAO activity, and3H-imipramine binding in heroin and cocaine addicts

AbstractThis work evaluated in a population of heroin and heroin plus cocaine human addicts:1.Norepinephrine (NE), epinephrine (Epi), and 3-methoxy-4-hydroxyphenylglycol (MHPG) (the principal metabolite of brain NE) plasma levels;2.Monoamine oxidase (MAO) activity; and3.3H-imipramine specific binding to the amine carrier in platelets. NE plasma levels were significantly lower in the short-term heroin user groups (1–3 and 4–6 yr), a finding not observed in both the long-term heroin user (>6 yr) and heroin plus cocaine user (>6 yr) groups. Epi levels changed in a similar manner, except that a significant increase was noted in heroin plus cocaine abusers. Conversely, dopamine and MHPG plasma levels increased with the duration of heroin use, and even more with cocaine abuse. Platelet MAO activity increased in all groups. Specific3H-imipramine binding sites showed an increase after 3 yr of heroin abuse and in all heroin plus cocaine addicts. In conclusion, short-term use of heroin decreases NE or Epi release, but with prolonged use, a slow adpatation occurs. In contrast, cocaine inhibits the neuronal Epi uptake, even in a situation of long duration of abuse. Probably the amine levels additionally regulate the amine carrier, resulting in changes that show a different pattern from major depression. These drugs of abuse may also influence directly or indirectly related enzymatic systems.

Presynaptic dopamine receptors involved in the inhibition of noradrenaline and dopamine release in the human gastric and uterine arteries

Abstract— Electrical stimulation‐induced depolarization releases both dopamine (DA) and noradrenaline (NA) from sympathetic neurones of the human gastric and uterine arteries. The overflow of catecholamines elicited by electrical stimulation was measured by using high performance liquid chromatography with electrochemical detection. The addition of yohimbine (0.01–10 μM), an α2‐adrenoceptor antagonist, to the perfusion fluid increased, in a concentration‐dependent manner, the electrically‐evoked DA and NA overflow from gastric and uterine arteries. In the presence of sulpiride (0.1–10 μM), a dopamine D2‐type receptor antagonist, the overflow of both amines was found to be increased in the uterine artery, but not in the gastric artery. Apomorphine (0.1–10 μM), a dopamine receptor agonist, produced a dose‐dependent inhibition in the amount of DA and NA released from gastric and uterine arteries. SCH 23390 (0.1–10 μM), a dopamine D1 receptor antagonist, had no effect on the release of both amines in both preparations. The inhibitory effect of apomorphine was blocked by sulpiride in the gastric and uterine arteries but not by SCH 23390. The results presented suggest the existence of dopamine D2‐type receptors in the human gastric and uterine arteries. They seem to have, in each artery, a different physiological importance.

Electrical stimulation-induced release of dopamine and noradrenaline in human blood vessels

Abstract Noradrenaline (NA), dopamine (DA) and DA metabolites levels, as well as their ratios, have been compared in various human vessels. In the same tissue we have also studied the influence of electrical stimulation in the presence or absence of pargyline, or pargyline plus cocaine. Catecholamines and DA metabolites have been measured by HPLC with electrochemical detection. The highest levels of NA and DA were found in the splenic artery and the lowest in the pulmonary artery and saphenous vein. Appreciable concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) were found in splenic, gastric, mesenteric and uterine arteries, whereas homovanillic acid (HVA) was not measurable in any tissue. However, the vascular segments showed a different DA/NA ratio, which was significantly higher in the mesenteric artery. The electrical stimulation increased this ratio, especially in the mesenteric artery. The ratio increased still more after treatment with pargyline plus cocaine. After pargyline pretreatment and in the presence of cocaine, electrical stimulation significantly increased NA and DA release from all blood vessels, except pulmonary artery and saphenous vein. During a second period of electrical stimulation only the DA release remained high. The results suggest that DA is coreleased with NA from the nerve endings of the vascular wall, and after neuronal uptake it is metabolized to DOPAC. Moreover, deamination is more important than methylation. When the sympathetic nerve endings are depleted of NA, the synthesis of DA increases. The DA/NA ratio differs between the various vessels, suggesting different roles for DA. Since this ratio was higher in the mesenteric artery, DA probably works as a cotransmitter in this vessel.