3,4-methylenedioxymethamphetamine (ecstasy)-induced learning and memory impairments depend on the age of exposure during early development

Use of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) has increased dramatically in recent years, yet little is known about its effects on the developing brain. Neonatal rats were administered MDMA on days 1-10 or 11-20 (analogous to early and late human third trimester brain development). MDMA exposure had no effect on survival but did affect body weight gain during treatment. After treatment, body weight largely recovered to 90-95% of controls. MDMA exposure on days 11-20 resulted in dose-related impairments of sequential learning and spatial learning and memory, whereas neonatal rats exposed on days 1-10 showed almost no effects. At neither stage of exposure did MDMA-treated offspring show effects on swimming ability or cued learning. Brain region-specific dopamine, serotonin, and norepinephrine changes were small and were not correlated to learning changes. These findings suggest that MDMA may pose a previously unrecognized risk to the developing brain by inducing long-term deleterious effects on learning and memory.

Adult learning deficits after neonatal exposure to D-methamphetamine: selective effects on spatial navigation and memory

The effects of neonatal d-methamphetamine (MA) treatment on cued and spatial learning and memory were investigated. MA was administered to neonatal rats on postnatal days 11-20. All groups received four subcutaneous injections per day. Group MA40-4 received 40 mg. kg(-1). d(-1) of MA in four divided doses (10 mg/kg per injection). Group MA40-2 received 40 mg. kg(-1). d(-1) of MA in two divided (20 mg/kg/injection) and saline for the other two injections per day. Controls received saline for four injections per day. As adults, both MA groups showed no differences in swimming ability in a straight swimming channel. The MA40-4 group showed no differences in cued learning, but was impaired in hidden platform learning in the Morris water maze on acquisition. They also showed reduced memory performance on probe trials. Similar trends were seen on reversal learning and reversal probe trials. Reduced platform-size learning trials caused spatial learning impairments to re-emerge in the MA40-4 group. The MA40-2 group showed no differences in straight channel swimming, but was slower at finding the visible platform during cued learning. They were also impaired during acquisition and memory trials in the Morris hidden platform maze. They showed a similar trend on reversal learning and memory trials, but were not different during reduced platform-size learning trials. When the MA40-2 group's performance on hidden platform learning and memory trials was adjusted for cued trial performance, the spatial learning deficits remained. Deficits of spatial learning and memory are a selective effect of neonatal methamphetamine treatment irrespective of other learning and performance variables.

A single dose model of methamphetamine-induced neurotoxicity in rats: effects on neostriatal monoamines and glial fibrillary acidic protein

The neurotoxic effects of a single administration of methamphetamine (MA) were studied under conditions conducive to MA-induced hyperthermia. After a single dose of MA (10, 20, 30, or 40 mg/kg, s. c.) or saline (3 ml/kg) to Sprague-Dawley CD rats, rectal temperatures were monitored for 9 h in a room with an ambient temperature of 22.0+/-0.5 degrees C. MA induced significant dose-dependent hyperthermia, however, no significant increase in mortality occurred. Neostriatal DA, 5-HT, TH, and GFAP were assayed 3 days following treatment. MA induced dose-dependent reductions of DA, 5-HT and TH, and increased GFAP. For DA, at doses of 20, 30, or 40 mg/kg the reductions were to 71%, 49%, and 29%, and for 5-HT were to 73%, 44%, and 19% of control values. No reductions were seen after the 10 mg/kg dose. Semiquantitative analysis Western blots of TH and GFAP demonstrated that TH was reduced to 52%, 75%, and 28%, and GFAP was increased to 125%, 134%, and 149% of control values at MA doses of 20, 30, or 40 mg/kg, respectively. No significant changes in TH or GFAP were seen at the 10 mg/kg MA dose. These results demonstrate that a single-dose of MA can be as effective as the widely used four-dose every 2 h regimen. Moreover, mortality can be minimized by monitoring core body temperature and preventing MA-induced hyperthermia from exceeding 41.5 degrees C.

Methamphetamine-induced dopamine and serotonin reductions in neostriatum are not gender specific in rats with comparable hyperthermic responses

Methamphetamine (MA)-induced monoamine depletions in male and female Sprague-Dawley CD rats were studied under conditions in which the magnitude of MA-induced hyperthermia was comparable between the sexes. MA (5 or 10 mg/kg) or saline (3 ml/kg) was administered SC four times at 2-h intervals. Animals were sacrificed 3 days posttreatment for the determination of dopamine (DA), serotonin (5-HT), and metabolites. MA induced significant monoamine reductions but the magnitude of these reductions was not significantly different between males and females. In the MA 5 mg/kg groups, neostriatal DA content was reduced by 51.2% and 44.8%, whereas 5-HT content was reduced by 30.6% and 23.9% of controls for males and females, respectively. In the MA 10 mg/kg groups, neostriatal DA content was reduced by 72.9% and 65.8%, whereas striatal 5-HT content was reduced by 77.4% and 73.6% of controls for males and females, respectively. No significant differences in thermal responses to MA were observed between genders. Unlike reports in mice, gender does not play a role in MA-induced monoamine reductions in rat neostriatum when MA-induced hyperthermia is comparable across sexes. The data also showed a threshold effect in which dopamine depletions were not correlated with hyperthermia at core body temperatures above approximately 41 degrees C.

Methamphetamine selectively damages dopaminergic innervation to the nucleus accumbens core while sparing the shell

Dopaminergic innervation to the nucleus accumbens was investigated following a neurotoxic regimen of methamphetamine (MA) treatment. Four 10 mg/kg doses of MA were administered s.c. to male Sprague-Dawley rats with a 2 h interval between doses. Rectal temperatures were monitored for the induction of MA-induced hyperthermia. Three days or 2 weeks after MA treatment the animals were sacrificed by transcardial perfusion and processed for tyrosine hydroxylase (TH-IR) and glial fibrillary acidic protein immunoreactivity (GFAP-IR). MA treatment produced a severe loss of TH-IR throughout the striatum, including the nucleus accumbens. However, within the nucleus accumbens, there was substantial sparing of TH-IR in the shell, while in the core immunoreactivity was almost entirely lost. Furthermore, astrogliosis, as demonstrated by GFAP-IR, was prevalent in the core but present only in sparse patches in the medial and lateral shell. Thus, dopaminergic innervation to the nucleus accumbens core undergoes degeneration following MA treatment, while innervation to the shell is resistant to the neurodegenerative effects of MA.

alpha-Phenyl-N-tert-butyl nitrone attenuates methamphetamine-induced depletion of striatal dopamine without altering hyperthermia

Methamphetamine (MA) administration to adult rats (4 x 10 mg/kg s.c.) induces neurotoxicity predominately characterized by a persistent reduction of neostriatal dopamine (DA) content. Hyperthermia following MA administration potentiates the resulting DA depletion. DA-derived free radicals are postulated to be a mechanism through which MA-induced neurotoxicity is produced. The spin trapping agent PBN reacts with free radicals to form nitroxyl adducts, thereby preventing damaging free radical reactions with cellular substrates. MA with saline pretreatment (Sal-MA) reduced neostriatal DA by 55% (P < 0.01 vs. Sal-Sal). MA with PBN pretreatment (PBN-MA) at 36 or 60 mg/kg reduced neostriatal DA by 36 and 22%, respectively (P < 0.05 and P < 0.01 vs Sal-MA) indicating partial protection. PBN pretreatment did not alter MA-induced hyperthermia. Thus, PBN does not attenuate MA-induced neurotoxicity by reducing MA-induced hyperthermia. These results support a role for free radicals in the generation of MA-induced dopaminergic neurotoxicity.

Effect of methamphetamine on glutamate-positive neurons in the adult and developing rat somatosensory cortex

The neurotoxic effects of methamphetamine (MA) on dopaminergic and serotonergic terminals have been well-documented. Another neurotoxic effect of MA is neuronal degeneration in the somatosensory cortex, as seen by silver staining. The neurochemical characteristics of these degenerating neurons are unknown. Using glutamate and glial fibrillary acid protein (GFAP) immunohistochemistry, it was found that MA exposure in adult rats (10 mg/kg given 4 times intraperotoneally (i.p.) at 2-h intervals) causes localized depletion of glutamate-positive neurons and astrogliosis in the somatosensory cortex 3 days following treatment. The affected region covered the middle one-third portion from the longitudinal fissure to the rhinal sulcus and was predominately seen in layers II-III of the cortex. This pattern of depletion is consistent with that demonstrated previously with silver staining following MA, d-amphetamine, and 3,4-methylenedioxymethamphetmine (MDMA) exposures. Comparable efforts were not found in developing animals at ages previously shown to also be resistant to MA-induced effects on dopaminergic terminals (age 20 and 40 days). Results suggest that MA exposure induces degeneration of glutamatergic neurons in the somatosensory cortex of adult rats.

Age-dependent sensitivity of rats to the long-term effects of the serotonergic neurotoxicant (+/-)-3,4-methylenedioxymethamphetamine (MDMA) correlates with the magnitude of the MDMA-induced thermal response

The effects of developmental age on (+/-)-3,4-methylenedioxymethamphetamine (MDMA)-induced reductions in 5-hydroxytryptamine (5-HT) content and 5-HT reuptake sites were investigated in conjunction with the effects of developmental age on MDMA-induced thermoregulatory responses. MDMA was administered to rats at postnatal days (PND) 10, 40 and 70 in a range of ambient temperature environments (10 degrees C, 25 degrees C and 33 degrees C). Animals were monitored for alterations in body temperature and sacrificed 1 week after MDMA administration. MDMA administration at PND 10 did not result in persistent reductions in 5-HT content or 5-HT reuptake sites in frontal cortex, nor could a hyperthermic response be elicited. In contrast, MDMA administration at PND 40 and PND 70 resulted in a hypothermic response in cold environments (10 degrees C) and a hyperthermic response in warm environments (> or = 25 degrees C). When hypothermia was observed after MDMA (10 degrees C environment), long-term reductions in 5-HT content and 5-HT reuptake sites were significantly attenuated or abolished. Conversely, when a hyperthermic response was observed (25 degrees C and 33 degrees C environments), long-term MDMA-induced reductions in 5-HT content and 5-HT reuptake sites were significantly enhanced. Thus, thermal responses significantly correlated with MDMA-induced reductions in 5-HT content and 5-HT reuptake sites. These experiments demonstrate a role for hyperthermia in the expression of serotonergic neurotoxicity after MDMA administration.

Age modulates the long-term but not the acute effects of the serotonergic neurotoxicant 3,4-methylenedioxymethamphetamine

Tissue levels of serotonin (5-HT), levels of its metabolite 5-hydroxyindoleacetic acid (5-HIAA) and populations of 5-HT reuptake sites were measured in the brains of rats exposed to 3,4-methylenedioxymethamphetamine (MDMA) at selected developmental ages. MDMA exposure at postnatal day (PND) 10 did not result in altered 5-HT or 5-HIAA levels 1 week after administration in any brain region examined. However, MDMA exposure at PND 40 and PND 70 resulted in dose-dependent reductions in 5-HT and 5-HIAA levels at 1 week in all brain regions examined. Time course studies revealed that at PND 10, MDMA acutely (< or = 24 hr) reduced 5-HT levels and that these levels later recovered to control levels. MDMA also acutely reduced 5-HT levels at PND 40 and PND 70, but at these ages the 5-HT levels were persistently depressed ( > or = 72 hr). Time course studies also revealed that MDMA acutely elevated dopamine levels in caudate putamen at PND 40 and PND 70, but no alterations in dopamine levels were observed at PND 10. Analysis of 5-HT reuptake site populations revealed that at PND 10 and PND 40, MDMA had little effect on reuptake site populations. At PND 70, however, MDMA reduced 5-HT reuptake site populations as early as 24 hr after administration. These experiments demonstrate not only that the biochemical effects of MDMA exposure are altered by the developmental status of the experimental animal, but also that each individual biochemical component may show differing sensitivities to alteration by MDMA at different developmental ages.

Further studies of the role of hyperthermia in methamphetamine neurotoxicity

The depletion of striatal dopamine (DA) that can occur after methamphetamine (METH) administration has been linked to METH-induced hyperthermia. The relationship between METH-induced hyperthermia, neurotoxicity (striatal DA depletions) and compounds that protect against METH neurotoxicity was further investigated in this study. Typically, rats exposed to METH die when their body temperatures exceed 41.3 degrees C but such hyperthermic rats can be saved by hypothermic intervention. Subsequently, rats saved by hypothermic intervention have greater depletion of striatal DA at an earlier time of onset (18 hr or less post-METH) than do METH-exposed rats that do not attain such high temperatures. Striatal damage was present 3 days post-METH in these hyperthermic rats, as assessed by silver degeneration of terminals and increases in the astrocytes that express glial fibrillary acidic protein immunoreactivity. By contrast, alterations in the number of [3H]dizoclipine (MK-801) binding sites in cortical or striatal membranes at 1, 3 or 14 days post-METH were not detected. The experiments showed that mean and maximal body temperature correlated well with striatal DA concentrations 3 days post-METH (r = -0.77, n = 58), which suggests a role for hyperthermia in METH neurotoxicity. However, hyperthermia (alone or with haloperidol present) induced by high ambient temperatures did not deplete striatal DA in the absence of METH. Haloperidol, diazepam and MK-801 all reduced METH-induced striatal DA depletion to a degree predicted by their inhibition of hyperthermia and increased ambient temperature abolished their neuroprotection. Although an interleukin-1 receptor antagonist reduced maximal body temperature enough to lower the lethality rate, it did not reduce the temperature sufficiently to block METH neurotoxicity. It was concluded that short- and long-term decreases in striatal DA levels depend on the degree of hyperthermia produced during METH exposure but cannot be produced by hyperthermia alone. In addition, several agents that block DA depletions do so by inhibiting METH-induced hyperthermia. Finally, the results suggested a role for interleukin-1 in the extreme hyperthermia and lethality produced by METH.

Fluoro-gold and pentamidine inhibit the in vitro and in vivo release of dopamine in the striatum of rat

Fluoro-Gold (FG), first developed as an antifungal/antiparasitic agent, is now also used extensively as a retrograde tracer in histological studies of nervous tissue. The fact that FG is taken up by dopamine (DA) terminals before its retrograde transport to DA cell bodies implies a presynaptic interaction, though the biochemical target(s) and mechanism(s) are unknown. To further elucidate, FG and another aromatic diamidine, pentamidine, were tested on [3H]DA release and uptake in vitro from striatal slices and synaptosomes. Neither compound affected [3H]DA uptake in synaptosomes and slices, and neither inhibited DA efflux mediated through reversal of DA uptake mechanisms. NMDA-mediated glutamate-evoked DA release was completely inhibited by either FG (IC50 approximately 3 microM) or pentamidine (IC50 approximately 1 microM), and 20 mM K(+)-evoked DA release was inhibited by similar concentrations but only to 60% of control. Arginine (up to 500 microM) and spermidine (200 microM) failed to reverse 33 microM FG inhibition of either the spontaneous or the glutamate-evoked DA release, indicating that FG inhibition of release was not necessarily via blockade of either nitric oxide generation or spermidine binding to NMDA receptors. Interestingly, FG (33 microM) and pentamidine (10 microM) inhibited 1 and 5 microM D-methamphetamine (METH)-evoked [3H]DA release to approximately 50% of control, and in striatal synaptosomes, FG (33 microM) and pentamidine (10 microM) inhibited 5 microM METH- and 1.25 mM Ca(++)-evoked DA release. Additionally, in vivo brain microdialysis supported the in vitro results; 100 microM FG in the microdialysis buffer inhibited 70% of the increase in extracellular DA in the striatum produced by 2.5 mg/kg METH.(ABSTRACT TRUNCATED AT 250 WORDS)