Differential effects of chronic imipramine and fluoxetine on basal and amphetamine-induced extracellular dopamine levels in rat nucleus accumbens

The effect of chronic treatment with the tricyclic antidepressant drug, imipramine (10 mg/kg per day), the selective serotonin (5-HT) reuptake inhibitor, fluoxetine hydrochloride (10 mg/kg per day), and vehicle, in drinking water for 24–28 days followed by 3–5 days withdrawal, on extracellular dopamine levels was studied in rat nucleus accumbens by in vivo microdialysis. Basal extracellular dopamine levels in the nucleus accumbens were increased after chronic imipramine (12.7±1.5 fmol/20 μl per 30 min, P=0.019), and moderately decreased after chronic fluoxetine (6.5±0.6, P=0.047), as compared to the vehicle controls (9.1±0.7), determined by one-way analysis of variance (ANOVA). Repeated measure ANOVA indicated that the

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-amphetamine sulfate (0.5 mg/kg, s.c.)-induced increase in extracellular dopamine levels in the nucleus accumbens was potentiated after chronic imipramine (P=0.002), but unchanged after chronic fluoxetine (P=0.83). The difference in the effect of amphetamine could be influenced by the significant differences in basal levels. However, these results were also confirmed by analysis of the net area under the curve (net-AUC) for a 180-min period (six samples): for chronic imipramine (337±45 fmol/180 min, P=0.005) and chronic fluoxetine (249±38, P=0.57), as compared to the vehicle controls (178±29), determined by one-way ANOVA. We suggest that the effect of treatment with these agents on mesolimbic dopamine is unlikely to be involved in their shared antidepressant action, but may be relevant to other aspects of the therapeutic profile of these two drugs, e.g. the switch into mania which is more common after treatment with imipramine than fluoxetine and exacerbation of positive symptoms in patients with schizophrenia or schizoaffective disorder.     

Differential effects of ceruletide on amphetamine-induced behaviors and regional dopamine release in the rat

This study concerned the effects of ceruletide, a cholecystokinin (CCK)-related peptide, on amphetamine-stimulated behaviors (hyperlocomotion and stereotypy) and amphetamine-induced dopamine (DA) release from the striatum and the nucleus accumbens of the rat. Also, behavioral alterations due to ceruletide administration were compared with the change in DA release from these areas. Ceruletide 160 μg/kg s.c., attenuated hyperlocomotion induced by amphetamine, 1 mg/kg and 3 mg/kg s.c., but had no effect on amphetamine-induced stereotypy. Results from in vivo microdialysis experiments showed that s.c. administration of ceruletide caused a significant inhibition of the amphetamine-induced increase in DA release in the nucleus accumbens but not in the striatum. These neurochemical inhibitory effects of ceruletide dissappeared completely with bilateral subdiaphragmatic vagotomy. However, infusion of 1 μM of ceruletide into the nucleus accumbens through the dialysis probe had no effect on amphetamine-induced DA release. These results suggest that the inhibitory effect of peripheral administration of ceruletide on amphetamine-induced hyperlocomotion is closely related to the change in DA release from the nucleus accumbens. In the nucleus accumbens, systematically administered ceruletide acts initially on the peripheral organs and influences the activity of DA terminals via an unknown path related to the vagus. Ceruletide had different actions on the dopaminergic system in the striatum and that in the nucleus accumbens.     

Effects of subchronic exposure to styrene on the extracellular and tissue levels of dopamine, serotonin and their metabolites in rat brain

At present, there is controversy over the neurotoxic potential of styrene. Several epidemiological and clinical studies have shown that styrene exposure causes alterations of central nervous system functions in humans. Neurotransmitters have been implicated in the pathogenesis of styrene neurotoxicity in rodents. Several studies carried out on postmortem brain tissue suggest that styrene may alter dopaminergic neurotransmission in rabbit or rat brain. Moreover, in vitro studies suggest that both styrene and styrene oxide inhibit the uptake of dopamine (DA) in purified synaptic vesicles prepared from rat brain striata. To date, biochemical studies on animals have explored global tissue levels of neurotransmitters with sub-acute exposures to styrene. However, extracellular levels of neurotransmitters are more closely related to behaviour than are global tissue levels. The present study determined changes in the extracellular concentrations of DA, serotonin (5-HT) and their acid metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA), in striatal dialysates from freely moving adult male rats after exposure to 750 and 1,000 ppm styrene, 6 h per day, 5 days per week for 4 weeks. We also determined the concentrations of DA, 5-HT and their acid metabolites in striatum, nucleus accumbens and prefrontal cortex obtained postmortem from similarly exposed rats. Exposure to 1,000 ppm of styrene caused a significant decrease in extracellular acid metabolite concentrations. Tissue levels of acid metabolites were also decreased to a lesser extent. The effects were observed 72 h after discontinuing exposure but had vanished 17 days later. There was no change in DA or 5-HT concentrations either in the dialysates or tissues. Exposure to 750 ppm styrene caused no changes in the concentrations of DA, 5-HT and their acid metabolites either in the dialysates or tissues. The possibility that the effect of styrene is mediated by monoamine oxidase (MAO) inhibition is discussed.     

Sex-dependent long-term effects of adolescent exposure to THC and/or MDMA on neuroinflammation and serotoninergic and cannabinoid systems in rats

Background and PurposeMany young people consume ecstasy as a recreational drug and often in combination with cannabis. In this study, we aimed to mimic human consumption patterns and investigated, in male and female animals, the long-term effects of Δ⁹-tetrahydrocannabinol (THC) and 3,4-methylenedioxymethamphetamine (MDMA) on diverse neuroinflammation and neurotoxic markers.Experimental ApproachMale and female Wistar rats were chronically treated with increasing doses of THC and/or MDMA during adolescence. The effects of THC and/or MDMA on glial reactivity and on serotoninergic and cannabinoid systems were assessed by immunohistochemistry in the hippocampus and parietal cortex.Key ResultsTHC increased the area staining for glial fibrilar acidic protein in both sexes. In males, both drugs, either separately or in combination, increased the proportion of reactive microglia cells [ionized calcium binding adaptor molecule 1 (Iba-1)]. In contrast, in females, each drug, administered alone, decreased of this proportion, whereas the combination of both drugs resulted in a ‘normalization’ to control values. In males, MDMA reduced the number of SERT positive fibres, THC induced the opposite effect and the group receiving both drugs did not significantly differ from the controls. In females, MDMA reduced the number of SERT positive fibres and the combination of both drugs counteracted this effect. THC also reduced immunostaining for CB₁ receptors in females and this effect was aggravated by the combination with MDMA.Conclusions and ImplicationsAdolescent exposure of rats to THC and/or MDMA induced long-term, sex-dependent neurochemical and glial alterations, and revealed interactions between the two drugs.Linked ArticlesThis article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6     

Effects of subchronic methamphetamine exposure on basal dopamine and stress-induced dopamine release in the nucleus accumbens shell of rats

Rationale Subchronic administration of stimulants reduces basal dopamine (DA) concentrations and blocks stress-induced DA release in the nucleus accumbens (NA) of rats during withdrawal. However, no studies have attempted to relate early withdrawal from chronic drug exposure to stress reactivity and changes in DA transmission. Objectives The effects of subchronic low-dose methamphetamine (METH) administration on regional changes in dopamine transporter (DAT) and norepinephrine transporter (NET) immunoreactivity and function during early withdrawal were examined. The effects of subchronic METH on stress responsivity measured by DA release in the nucleus accumbens shell (NA SHELL) and core (NA CORE) during acute restraint stress were also examined. Methods Male rats received single injections of METH (2.0 mg/kg i.p.) or saline (SAL) for 10 days and then were killed 24 h after the last injection. DAT and NET protein in NA, striatum (STR), medial prefrontal cortex (mPFC), and hippocampus were assayed by Western blot analysis. Experiment 2 measured basal extracellular DA concentrations and restraint-stress-induced DA release in vivo in the NA SHELL and CORE of SAL- and METH-pretreated rats after 24-h withdrawal. Experiment 3 examined the in vivo regulation of extracellular DA in the NA SHELL and/or CORE after local administration of GBR12909 (50 μM) or nisoxetine (100 μM; NA SHELL). Results Subchronic METH increased DAT but not NET immunoreactivity in the NA compared to the STR and mPFC. METH reduced basal extracellular DA and blocked restraint-stress-induced DA release in the NA SHELL. DA uptake blockade increased extracellular DA more in the NA SHELL of METH rats, whereas NE uptake blockade increased basal DA concentrations to a similar extent in METH and SAL rats. Conclusions These results suggest that subchronic METH exposure selectively increases NA DAT and consequently reduces basal and stress-induced DA release in the NA SHELL during early withdrawal.     

Amphetamine: Differential effects on defensive flight and motor behavior in the rat

As in previous research, hooded rats treated with an acute high dose of d-amphetamine sulfate (5 mg/kg free base) showed a dramatic defensive flight reaction to a novel stimulus (mechanical robot) that did not elicit flight from saline controls. Both the defense response and stereotypy behavior (repetitive movements and oral, licking chewing) were assessed at eight time periods after injection: 1, 15, 30, 45, 75, 105, 135, and 165 min. The defense response peaked early (15–30 min) after injection and showed a significant decline by 75 min, with no reemergence as stereotypy subsided. Stereotypy peaked later (45 min) and did not decline until 105 min. Tests in the absence of the robot provided a control for motor effects of the drug. Whereas stereotypy occurred in both Robot and No Robot conditions, the defense response occurred only in the Robot condition. These results were thought to provide further evidence that the effects of amphetamine on defensive flight could not be attributed to purely motor reactions. Thus, amphetamine-induced defensive flight may be an appropriate nharmacological model of affective psychosis. As such, it may be helpful in establishing differential pharmacological profiles for effective versus motor potencies of potential antipsychotic compounds.     

Oral bioavailability of the novel cannabinoid CB1 antagonist AM6527: effects on food-reinforced behavior and comparisons with AM4113

Drugs that interfere with cannabinoid CB1 transmission suppress food-motivated behaviors, and may be clinically useful as appetite suppressants. Several CB1 receptor inverse agonists, such as rimonabant and AM251, as well as the CB1 receptor neutral antagonist, AM4113, have been assessed for their effects on food-motivated behavior. One important criterion for establishing if a drug may be useful clinically is the determination of its oral bioavailability. The present studies compared the effects of AM4113 and a novel CB1 antagonist, AM6527, on the suppression of food-reinforced behavior following intraperitoneal (IP) and oral administration. AM4113 and AM6527 both suppressed lever pressing after IP injections. The ED₅₀ for the effect on FR5 responding was 0.78 mg/kg for IP AM4113, and 0.5763 mg/kg for IP AM6527. AM6527 also was effective after oral administration (ED₅₀ = 1.49 mg/kg), however, AM 4113 was ineffective up to oral doses of 32.0 mg/kg. AM 4113 may be very useful as a research tool, but its lack of oral activity suggests that this drug might not be effective if orally administered in humans. In contrast, AM 6527 is an orally active CB1 antagonist, which may be useful for clinical research on the appetite suppressant effects of CB1 antagonists.     

The effects of chronic buprenorphine on intake of heroin and cocaine in rats and its effects on nucleus accumbens dopamine levels during self-administration

Rationale Buprenorphine reduces both heroin and cocaine intake in opioid addicts, but the mechanisms remain unclear.Objectives To determine the effects of chronic buprenorphine treatment on intake of heroin and/or cocaine and measure nucleus accumbens (NAc) dopamine (DA) levels during self-administration.Methods In experiment 1, plasma levels of buprenorphine were determined in rats with buprenorphine osmotic minipumps (3.0 mg/kg/day) using an ELISA. In experiment 2, rats self-administered (FR1) one dose of heroin [(0.025, 0.05, or 0.1 mg/kg/infusion (inf)] and one dose of cocaine (0.25, 0.5, or 1.0 mg/kg/inf) before and under sham or chronic buprenorphine treatment (1.5 or 3.0 mg/kg/day). In experiment 3, the effect of sham or chronic buprenorphine treatment (3.0) on heroin (0.05 mg/kg/inf) or cocaine (0.5 mg/kg/inf) self-administration under FR5 and progressive ratio (PR) schedules was evaluated. In experiment 4, in vivo microdialysis sampling from the NAc was carried out during heroin (0.05 mg/kg/inf) or cocaine (0.5 mg/kg/inf) self-administration (FR1) under sham or buprenorphine treatment (3.0).Results Buprenorphine levels in plasma were stable over time. Buprenorphine treatment had no effect on total heroin intake at any dose or under any schedule, whereas it suppressed cocaine intake at all doses and under all schedules. Buprenorphine enhanced basal levels of DA, attenuated the NAc DA response to heroin, and enhanced the DA response to cocaine. It is interesting to note that buprenorphine increased the latency to respond to drug-associated cues at the start of self-administration sessions.Conclusions Chronic buprenorphine reduces cocaine, but not heroin, intake and possibly reduces drug seeking by reducing the salience of the drug-associated cues.     

Effects of halothane anaesthesia on extracellular levels of dopamine,dihydroxyphenylacetic acid,homovanillic acid and 5-hydroxyindolacetic acid in rat striatum: a microdialysis study

Summary The effects of halothane anaesthesia on striatal extracellular levels of dopamine, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5HIAA) were investigated in microdialysis experiments. Induction of anaesthesia was accompanied by a rapid increase in dopamine levels and a slower increase in DOPAC and HVA. 5HIAA was not affected. The reduction of dopamine levels induced by apomorphine 0.05 mg/kg appeared with a shorter latency in conscious rats than in anaesthetised rats but the maximum decrease was unaffected by anaesthesia. The decreases in dopamine and DOPAC induced by -methyl-p-tyrosine 50 mg/kg were affected in opposite directions by halothane: the dopamine reduction was more pronounced while the DOPAC reduction was less pronounced in anaesthetized than in conscious animals. In no case was a qualitative shift in the response observed. It is concluded that halothane may influence the levels of dopamine as well as the response to dopaminergic drugs.Send offprint requests to L. Ståhle at the above address     

Role of muscarinic receptors in the activation of the ventral subiculum and the consequences for dopamine release in the nucleus accumbens

Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is an active herbal component traditionally used in China for treating various ailments. Emodin exerts antiproliferative effects in many cancer cell lines and the actual molecular mechanism of which is still not clear. Since apoptosis could be a potential mechanism to explain these effects, we tested whether emodin induces cell death in human cervical cancer cells. Our results suggest that emodin exerts antiproliferative effects in human cervical cancer cells. Emodin inhibited DNA synthesis and induced apoptosis as demonstrated by increased nuclear condensation, annexin binding and DNA fragmentation in Bu 25TK cells in the presence of emodin. Moreover, we demonstrate for the first time in human cervical cancer cells that the apoptotic pathway involved in emodin-induced apoptosis is caspase-dependent and presumably through the mitochondrial pathway, as shown by the activation of caspases-3, -9 and cleavage of poly(ADP-ribose) polymerase.     

Apoptosis induction and histological changes in rat kidney following Cd-doped silica nanoparticle exposure: evidence of persisting effects

Abstract

Histological and immunocytochemical methods were used to examine rat’s renal responses to intratracheal (i.t.) instillation of model cadmium-containing silica nanoparticles (Cd-SiNPs) and also exploring whether these potential modifications would be associated with toxicogenomic changes. Renal effects of Cd-SiNPs (1?mg/rat), CdCl₂ (400?µg/rat), SiNPs (600?µg/rat) or 0.1?ml saline (control), assessed 7 and 30?d post-i.t., included (i) induction of apoptosis, (ii) cell proliferation and (iii) the overall toxic response evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, proliferating cell nuclear antigen (PCNA) immunohistochemistry as well as Periodic acid Schiff and Hematoxylin & Eosin, respectively. Area-specific apoptosis was observed in all treatment groups, the cortex and inner medulla being the most affected regions: the apoptotic changes were apparent seven days post-exposure in both areas and were still observable in inner medulla at day 30. Apoptotic frequency increase was more pronounced in Cd-SiNP-treated animals compared to either CdCl₂ or SiNPs groups. At day 7, the observed parallel increased number of PCNA immunopositive cells may be associated with an enhanced cell proliferation aimed at replacing the damaged cells. Histopathological findings demonstrated comparable morphological changes of the renal structure (at glomerular and tubular levels) occurring after all treatments at both time-points and more markedly 30?d after instillation. Both morphological and toxicogenomic evaluations confirmed long-lasting renal effects of Cd-SiNPs on apoptosis and regulatory processes. Bare SiNPs i.t. administration caused morphological and apoptotic changes but did not modify gene expression profile in kidney. These findings substantiate the notion that multiple assays and an integrated testing strategy should be recommended to characterize toxicological responses to nanoparticles in mammalian systems.     

Preliminary evidence for methamphetamine-induced behavioral and ocular effects in rat offspring following exposure during early organogenesis

Gravid Sprague-Dawley CD (VAF) rats received 50 mg/kg (d,l)-methamphetamine (MA) HCl (expressed as free base,N=15) or distilled water (N=6) by SC injection × 2/day in a 3 ml/kg volume on embryonic (E) days 7–12. Control rats were pair-fed to MA-exposed dams on days E7–18. No control dams failed to deliver; however, of 15 MA-exposed dams 4 did not deliver (2 died and 2 had completely resorbed litters). One additional MA litter had all the offspring die shortly after birth. There was no difference between groups on offspring postnatal (P) body weight. The offspring exposed prenatally to MA had significantly lower olfactory orientation scores (P9, 11, 13) to their home cage scent. In a test of early activity (P10, 12, 14) the MA-exposed progeny were marginally less active than controls. MA-exposed offspring exhibited hyperreactivity and marginally shortened response latency on a test of acoustic startle (P27). Motor activity showed no differential response in MA treated or control offspring to MA (P63) or fluoxetine challenge (P70). However, the MA offspring were more active than controls with respect to central and side activity during the second week of testing. No group differences were found for performance in a straight swimming channel or on the number of errors committed or latency to escape in a complex (Cincinnati) water maze (P84). Prenatal exposure to MA also induced eye defects (i.e., anophthalmia, microphthalmia and folded retina) in 16.7% of the progeny. However, MA did not effect hippocampal or neostriatal monoamine levels when measured on P28. These data support the hypothesis that MA is behaviorally and ocularly teratogenic to the developing rat and results in functional deficits when compared to offspring of pair-fed controls.     

Triclosan exposure reduces thyroxine levels in pregnant and lactating rat dams and in directly exposed offspring

Thyroid disrupting chemicals can potentially disrupt brain development. Two studies investigating the effect of the antibacterial compound triclosan on thyroxine (T₄) levels in rats are reported. In the first, Wistar rat dams were gavaged with 75, 150 or 300 mg triclosan/kg bw/day throughout gestation and lactation. Total T₄ serum levels were measured in dams and offspring, and all doses of triclosan significantly lowered T₄ in dams, but no significant effects on T₄ levels were seen in the offspring at the end of the lactation period. Since this lack of effect could be due to minimal exposure through maternal milk, a second study using direct per oral pup exposure from postnatal day 3–16 to 50 or 150 mg triclosan/kg bw/day was performed. This exposure pointed to significant T₄ reductions in 16 day old offspring in both dose groups. These results corroborate previous studies showing that in rats lactational transfer of triclosan seems limited. Since an optimal study design for testing potential developmental neurotoxicants in rats, should include exposure during both the pre- and postnatal periods of brain development, we suggest that in the case of triclosan, direct dosing of pups may be the best way to obtain that goal.     

The effects of exposure to diazepam during various stages of gestation or during lactation on the development and behavior of rat pups

In the present study we have investigated the effects of diazepam (DZP) (10 mg/kg) treatment of rat dams during different periods of gestation or during lactation on the development and behavior of their offspring. The results show that DZP exposure during different phases of early development has differing effects on later behavior. Exposure during mid-gestation resulted in early and transient hyperactivity, but no learning or memory deficits at 2 months of age were observed. However, both late prenatal and early postnatal exposure to DZP resulted in significant behavioral changes. Late prenatal treatment caused no hyperactivity but resulted in poor performance on the learning and retention of a choice discrimination task, while early postnatal exposure resulted in consistent and lasting hyperactivity and in substantial discrimination learning and retention deficits at 2 months of age.     

Behavioural pharmacology of the non-competitive NMDA antagonists dextrorphan and ADCI: relations between locomotor stimulation, anticataleptic potential and forebrain dopamine metabolism

The effects of systemic administration of the non-competitive N-methyl-D-aspartate (NMDA) antagonists dextrorphan (10–40mg/kg, i.p.) and [±]-5-aminocarbonyl-10,11-dihydro-5H-dibenzo[a,d]cycloheptan-5,10-imine (ADCI) (25–70mg/kg, i.p.) on basal ganglia-mediated behaviour and on forebrain dopamine metabolism were investigated in rats. Dextrorphan increased locomotor activity but did not induce stereotyped sniffing. ADCI failed to produce any significant motor stimulant and motor depressant actions. Both dextrorphan and ADCI dose-dependently antagonized catalepsy induced by the D-1 dopamine receptor antagonist SCH 23390 or the D-2 dopamine receptor antagonist haloperidol. Only the highest doses of dextrorphan and ADCI increased dopamine metabolism in the prefrontal cortex and/or in the nucleus accumbens, but not in the dorsal striatum. Our results show that dextrorphan and ADCI produce some of the behavioural effects (antagonism of experimentally induced catalepsy) and neurochemical actions (regionally selective stimulation of dopamine metabolism) that have previously been observed in the prototypical non-competitive NMDA antagonist, dizocilpine. The failure of ADCI to induce hyperlocomotion and stereotypy suggests that anticataleptic doses of ADCI may be devoid of the psychotomimetic actions commonly associated with non-competitive blockade of NMDA receptor function. Received: 10 September 1996 / Accepted: 30 January 1997     

Differential experience following developmental lead exposure: effects on brain and behavior

Long Evans hooded rat pups were exposed to lead (Pb) via the maternal milk supply from Postnatal Day 1 (PN 1) to PN 25. Mothers were fed diets containing either 4% Pb CO3 (High Pb), 0.4% Pb CO3 (Low Pb) or 2.2% Na2 CO3 (Controls) throughout this period. Pups were weaned at PN 30 and littermates randomly assigned to either an Enriched or Isolated environment for a period of 30 days. Increases in activity levels and decreases in passive avoidance latencies were observed in Pb exposed animals. However, there were minimal effects due to Pb on symmetrical maze performance. Experience in the enriched environment had no effect on open field activity levels but resulted in a marked reduction in symmetrical maze errors. While enrichment had no effect on passive avoidance performance in High Pb animals, it was capable of raising latencies in Low Pb animals to Control values. Thus, the therapeutic value of environmental enrichment in Pb exposed animals depends on both the task employed and the severity of the pre-enrichment brain damage. From both brain regional analysis and behavioral testing results, it appeared that the hippocampus was a major site of Pb action. From comparison of blood Pb levels of our animals and those reported in children, it became apparent that the rat may have a greater tolerance for Pb, and as such, caution must be used in making direct comparisons between the two species in terms of blood Pb levels.     

Identification and human exposure prediction of two aldehyde oxidase-mediated metabolites of a methylquinoline-containing drug candidate

1. Aldehyde oxidase (AO enzymes)-mediated oxidation predominantly occurs at a carbon atom adjacent to the nitrogen on aromatic azaheterocycles. In the current report, we identified that AO enzymes oxidation took place at both the C-2 and C-4 positions of the methylquinoline moiety of Compound A based on data from mass spectrometric analysis, AO enzymes “litmus” test, and comparison with authentic standards.

2. To assess the potential for inadequate coverage for these two AO enzyme-mediated metabolites in nonclinical safety studies, given concerns due to differences in AO enzymes expression between preclinical species and humans, the human circulating levels of the two AO enzyme-mediated metabolites were predicted prospectively using in vitro and in vivo models. Both formation clearance and elimination clearance of the two metabolites were predicted based on in vitro to in vivo correlation and comparison with in vivo data from rats.

3. The result showed that the 4-OH metabolite of Compound A would account for less than 3% of the total drug-related exposure in human plasma, while the exposure to the 2-oxo metabolite would be relatively high (～70%).

4. The predicted human exposure levels for the two metabolites are in similar ranges as those observed in monkeys. These data taken together support the advancement to clinical development of Compound A.     

Perinatal exposure to cannabichromene and delta 9-tetrahydrocannabinol: separate and combined effects on viability of pups and on male reproductive system at maturity

The effects of cannabichromene (CBC), delta 9-tetrahydrocannabinol (delta 9-THC) and their combination (all doses 50 mg/kg orally) were determined after being administered to female mice for 7 days beginning on the 20th day of gestation. The THC treatment reduced postnatal viability, impaired male reproductive behavior at maturity and significantly reduced seminal vesicle weights. No changes from control values occurred after CBC or CBC + THC. Thus, CBC alone at this dosage did not act like THC; moreover, it antagonized the effects of THC when the two were given in combination.     

Differential effects of methamphetamine and cocaine on behavior and extracellular levels of dopamine and 3,4-dihydroxyphenylalanine in the nucleus accumbens of conscious rats

The stress-induced hyperthermia procedure, in which effects of drugs on basal (T₁) and stress-induced body temperature (T₂) are measured, predicts anxiolytic drug effect. Serotonergic drugs alter these responses and here, we studied the role of 5-HT_1A receptors in stress-induced hyperthermia by using 5-HT_1A receptor knockout mice. Three strains (129/Sv, Swiss Webster and C57Bl6) were used because genetic background can significantly modulate the null phenotype. We found that GABA-ergic drugs with an anxiolytic profile and stimulate ₂ subunit containing GABA_A receptors, including diazepam and L838,417, result in reduced ΔT (ΔT = T₂ − T₁). The ₁ subunit containing GABA_A receptor was found to be primarily involved in regulation of basal body temperature T₁ and its stimulation can induce hypothermia. In addition, stimulation of 5-HT_1A receptors by buspirone results in a reduced ΔT, while stimulation of 5-HT₇ receptors primarily results in hypothermia. The null mutation of 5-HT_1A receptors resulted in differences in drug-sensitivity that was further modulated by the genetic background. In particular, the null mutation on the SW and C57Bl6 backgrounds resulted in differential diazepam/L838,417 and 5-CT responses respectively. This indicates an interaction between the 5-HT_1A receptor and genetic background and demonstrates the importance of selecting the background strain in a receptor knockout model.     

Cardiogenic effects of trichloroethylene and trichloroacetic acid following exposure during heart specification of avian development.

Trichloroethylene (TCE) and its metabolite trichloroacetic acid (TCA) are common drinking water contaminants in the United States. Both chemicals have been implicated in causing congenital heart defects (CHD) in human epidemiological and animal model studies. However, the latter studies have primarily focused on assessment of cardiac morphology at late embryonic stages. Here, we tested whether treating avian embryos with TCE or TCA during an exposure window encompassing cardiac specification (Hamburger-Hamilton [HH] 3+) until the onset of chambering (HH 17) informs the etiology of CHD at later stages of development. Embryos were exposed to TCE or TCA via direct injection into the yolk, over a range of doses that included each compound's maximum contaminant level as established by the U.S. Environmental Protection Agency. A modified TUNEL (Terminal deoxynucleotide transferase mediated dUTP-biotin Nick-End Labeling) assay indicated that neither compound induced apoptotic cell death in ventricular myocytes or endocardiocytes at HH 18. However, mid-range dosages of TCE increased myocyte and endocardiocyte proliferation by this time, as determined by monitoring BrdU incorporation; in contrast, an intermediate dose of TCA inhibited proliferation in endocardiocytes. These cellular changes had no apparent functional consequences because all measured hemodynamic parameters were normal for TCE- and TCA-exposed embryos at HH 18, HH 21, and HH 23. In summary, TCE or TCA exposure during the cardiac specification window has only minimal effects on the developing avian heart. These results sharply contrast with our previously reported observations following administration of equivalent doses during a window of valvuloseptal morphogenesis. Taken together, these findings indicate that, as for other teratogens, sensitivity is dictated by the embryo's stage of development.