Luigi Pira

Δ9-Tetrahydrocannabinol decreases extracellular GABA and increases extracellular glutamate and dopamine levels in the rat prefrontal cortex: an in vivo microdialysis study

Cannabinoid modulation of prefrontal cortex and hippocampus neuronal functioning has been correlated to the disruptive action of marijuana on memory tasks. This study investigates the effects of Δ9-tetrahydrocannabinol (Δ9-THC) on dopamine, glutamate and GABA levels in vivo by brain microdialysis in the prefrontal cortex. Δ9-THC (1 mg/kg, i.v.) significantly increased extracellular dopamine and glutamate levels and decreased GABA levels. These effects were prevented by the cannabinoid antagonist SR141716A (1 mg/kg, i.v.), which per se was ineffective. These results suggest that Δ9-THC disrupt the normal interplay between neurotransmitters in this area and may bear relevance in understanding neuronal mechanisms underlying cannabinoid-induced cognitive deficits.

Alpha2‐adrenoceptor mediated co‐release of dopamine and noradrenaline from noradrenergic neurons in the cerebral cortex

Previous results suggest that extracellular dopamine (DA) in the rat cerebral cortex originates from dopaminergic and noradrenergic terminals. To further clarify this issue, dialysate DA, dihydroxyphenylacetic acid (DOPAC) and noradrenaline (NA) were measured both in the medial prefrontal cortex (mPFC) and in the occipital cortex (OCC), with dense and scarce dopaminergic projections, respectively. Moreover, the effect of the α2‐adrenoceptor antagonist RS 79948 and the D2‐receptor antagonist haloperidol on extracellular DA, DOPAC and NA was investigated. Extracellular DA and DOPAC concentrations in the OCC were 43% and 9%, respectively, those in the mPFC. Haloperidol (0.1 mg/kg i.p.) increased DA and DOPAC (by 35% and 150%, respectively) in the mPFC, but was ineffective in the OCC. In contrast, RS 79948 (1.5 mg/kg i.p.) increased NA, DA and DOPAC, both in the mPFC (by approximately 50%, 60% and 130%, respectively) and the OCC (by approximately 50%, 80% and 200%, respectively). Locally perfused, the DA transporter blocker GBR 12909 (10 µm) was ineffective in either cortex, whereas desipramine (DMI, 100 µm) markedly increased extracellular NA and DA in both cortices. The weak haloperidol effect on DA efflux was not enhanced after DA‐ and NA‐transporter blockade, whereas after DMI, RS 79948 markedly increased extracellular NA, and especially DA and DOPAC in both cortices. The results support the hypothesis that most extracellular DA in the cortex is co‐released with NA from noradrenergic terminals, such co‐release being primarily controlled by α2‐adrenoceptors.

Inhibition of stress- or anxiogenic-drug-induced increases in dopamine release in the rat prefrontal cortex by long-term treatment with antidepressant drugs

The effects of long‐term treatment with imipramine or mirtazapine, two antidepressant drugs with different mechanisms of action, on the response of cortical dopaminergic neurons to foot‐shock stress or to the anxiogenic drug FG7142 were evaluated in freely moving rats. As expected, foot shock induced a marked increase (+ 90%) in the extracellular concentration of dopamine in the prefrontal cortex of control rats. Chronic treatment with imipramine or mirtazapine inhibited or prevented, respectively, the effect of foot‐shock stress on cortical dopamine output. Whereas acute administration of the anxiogenic drug FG7142 induced a significant increase (+ 60%) in cortical dopamine output in control rats, chronic treatment with imipramine or mirtazapine completely inhibited this effect. In contrast, the administration of a single dose of either antidepressant 40 min before foot shock, had no effect on the response of the cortical dopaminergic innervation to stress. These results show that long‐term treatment with imipramine or mirtazapine inhibits the neurochemical changes elicited by stress or an anxiogenic drug with an efficacy similar to that of acute treatment with benzodiazepines. Given that episodes of anxiety or depression are often preceded by stressful events, modulation by antidepressants of the dopaminergic response to stress might be related to the anxiolytic and antidepressant effects of these drugs.

Analysis of CYP2D6 Allele Frequencies and Identification of Novel SNPs and Sequence Variations in Sardinians

The CYP2D6 enzyme is involved in the metabolism of many commonly prescribed drugs. The presence of polymorphisms in the CYP2D6 gene may modulate the enzyme level and activity affecting individual responses, to pharmacological treatment in drug level, response and adverse reactions. Aims. This study aimed to analyze the determination of allele frequencies in Sardinians and the comparison to frequencies found in the Caucasian Population. Methods and Materials. We used a Long PCR strategy coupled to direct genomic DNA sequencing analysis. An amplification allele-specific was carried out to infer the correct allelic phase. The TaqMan Gene Copy Number Assay (Applied Biosystems) was used to verify the presence of gene deletions/multiplications. Results and Conclusions. Our results indicated that CYP2D6 allele frequencies in Sardinians differed from those previously detected in the Caucasian Population. Moreover, three new SNPs and four novel haplotypes were identified.

In vivo pharmacological profile of S 38093, a novel histamine H3 receptor inverse agonist

Abstract S 38093, a novel histamine H3 receptor inverse agonist, was tested in a series of neurochemical and behavioral paradigms designed to evaluate its procognitive and arousal properties. In intracerebral microdialysis studies performed in rats, S 38093 dose‐dependently increased histamine extracellular levels in the prefrontal cortex and facilitated cholinergic transmission in the prefrontal cortex and hippocampus of rats after acute and chronic administration (10 mg/kg i.p.). Acute oral administration of S 38093 at 0.1 mg/kg significantly improved spatial working memory in rats in the Morris water maze test. The compound also displayed cognition enhancing properties in the two‐trial object recognition task in rats, in a natural forgetting paradigm at 0.3 and 1 mg/kg p.o. and in a scopolamine‐induced memory deficit situation at 3 mg/kg p.o. The property of S 38093 to promote episodic memory was confirmed in a social recognition test in rats at 0.3 and 1 mg/kg i.p. Arousal properties of S 38093 were assessed in freely moving rats by using electroencephalographic recordings: at 3 and 10 mg/kg i.p., S 38093 significantly reduced slow wave sleep delta power and induced at the highest dose a delay in sleep latency. S 38093 at 10 mg/kg p.o. also decreased the barbital‐induced sleeping time in rats. Taken together these data indicate that S 38093, a novel H3 inverse agonist, displays cognition enhancing at low doses and arousal properties at higher doses in rodents.

Quetiapine anxiolytic-like effect in the Vogel conflict test is serotonin dependent.

There is growing evidence to show that atypical antipsychotic quetiapine might exert an anxiolytic effect in patients. Nevertheless, the mechanism underlying this effect has not yet been fully explored. Like other anxiolytic drugs, quetiapine exhibits partial agonistic activity toward serotonergic 1A (5HT1A) receptors. The involvement of the serotonin system in anxiety, particularly of 5HT1A receptors, has been widely documented. In this study we have investigated whether different doses of quetiapine (5, 10, and 30 mg/kg, oral gavage) administered to C57BL6/N mice could produce an anxiolytic effect in the Vogel conflict test, a classical model of anxiety, and whether or not the selective 5HT1A antagonist WAY100635 (0.1 mg/kg, subcutaneously) might prevent such an effect. Our results show that 10 mg/kg quetiapine exhibits an anxiolytic effect, that is, at least in part, 5HT1A-mediated, because it is completely eliminated by WAY100635.

Genotyping of CYP2D6 Polymorphisms by MALDI-TOF Mass Spectrometry in Sardinian People

The CYP2D6 enzyme is involved in the metabolism of many commonly prescribed drugs. The presence of CYP2D6 gene SNPs can alter CYP2D6 enzymatic activity with effects ranging considerably within a population. Objectives. In this study, we have developed a genotyping platform able to determine the alleles related to interindividual variability in the CYP2D6 gene. Design and Methods. We used a long PCR strategy coupled to MALDI-TOF mass spectrometry (Sequenom) to develop a SNPs genotyping method. Furthermore, an amplification allele specific was carried out to infer the correct allelic phase. Results. We tested the multiplex platform in 250 DNA Sardinian samples and found it to be 100% concordant with the sequencing results of our previous work. Conclusions. The MALDI-TOF-based multiplexing system allowed simultaneous and efficient genotyping of a set of CYP2D6 SNPs, evidencing its potential use in diagnostic test development to predict drug responses and clinical outcomes.