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To gain insights into the role of purinergic receptors in oligodendrocyte development, we characterized the expression and functional activity of P2 receptors in cultured rat oligodendrocyte progenitors and investigated the effects of ATP and its breakdown products on the migration and proliferation of this immature glial cell population. Using Western blot analysis, we show that oligodendrocyte progenitors express several P2X (P2X(1,2,3,4,7)) and P2Y (P2Y(1,2,4)) receptors. Intracellular Ca(2+) recording by Fura-2 video imaging allowed to determine the rank potency order of the P2 agonists tested: ADPbetaS = ADP = Benzoyl ATP > ATP > ATPgammaS > UTP, alpha,beta-meATP ineffective. Based on the above findings, on pharmacological inhibition by the antagonists oxATP and MRS2179, and on the absence of alpha,betameATP-induced inward current in whole-cell recording, P2X(7) and P2Y(1) were identified as the main ionotropic and metabotropic P2 receptors active in OPs. As a functional correlate of these findings, we show that ATP and, among metabotropic agonists, ADP and the P2Y(1)-specific agonist ADPbetaS, but not UTP, induce oligodendrocyte progenitor migration. Moreover, ATP and ADP inhibited the proliferation of oligodendrocyte progenitors induced by platelet-derived growth factor, both in purified cultures and in cerebellar tissue slices. The effects of ATP and ADP on cell migration and proliferation were prevented by the P2Y(1) antagonist MRS2179. By confocal laser scanning microscopy, P2Y(1) receptors were localized in NG2-labeled oligodendrocyte progenitors in the developing rat brain. These data indicate that ATP and ADP may regulate oligodendrocyte progenitor functions by a mechanism that involves mainly activation of P2Y(1) receptors.

The recurrence rates during lithium preventive treatment were investigated in a sample of 270 Mood Disorder subjects subdivided according to their onset time for lithium prophylaxis as very early (within 5 years from the onset of illness), early (6-10 years), late (11-20 years) and very late (more than 21 years). 131 subjects of the sample followed for 4 years prolonged the observation for a further period of 8 years. Results indicated that beginning lithium therapy within the first ten years of illness predicts better preventive outcomes than beginning prophylaxis later, both in major depression, recurrent and bipolar patients.

A double-blind study was undertaken to investigate the period of treatment with the beta-adrenoreceptor/5-hydroxytryptamine 1A (5-HT1A) antagonist pindolol required to enhance the antidepressant effects of paroxetine. After 1 week of a placebo run-in period, 63 untreated major depressive inpatients were randomly assigned to three different groups. Group 1 received paroxetine (20 mg/day) plus placebo (4 weeks). Group 2 received paroxetine (20 mg/day) plus pindolol (7.5 mg/day) for 1 week and placebo for 3 weeks. Group 3 received both active treatments for the entire duration of the study (4 weeks). Clinical response was defined as a reduction of the score in the Hamilton Rating Scale for Depression (HAM-D) to 8 or below. Also, to preliminarily examine whether beta-adrenoreceptor blockade was involved in the action of pindolol, another group of 10 inpatients was treated in an open-label manner with paroxetine (20 mg/day) plus 50 mg/day of the beta-adrenergic antagonist metoprolol, devoid of significant affinity for 5-HT1A receptors. At endpoint, the incidence of treatment-emergent side effects did not significantly differ among the three groups. After 1 and 2 weeks of treatment, the two groups treated with paroxetine plus pindolol displayed a significantly greater response rate than the group treated with paroxetine plus placebo. At study completion, only the patients treated with pindolol for the entire period showed a significantly greater response rate (p = 0.05). HAM-D score were also significantly lower at endpoint in patients treated with the combination for 4 weeks (p = 0.00003). The group of patients treated with paroxetine and metoprolol exhibited a side-effect profile comparable to that of paroxetine alone. Response rates were also comparable. These findings support the efficacy of pindolol, but not of metoprolol, in accelerating the antidepressant effect of paroxetine and suggest that the administration of pindolol for the entire period of the acute treatment may increase the efficacy of paroxetine.

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