Semaphorin 3d and Semaphorin 3e Direct Endothelial Motility through Distinct Molecular Signaling Pathways

Class 3 semaphorins were initially described as axonal growth cone guidance molecules that signal through plexin and neuropilin coreceptors and since then have been established to be regulators of vascular development. Semaphorin 3e (Sema3e) has been shown previously to repel endothelial cells and is the only class 3 semaphorin known to be capable of signaling via a plexin receptor without a neuropilin coreceptor. Sema3e signals through plexin D1 (Plxnd1) to regulate vascular patterning by modulating the cytoskeleton and focal adhesion structures. We showed recently that semaphorin 3d (Sema3d) mediates endothelial cell repulsion and pulmonary vein patterning during embryogenesis. Here we show that Sema3d and Sema3e affect human umbilical vein endothelial cells similarly but through distinct molecular signaling pathways. Time-lapse imaging studies show that both Sema3d and Sema3e can inhibit cell motility and migration, and tube formation assays indicate that both can impede tubulogenesis. Endothelial cells incubated with either Sema3d or Sema3e demonstrate a loss of actin stress fibers and focal adhesions. However, the addition of neuropilin 1 (Nrp1)-blocking antibody or siRNA knockdown of Nrp1 inhibits Sema3d-mediated, but not Sema3e-mediated, cytoskeletal reorganization, and siRNA knockdown of Nrp1 abrogates Sema3d-mediated, but not Sema3e-mediated, inhibition of tubulogenesis. On the other hand, endothelial cells deficient in Plxnd1 are resistant to endothelial repulsion mediated by Sema3e but not Sema3d. Unlike Sema3e, Sema3d incubation results in phosphorylation of Akt in human umbilical vein endothelial cells, and inhibition of the PI3K/Akt pathway blocks the endothelial guidance and cytoskeletal reorganization functions of Sema3d but not Sema3e.     

Tricyclic antidepressant drugs: Attenuation of excitatory effects of d-lysergic acid diethylamide (LSD) on acoustic startle response

At a dose of 5 mg/kg, the tricyclic antidepressant drugs chlorimipramine (CIMI), desipramine (DMI), imipramine (IMI), and chlordesipramine (C-DMI) all blocked the excitatory effects of a low dose (30 μg/kg) of LSD on the acoustic startle response in the rat. Over a dose range from 1–5 mg/kg, CIMI and DMI were about equally potent in blocking the LSD effect, despite the fact that both drugs actually increased brain levels of LSD. In contrast, α-methyl-p-tyrosine did not block the effect of LSD on startle. By themselves, DMI, IMI and C-DMI increased startle amplitude 20–30% whereas CIMI alone had no effect on startle. The ability of CIMI and IMI to block the excitatory effect of LSD on startle is consistent with the hypothesis that prior cessation of raphe cell firing caused indirectly by these drugs with no resultant change in 5-HT availability should pre-empt the ability of LSD to increase startle by directly inhibiting raphe cell firing and decreasing 5-HT availability. The finding that the other tricyclics also block the effect of LSD is not explained by that hypothesis. Results are discussed in terms of the serotonin hypothesis of the action of hallucinogenic drugs on behavior.     

Dopamine and norepinephrine innervated cells in the rat prefrontal cortex: Pharmacological differentiation using microiontophoretic techniques

Biochemical and fluorescence histochemical evidence suggest dopaminergic and noradrenergic projections to the prefrontal cortex which primarily innervate the deep layers (V & VI) and superficial layers respectively. Using microiontophoretic techniques, we determined the sensitivity of cells in the rat prefrontal cortex to the inhibitory effects of dopamine (DA) and norepinephrine (NE). A clear correspondence was found between the response of a cell to DA and NE and the layer in which that cell resided. Thus cells in layers II and III were more sensitive to NE than DA, whereas the opposite was true for layers V and VI. Applied microiontophoretically, desmethylimipramine, a selective NE uptake blocker, potentiated the inhibitory effects of NE in layers II and III but not in layers V and VI. Benztropine, a DA uptake blocker, potentiated the inhibitory effects of DA only on DA sensitive cells in layers V and VI. Trifluoperazine, a DA receptor blocker, selectively blocked DA inhibition of cell activity in the deep layers. Similar experiments performed in the hippocampus and accumbens nucleus yielded results identical to those obtained for cortical layers II and III (primary NE innervation) and V and VI (primary DA innervation, respectively).These findings suggest that using microiontophoretic techniques one can pharmacologically differentiate between DA and NE innervated cells in the rat prefrontal cortex.