| Abstract No.: | B-A2004 |
| Country: | Canada |
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| Title: | DEVELOPMENT AND PERSISTENCE OF 5-HT1A-MEDIATED HYPERPOLARIZATION OF CORTICOCORTICAL NEURONS IN RAT PREFRONTAL CORTEX |
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| Authors/Affiliations: | 1 Nathalie M Goodfellow*; 1 Sameera M Kassam; 1 Evelyn K Lambe;
1 University of Toronto, ON, Canada
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| Content: | The serotonin [5-hydroxytryptamine (5-HT)]1A receptors have been implicated in determining anxiety levels (Ramboz et al., 1998) and alterations to this receptor in the early postnatal period appear critical for establishing normal anxiety levels in adulthood (Gross et al., 2002). While 5-HT1A currents have been examined in layer V neurons during development (Zhang et al., 2003; Beique et al., 2004), evidence from human and animal studies suggests there may also be abundant 5-HT1A receptors in superficial layers of prefrontal cortex (Aznavour et al., 2006; Burnet al., 1995; Palchaudhuri and Flugg, 2005). These layer II/III neurons are of particular interest since they are involved in the intracortical processing which contributes to the interpretation of threatening stimuli. Using whole-cell patch-clamp recordings in brain slices of rat prefrontal cortex, we observed that bath application of 5-HT [10 µM] elicits large hyperpolarizing currents in layer II/III pyramidal neurons. These currents could be completely blocked the selective 5-HT1A antagonist, WAY100635 [30 nM]. Consistent with mediation by somatodendritic 5-HT1A receptors, the 5-HT-elicited hyperpolarizations persisted in the presence of glutamatergic blockers (CNQX [10μM] and AP5 [50μM]), GABAergic blocker (bicuculline [10μM]) as well as action potential blockade (TTX [2μM]). A developmental examination revealed that 5-HT induced hyperpolarizing currents in layer II/III pyramidal neurons at all ages studied (postnatal day 6 – 40). It appears that 5-HT1A receptors are present much earlier in layer II/III corticocortical neurons than in layer V cortical output neurons. Previous work has shown that 5-HT1A effects only occur in layer V neurons in older rats (
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