of inducible nitric oxide synthase (iNOS) and NO, followed by an increase in adenosine (AD). This cascade is critical in promoting recovery sleep (RS); however, it's triggers are unknown. We hypothesized that iNOS induction is triggered by an increase in extracellular glutamate (Glu), and that increase in AD prevents a prolonged toxic increase in Glu. This is because of the activation of the inhibitory AD A1 receptor (A1R). To test this hypothesis, we: 1) examined the time course of Glu and AD during 8h SD in the basal forebrain (BF) and prefrontal cortex (PFC); and 2) blocked A1R in the BF and PFC using the selective antagonist 8 cyclopentyltheophylline (CPT) during SD, and examined whether this treatment effects Glu level. Methods: Male rats were implanted with EEG/EMG recording electrodes and microdialysis guide cannulae targeting the BF and PFC. Microdialysis samples were collected during 8h SD or SD combined with CPT infusion. AD and Glu were measured using high performance liquid chromatography (HPLC) and ultra HPLC. Results: In the BF, Glu dramatically increased at the beginning of SD by 660 ± 130% (p=0.002, N=5), followed by increases in AD at 2 nd h of SD. When AD maximized at 4 th h of SD, Glu levels concurrently decreased to 76 ± 32% of baseline. High AD levels were maintained till the end of SD. In the PFC, Glu increased by 769 ± 155% (p=0.02, N=4) within 2h of SD. Similar to BF, when AD increased at 5 th h of SD, Glu returned to the baseline (-10 ± 12%). Infusion of CPT to the BF and PFC induced dramatic increases in Glu till the end of SD (BF: 488 ± 250% of baseline, p<0.001 and PFC: 684 ± 222%, p<0.001). Conclusion: A rapid increase in Glu during SD may be a trigger for the induction of iNOS-NO-AD cascade in both the BF and PFC. AD via A1R exerts a negative feedback on Glu neurotransmission, preventing its further rise and potential toxicity during long-term SD. Support (If Any): VA Merit Grant 2I01BX001404, NIMH R01 MH099180, NIMH R01 MH039683. Results: TRN-PV neurons exhibited low-threshold spikes/inward currents after removal of hyperpolarizing currents/voltage steps respectively, which were blocked by TTA-P2 (3 µM, n=4), confirming the expression of low threshold T-type Ca channels in TRN PV neurons. In 6/8 mice with probe locations in TRN (uni-or bi-lateral), TTA-P2 infusion at ZT2-6 significantly decreased (-27.0 ± 11.6%, p=0.008) spindle density (ACSF: 4.25 ± 0.19; TTA-P2: 3.13 ± 0.37) without any significant effect on amplitude or duration. There was no effect on NREM sleep duration, delta (0.5-4Hz) or slow-wave activity (0.5-1.5Hz). Conclusion: Localized pharmacological inhibition of T-type calcium channels within TRN selectively decreased NREM spindle density without an effect on NREM sleep. These results contrast with those observed with a constitutive, global knockout of Cav3.3, where sleep fragmentation was observed in addition to reduced spindles (Astori et al., 2011).
SENSORY DEPRIVATION SUPPRESSES CORTICAL ACTIVITY IN A STATE AND ENVIRONMENT DEPENDENT MANNER