Tonic Regulation of GABAergic Synaptic Activity on Vasopressin Neurones by Cannabinoids

摘要: Synaptic activity in magnocellular neurosecretory neurones is influenced by the retrograde (i.e., somatodendritic) release of vasopressin, oxytocin and cannabinoids (CBs). For neurones, exerts constitutive effects on presynaptic through its ability to CBs postsynaptically. In present study we examined evoked spontaneous inhibitory postsynaptic currents (IPSCs) identified vasopressin (VP) coronal slices from virgin rats determine: 1) extent which may also tonically modulate VP synaptic activity; 2) determine if depolarization induced suppression inhibition was so, whether it mediated or CBs. The CB1 antagonists AM251 (1 μM) SR14171 consistently increased frequency IPSCs (sIPSCs) without affecting their amplitude, suggesting a tonic CB presence. This effect independent action potential activity, blocked chelating intracellular calcium with10 mM EGTA. amplitude (eIPSCs) decreased paired-pulse ratio (PPR) neurones- that were completely with even low EGTA) internal chelation. Bouts firing suppressed sIPSCs, but had no eIPSCs PPR. depolarizationinduced reduced AM251, totally 10 μM mixed vasopressin/oxytocin antagonist, Manning Compound. We then tested while blocking receptors. Vasopressin (10-100 nM) inhibited sIPSC frequency, eIPSC amplitudes, PPR, presence AM251. Together these results suggest tonic, modulation largely dependent calcium, an release.