Role of vasoactive intestinal peptide in the light input to the circadian system

Abstract

The neuropeptide vasoactive intestinal peptide is expressed at high levels in a subset of neurons in ventral region of the suprachiasmatic nucleus (SCN). While VIP is known to be important for the synchronization of the SCN network, the role of VIP in photic regulation of the circadian system has received less attention. In the present study, we found that the light-evoked increase in electrical activity in vivo was unaltered by the loss of VIP. In the absence of VIP, the ventral SCN still exhibited NMDA-evoked responses in a brain slice preparation although the absolute levels of neural activity before and after treatment were significantly reduced. Next, we used calcium imaging techniques to determine if the loss of VIP altered the calcium influx due to retinohypothalamic tract stimulation. The magnitude of the evoked calcium influx was not reduced in the ventral SCN but did decline in the dorsal SCN regions. We examined the time course of the photic induction of Period1 in the SCN using in situ hybridization in VIP-mutant mice. We found that the initial induction of Period1 was not reduced by the loss of this signaling peptide. However, the sustained increase in Period1 expression (after 30 min) was significantly reduced. Similar results were found by measuring the light-induction of cFOS in the SCN. These findings suggest that VIP is critical for longer term changes within the SCN circuit but does not play a role in the acute light response.

Resynchronization Dynamics Reveal that the Ventral Entrains the Dorsal Suprachiasmatic Nucleus

“…DeWoskin et al (2015) demonstrated that fast GABA signaling likely regulated neuronal output while slow GABA signaling modulated synchrony. VIP has been shown to regulate entrainment at even longer timescales - loss of VIP did not affect the acute response to light of period1 or electrical activity, but it did significantly reduce long-term increases (Vosko et al, 2015). Our model did not include separate effects for GABA and VIP signaling nor did it account for slow-scale changes in the network.…”

Anatomical identification of the neuroendocrine system in the Nothobranchius furzeri brain

“…After synthesis by the hypothalamus, VIP is hypothesized to travel via the blood stream through the RPD, and is then stored in the PN. VIP is also known to play crucial roles in regulating the circadian clock (Colwell et al, 2003;Hamnett et al, 2019;Vosko et al, 2015;Vosko et al, 2007) because it is strongly localized in the suprachiasmatic nucleus of the mammalian brain.…”

Therapeutic effect of vasoactive intestinal peptide on form-deprived amblyopic kittens

“…Decreased expression of VIP in the LGBd will lead to a corresponding reduction in the binding of VIP to its related receptors, thereby inhibiting the physiological effect of vascular endothelial growth factor on visual development. At the same time, the decrease in VIP reduces the diurnal discharge frequency of neurons, affecting the long-term electrical activity in the suprachiasmatic nucleus of the central system [19,20] and inhibiting electrical transmission between neurons through the VPAC2-mediated cAMP pathway [21], thereby blocking the transmission of information in the visual nervous system. These effects, in turn, accelerate the emergence of amblyopia.…”