Target areas innervated by PACAP-immunoreactive retinal ganglion cells

@article{Hannibal2004TargetAI,
  title={Target areas innervated by PACAP-immunoreactive retinal ganglion cells},
  author={Jens Hannibal and Jan Fahrenkrug},
  journal={Cell and Tissue Research},
  year={2004},
  volume={316},
  pages={99-113}
}
The retinohypothalamic tract (RHT) originates from a subset of retinal ganglion cells (RGCs). The cells of the RHT co-store the neurotransmitters PACAP and glutamate, which in a complex interplay mediate light information to the circadian clock located in the suprachiasmatic nuclei (SCN). These ganglion cells are intrinsically photosensitive probably due to expression of melanopsin, a putative photoreceptor involved in light entrainment. In the present study we examined PACAP-containing retinal… 

Central projections of intrinsically photosensitive retinal ganglion cells in the macaque monkey

PACAP‐immunoreactive projections with colocalized CtB represent retinal projections of ipRGCs in the macaque monkey, supporting previous retrograde tracer studies demonstrating that melanopsin‐containing retina projections reach areas in the primate brain involved in both image‐ and nonimage‐forming visual processing.

Melanopsin is expressed in PACAP-containing retinal ganglion cells of the human retinohypothalamic tract.

Given the expression of melanopsin in PACAP-containing RGCs of the human RHT, this photoreceptor is a likely first base in the chain of events leading to photoentrainment of both normal and blind people.

The Dorsal Raphe Nucleus Receives Afferents From Alpha-Like Retinal Ganglion Cells and Intrinsically Photosensitive Retinal Ganglion Cells in the Rat.

An ipRGC component of the retino-raphe projection may contribute to a sustained light-mediated modulation of DRN serotonin release and could be retrogradely labeled following tracer injection into all rostrocaudal aspects of the DRN.

Central projections of melanopsin‐expressing retinal ganglion cells in the mouse

Staining patterns after monocular enucleation revealed that the projections of these cells are overwhelmingly crossed except for the projection to the SCN, which is bilaterally symmetrical, and that other ganglion cells do contribute at least some retinal input to these targets.

Photic induction of c-Fos in enkephalin neurons of the rat intergeniculate leaflet innervated by retinal PACAP fibres

It is suggested that PACAP-immunoreactive retinal afferents in the IGL primarily innervate enkephalin-immonoactive neurons and that the enkePHalin-containing neurons, which project locally and to the contralateral IGL, are activated by light independent of diurnal time.

PACAP in the Circadian Timing System: Learning from Knockout Models

Together, the data provides evidence for PACAP being a neurotransmitter in the RHT acting together with glutamate regulating light entrainment, masking behavior, and the pupillary light reflex.

Vesicular glutamate transporter 2 (VGLUT2) is co-stored with PACAP in projections from the rat melanopsin-containing retinal ganglion cells

There is evidence to support the use of glutamate and PACAP as neurotransmitters in NIF photoperception by rat ipRGCs, and that these neurotransmitter are co-stored and probably released from the same nerve terminals.
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