Target areas innervated by PACAP-immunoreactive retinal ganglion cells

  title={Target areas innervated by PACAP-immunoreactive retinal ganglion cells},
  author={Jens Hannibal and Jan Fahrenkrug},
  journal={Cell and Tissue Research},
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.



Immunoreactive substance P is not part of the retinohypothalamic tract in the rat

These findings together with the demonstration that bilateral eye enucleation does not decrease the number of SP-immunoreactive nerve fibres in the SCN indicate that SP is not a neurotransmitter in the RHT but could be an intrinsic neurotransmitter of theSCN modulating photic input to the clock.

Melanopsin and non-melanopsin expressing retinal ganglion cells innervate the hypothalamic suprachiasmatic nucleus

It appears that the rod/cone system of photoreceptors may provide signals to the SCN circadian system independent of intrinsically light-sensitive melanopsin ganglion cells.

Retinal ganglion cell projections to the hamster suprachiasmatic nucleus, intergeniculate leaflet, and visual midbrain: Bifurcation and melanopsin immunoreactivity

The presence of moderately widespread bifurcation among ganglion cells projecting to theSCN, and projection by melanopsin‐IR cells to locations distinct from the SCN and without known rhythm function, suggest that this ganglions cell type is generalized, rather than specialized, with respect to the conveyance of photic information to the brain.

Neuropeptide Y and enkephalin immunoreactivity in retinorecipient nuclei of the hamster pretectum and thalamus

The data show for the first time that the posterior limitans nucleus (PLi) receives a moderately dense, direct retinal input and Peptidergic innervation of the visual nuclei does not appear to be derived from the retina.

The retinohypothalamic tract originates from a distinct subset of retinal ganglion cells

The retinal ganglion cells giving rise to retinohypothalamic projections in the rat were identified using retrograde transport of horseradish peroxidase (HRP) or Fluoro Gold injected into the

Neurotransmitters of the retino-hypothalamic tract

The anatomical and physiological evidence for glutamate and pituitary adenylate cyclase-activating polypeptide (PACAP) as principal transmitters of the RHT will be considered and possible targets for PACAP and glutamate are the recently identified clock genes Per1 and Per2, which are induced in the SCN by light, glutamate and PACAP at night.

A retinohypothalamic projection in the rat

The retinohypothalamic tract in the rat appears to arise from the ganglion cells of the retina and to terminate on the smaller dendritic branches of the neurons of the suprachiasmatic nucleus.

A Broad Role for Melanopsin in Nonvisual Photoreception

The results suggest that melanopsin expression defines a subset of RGCs that play a broad role in theregulation of nonvisual photoreception, providing collateralized projections that contribute to circadian entrainment, negative masking, the regulation of sleep-wake states, and the pupillary light reflex.

Melanopsin-Containing Retinal Ganglion Cells: Architecture, Projections, and Intrinsic Photosensitivity

It is shown that melanopsin is present in cell bodies, dendrites, and proximal axonal segments of a subset of rat RGCs, most likely the visual pigment of phototransducing R GCs that set the circadian clock and initiate other non–image-forming visual functions.

Light-Dependent Induction of cFos during Subjective Day and Night in PACAP-Containing Ganglion Cells of the Retinohypothalamic Tract

Data indicate that PACAP is present in ganglion cells that give rise to the RHT and suggest a role for this peptide in the light entrainment of the clock.