Immunocytochemical localization of vasoactive intestinal polypeptide- containing cells and processes in the suprachiasmatic nucleus of the rat: light and electron microscopic analysis

Abstract

The distribution of vasoactive intestinal polypeptide-like (VIP) immunoreactivity in neurons and processes within the suprachiasmatic nuclei (SCN) of the rat was investigated with light and electron microscopic immunocytochemical techniques. These studies utilized well characterized antisera directed to synthetic vasoactive intestinal polypeptide. Specificity was established by absorption of the antisera with synthetic vasoactive intestinal polypeptide. Neurons and dendrites exhibiting specific VIP immunoreactivity are concentrated in the ventral half of the nucleus, with the greatest concentration of immunoreactive perikarya occurring in the ventral SCN immediately adjacent to and within the optic chiasm (OC). Thin varicose axons containing VIP immunoreactivity are present throughout the SCN. A large number of immunoreactive axons leave the dorsal aspect of the SCN to reach the periventricular hypothalamic nucleus and continue dorsally to form an extensive plexus along the ventral border of the paraventricular hypothalamic nucleus. Other immunoreactive axons project upon the contralateral SCN via the OC. Ultrastructurally, VIP-containing neurons in the SCN are characterized by a spherical to slightly elongated soma and an invaginated nucleus that fills the majority of the cell body. In the soma, peroxidase reaction product is localized on the outer membrane of all cellular organelles. The reaction product of immunoreactive boutons is related primarily to vesicles, and some of these boutons establish axodendritic synaptic contacts in the SCN. The demonstration of VIP-containing neurons in the SCN provides further evidence that this nucleus is composed of a heterogeneous population of neurons which form distinct subfields within it.

VIP-like Immunoreactive and Vasopressin-like Immunoreactive Neuronal Elements in the Suprachiasmatic Nucleus of Japanese Monkey (Macaca fuscata): Light and Electron Microscopic Immunocytochemical Study

“…Asymmetrical synapses on non-immunoreactive dendritic spines were also found particularly in the dorsal portion of the SCN where numerous VIP-LIR processes were located. Similar findings have been reported in the rat SCN by Card et al [3]. From the above findings, the VIP-LIR neurons are considered to be at least partially intrinsic neurons as well as those having projections to other CNS area.…”

“…We also found VIP-LIR neuronal perikarya intermingled with myelinated axons in the optic chiasm. Their processes extend to the SCN among the myelinated axons of the optic chiasm in a fashion previously observed in the rat optic chiasm [3].…”

“…Destruction of this nucleus induces a disorder of the circadian rhythmicity of the above mentioned physiological phenomena [10,17,23]. Neuronal perikarya, containing neuropeptides such as vasopressinlike immunoreactive (VP-LIR), vasoactive intestinal peptide-like immunoreactive (VIP-LIR) and somatostatin-like immunoreactive neurons, have been reported to exist in this nucleus in rodents [3,20,29]. Among these, VP-LIR and VIP-LIR neurons are the main neuronal components and they are located in specific regions of the SCN.…”

“…On the other hand, mRNA of vasopressin has been shown to be altered via circadian rhythms [28]. To date, morphological and physiological experiments examining immunocytochemistry of the neuropeptides [3,29] and in situ hybridization of mRNA in the SCN have been done using rodents.…”

<b>VIP-LIKE IMMUNOREACTIVE NEURONS AND RETINAL PROJECTIONS IN THE RAT SUPRACHIASMATIC </b><b>NUCLEUS </b>

“…Immunocytochemical investigations have shown immunoreactivities for various peptides such as arginine vasopressin (AVP) (25), vasoactive intestinal peptide (VIP) (2), peptide histidine isoleucine amide (PHI) (18), somatostatin (12), and gastrin releasing peptide (GRP) (18) exist in the neuronal perikarya of this nucleus. These peptide-containing neurons exhibit a characteristic distributional pattern: VIP-immunoreactive perikarya are densely distributed in the ventrolateral part of the nucleus (2,18), whereas AVP-immunoreactive perikarya are found in the mediodorsal part of the nucleus (25).…”