Ontogenesis of the retinohypothalamic tract, vasoactive intestinal polypeptide- and peptide histidine isoleucine-containing neurons and melatonin binding in the hypothalamus of the mink

Abstract

The development of the retinohypothalamic tract (RHT) labeled with cholera toxin and of the vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) systems was studied in the hypothalamus of neonatal mink by using immunohistochemistry. Retinal fibers were observed in the suprachiasmatic nucleus (SCN) from birth and were adult-like by day 14. VIP and PHI immunoreactivity was also present from birth. Melatonin binding was studied by autoradiography using [125I]melatonin as a ligand. A specific binding was detected in near-term fetal and neonate brains in the olfactory epithelium, various thalamic nuclei, the pineal gland, and the pars tuberalis of the pituitary gland, but never in the SCN. These results are discussed in the context of the potential role of daylight cycles and/or melatonin in entraining circadian rhythms in neonate mink.

Distinct retinohypothalamic innervation patterns predict the developmental emergence of species‐typical circadian phase preference in nocturnal Norway rats and diurnal nile grass rats

“…Keeping in mind the need for caution when comparing data from multiple laboratories using different techniques, published reports suggest that this hypothesis is supported by a variety of other species. As shown in Table 2, nocturnal species including hamsters (Speh and Moore, 1993; Morin et al, 2003), mink (Peytevin et al, 1997), mice (Cassone et al, 1988; Hattar et al, 2006), and opossums (Cassone et al, 1988) possess robust RHT projections extending beyond the SCN to the vSPVZ. In contrast to nocturnal species and in addition to grass rats, RHT afferents do not extend significantly beyond the boundary of the SCN in such diurnal species as humans (Dai et al, 1998), Cebus monkeys (Pinato et al, 2009), ground squirrels (Smale et al, 1991), and four‐striped field mice (Schumann et al, 2006).…”

“…Interestingly, these two species are precocial in relation to all of the nocturnal species discussed above. Moreover, this direct projection develops prenatally in sheep (Torrealba et al, 1993), whereas it develops postnatally in rats (Speh and Moore, 1993), hamsters (Speh and Moore, 1993), and mink (Peytevin et al, 1997). Thus, we hypothesize further that, for animals that develop the direct retina‐to‐vSPVZ connection, the precise timing of innervation may influence its subsequent effect on circadian phase preference.…”

Vipergic innervation of the mammalian pineal gland

“…Interestingly, preproVIP and PHI are colocalized in the SCN (Albers et al, 1991), and VIP levels show circadian variations in the same structure (Shinohara and Inouye, 1995). The pathway between the SCN and the PVN, important for retina-pineal relationships (see above) contains a significant VIPergic (Peytevin et al, 1997;Teclemariammesbah et al, Fig. 1.…”

“…ϫ128. (Peytevin et al, 1997) component, thus underlining the importance of VIP in the generation and control of circadian rhythms (for review see Reuss, 1996).…”

Night and day

“…Keeping in mind the need for caution when comparing data from multiple laboratories using different techniques, published reports suggest that this hypothesis is supported by a variety of other species. As shown in Table 2, nocturnal species including hamsters (Speh and Moore 1993;Morin, Blanchard et al 2003), mink (Peytevin, Masson-Pevet et al 1997), mice (Cassone, Speh et al 1988;Hattar, Kumar et al 2006), and opossums (Cassone, Speh et al 1988) possess robust RHT projections extending beyond the SCN to the vSPVZ.…”