GAP-43 Immunoreactivity in the brain of the developing and adult wallaby ( Macropus eugenii )

CART (cocaine- and amphetamine-regulated transcript) is a neuromodulator involved in feeding, drug reward, stress and cardiovascular function. We have immunohistochemically studied the distribution of the CART peptide in the brains of two adult marsupial species: the brown antechinus (Antechinus stuartii) as a representative of polyprotodont marsupials and the tammar wallaby (Macropus eugenii) as a representative of diprotodont marsupials. We have also examined the distribution of CART during postnatal development in the tammar wallaby. There were similarities and differences both between the two marsupial species and between the marsupials and eutherians in CART distribution. Both marsupials showed immunoreactivity to CART in the olfactory bulb, piriform cortex, extended amygdala, the supraoptic, paraventricular and arcuate nuclei of the hypothalamus, somatosensory and auditory nuclei of the brainstem, vagal/solitary complex, raphe obscurus and raphe pallidus and presumptive presympathetic neurons of the ventrolateral medulla, as has been seen in eutherians. On the other hand, immunoreactivity to CART was weak in or absent from isocortical areas, and immunoreactivity to CART was poor or minimal in the ventral tegmental area and nucleus accumbens of both species; regions where immunoreactivity to CART is very strong in the brains of eutherians. During development, CART was present at birth (P0) in the lateral trigeminal ganglion, spinal trigeminal tract and the vagal sensorimotor complex, but did not appear in mid- or forebrain regions until much later (from P37). These anatomical findings indicate that although CART is likely to serve very similar functions in both eutherians and marsupials, there are potentially functionally significant differences between the two mammalian groups.

Section: Animalsmentioning

confidence: 99%

Distribution of CART (Cocaine- and Amphetamine-Regulated Transcript) Peptide in Mature and Developing Marsupial Brain

Ashwell

Mai²

2010

“…Immunohistochemical methods to reveal GAP-43-like immunoreactivity in this material have been described previously [Hassiotis et al, 2002]. This antibody recognizes an epitope on both kinase C phosphorylated and dephosphorylated forms of GAP-43.…”

Section: Immunohistochemistrymentioning

confidence: 99%

“…The manner in which the newborn tammar redirects its movements when it reaches the edge of the pouch and enters it might indicate a response to either the odor of the pouch or the texture of its moist hairless skin [Tyndale-Biscoe, 2005]. Olfactory knobs have been identified in the nasal epithelium of the newborns of several species of diprotodont and polyprotodont marsupials [Gemmell and Nelson, 1988;Gemmell and Rose, 1989;Gemmell and Selwood, 1994] and well-developed nerve fibers have been shown to connect the olfactory epithelium to the relatively large olfactory bulbs at birth in the native cat and the tammar [Hill and Hill, 1955;Hassiotis et al, 2002]. These findings stand in contrast to the delayed development of neuronal activity in the olfactory bulb of the tammar, investigated in vivo under anesthesia [Ellendorff et al, 1988].…”

Section: Introductionmentioning

confidence: 99%

Development of the Olfactory System in a Wallaby <i>(Macropus eugenii)</i>

Ashwell¹,

Marotte

Cheng³

2008

We used carbocyanine dye tracing techniques in conjunction with hematoxylin and eosin staining, immunohistochemistry for GAP-43, and tritiated thymidine autoradiography to examine the development of the olfactory pathways in early pouch young tammar wallabies (Macropus eugenii). The overarching aim was to test the hypothesis that the olfactory system of newborn tammars is sufficiently mature at birth to contribute to the guidance of the pouch young to the nipple. Although GAP-43 immunoreactive fibers emerge from the olfactory epithelium and enter the olfactory bulb at birth, all other components of the olfactory pathway in newborn tammars are very immature at birth, postnatal day (P0). In particular, maturation of the vomeronasal organ and its projections to the accessory olfactory bulb appears to be delayed until P5 and the olfactory bulb is poorly differentiated until P12, with glomerular formation delayed until P25. The lateral olfactory tract is also very immature at birth with pioneer axons having penetrated only the most rostral portion of the piriform lobe. Interestingly, there were some early (P0) projections from the olfactory epithelium to the medial septal region and lamina terminalis (by the terminal nerve) and to olfactory tubercle and basal forebrain. The former of these is presumably serving the transfer of LHRH⁺ neurons to the forebrain, as seen in eutherians, but neither of these very early pathways is sufficiently robust or connected to the more caudal neuraxis to play a role in nipple finding. Tritiated thymidine autoradiography confirmed that most piriform cortex pyramidal neurons are generated in the first week of life and are unlikely to be able to contribute to circuitry guiding the climb to the pouch. Our findings lead us to reject the hypothesis that olfactory projections contribute to guidance of the newborn tammar to the pouch and nipple. It appears far more likely that the trigeminal pathways play a significant role in this behavior because the central projections of the trigeminal nerve are more mature at birth in this marsupial.

“…most differentiated cellular architecture at birth. Sections immunoreacted for GAP-43 showed that the vestibular area in general typically featured low immunoreactivity compared with other neural structures [Hassiotis et al, 2002], suggesting that there has been minimal development of afferents to the nuclei at birth. The LVe, however, featured more prominent immunoreactivity, perhaps indicating a greater degree of afferent development than other areas in the vestibular complex.…”

Section: Discussionmentioning

confidence: 99%

“…These sections have been used in previous studies on wallaby development, with description of control procedures [Hassiotis et al, 2002]. Deparaffinized sections were incubated in 3% H 2 O 2 in anhydrous methanol for 30 min to block endogenous peroxidase activity.…”

Section: Immunohistochemistrymentioning

confidence: 99%

Development of the Vestibular Apparatus and Central Vestibular Connections in a Wallaby <i>(Macropus eugenii)</i>

McCluskey¹,

Marotte

Ashwell³

2008

We have studied the early development of the vestibular apparatus and its central connections in the tammar wallaby (Macropus eugenii) in order to determine whether the vestibular system anatomy is sufficiently mature at birth to assist in climbing to the pouch. Structural development was studied with the aid of hematoxylin and eosin stained sections and immunoreactivity for GAP-43, whereas the development of vestibular system connections was examined by carbocyanine dye tracing. At the time of birth, the otocyst has distinct utricle, saccule and semicircular canals with immature sensory regions receiving innervation by GAP-43 immunoreactive fibers. Vestibular nerve fibers can be traced into the brainstem to the developing vestibular nuclei, which are not yet cytoarchitectonically distinct. The vestibular nuclei do not contribute direct projections to the lower cervical spinal cord at birth; most bulbospinal projections in the newborn appear to be derived bilaterally from the gigantocellular, lateral paragigantocellular reticular and ventral medullary nuclei. A substantial bilateral projection to the vestibular ganglion and apparatus from the region of the gigantocellular and lateral paragigantocellular nuclei was seen at birth, but not in subsequent ages. This is similar to a projection seen in newborn Ameridelphians. By postnatal day (P) 5, the vestibular apparatus had extensive projections to all vestibular nuclei and neurons projecting in the lateral vestibulospinal tract could be identified in the lateral vestibular nucleus. Cytoarchitectonic differentiation of the vestibular nuclei proceeded over the next 3 to 4 weeks with the emergence of discrete parvicellular and magnocellular components of the medial vestibular nucleus by P19. GAP-43 immunoreactivity stayed high in the lateral vestibulospinal tract for several months after birth, suggesting that the development of this tract followed a prolonged timecourse. Our findings indicate that central and peripheral connections of the vestibular ganglion are present at birth, but that there is no direct projection from the vestibular nuclei to the cervical spinal cord until P5. Nevertheless, the possibility remains that an indirect projection between the vestibular nuclei and the medial reticular formation is present at birth and mediates control of the climb.