SCG postnatal remodelling – hypertrophy and neuron number stability – in Spix's Yellow‐toothed Cavies (Galea spixii)

Abstract

Whilst a fall in neuron numbers seems a common pattern during postnatal development, several authors have nonetheless reported an increase in neuron number, which may be associated with any one of a number of possible processes encapsulating either neurogenesis or late maturation and incomplete differentiation. Recent publications have thus added further fuel to the notion that a postnatal neurogenesis may indeed exist in sympathetic ganglia. In the light of these uncertainties surrounding the effects exerted by postnatal development on the number of superior cervical ganglion (SCG) neurons, we have used state-of-the-art design-based stereology to investigate the quantitative structure of SCG at four distinct timepoints after birth, viz., 1-3 days, 1 month, 12 months and 36 months. The main effects exerted by ageing on the SCG structure were: (i) a 77% increase in ganglion volume; (ii) stability in the total number of the whole population of SCG nerve cells (no change--either increase or decrease) during post-natal development; (iii) a higher proportion of uninucleate neurons to binucleate neurons only in newborn animals; (iv) a 130% increase in the volume of uninucleate cell bodies; and (v) the presence of BrdU positive neurons in animals at all ages. At the time of writing our results support the idea that neurogenesis takes place in the SCG of preás, albeit it warrants confirmation by further markers. We also hypothesise that a portfolio of other mechanisms: cell repair, maturation, differentiation and death may be equally intertwined and implicated in the numerical stability of SCG neurons during postnatal development.

Stereological and Allometric Studies on Neurons and Axo-Dendritic Synapses in Superior Cervical Ganglia

“…This ganglion is also very closely adjacent to the hypoglossal nerve. In all species studied, the SCG was white in color and roughly spindle shaped, independently of the animal age (Abrahão et al, 2009;Coppi and Loesch, 2011;Fioretto et al, 2007Fioretto et al, , 2011Ladd et al, 2012;Loesch et al, 2010;Melo, 2009;Ribeiro, 2006;Ribeiro et al, 2004;Toscano et al, 2009). s0025 2.1.2 Macromorphometry p0040 The macromorphometric aspects of the SCG-length, width, and thickness-vary greatly according to the animal species and animal age Macrostructure of the SCG of an adult dog (A), cat (B), and horse (C).…”

“…Recognizing this gap in the literature, over the past 10 years, we have investigated the quantitative structure of SCG from a broad range of mammals, including both small laboratory and exotic rodents such as rats and capybaras (Loesch et al, 2010;Ribeiro et al, 2004), pacas (Abrahão et al, 2009;Au2 Melo, 2009), guinea pigs (Toscano et al, 2009), and preás (Ladd et al, 2012) and also domestic large mammals such as dogs and cats (Fioretto et al, 2007), sheep (Fioretto et al, 2011), and horses (Fioretto et al, 2007;Loesch et al, 2010;Ribeiro et al, 2004). In our own published work, the quantitative assessment of SCG structure-neurons, sypnases, neuropil, vessels, and connective tissue among others-was conducted using 3D technology employing the design-based stereology.…”

“…The SCG of rats, guinea pigs, preás, cutias, pacas, capybaras, sheep, dogs, cats, and horses is located near the base of the skull and deeply into the bifurcation of the common carotid artery, in the origin of the external and internal carotid arteries close to the distal ganglion of the vagus nerve (Abrahão et al, 2009;Coppi and Loesch, 2011;Fioretto et al, 2007Fioretto et al, , 2011Gabella, 2004;Hedger and Webber, 1976;Ladd et al, 2012;Loesch et al, 2010;Melo, 2009;Ribeiro, 2006;Ribeiro et al, 2004;Toscano et al, 2009) (Fig. 2.1).…”

“…Image and legend extracted from Fioretto et al (2007). B978-0-12-800179-0.00002-7, 00002 IRCMB, 978-0-12-800179-0 investigated, that is, rats, guinea pigs, preás, rabbits, cutias, pacas, capybaras, cats, dogs, sheep, horses, and camels (Abrahão et al, 2009;Coppi and Loesch, 2011;Fioretto et al, 2007Fioretto et al, , 2011Kabak, 2007;Ladd et al, 2012;Loesch et al, 2010;Melo, 2009;Najafi and Nejati, 2009;Ribeiro, 2006;Ribeiro et al, 2004;Sheng et al, 1998;Toscano et al, 2009) In mammals, the SCG provides sympathetic innervation to the head and neck as well as to the mandible, submandibular and pineal glands, cephalic blood vessels, choroid plexus, eye, carotid body, salivary, and thyroid glands (Arbab et al, 1986;…”

“…s0045 2.2.2 SCG neurons p0080 SCG neurons are generally spindly shaped-or circular-and readily distinguishable due to their large size, clear nucleus, and the evident nucleolus. Ganglion neuron profiles are normally surrounded by one to two intraganglionic capillaries (in this case they are named intraunit capillaries) as well as by one to three glial cell nuclei (satellite cells) whose processes formed the ganglion neuron glial capsule (Abrahão et al, 2009;Coppi and Loesch, 2011;Fioretto et al, 2007Fioretto et al, , 2011Ladd et al, 2012;Loesch et al, 2010;Melo, 2009;Toscano et al, 2009) (Fig. 2.4).…”