Estimate of size and total number of neurons in superior cervical ganglion of rat, capybara and horse

Abstract

The superior (cranial) cervical ganglion was investigated by light microscopy in adult rats, capybaras (Hydrochaeris hydrochaeris) and horses. The ganglia were vascularly perfused, embedded in resin and cut into semi-thin sections. An unbiased stereological procedure (disector method) was used to estimate ganglion neuron size, total number of ganglion neurons, neuronal density. The volume of the ganglion was 0.5 mm3 in rats, 226 mm3 in capybaras and 412 mm3 in horses. The total number of neurons per ganglion was 18,800, 1,520,000 and 3,390,000 and the number of neurons per cubic millimetre was 36,700, 7,000 and 8,250 in rats, capybaras and horses, respectively. The average neuronal size (area of the largest sectional profile of a neuron) was 358, 982 and 800 microm2, and the percentage of volume occupied by neurons was 33, 21 and 17% in rats, capybaras and horses, respectively. When comparing the three species (average body weight: 200 g, 40 kg and 200 kg), most of the neuronal quantitative parameters change in line with the variation of body weight. However, the average neuronal size in the capybara deviates from this pattern in being larger than that of in the horse. The rat presented great interindividual variability in all the neuronal parameters. From the data in the literature and our new findings in the capybara and horse, we conclude that some correlations exist between average size of neurons and body size and between total number of neurons and body size. However, these correlations are only approximate and are based on averaged parameters for large populations of neurons: they are less likely to be valid if one considers a single quantitative parameter. Several quantitative features of the nervous tissue have to be taken into account together, rather than individually, when evolutionary trends related to size are considered.

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).…”

“…The SCG is divided into distinct compartments by capsular septa of connective tissue as reported for mammalian sympathetic ganglia (Fioretto et al, 2007;Gabella et al, 1988;Miolan and Niel, 1996;Ribeiro et al, 2004;Schmidt, 1996;Szurszewski and King, 1989;Szurszewski and Miller, 1994). In addition, Gabella (1976) postulated that the capsule of connective tissue which surrounds the ganglia of the sympathetic trunk is continuous with the epineurium of the associated nerves.…”

“…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;…”