title: Stereological and allometric studies on neurons and axo-dendritic synapses in the superior cervical ganglia of rats, capybaras and horses.
abstract: The superior cervical ganglion (SCG) in mammals varies in structure according to developmental age, body size, gender, lateral asymmetry, the size and nuclear content of neurons and the complexity and synaptic coverage of their dendritic trees. In small and medium-sized mammals, neuron number and size increase from birth to adulthood and, in phylogenetic studies, vary with body size. However, recent studies on larger animals suggest that body weight does not, in general, accurately predict neuron number. We have applied design-based stereological tools at the light-microscopic level to assess the volumetric composition of ganglia and to estimate the numbers and sizes of neurons in SCGs from rats, capybaras and horses. Using transmission electron microscopy, we have obtained design-based estimates of the surface coverage of dendrites by postsynaptic apposition zones and model-based estimates of the numbers and sizes of synaptophysin-labelled axo-dendritic synaptic disks. Linear regression analysis of log-transformed data has been undertaken in order to establish the nature of the relationships between numbers and SCG volume (V(scg)). For SCGs (five per species), the allometric relationship for neuron number (N) is N=35,067xV (scg) (0.781) and that for synapses is N=20,095,000xV (scg) (1.328) , the former being a good predictor and the latter a poor predictor of synapse number. Our findings thus reveal the nature of SCG growth in terms of its main ingredients (neurons, neuropil, blood vessels) and show that larger mammals have SCG neurons exhibiting more complex arborizations and greater numbers of axo-dendritic synapses.
authors.affiliation: Research Department of Inflammation, University College London Medical School, Royal Free Campus, London, UK.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Loesch
authors.forename: Terry M
authors.initials: TM
authors.lastname: Mayhew
authors.forename: Helen
authors.initials: H
authors.lastname: Tang
authors.forename: Fernando V Lobo
authors.initials: FV
authors.lastname: Ladd
authors.forename: Aliny A B Lobo
authors.initials: AA
authors.lastname: Ladd
authors.forename: Mariana Pereira
authors.initials: MP
authors.lastname: de Melo
authors.forename: Andrea Almeida P
authors.initials: AA
authors.lastname: da Silva
authors.forename: Antonio Augusto
authors.initials: AA
authors.lastname: Coppi
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D049108:Cell Enlargement; D049109:Cell Proliferation; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure*; D006736:Horses; D008297:Male; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012377:Rodentia; D012727:Sex Characteristics; D017783:Superior Cervical Ganglion / Q000166:cytology* / Q000254:growth & development; D013569:Synapses / Q000648:ultrastructure*; D016708:Synaptophysin / Q000276:immunology / Q000648:ultrastructure
chemical_list: D016708:Synaptophysin