The development of the pelvic ganglion was studied in female rats from birth to 90 days (adult) by electron microscopy, by morphometry on plastic sections and by histochemistry on whole-mount preparations.
The pelvic ganglion of the adult female Sprague-Dawley rat had a volume (measured by the Cavalieri method) of 210 million pm3 and contained a total of 8185 ± 2147 neurons (counted by full reconstruction of three ganglia), which ranged in size from 1100-24500 gm3 (average 4942). In the newborn, the pelvic ganglion had similar topographical relations with surrounding organs as in the adult, was immersed in loose connective tissue rather than possessing a proper capsule, and had a volume about one quarter that in the adult. The ganglion was made of neurons, non-neuronal cells and blood vessels but it contained notably less collagen and fewer nerve bundles than in the adult; in contrast, SIF cells were abundant. Neuronal sizes ranged from 350 to 2250 p.m3 with an average of 596. The number of neurons was not evaluated at the developmental stages, but other studies have shown that in the female rat neurons are markedly more numerous in the newborn than in the adult. Intermediate stages in ganglion volume and neuronal size growth were found at 3, 7, 14, and 30 days.
The neurons at birth were similar to those of the adult in shape; however, they lacked a glial sheath and had extensive membrane to membrane contacts with each other and with SIF cells. Only few Schwann cells were present and many nerve bundles were devoid of them. The intracellular organelles observed at birth were the same as those in the adult, but some, notably microtubules, were less abundant. Both axo-dendritic and axo-somatic synapses were observed from the time of birth.
The growth of the pelvic ganglion was also investigated in experimental conditions of polyuria. For this, Brattleboro rats, with congenital diabetes insipidus, and their control parent strain Long-Evans, were used. In the adult Brattleboro rat there was hypertrophy of pelvic ganglion neurons and of urinary bladder: bladder weight was increased 4 fold and bladder capacity 3 fold. The muscle coat was increased in extent but not in
thickness over the controls, and the muscle cells much enlarged in size. Brattleboro rats studied at 14 days of age were already displaying significant enlargement of bladder and pelvic ganglion over age matched controls
