The neurohistology of quiescent mammary tissue in Lepus albus

Abstract

The neurohistology of quiescent mammary tissue from adult female albino rabbits was investigated by cholinesterase histochemistry.Dense plexuses of nerve fibers enter the nipple i n the dermis surrounding the lactiferous ducts, and unite a t the summit of the nipple to form an apical plexus. From the plexuses at the base of the nipple nerves pass between deep epidermal invaginations, to form a basal nipple sub-epidermal plexus. A sub-epidermal plexus of fibers of small diameter arises from the apical dermal plexus. At the base of the nipple extensive nerve plexuses occur around smooth muscle. The only endings are intraepidermal nerve terminals from the apical sub-epidermal plexus. In mammary skin outside the nipple area the dermal and sub-epidermal plexuses are more attenuated. Longitudinally or circularly arranged nerves occur around hair follicles.Peri-arterial plexuses are present throughout the mammary tissue. The myo-epithelial cells and alveoli are not innervated.The neurohistological pattern suggests a spatio-temporal sensory innervation concerned in neurohormonal reflexes of milk secretion and ejection, and neural reflexes of nipple erection. Autonomic motor innervation regulates blood flow and promotes nipple erection. The absence of myo-epithelial cell and alveolar innervation indicates a solely endocrine effector regulation of milk ejection and secretion.As a result of physiological and pharmacological experiments i t is recognized that the intrinsic nerves of the mammary gland play a significant role in erection of the nipple, the regulation of blood flow, and reflex hypothalamo-hypophysial stimulation. There are, however, few published observations on the neurohistology of mammary tissue, and the available literature reveals differences of opinion as to the degree of innervation, the presence or absence of specific nerve endings, the innervation of the alveoli, and the artifacts inherent in particular neurohistological techniques. The published observations are based on methylene blue or metallic impregnation techniques, the limitations of which are well recognized (Ballantyne, '59). An investigation was therefore undertaken into the intrinsic innervation of the mammary gland using a histochemical technique for the localization of neuronal cholinesterases, and the findings correlated with the known physiological characteristics of the gland. MATERIALS AND METHODSTwelve adult female albino rabbits were used in this investigation. The animals J. COMP. NEUR., 127: 471-488.were killed by an overdose of sodium pentobarbitone injected into the left marginal ear vein. In one group of animals the mammary tissue was excised rapidly after death, and immediately transferred to the fixation fluid. In a second group the vascular pattern of the mammary tissue was outlined by Berlin blue perfusion (Trueta et al., '47) prior to removal. This was carried out by rapidly opening the thorax and injecting directly into the left ventricle 100 ml of 0.9% sodium chloride followed by 100 ml of 2% Berlin blue, both a...

Nitric Oxide May Mediate Nipple Erection

“…It has been stated that NE occurs via activation of the sympathetic adrenergic nerves (Eriksson et al, 1996a; Uvnäs‐Moberg and Eriksson, 1996; Franke‐Radowiecka et al, 2002). In addition to adrenergic nerve fibers that control blood flow regulation and smooth muscle contractility, cholinergic nerve fibers innervate NAC blood vessels and smooth muscles (Ballantyne and Bunch, 1966; Hebb and Linzell, 1966; Franke‐Radowiecka et al, 2002; Franke‐Radowiecka and Wasowicz, 2002); however, adrenergic nerves cause vasoconstriction, decreases in blood flow in the breast, and smooth muscle contraction, whereas cholinergic nerves cause vasodilation. Similarly, it has been stated that local injections of NPY, which originates from the sympathetic nervous system and is expressed in the NAC, contribute to NE and decrease breast blood flow (Ballantyne and Bunch, 1966; Eriksson et al, 1996a; Hebb and Linzell, 1966; Franke‐Radowiecka et al, 2002; Franke‐Radowiecka and Wasowicz, 2002).…”

Proceedings of the Physiological Society, 28‐29 June 1990, Glasgow Meeting: Demonstrations

“…Departments of Clinical Physics and Bioengineering* and Neurology, Institute of Neurological Scienes, Glsgow G51 4TF Application of finely graded electrical stimuli to a peripheral motor nerve produces sequential recruitment of axons dependent on their relative positions in the nerve trunk (McComas et al 1971). Surface-recorded compound muscle action potentials (CMAP) in the extensor digitorum brevis muscle may be used to count the numbers of motor units and characterize the motor unit potentials (MUP) within that muscle using a template-matching technique (Ballantyne & Hansen, 1974).…”

Proceedings of the Physiological Society, 14‐15 April 1967, Leeds Meeting: Demonstrations

“…(Coupland & Holmes, 1957); but the biochemical detection of cholinesterase activity in tissue homogenates, often interpreted as evidence of an innervation, does not alone furnish sufficient grounds for assuming the presence of nerves. Since these enzymes occur in cells other than neurones, and may play a role in such mechanisms as ionic transport, lipid metabolism, inactivation of bacterial toxins and other toxic esterases (see Ballantyne & Bunch, 1966;Ballantyne, 1967), it is necessary before making any statement about the functional significance of cholinesterase activity in a given tissue to know accurately the enzyme's distribution.…”