THE ADRENERGIC INNERVATION OF THE NASAL MUCOSA OF CERTAIN MAMMALS

Occurrence and distribution of VIP nerves in the nasal mucosa and tracheobronchial wall

Nerves displaying vasoactive intestinal peptide (VIP) immunoreactivity were detected in the upper respiratory tract of guinea pigs, rabbits and cats. VIP nerves were numerous in the cat, less numerous in the rabbit and rare in the guinea pig. In the nasal mucosa, fine varicose VIP nerves were found to surround nasal glands and small blood vessels. In the tracheobronchial wall VIP nerves were observed around seromucous glands, blood vessels and smooth muscle. Ganglia located in the walls of the trachea and main bronchi contained clusters of VIP immunoreactive nerve cell bodies, conceivably representing the origin of the VIP fibres found in this region.

Sympathetic nerves and nasal secretion in the cat

The influence of sympathetic nerves on nasal secretion was examined in anaesthetized cats. The results from experiments in which the Vidian nerve was stimulated supramaximally for 3 min show that vasoconstriction occurs in the nasal cavity during the production of nasal secretion. The amount of nasal secretion produced in the normal cavity on Vidian nerve stimulation was greater than that produced in the sympathectomized nasal cavity but only significantly so at 2 and 5 Hz. It is concluded that at these lower frequencies sympathetic activity induced by Vidian nerve stimulation increases nasal secretion.

Relaxation of smooth muscle following contraction elicited by sympathetic nerve stimulation in vivo

1. A method for studying in vivo the process of neuroeffector transmission in the nictitating membrane and nasal blood vessels of the cat is described. 2. Administration of desmethylimipramine or cocaine caused increases in both the amplitude and duration of the nasal and membrane responses which may be explained by inhibition of neuronal uptake of noradrenaline. 3. Phenoxybenzamine depressed the responses to nerve stimulation, but had little effect on the relationship between response amplitude and rate of recovery. 4. The relationship between response amplitude and rate of recovery is discussed and related to the sigmoid shape of a log concentration-response curve.

Characteristics of the sympathetic innervation of the nictitating membrane and of the vasculature of the nose and tongue of the cat

Vasomotor responses from the nasal mucosa and tongue, and contractions of the nictitating membrane, were recorded on stimulation of the cervical sympathetic or internal carotid nerves. Preganglionic sympathetic nerve fibres which elicited a membrane response possessed a lower threshold than those which evoked nasal vasoconstriction, while the latter displayed a lower threshold than fibres which evoked tongue vasoconstriction. The sympathetic vasodilator fibres to the tongue whose activity was revealed after alpha-receptor blockade, had a similar threshold to the vasoconstrictor fibres. Membrane contraction, nasal vasoconstriction and occasionally tongue vasoconstriction could be evoked by stimulating the internal carotid nerve. The postganglionic fibres innervating the nasal mucosa had a similar threshold to those of the nictitating membrane, which may indicate that there are small myelinated fibres innervating the mucosa. The preganglionic compound nerve action potential had four major components, S1-S4. S1, S2 and usually S3 fibres were associated with membrane contraction; S2, S3 and sometimes S1 fibres were associated with nasal vasoconstriction; and S3, usually S2 and occasionally S1 fibres were associated with vasoconstriction in the tongue. It is concluded that each of these three groups of nerve fibres, but not S4 fibres, may include fibres associated functionally with the three effectors. There was a considerable difference between the relative amplitude of the responses of the three effectors elicited by stimulation of the cervical sympathetic nerve at frequencies between 0.2 and 2 Hz. Vasoconstrictor responses were relatively larger than membrane contractions suggesting differences in the mechanisms of neurotransmission at the neuroeffector junctions.

Demonstration of terminalis, olfactory, trigeminal and perivascular nerves in the rat nasal septum

The innervation of the nasal septum and around the olfactory bulb has been investigated in rats by means of whole-mount preparations and histological sections. Silver staining, OsO4 staining, PAS staining, cholinesterase reaction and fluorescence for catecholamine-containing nerves were used. The nervus terminalis forms on the medial side of the olfactory bulb a ganglionated plexus, from which branches are given off which course peripherally with the vomeronasal nerves. From a dorsal part of the terminalis nerve plexus an anterior branch is given off which runs along the anterior ethmoidal nerve to the nasal vestibule where it connects with a group of ganglia. The peripheral branches of the nerve run from here along two epithelial cristae formed histologically like dermal papillae. Ventrally in the respiratory region at the junction of the nasal cavity and the nasopharynx is a 1 times 2 mm area with olfactory epithelium, glands of Bowman and an independent innervation from the olfactory bulb. This is the so-called septal olfactory organ. Trigeminal nerves form a plexus in the respiratory region and in the vestibule, but do not supply the olfactory region. Catecholamine-containing and cholinesterase-positive nerves run along the meningeal arteries on the cribriform plate and accompany their branches to the vascular plexus in the olfactory and respiratory regions. Double innervation is found not only of this vascular plexus but of the venous sinuses in the swell bodies of the vestibule. The glands of the nose are not surrounded by catecholamine-containing nerves.

Selective denervation of the autonomic nerve supply of the nasal mucosa

The autonomic innervation of the nasal mucosa has been studied in normal rats and in rats in which the supplying nerves had seen selectively transected; postoperative survival times varied from 2 weeks up to 18 months. The vascular structures appeared to be innervated both by acetylcholinesterase- and noradrenalin-containing fibres. Furthermore a nerve plexus consisting of both types of fibres was observed in the subepithelial region. The nasal glands however showed only a cholinergic innervation. The pattern of the autonomic nerve supply deduced from these selective denervation experiments does not differ fundamentally from the generally accepted scheme of this system in the nose of other mammals. Denervation occurred within 2 weeks after transection of the supplying nerves, but after longer survival times reinnervation was observed.

Association of nerve fibers and plasma cells in abnormal human nasal respiratory mucosa

Degeneration of sensory and autonomic nerve endings and intimate association of preterminal nerve fibers with plasma cells are described in eight patients suffering from nasal congestion. Two of the patients also suffered from nasal polyps. The association between nerve fibers and plasma cells is characterized by membrane to membrane apposition, absence of the nerve basement membrane in the contact area, and by extension of the nerve basement membrane from the free surface of the nerve fiber over the free surface of the plasma cell. It is suggested that the degeneration of nerves may be caused by autoimmune reaction as a result of tissue exposure to infection or drugs, and that the development of polyps may be the consequence of chronic tissue denervation.

NORADRENALINE STORES IN NERVE TERMINALS OF THE SPLEEN: CHANGES DURING HEMORRHAGIC SHOCK

In dogs subjected to hemorrhagic shock, a marked decrease in the noradrenaline content of the sympathetic nerve terminals in the normally innervated spleen is revealed by means of a histochemical fluorescence method. Deprivation of the sympathetic impulse-flow to the tissue immediately before the animals are subjected to shock prevents this depletion. The results support the hypothesis that the vasoconstriction which occurs during shock is due to the effect of noradrenaline released locally in the tissues, and not to circulating noradrenaline.