New synapses associated with the granule-containing cells of rat sympathetic ganglia

The synapses of the rat superior cervical sympathetic ganglion were studied with both conventional and ultrastructural histochemical methods. Besides the cholinergic synapses polarized from preganglionic fibers to sympathetic ganglion neurons, two morphologically and functionally different types of synapses were observed in relation to the small granule-containing (catecholamine-containing) cells of the rat superior cervical ganglion. The first type is an efferent adrenergic synapse polarized from granule-containing cells to the dendrites of the sympathetic ganglion neurons. This type of synapse might mediate the inhibitory effects (slow inhibitory postsynaptic potentials) induced by catecholamines on the sympathetic neurons. The second type is a reciprocal type of synapse between the granule-containing cells and the cholinergic preganglionic fibers. Through such synapses, these cells could exert a modulating effect on the excitatory preganglionic fibers. Therefore, we propose that these cells, through their multiple synaptic connections, exhibit a local modulatory feedback system in the rat sympathetic ganglia and may serve as interneurons between the preganglionic and postganglionic sympathetic neurons.     

Quantitative studies of superior cervical sympathetic ganglia in a variety of primates including man. I. The ratio of preganglionic fibers to ganglionic neurons

Estimates of the number of ganglionic neurons of superior cervical sympathetic ganglia and the number of preganglionic axons in the trunks just caudal to these ganglia were obtained from a sample of primates that included: man, chimpanzee, baboon, stump-tailed macaque, rhesus monkey, and squirrel monkey. The number of ganglionic neurons ranged from 63,625 in a squirrel monkey ganglion to 1,041,652 neurons in a human ganglion. Estimates of the number of preganglionic fibers varied between 2,285 in a cervical sympathetic trunk of a squirrel monkey and 12,008 in a human specimen. The resulting ratios of preganglionic fibers to ganglionic neurons ranged from 1:28 in a squirrel monkey ganglion to 1:196 in a human ganglion. The data reported in this study reveal considerable variation in the ratio of pre- to post-ganglionic neurons, and as was noted in regard to the number of cells in the ganglion, the ratios of ganglionic to preganglionic neurons appear to increase as a function of body size. In contrast, the number of preganglionic fibers does not increase as strikingly with body size, but varies greatly in the same species. The resulting ratio between the two orders of neurons is, therefore, less predictable than the number of ganglionic neurons in any given ganglion.     

Cholinesterases of rat sympathetic ganglia after immunosympathectomy, decentralization and axotomy

Abstract— Immunosympathectomy was produced in Sprague-Dawley rats by the subcutaneous injection of 300 units of nerve growth factor (NGF)-antiserum (1.56 mg of freeze-dried serum)/g/day for 6 days, the first dose being given 5–8 hr after birth. The immunosympathectomized rats and their control littermates were killed 2½ and 7 months after birth. Ganglionic acetylcholinesterase and pseudocholinesterase activities were measured by an adaption (Kungman , Kungman and Pouszczuk , 1968) of the colorimetric method of Ellman , Courtney , Andres and Featherstone (1961). Following immunosympathectomy the activities of these enzymes decreased significantly in superior cervical, stellate, thoracic chain, cardiac (abdominal), coeliac and superior mesenteric ganglia. The reduction of the acetylcholinesterase activity was greater than expected in a number of sympathetic ganglia, e.g. superior cervical, stellate, coeliac and cardiac ganglia, if one considered that only the postganglionic neurons were affected by immunosympathectomy. The activities of these enzymes were also reduced in the cervical sympathetic trunks from NGF-antiserum-treated rats. By means of decentralization and axotomy it was shown that 45 per cent of the total ganglionic acetylcholinesterase activity was associated with the preganglionic and 55 per cent with the postganglionic elements of the superior cervical ganglion from control rats. It was concluded that immunosympathectomy also affects the preganglionic sympathetic neurons. It is not known whether this is a primary effect of the NGF-antiserum or a secondary effect resulting from the absence of over 90 per cent of the postganglionic sympathetic cell bodies.     

The coexistence and release of bovine pancreatic polypeptide-like immunoreactivity from noradrenergic superior cervical ganglia neurons

The coexistence of bovine pancreatic polypeptide-like (BPP) immunoreactivity within the cell bodies and axons of the superior cervical ganglia (SCG) was studied. Adjacent sections stained by the indirect immunofluorescence technique for either BPP or dopamine-β-hydroxylase (DBH) revealed that virtually all (90–95%) SCG cells contained DBH and a subpopulation (30–50%) also contained BPP. Ligation of the pre- and postganglionic nerves of the SCG demonstrated BPP-positive fibers emanating from the SCG via both axonal trunks. BPP-containing fibers were also observed entering the SCG via the preganglionic nerve. The peptide was co-released with catecholamine by electrical stimulation of the preganglionic cervical sympathetic nerve trunk, but was not effected by reserpine. The extensive distribution and unique coexistence of a PP-like peptide with peripheral sympathetic nerves suggests a neuromodulatory role in autonomic functions.     

Electrophysiological investigation of pathways in the middle cervical sympathetic ganglion of the turtle

Single unit responses in the middle cervical sympathetic ganglion ofEmys orbicularis to stimulation of other nerves and changes in these responses during the action of sympathetic blocking agents on the ganglion were investigated. The results showed that some fibers of the cervical sympathetic trunk of the turtle are interrupted in this ganglion. Postganglionic fibers pass out of the ganglion and enter the lateral branch and the sympathetic trunk. Other fibers pass through the ganglion without interruption and, together with postganglionic fibers, leave the ganglion in the cervical sympathetic trunk in a cranial direction. The velocity of conduction of excitation along the preganglionic fibers is between 4–3 and 2–1.5 m/sec and along the postganglionic fibers between 4–2.6 and 0.7–0.5 m/sec (fibers of types B₂ and C). Synaptic delay in the fast-conducting fibers averages 6.6 msec. Preganglionic fast-conducting fibers form synaptic contacts on neurons with type B₂ axons, while preganglionic slow-conducting fibers form contacts on neurons with type C axons. Terminals of two preganglionic fibers differing very slightly in their threshold of excitability, and probably constituting the same group, converge on some neurons.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukranian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 1, pp. 83–89, January–February, 1972.     

Tonic impulsation in preganglionic and postganglionic sympathetic fibers of mammals

A study of the tonic electrical activity of nerves containing preganglionic and postganglionic fibers in the superior cervical and stellate sympathetic ganglia of cats and rabbits has shown that this activity consists of groups of spikes synchronous with the pulse or respiration, and occurs on a background of irregular low-amplitude impulses. The frequency of spikes is higher (250/sec) in nerves containing preganglionic fibers than in those containing postganglionic fibers (100/sec). Groups of spikes in a nerve containing preganglionic fibers correspond in some preparations to groups of spikes of lower frequency in a nerve containing postganglionic fibers of the same ganglion; in other preparations, this correspondence was lacking, apparently due to the absence of synaptic contacts between those groups of pre- and postganglionic neurons whose activity was recorded. Neurons send axons to different nerves (cardiac and vertebral) of the stellate ganglion discharged synchronously in some preparations, and asynchronously in others. Where synchronization was observed, the neurons discharged in rhythm with cardiac contractions.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 3, pp. 303–308, November–December, 1969.     

Electrical activity of the sympathetic ganglia during the depressor reflex

Tonic activity of neurons of the superior cervical sympathetic ganglion was recorded by the "sucrose gap" method and in the 4th and 5th lumbar sympathetic ganglia with the aid of focal nonpolarizing electrodes in acute experiments on anesthetized cats and rabbits. The preganglionic fibers of the ganglia were left intact. Stimulation of the depressor nerve not only sharply inhibited the tonic activity of the ganglia but also led to the appearance of electropositive potentials of 0.7 ± 0.2 mV in the superior cervical ganglion and 20–250 µV in the lumbar ganglia. The amplitude of this potential was unchanged by atropine (1 · 10^–6M). A similar effect occured without stimulation of the depressor nerve, after division of the preganglionic fibers or blocking of their conduction; it is attributed to the cessation of preganglionic tonic impulses which induce not only spikes, but also many EPSPs in neurons of the ganglion. Their frequency in the lumbar ganglia was 4/sec. Summation of these EPSPs leads to constant electronegativity of the ganglion surface relative to the postganglionic fibers, and its disappearance is recorded as a positive potential. Stimulation of the depressor nerve thus does not induce IPSPs in the ganglion; consequently, the inhibition of synaptic activity observed under these circumstances is located in the CNS and not in the ganglion.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 6, No. 5, pp. 519–524, September–October, 1974.     

Galanin and vasoactive intestinal peptide messenger RNAs increase following axotomy of adult sympathetic neurons

The adult rat superior cervical ganglion (SSG) contains low levels of galanin- and vasoactive intestinal peptide-(VIP) like immunoreactivity, with very few immuno-stained principal neurons. Immunoreactivity for both neuropeptides increases in these neurons after explanation or postganglionic axotomy in vivo. Northern blot analysis had demonstrated concomitant increases in mRNAs encoding these peptides. To localize cells in axotomized ganglia which increase their expression of these mRNAs, we performed in situ hybridization studies. In control SCG, only a few principal neurons contained mRNA for either galanin or VIP. After 48 h in organ culture, galanin mRNA was expressed in the majority of principal neurons. At 48 h after in vivo axotomy of both postganglionic trunks of the SCG, the internal and external carotid nerves, the distribution and number of neurons expressing galanin mRNA increased similarly to that seen in culture. Lesioning either trunk alone produced increases in galanin mRNA localized to those regions of the ganglion containing neurons that project into the lesioned trunk. Transection of the predominantly preganglionic cervical sympathetic trunk increased galanin mRNA expression in a small population of neurons that nerve trunk. The distributions of these labeled neurons, together with previous neuroanatomical studies, suggests that they had been axotomised by the lesions. Similar studies examining VIP mRNA expression demonstrated that although considerably fewer VIP mRNA expressing neurons than galanin mRNA expressing neurons were present after axotomy, the distribution of neuropeptide mRNA-positive cells were similar in both cases. These observations suggest that increases in the peptide galanin and VIP after nerve transection result from changes in the levels of their mRNAs in those neurons that have been axotomized. 1994 John Wiley & Sons, Inc.     

Identification of neurons that express ghrelin receptors in autonomic pathways originating from the spinal cord

Functional studies have shown that subsets of autonomic preganglionic neurons respond to ghrelin and ghrelin mimetics and in situ hybridisation has revealed receptor gene expression in the cell bodies of some preganglionic neurons. Our present goal has been to determine which preganglionic neurons express ghrelin receptors by using mice expressing enhanced green fluorescent protein (EGFP) under the control of the promoter for the ghrelin receptor (also called growth hormone secretagogue receptor). The retrograde tracer Fast Blue was injected into target organs of reporter mice under anaesthesia to identify specific functional subsets of postganglionic sympathetic neurons. Cryo-sections were immunohistochemically stained by using anti-EGFP and antibodies to neuronal markers. EGFP was detected in nerve terminal varicosities in all sympathetic chain, prevertebral and pelvic ganglia and in the adrenal medulla. Non-varicose fibres associated with the ganglia were also immunoreactive. No postganglionic cell bodies contained EGFP. In sympathetic chain ganglia, most neurons were surrounded by EGFP-positive terminals. In the stellate ganglion, neurons with choline acetyltransferase immunoreactivity, some being sudomotor neurons, lacked surrounding ghrelin-receptor-expressing terminals, although these terminals were found around other neurons. In the superior cervical ganglion, the ghrelin receptor terminals innervated subgroups of neurons including neuropeptide Y (NPY)-immunoreactive neurons that projected to the anterior chamber of the eye. However, large NPY-negative neurons projecting to the acini of the submaxillary gland were not innervated by EGFP-positive varicosities. In the celiaco-superior mesenteric ganglion, almost all neurons were surrounded by positive terminals but the VIP-immunoreactive terminals of intestinofugal neurons were EGFP-negative. The pelvic ganglia contained groups of neurons without ghrelin receptor terminal innervation and other groups with positive terminals around them. Ghrelin receptors are therefore expressed by subgroups of preganglionic neurons, including those of vasoconstrictor pathways and of pathways controlling gut function, but are absent from some other neurons, including those innervating sweat glands and the secretomotor neurons that supply the submaxillary salivary glands.     

Neurofilament-like and glial fibrillary acidic protein-like immunoreactivities in rat and guinea-pig sympathetic ganglia in situ and after perturbation

Summary The presence of neurofilament (NF)-like and glial fibrillary acidic protein (GFAP)-like immunoreactivities was studied in sympathetic ganglia of adult rats and guinea pigs during normal conditions and after perturbation. In the superior cervical ganglion (SCG) of normal rats, many ganglion cells and nerve fibers show NF immunoreactivity. Some of these nerve fibers disappear after preganglionic decentralization of SCG; this indicates the presence of a mixture of preand postganglionic NF-positive nerves in the ganglion. Cuts in both preand postganglionic nerves result in a marked increase in GFAP immunoreactivity in SCG, whereas NF immunoreactivity increases in nerve cell bodies after preganglionic cuts. Only a few ganglion cells show NF immunoreactivity in the normal SCG of guinea pig. All intraganglionic NF-positive nerves are of preganglionic origin; decentralization abolishes NF immunoreactivity in these nerve fibers. The inferior mesenteric ganglion, the hypogastric nerves and colonic nerves in guinea pigs contain large numbers of strongly NF-immunoreactive nerve fibers.When the SCG of adult rat is grafted to the anterior eye chamber of adult rat recipients, both ganglionic cell bodies and nerve fibers, forming on the host iris from the grafted ganglion, are NF-positive. As only the perikarya of these neurons normally exhibit NF immunoreactivity, and the terminal iris arborizations are NF-negative, it appears that the grafting procedure causes NF immunoreactivity to become more widespread in growing SCG neurons.     

The localization of the beta-subtype of protein kinase C (PKC-beta) in rat sympathetic neurons

The localization of PKC-beta was studied in rat sympathetic neurons using a polyclonal antibody specific for the beta 1- and beta 2-subspecies. The tissues studied included the superior cervical (SCG) and hypogastric (HGG) ganglia and the target tissues of the SCG and HGG neurons: the submandibular gland, iris, prostate and vas deferens. PKC-beta-LI was found in nerve fibers in both ganglia. A proportion of the fibers in the SCG disappeared after decentralization, suggesting that the fibers were of both pre- and postganglionic origin. The somata of the HGG and SCG neurons expressed varying amounts of PKC-beta-LI, the majority of SCG neurons being labelled only after colchicine treatment. In all target tissues there were PKC-beta-immunoreactive nerve fibers in bundles, but the most peripheral branches of the fibers were negatively labelled. The results show that PKC-beta-LI is widely present in sympathetic postganglionic neurons with mainly quantitative differences. The lack of PKC-beta in the most peripheral branches of nerve fibers might be a general feature of sympathetic postganglionic neurons, suggesting that the participation of PKC-beta in neurotransmitter release and in other functions in nerve terminals in sympathetic adrenergic neurons is unlikely.     

Effect of preganglionic sympathectomy on the cholinesterase activity in the superior cervical ganglia of rats and hamsters

Summary By employing biochemical assay and histochemical enzyme techniques the effect of preganglionic sympathectomy on the cholinesterase (ChE) activity in the superior cervical ganglia of rats and hamsters was investigated. Biochemical assays indicate that the ChE activity in the superior cervical ganglia of adult rats and hamsters is 57.19 and 28.63 respectively (expressed in u moles acetylcholine hydrolyzed per min per g of tissue); two weeks after preganglionic denervation, about 50% and 60% of ChE activity are lost respectively. Histochemical enzyme examination reveals that in the rat superior cervical ganglion, the majority of the neurons are adrenergic with weak to moderate acetylcholinesterase (AChE) reaction and the minority of the neurons are cholinergic with strong AChE activity, while only one type of adrenergic neurons exhibits a weak AChE activity in the hamster superior cervical ganglion. The AChE activity is localized in the perinuclear area, in the cisternae of the rough surfaced endoplasmic reticulum, in the Golgi complex and on the plasma membrane of the hamster's neurons; it is mainly localized in the cisternae of the rough surfaced endoplasmic reticulum of the rat's neurons. AChE reaction product is also detected on the axolemmal membranes of the preganglionic nerve fibers in the sympathetic ganglia of rats and hamsters.After preganglionic sympathectomy, the AChE activity in the adrenergic neurons and in the preganglionic unmyelinated nerve fibers is markedly reduced, whereas the cholinergic neurons and preganglionic myelinated nerve fibers remain unchanged. On the basis of these results two conclusions have been reached: (1) The fact that strong AChE activity localized in the cholinergic neurons and preganglionic myelinated fibers is not influenced by denervation, suggests that these structures are able to produce AChE. (2) The reduction of AChE activity in the rat and hamster superior cervical ganglia two weeks after preganglionic denervation, observed by histochemical examination, can be correlated with a concomitant measurable reduction determined by biochemical assays.Supported in part by a grant from the National Science Council, Republic of China. The author wishes to express his gratitude to the Department of Pharmacology, College of Medicine, National Taiwan University, for the use of its equipment for biochemical assays     

Alpha-adrenergic receptor modulation of the intrathoracic efferent sympathetic nervous system regulating the canine heart

The augmentation of ventricular inotropism induced by electrical stimulation of acutely decentralized efferent sympathetic preganglionic axons was reduced, but still present, following administration of hexamethonium (10 mg/kg i.v.). While hexamethonium continued to be administered, the cardiac augmentations so induced were enhanced significantly following administration of the alpha-adrenergic receptor blocking agent, phentolamine myselate (1 mg/kg i.v.). Stimulation of the sympathetic efferent postganglionic axons in cardiopulmonary nerves induced cardiac augmentations that were unchanged following administration of these agents singly or together. The cardiac augmentations induced by stimulation of efferent preganglionic sympathetic axons were unchanged when phentolamine was administered alone. The augmentations of cardiac inotropism induced by efferent postganglionic sympathetic axonal stimulation were decreased following local administration of the beta-adrenergic antagonist timolol into the ipsilateral stellate and middle cervical ganglia. Thereafter, these augmentations were unchanged following the subsequent intravenous administration of phentolamine. It is concluded that the activation of cardiac neurons in the stellate and middle cervical ganglia by stimulation of efferent preganglionic sympathetic axons can be modified by alpha-adrenergic receptors and that these effects are dependent upon beta-adrenergic receptors, not nicotinic ones, in intrathoracic ganglia.     

Noradrenaline-Induced Prostaglandin Production by Sympathetic Postganglionic Neurons Is Mediated by α2-Adrenergic Receptors

In this study we have demonstrated that noradrenaline increases the levels of prostaglandin E2 and prostaglandin I2 (detected as the stable metabolite 6-keto-prostaglandin F1 alpha) synthesized by homogenates of superior cervical ganglia from the adult rat. This noradrenaline-induced prostaglandin production was further characterized: (a) Selective destruction of adrenergic sympathetic postganglionic neurons in the ganglia using 6-hydroxydopamine abolished both basal and stimulated prostaglandin production. (b) Elimination of preganglionic cholinergic sympathetic nerve terminals in the ganglia had no effect. (c) Mepacrine (a phospholipase inhibitor) and indomethacin (a cyclooxygenase inhibitor) attenuated both basal and stimulated prostaglandin production. (d) Yohimbine, but not prazosin, suppressed the noradrenaline dose-response curve for prostaglandin production. The results of these experiments show that, in vitro, noradrenaline stimulates de novo synthesis of prostaglandin E2 and prostaglandin I2 by sympathetic postganglionic neurons. This stimulation by noradrenaline appears to result from action at an alpha 2-adrenergic receptor.     

Horseradish peroxidase localization of sympathetic postganglionic and parasympathetic preganglionic neurons innervating the monkey heart

The localization of the sympathetic postganglionic and parasympathetic preganglionic neurons innervating the monkey heart were investigated through retrograde axonal transport with horseradish peroxidase (HRP). HRP (4 mg or 30 mg) was injected into the subepicardial and myocardial layers in four different cardiac regions. The animals were euthanized 84-96 hours later and fixed by paraformaldehyde perfusion via the left ventricle. The brain stem and the paravertebral sympathetic ganglia from the superior cervical, middle cervical, and stellate ganglia down to the T9 ganglia were removed and processed for HRP identification. Following injection of HRP into the apex of the heart, the sinoatrial nodal region, or the right ventricle, HRP-labeled sympathetic neurons were found exclusively in the right superior cervical ganglion (64.8%) or in the left superior cervical ganglion (35%). Fewer labeled cells were found in the right stellate ganglia. After HRP injection into the left ventricle, labeled sympathetic cells were found chiefly in the left superior cervical ganglion (51%) or in the right superior cervical ganglion (38.6%); a few labeled cells were seen in the stellate ganglion bilaterally and in the left middle cervical ganglion. Also, in response to administration of HRP into the anterior part of the apex, anterior middle part of the right ventricle, posterior upper part of the left ventricle, or sinoatrial nodal region, HRP-labeled parasympathetic neurons were found in the nucleus ambiguus on both the right (74.8%) and left (25.2%) sides. No HRP-labeled cells were found in the dorsal motor nucleus of the vagus on either side.     

Preganglionic discharge induced by acetylcholine in the superior cervical ganglia of the rat

ACh (5.10(-4) M), when applied to isolated ganglion preparations elicited an apparently antidromic discharge in the cervical sympathetic trunk. The intensity of this back-firing was found to be about 10 times lower than that of the postganglionic discharge evoked by ACh in the internal carotid nerve. Both responses however displayed a similar time course consisting mainly of an early and a late component. In the back-firing the early component died out in few seconds, while the late one lasted 20-30 seconds. The two components were cancelled by d-tubocurarine (5.10(-6) M) and atropine (10(-6) M) respectively, suggesting that both nicotinic and muscarinic cholinoceptive sites are involved. In chronically decentralized preparations ACh evoked a clear back-firing response not substantially different from that elicited in normal ganglia. Therefore it is likely that the back-firing phenomenon is not due to antidromic activation of preganglionic fibers. The back-firing observed in the rat superior cervical ganglion was interpreted as being due to activation of sympathetic neurons, known to give rise to recurrent axons in the cervical sympathetic cord.     

Origins of the afferent fibers to the cat superior cervical ganglion.

The origins of the afferent fibers to the cat's superior cervical ganglion (SCG) were demonstrated by using the retrograde horseradish peroxidase tracing method. We found that the preganglionic neurons were located in the spinal segments C8-T5, particularly in T1-T3. These neurons were situated mainly in the intermediolateral column. The extra-SCG neurons along with the cervical sympathetic trunk originated ipsilaterally from the middle cervical and stellate ganglia, and contralaterally from the caudal part of the SCG. Labeled neurons also originated from the mandibular division of the trigeminal ganglion. Our results demonstrated that many fiber sources projected to the SCG, which plays a complicated synaptic role in controlling the visceral organs of the head and neck region.     

Retroperitoneal paraganglia and the peripheral autonomic nervous system in the human fetus

By means of the AChE in toto staining method retroperitoneal paraganglia and the peripheral autonomic nervous system in human fetuses have been investigated. Many small retroperitoneal paraganglia are present near the sympathetic trunks close to the sympathetic trunk ganglia. In the thoracic region small paraganglia are present in the intercostal spaces. Small splanchnic nerves entering small paraganglia have been described. In the lower sacral region no paraganglia are present. The major splanchnic nerve arises at various levels from the sympathetic trunks as well as many smaller thoracic splanchnic nerves. Intermediate ganglia are present in the major splanchnic nerve, the smaller splanchnic nerves and the communicating rami. In the sympathetic trunks many ganglia are fused. In the human fetus there exists a large variability in number and diameter of the communicating rami. Interconnecting bundles of nerve fibers between the left and right sympathetic trunks are present at all levels, but most numerous at the sacral level.     

Structure and innervation of the pineal gland of the rabbit,Oryctolagus cuniculus (L.)

In the rabbit pineal gland two types of postganglionic nerve endings were found which are characterized by the presence of small dense-core vesicles or small clear vesicles. Pharmacological and cytochemical experiments showed then to be noradrenergic and cholinergic, respectively. Both types were often present in the same nerve bundle, occasionally in close opposition. Intrapineal neurons were only rarely observed. They showed cholinergic synapses on their perikaryon and dendrites as well as noradrenergic axo-dendritic close contacts. Bilateral extirpation of the superior cervical ganglia revealed the postganglionic sympathetic origin of the pineal noradrenergic nerve fibres. Moreover, it appeared that these ganglia are hardly, if at all, involved in the pathway of pineal cholinergic innervation. The results obtained from lesions of both facial nerves, taken together with the results reported in the literature, led to the conclusion that the postganglionic cholinergic nerve fibers in the pineal are of parasympathetic origin. A model for the sympathetic and parasympathetic pineal innervation is proposed.