Cranial Origin Research Articles

Presentation of a case of a dermoid cyst with a rare location

Dermoid cysts are choristoma that accumulate normal embryonic tissue in abnormal locations, making up 3% to 5% of congenital orbit conditions. They are found in various parts of the body, including the head and neck, frontal, periorbital, scalp, cervical, and nasoethmoidal regions. Nasoethmoidal dermoid cysts can compromise deep structures and may extend intracranially, with a frequency of 1% to 45%. They are usually diagnosed in the first 3 years of life, but some may go undetected until adulthood. Two theories explain the origin of nasal dermoids: the cranial origin theory and the superficial inclusion theory. Nasal dermoids can be pale, flesh-colored, pearly, or erythematous and may be accompanied by congenital anomalies. Different diagnoses include epidermal cysts, gliomas, meningoencephaloceles, tumors of vascular origin, fibromas, neurofibromas, osteomas, and lipomas. Imaging evaluations are necessary for diagnosis, determining the degree of involvement of neighboring structures, rule out associated malformations, and establish potential intracranial extension. The only curative treatment for nasoethmoidal dermoid cysts is surgical removal, as untreated lesions can cause nasal deformities, recurrent infections, and intracranial extension.

Furcula Diversity Within the Avian Flight Apparatus

A major unknown in avian biology is the morphological basis of flight style diversity. While certain aspects of avian pectoral anatomy, such as an enlarged sternum and hypertrophied pectoral muscles, clearly relate to aerial locomotion in general, the finer details of form-function correspondence are less apparent. Nevertheless, furcula shape has been used to infer flight style in extinct avians because the furcula is the cranial origin of the largest flight muscle, m. pectoralis, in most extant birds. However, previous studies, which examined the furcula in isolation, indicate only a modest correlation between furcula shape and flight style. We hypothesized that the relationship of the furcula to flight style may be heavily mediated by other aspects of pectoral anatomy, particularly furcula orientation and flight muscle morphology. We used computed tomography and digital dissection techniques to collect in situ morphological data on a large (n=108) and diverse (21 orders) sample of formalin-fixed specimens. While some specimens required the addition of Lugol's iodine to visualize soft tissue, most specimens did not require contrast enhancement to permit bone and muscle reconstruction. We found moderate correspondence between flight style and furcula shape consistent with previous studies (e.g., soaring birds have flatter, more V-shaped furculae), however the magnitude of shape differences between flight style and taxonomic categories was smaller, perhaps due to different measurement techniques. Novel measures of furcular orientation in the pectoral girdle revealed that larger, slower-flapping birds tend to have more cranially-positioned furculae, which may relate to a greater need for wing protraction via m. pectoralis. Further, the centers-of-mass of the main pectoral muscles tend to be more cranial in large birds with more laterally-bowed furculae. In most measures, hummingbirds did not group with birds of similar mass or furcula shape, likely owing to their kinematically-unique flight style. Overall, our findings recommend caution in inferring flight style from furcula shape alone. Rather, furcula shape may be better viewed as part of a larger functional unit including the sternum, coracoids, and major flight muscles.

Congenital Anatomical Variant with Cranial Origin of Internal Iliac Arteries.

We report the case of a 73-year-old male who underwent abdominal multidetector computed tomography with vascular reconstruction that highlighted a congenital variant of iliac arteries. Iliac artery anatomical variants are exceedingly rare and only a few cases have been reported in the literature.

Hemiplegia complicated by opposite hemichorea

Hemiplegias of cranial origin are among such clinical pictures, with which a neuropathologist meets especially often. But, in spite of this, science has not yet said its last word about them. Moreover, some of the symptoms of suffering still remain poorly understood even from the outside, not to mention their pathogenesis. We know, for example, that movement disorders during hemiplegias also extend to the healthy half of the body; these disorders, which have long attracted the attention of observers, are in their considerable part described with sufficient detail; However, at least from time to time, the clinic presents us with new combinations, which indicate how deeply and together with how differently the disease of one hemisphere can affect the motor functions of the other.

The 2-Dimensional and 3-Dimensional Anatomy of the Adult Brachial Plexus Divisions and Cords.

Background: The objective of this work was to perform a critical review of the 2-dimensional and 3-dimensional anatomy of the adult brachial plexus divisions and cords. Methods: Twelve adult brachial plexuses from fresh cadavers were dissected. All were male and aged between 30 and 50 years. Only corpses without brachial plexus injuries were selected. The purpose of the dissections was to identify the origin of the anterior and posterior divisions of the adult brachial plexus in their respective trunks, as well as the positioning of the posterior, lateral, and medial cords. Results: The posterior division of all trunks had a cranial and dorsal origin, while the anterior division of all trunks had a caudal and ventral origin. The posterior cord was the most cranial of all, the lateral cord was central, and the medial cord was the most caudal of all cords. The posterior division of the superior trunk was always between the suprascapular nerve and the anterior division. Conclusions: Brachial plexus diagrams in most textbooks and papers are different from what was found in our dissections. Contrary to the known diagram, the posterior divisions always had a cranial origin in the superior, middle, and inferior trunks.

A Cranial Mesoderm Origin for Esophagus Striated Muscles

The esophagus links the oral cavity to the stomach and facilitates the transfer of bolus. Using genetic tracing and mouse mutants, we demonstrate that esophagus striated muscles (ESMs) are not derived from somites but are of cranial origin. Tbx1 and Isl1 act as key regulators of ESMs, which we now identify as a third derivative of cardiopharyngeal mesoderm that contributes to second heart field derivatives and head muscles. Isl1-derived ESM progenitors colonize the mouse esophagus in an anterior-posterior direction but are absent in the developing chick esophagus, thus providing evolutionary insight into the lack of ESMs in avians. Strikingly, different from other myogenic regions, in which embryonic myogenesis establishes a scaffold for fetal fiber formation, ESMs are established directly by fetal myofibers. We propose that ESM progenitors use smooth muscle as a scaffold, thereby bypassing the embryonic program. These findings have important implications in understanding esophageal dysfunctions, including dysphagia, and congenital disorders, such as DiGeorge syndrome.

Thomas Willis, a pioneer in translational research in anatomy (on the 350th anniversary of Cerebri anatome).

The year 2014 marked the 350th anniversary of the publication in London of Cerebri anatome, a ground-breaking work of neuroscience heavily influenced by the political and cultural context of Baroque Europe and mid-17th century England. This article aims to review the work of the English physician and anatomist Thomas Willis, specifically with regard to the contents of his Cerebri anatome. Willis's academic and professional career was influenced by the turbulent period of the English Civil War during which he studied medicine. Willis went from chemistry to dissection arguably because of his need to justify the body-brain-soul relationship. As a result, he became a fellow of a select club of eminent experimentalists, and afterward was a Fellow of the Royal Society. Later on, he went to London, leaving the academic life to dedicate himself fully to the profession of medicine. As a physician, Willis did not base his practice on aphorisms but on a 'bench to bedside' approach to medicine, while studying neuroanatomy--covering embryology, comparative anatomy and pathological anatomy--as a basis for the comprehension of neurological pathology. He developed innovative anatomical methods for the preservation and dissection of the brain, injection of coloured substances and illustration of his findings. In Cerebri anatome, Willis recognized the cerebral cortex as the substrate of cognition. He also claimed that the painful stimuli came from the meninges, but not from the brain itself. He explained for the first time the pathological and functional meaning of the brain's circular arterial anastomosis, which is named after him. He also specified some features of the cranial origin of the sympathetic nerves and coined the term 'neurologie'. Cerebri anatome marked the transition between the mediaeval and modern notions of brain function, and thus it is considered a cornerstone of clinical and comparative anatomy of the nervous system. The new contributions and methods employed by Willis justify his place as a father of neurology and a pioneer of translational research.

Correspondence

To the Editor: RE: ‘Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition’ by Kawai et al. Journal of Anatomy, Vol. 215, pp. 656–662. Kawai et al. present an interesting study of the relationship between electromyographic activity in jaw muscles and their fibre type composition (Kawai et al. 2009). The concept of functional adaptation has been widely accepted since I introduced it in the 1970s (Salmons & Sréter, 1976; Salmons, 1980; Salmons & Henriksson, 1981). The evidence comes entirely from muscles of the limbs and trunk, but it is reasonable to expect the same regulatory phenomena to be present in skeletal muscles of cranial origin even though they contain, and often co-express, a greater diversity of myosin heavy chain isoforms. The authors of this paper appear, however, to have misinterpreted the adaptive hypothesis. This states that sustained high levels of activity induce slow, fatigue-resistant properties; low or intermittent levels of activity allow the fibers to retain, or revert to, a native fast, fatigue-susceptible state. Accordingly, where there is a high proportion of type IIX fibres it would be associated not with the generation of large forces, as the authors propose, but with a low aggregate amount of activity. The high-frequency patterns needed to produce large forces do not differ from low-frequency patterns in their effect on myosin isoform composition (Hudlicka et al. 1982; Kernell et al. 1987; Sutherland et al. 2003). It is certainly true that the muscles of smaller animals have a lower proportion of slow fibres. This is associated with a higher threshold for the transition from fast to slow myosin isoforms (Salmons & Henriksson, 1981; Sutherland et al. 1998, 2006). The transition, although present in the rat, is correspondingly more difficult to demonstrate than in larger species (Jarvis et al. 1996). On this basis a better correlation between the proportion of type I fibres and muscle activity should be seen in a larger experimental animal, and has in fact been found in rabbit jaw muscles by van Wessel et al. (2005). This citation is curiously absent from the present paper. There is a good deal of published evidence to show that myosin heavy chain composition responds to the aggregate number of impulses reaching the muscle (see Salmons, 2009 for a recent review). Unfortunately this is not measured by the overall duration and amplitude of electromyographic activity over the same period: high-frequency bursts of short duration could deliver the same number of impulses as low-frequency trains of longer duration. If the authors were able to take this into account, the apparent inconsistencies in their data for the anterior temporalis muscle and the seeming departures from Henneman’s size principle would, I suggest, disappear.

The Axial Musculature of the Red Panda (Ailurus fulgens)

The red panda (Ailurus fulgens) is an endangered, scansorial carnivore found in the forests of the Himalayas and southern China. The phylogeny of the red panda has been the subject of debate, with molecular and morphological studies indicating a number of possible relationships, including affinities to ursids, procyonids, mustelids, and mephitids. The myology of the red panda, however, remains largely undocumented. The axial muscles of the red panda were evaluated to determine whether any evolutionary affinities with suggested relatives existed, and whether any adaptations to the red panda's scansorial lifestyle were present in these muscles. Two adult red pandas were dissected and photodocumented. The axial musculature of Ailurus was then compared to other carnivores. The dissections revealed several interesting findings. For example, m. biventer cervicis was found to have six tendinous intersections, similar to those found in the mm. rectus abdominis and likely allowing precise movement of the neck just as the rectus muscles allow for precise movements of the trunk. The comparison of the axial musculature of the red panda to that of other carnivores also revealed interesting findings; for example, the red panda had several differences from the giant panda (Ailuropoda melanoleuca), including a more superficial m. splenius with a significantly more cranial origin.Support from the Howard Hughes Medical Institute through the Undergraduate Science Education Program and from the ASU School of Life Sciences.

CONGENITAL PTERIONAL DERMAL SINUS IN AN 18-MONTH-OLD CHILD

Congenital dermal sinus tracts most frequently occur in the midline and are often associated with dermoid or epidermoid inclusion cysts. A lateral cranial origin is extremely rare and anatomically inconsistent with an etiology involving closure of the rostral neural tube during embryogenesis. We describe the first case of a pterional cranial dermal sinus tract associated with a small epidermoid, with extension to the dura of the anterior cranial fossa. The extra- and intracranial portions of the tract were visualized and resected with the use of an operating microscope. Pathological diagnosis confirmed dermal sinus tract. We review the existing literature and address the developmental and clinical features pertinent to the management of cranial dermal sinus tracts, emphasizing the need for exploration of these potentially harmful lesions.

Re‐examination of the medullary rootlets of the accessory and vagus nerves

The vagus (X) and cranial root of the accessory nerve (crXI) are traditionally described as arising from a series of rootlets from the medulla oblongata. Descriptions of the number of rootlets vary, and the existence of the crXI is contested. Here we report the results of dissections in six embalmed adult human specimens (11 sides). The rootlets forming the vagus were counted at three positions. At emergence from the brainstem there were between 12 and 21 rootlets, at the jugular foramen the range was 12-17, and midway between these two points it was 6-12. In addition, the origin of the most caudal X rootlet (cX) and the most rostral XI rootlet (rXI) was recorded in relation to the spino-medullary junction, defined as the caudal border of the olivary eminence. The position of the cX varied between -1 and +8 mm (median = +2 mm on left, +3.75 mm on right). The rXI varied between -5 and +7 mm (median = -0.5 mm on left, +1.75 mm on right). In five sides, rXI was above the caudal border of the olivary eminence and as such can be defined as being of cranial origin. These observations show the arrangement of rootlets contributing to the vagus to be more complex than what was described previously and provide evidence for the variable existence of a cranial root of the accessory nerve.

Comparative Anatomical Study of the Kidney Position in Amniotes Using the Origin of the Renal Artery as a Landmark

The anatomical relationship between the kidney position and its arterial supply was investigated in 21 mammals, 1 bird, and 3 reptiles (n = 1 for each species) and in 43 human cadavers. The following observations were made. (1) Although the right kidney was located caudal to the left kidney in 29 out of 43 human cadavers (67.4%), the origin of the right renal artery from the aorta was located cranial to the origin of the left renal artery in 36 human cadavers (83.7%). Therefore, the relative positions of the kidneys do not correspond with the relative origins of the renal arteries in humans. (2) Among the mammals that were examined, the position of the kidney and the branching level of the renal artery on the right side were usually cranial to those on the left side. (3) In the bird and most reptiles that were examined, kidneys were typically located in the pelvic region and were supplied by segmental arterial branches. These results suggest that the right kidney and its arterial supply are generally located cranial to the left kidney in phylogeny of mammals. While the presence of a human accessory renal artery in 9 out of 86 sides (10.5%) and a cranial origin of the left renal artery relative to the right renal artery in 7 out of 43 cadavers (16.3%), shows some variation in the arterial supply to the kidneys, the origin of the renal arteries can generally be used as phylogenetic landmarks indicating the relative positions of the kidneys. Hence, from an ontological perspective, the human right kidney may be initially situated cranial to the left kidney during the early stages of development. Thereafter, the human right kidney may shift downwards secondary.

Gabapentin produces dose-dependent antinociception in the orofacial formalin test in the rat

Background and Objectives: High neuraxial drug infusion has been advocated for the treatment of intractable cranial and facial pain in humans. Currently, parallel animal models have not been characterized to support this methodology. We combined an accepted animal model of pain of cranial origin with a novel technique of cervico-medullary drug delivery to determine the antinociceptive potential of gabapentin. Gabapentin was chosen because of its reported efficacy in a wide array of complex cranial pain syndromes. Methods: Male Wistar rats were implanted with intrathecal catheters that were advanced cephalad through a lumbar guide cannula to terminate in the high cervical spinal cord (C1-C4). Antinociception was assessed by the orofacial formalin test. Vehicle or gabapentin (3, 10, 30, 100 μg) was injected intrathecally followed 10 minutes later by injection of 2.5% formalin solution into the vibrissal pad. Motor assessment was evaluated in a separate group of animals. Results: Intrathecal gabapentin (10, 30, 100 μg) produced a dose-dependent decrease in the second phase of the behavioral response to formalin (P < .05). First-phase responses were unaffected by all doses of gabapentin. The ED50 (95% confidence limit) value for the second phase was 8.27 μg (3.50 to 14.5). No overt motor dysfunction or behavioral impairment was observed. Conclusions: Gabapentin produced dose-dependent antinociception in the second phase of the orofacial formalin test in the rat after injection into the cervico-medullary cerebrospinal fluid. This animal model may be useful to assess analgesics designed for parallel clinical application in humans for the treatment of intractable head and neck pain that is refractory to conventional modalities. Reg Anesth Pain Med 2002;27:277-283.

Cervicomedullary intrathecal injection of morphine produces antinociception in the orofacial formalin test in the rat.

High cervical and medullary drug delivery has been advocated for the treatment of refractory head and neck pain in humans. Currently, parallel models in animals have not been developed to support this methodology. We combined an accepted animal model of pain of cranial origin with a novel technique of neuraxial drug delivery to address this issue. Male Wistar rats were implanted with intrathecal catheters that were advanced cephalad through a lumbar guide cannula to the high cervical spinal cord. The orofacial formalin test was used to assess antinociception. Vehicle or morphine (1, 3, 6, 10, 30 microg) was injected intrathecally followed 10 minutes later by injection of formalin solution, 2.5%, into the vibrissal pad. Motor assessment and hemodynamic and respiratory blood gas measurements were evaluated in a separate group of animals. Intrathecal morphine produced a dose-dependent decrease in the first and second phases of the behavioral response (P < 0.05). The ED50 (95% confidence limits) values for the first and second phases were 6.65 microg (3.52-14.9 microg) and 3.40 microg (2.37-4.61 microg), respectively. Ten micrograms intrathecal naloxone antagonized the morphine effect (P < 0.05). Significant cardiovascular and respiratory depression was observed. No significant motor dysfunction was observed. Cervicomedullary injection of morphine produced antinociception in the orofacial formalin test in the rat. This animal model may be useful to assess analgesics designed for parallel clinical application in humans.

Diagnosis of lumbosacral nerve root anomalies by magnetic resonance imaging.

This study evaluates the use of magnetic resonance imaging (MRI) in the diagnosis of lumbosacral nerve root anomalies. Prevalence of anomalous nerve roots has been based on anatomic dissection or preoperative neuroradiologic investigations. Three hundred seventy-six patients with low back pain and/or radicular pain who underwent MRI of the lumbar spine were reviewed. Sixty-five cases of nerve root anomalies were found (an incidence of 17.3%) of which 1 case of cranial origin, 5 cases of caudal origin, 2 cases of conjoined nerve root, and 57 cases of furcal nerve roots (15.1%) were identified. Furcal nerve roots were most commonly found at L3 and L4 levels and were classified, according to their division, into intra-and extraforaminal. MRI provided accurate information on lumbosacral nerve root anomalies.

Dr Thomas Willis.

Thomas Willis (1621–1675) was born in Great Bedwyn in Wiltshire and made seminal contributions to neurology and neuroanatomy in the 17th century, including his famous arterial circle. After receiving his medical degree in 1646, Willis started practice in Oxford and became Sedleian Professor of Natural Philosophy. He later moved to London, at the invitation of the Archbishop of Canterbury, and remained closely associated with the church. He was one of the founders of the Royal Society of London.Willis devoted himself to the study of neuroanatomy and to the opportunity of “opening heads” and examining their contents. Richard Lower and Christopher Wren, pioneers in blood transfusion, assisted him in his study of cerebral vasculature and contributed drawings to Willis’ grand treatise, Cerebri Anatome. Lower and Wren had much input into the vascular injection studies, which employed india ink and other fluids. Before Willis, a basal arterial circle had been described by Fallopius, Casserio, Vesling, and Wepfer. Willis acknowledged these previous studies and realized the functional importance of the circle and cited examples where this anastomosis prevented apoplexy or paralysis. With animal experiments, he demonstrated that dye injected into 1 carotid stained the contralateral vasculature and that ligation of 1 carotid was compatible with life. He also described spinal vascular anatomy.Cerebri Anatome, published in 1664, also included Willis’ classification of the cranial nerves, which numbered 10, the first 6 being as we know today. Willis was the first to include the olfactory tract as the first cranial nerve. Willis’ seventh cranial nerve was the combined facial-vestibulocochlear, his eighth the combined glossopharyngeal-vagus-accessory, and his ninth the hypoglossal. He described the spinal accessory and the cranial origin of the sympathetic nerves (which he called “intercostal”) and created excellent illustrations of the peripheral autonomic nervous system. Willis not only understood the anatomical distinction between the vagus and sympathetic nerves, but also appreciated their functional significance.His numerous other contributions include introduction of the word “neurology,” distinguishing sympathetic nerves, naming the “lentiform bodies” and “corpus striatum,” theories on cerebral localization and function, and descriptions of myasthenia gravis, migraine, general paresis, and the phenomenon of “paracusis.” He also noted that the urine of diabetics was sweet.Willis died in 1675 of pneumonia.

Incisor and molar wear in the tammar wallaby (Macropus eugenii Desmarest)

The morphology of incisor and molar teeth of tammar wallabies (Macropus eugenii Desmarest) is similar to that of the archetypal grazing macropod (M. giganteus) but there are some resemblances in the wear pattern of molars to that of grazer/browsers. Incisor wear patterns show that cutting during biting is by scissor-like action of the elevated labial enamel edge of an attrition facet on each lower incisor being occluded with, and rotated supero-medially across, the buccal surface of the upper incisor arcade. With increase in age and body size, the cutting surface moves from anterior to lateral upper incisors, progressive wear on the inner surface of the lateral upper incisors permitting an increasing degree of incisor action coincident with medial molar movement in Phase 2 occlusion, which is similarly achieved by medial rotation of the jaw. Significant distal movement of the reference point for molar index, along the line of the upper jaw, with increase in body size, indicates that this index does not measure the absolute mesial movement of molars in the plane of occlusion. The estimated value of absolute mesial movement of the first upper premolar along the line of the jaw (2.45 mm year–1) is at the known limits of mesial drift. Studies of size-related changes in the linear dimensions of various bony landmarks on jawbone and skull indicate that the high rate of movement may result from deposition of bone in the rear of the tooth row, i.e. ‘mesial shift’, as well as mesial drift. However, mesial shift may not account for significant differences in rates of absolute mesial movement of upper molars with gender. With increase in body size, the caudal insertions of the masseter and temporalis and the cranial origin of the line of action of masseter all move distally along the plane of occlusion. However, a concurrent mesial movement in the cranial origin of the line of action of the temporalis may act to counter any distal movement of occlusive force along the jaw-line and to decrease the relative force of the retraction component that opposes Phase 1 occlusion.

Morphological and morphometric characterisation of Onuf's nucleus in the spinal cord in man.

In the absence of a systematic morphometric study of Onuf's nucleus in man, this investigation defines the limits of variation of segmental position and the range of length and volume of Onuf's nucleus in 6 normal humans displaying no neurological disease (2 males, 4 females). Serial section reconstruction methods in conjunction with the disector method provided information on the numbers, sizes and shapes of the constituent motor neurons of Onuf's nucleus. In contrast to previous descriptions, the cranial origin of Onuf's nucleus occurred in rostral S1 in 50% of subjects, and midcaudal S1 in the remaining subjects. Onuf's nucleus varied in length between 4 and 7 mm, and was 0.2-0.37 mm3 in volume. Differences in length or volume between males or females, or between the left and right side of the cord were not statistically significant. Neurons in Onuf's nucleus varied in diameter between 10 microns and 60 microns (mean 26 microns) and their mean number was 625 +/- 137. A higher density of neurons occurred at the cranial and caudal ends of the nucleus relative to the middle. While 37% of neurons were approximately spherical (shape index approximately 1), 44% were ellipsoid and 19% fusiform (shape indices varying between 0.26 and 0.8). These findings are compared with previous studies of Onuf's nucleus in man and animals. The results form a basis for further studies on Onuf's nucleus in normality and neurodegenerative diseases.

Treatment of Total Retinal Detachment in Morning Glory Syndrome

A 14-year-old girl had headaches and sudden loss of vision as a result of total retinal detachment in association with the morning glory optic nerve anomaly. Metrizamide cisternography with contrast dye introduced into the subarachnoid space disclosed migration of metrizamide with radiographic enhancement in the subretinal space. The demonstration of an abnormal communication between the subarachnoid and subretinal spaces suggested that the subretinal fluid is of cranial origin. The patient underwent surgical removal of a window of dura from the optic nerve sheath. This resulted in retinal reattachment and improvement of visual acuity to 20/200. The retina was still attached after a 15-month follow-up period.

Neuropharmacology of adrenergic neurons in teleost fish

Although this brief review is based on relatively few types of experiments in few species of teleosts, it is possible to summarize some points of interest regarding the similarities and differences in the mechanisms of adrenergic neurotransmission in fish compared to the higher vertebrates. 1. There is a substantial mixing of cranial autonomic (“parasympathetic”) and spinal autonomic (“sympathetic”) pathways in the cranial nerves. This close relationship between the two systems and the differences in the nature of the neurons of cranial origin (cholinergic, and non-adrenergic, non-cholinergic) and spinal origin (adrenergic, cholinergic and mixed “polynergic”) gives a basis in fish also for a complex pattern of innervation of the various organs. 2. Adrenaline is the major transmitter substance in the adrenergic neurons of most teleosts studied, but there are exceptions within the same species. For instance, in the swimbladder mucosa of the cod, noradrenaline dominates, while adrenaline is the major catecholamine in most other organs innervated by adrenergic neurons. The reasons for the regional differences are not known and further studies of the rate of catecholamine turn-over in the adrenergic neurons of fish are clearly indicated. 3. Adrenoceptors of both the α- and the β-type show great similarities with those of mammals. Some differences in the potencies of certain compounds (e.g., clonidine and methoxamine) exist and receptor binding studies should add valuable information about the adrenoceptors of teleosts. The existence of a subtype of β-adrenoceptor (if(β 2) has been proposed and further work is needed to confirm or deny the applicability of the β 1/ β 2 adrenoceptor terminology in fish. 4. There appears to be some differences in the mode of action of the so called “indirectly acting amines”, such as tyramine, between teleosts and mammals. While the uptake of tyramine into the nerve terminals in mammals appears to take place via the cocaine-sensitive neuronal uptake system which is also responsible for catecholamine uptake (uptake 1), tyramine uptake in cod neurons appears to be via a separate pathway. 5. Presynaptic supersensitivity of the type seen in mammals has also been demonstrated in teleost adrenergic neurons. Both denervation (chemical or surgical) and blockade of the neuronal uptake mechanism by cocaine or desipramine produce this type of supersensitivty, while post-synaptic supersensitivity has so far not been described in teleosts. The effects of removal of the uptake system shows that the uptake process may be as important in teleosts as in mammals in the removal of adrenergic transmitter from the synaptic cleft. 6. In the total picture of adrenergic functions in fish, the circulating catecholamines take a special role. Although the quantitative importance of control by circulating catecholamines compared to control by adrenergic neurons is not known in detail for any organ system, it seems likely that circulating catecholamines can provide a substantial adrenergic “tonus” which reinforces the adrenergic neurons in elasmobranch and teleost fish. 7. An interesting aspect of the autonomic nerve function in teleost fish is the possibility of neurons with more than one transmitter substance. So far, the evidence in favour of this hypothesis rests mainly on the assumed selectivity of 6-OH-DA and the histochemical picture of the sympathetic chain ganglia of the cod. Further work is obviously needed to establish the validity of this hypothesis.