Increased migration of IgA lymphocytes to VIP nerve fibers after DSS-induced colitis

Immunoglobulin-positive lymphocytes are present close to vasoactive intestinal polypeptide-positive (VIP(+)) nerve fibers in the lamina propria of the intestinal tract, and have an important role in mucosal defense. The number of immunoglobulin A-positive (IgA(+)) cells close to the epithelial basement membrane and nerve fibers is increased by the administration of lipopolysaccharides, which induce IgA secretion into the intestinal lumen. The relationship between immunoglobulin-positive lymphocytes and the VIP(+) nerve fibers during inflammation, such as in inflammatory bowel disease, however, is not well known. The morphological relationship between immunoglobulin-positive cells and the basement membrane or the VIP(+) nerve fibers in the colon was examined using double immunofluorescent labeling in an inflammatory bowel disease mouse model created by oral administration of dextran sodium sulfate (DSS). DSS administration induced goblet cell loss, crypt loss, intestinal epithelium deformation and infiltration of inflammatory cells in the mucosa. In the colon, the number and percentage of IgA(+) lymphocytes close to the basement membrane and the VIP(+) nerve fibers in the lamina propria increased after DSS administration, in parallel with the pathologic progress in the inflamed tissue. On the other hand, the percentage of immunoglobulin G-positive (IgG(+)) lymphocytes close to the basement membrane and the VIP(+) nerve fibers decreased, although the total number of IgG(+) lymphocytes in the lamina propria increased. We suggest that the immunoglobulin-producing lymphocytes and enteric nerve fibers in the colon normally have a close morphological relationship, and that this relationship is reinforced in a cell-specific manner during inflammation.

Differential development of TRPV1-expressing sensory nerves in peripheral organs

In mouse ontogeny, neurons immunoreactive for transient receptor potential vanilloid receptor 1 (TRPV1) were observed primarily in the dorsal root ganglia (DRG) at embryonic day 13 (E13). In the embryonic period, the number of TRPV1(+) neurons decreased, but then gradually increased postnatally. Some of TRPV1(+) neurons were also immunoreactive for calcitonin gene-related peptide (CGRP). At postnatal day 7 (P7), 66% of CGRP(+) neurons were TRPV1(+), and 55% of TRPV1(+) neurons were also CGRP(+) in the L4 DRG. In the peripheral organs, TRPV1-immunorective nerve fibers were transiently observed in the skin at E14. They were also observed in the urinary tract at E14, and in the rectum at E15. Many TRPV1(+) nerve fibers in these organs were also CGRP(+). At P1, TRPV1(+) nerve fibers were observed in the respiratory organs, and to a lesser extent in the stomach, colon, skin, and skeletal muscles. The number of TRPV1(+) nerve fibers on each organ gradually increased postnatally. At P7, TRPV1(+) nerve fibers were also observed in the small intestine and kidneys. The percentage of total TRPV1(+) nerve fibers that co-localized with CGRP was greater in most organs at P7 than at P1. The present results indicate that TRPV1 expression on peripheral processes differs among organs. The differential time course of TRPV1 expression in the cell bodies might be related to the organs to which they project. Co-localization of TRPV1 with CGRP on nerve fibers also varies among organs. This suggests that the TRPV1-mediated neuropeptide release that occurs in certain pathophysiologic conditions also varies among organs.

Selective projections of cholecystokinin-8 immunoreactive fibers to galanin immunoreactive sympathetic preganglionic neurons in a teleost, Stephanolepis cirrhifer

In the cellular column of sympathetic preganglionic neurons (SPNs) of the filefish Stephanolepis cirrhifer, neurons containing galanin (GAL) form a distinct population projecting specifically to non-adrenergic postganglionic neurons in the celiac and cranial sympathetic ganglia. The present study showed that virtually all of the GAL-immunopositive SPNs made contact with many nerve terminals immunopositive for cholecystokinin octapeptide (CCK-8). GAL-negative preganglionic neurons made contact with only 26% of this type of nerve terminal; CCK-8-immunopositive nerve fibers appeared to project selectively to GAL-immunopositive SPNs with projections to specific targets. The CCK-8-positive nerve fibers might be of primary sensory origin, and participate in the visceral reflexes.

Differential distribution of nerve terminals immunoreactive for substance P and cholecystokinin in the sympathetic preganglionic cell column of the filefish Stephanolepis cirrhifer

Immunoreactivity for substance P and cholecystokinin-8 was examined in the nerve fibers in the central autonomic nucleus, a cell column for sympathetic preganglionic neurons, in the filefish Stephanolepis cirrhifer. Substance P-immunoreactive fibers were distributed throughout the entire rostrocaudal extent, but were more abundant in the caudal part of the column, where substance P-immunoreactive varicosities sometimes made contacts with the sympathetic preganglionic neurons. Cholecystokinin-8-immunoreactive fibers were found almost entirely in the rostral part of the column, where a dense network of varicosities was in close apposition to a considerable number of the sympathetic preganglionic neurons. Double labeling immunohistochemistry showed that substance P fibers and cholecystokin-8 fibers were entirely different, and distinct from serotonin-immunoreactive fibers. By using immunoelectron microscopy, synaptic specialization was sometimes observed between the dendrites of preganglionic neurons and varicosities immunoreactive for substance P and cholecystokinin-8. Substance P- and cholecystokinin-8 fibers were seen from the descending trigeminal tract, through the dorsolateral funiculus and the ventral portion of the dorsal horn, to the central autonomic nucleus. After colchicine treatment, substance P-immunoreactive perikarya were found in the cranial and spinal sensory ganglia. These results suggest that the sympathetic preganglionic neurons of the filefish receive innervation by substance P fibers and cholecystokinin fibers, and that the former might be of primary sensory origin. Topographical distribution of cholecystokinin-8-immunoreactive terminals in the central autonomic nucleus along the rostrocaudal extent might underlie the differential regulation of sympathetic activity via a distinct population of sympathetic preganglionic neurons.

Ultrastructure of the capillary pericytes and the expression of smooth muscle alpha-actin and desmin in the snake infrared sensory organs

The infrared sensory membranes of pit organs of pit vipers have an extremely rich capillary vasculature that forms many vascular loops, each serving a small number of infrared nerve terminals. We clarified the ultrastructure of capillary pericytes in the pit membranes by scanning and transmission electron microscopy, and examined the immunoreactivity in their cytoplasm to two contractile proteins: smooth muscle alpha-actin (SM alpha-actin) and desmin. The capillary pericytes had two major cytoplasmic processes: thickened primary processes that radiate to embrace the endothelial tube and flattened secondary processes that are distributed widely on the endothelium. Coexpression of SM alpha-actin and desmin was observed in the pericytes of entire capillary segments, and SM alpha-actin was characterized by prominent filament bundles directed mainly at right angles to the capillary long axis. This expression pattern was different from that of capillary pericytes of the scales, where SM alpha-actin was expressed diffusely in the cytoplasm. In a series of electron microscopic sections, we often observed the pericyte processes depressing the endothelial wall. We also observed a close relationship of the pericytes with inter-endothelial cell junctions, and pericyte processes connected with the endothelial cells via gap junctions. From these findings, we surmised that capillary pericytes in the pit membrane have a close functional relationship with the endothelium, and through their contractile and relaxing activity regulate capillary bloodflow to stabilize production of infrared nerve impulses.

Differential innervation of the goldfish tonic red muscles and twitch white muscles by neuropeptide-immunoreactive motoneurons

Neuropeptides in the motor nerves innervating the red and white muscles of the goldfish Carassius auratus were examined. In the tonic red muscles, varicose nerve endings immunoreactive for both calcitonin gene-related peptide and substance P were found spread over the surface of the muscle fibers, but in the twitch white muscles only scattered nerve endings immunoreactive for calcitonin gene-related peptide were found. At the electron microscopic observation, dense electron products immunoreactive for calcitonin gene-related peptide and for substance P (SP) were detected in the motor nerve endings making synapses on the muscle fibers of the red muscles. In the spinal cord, all of the motor neurons showed immunoreactivity to calcitonin gene-related peptide, but the motor neurons immunoreactive for substance P were restricted to the ventrolateral group that has been shown to project predominantly to the red muscles. These results suggest that the motor neurons innervating the red and white muscles of the goldfish are distinct in their neuropeptide content. The present study also raises the possibility that SP might be related to the unique physiological properties of the tonic type red muscles, probably by direct binding to the acetylcholine receptors.

Distinct localization and target specificity of galanin-immunoreactive sympathetic preganglionic neurons of a teleost, the filefish Stephanolepis cirrhifer

Immunoreactivity for galanin was examined in the sympathetic preganglionic neurons in the spinal cord, adrenal glands, sympathetic ganglia, and some sensory ganglia of the filefish Stephanolepis cirrhifer. Galanin-immunoreactive neurons were found only in the rostral part, but not in the caudal part of the central autonomic nucleus (a column of sympathetic preganglionic neurons of teleosts). Many galanin-immunoreactive nerve terminals were found in contact with neurons in the celiac ganglia and the cranial sympathetic ganglia on both sides of the body. Most neurons encircled by galanin-immunoreactive nerve fibers were negative for tyrosine hydroxylase. Galanin-immunoreactive nerve fibers were very sparse in the spinal sympathetic paravertebral ganglia. No galanin-immunoreactive nerve fibers were found in the adrenal glands. No sensory neurons of the trigeminal, vagal, or spinal dorsal root ganglia were positive for galanin-immunoreactivity. These results suggest that galanin-immunoreactive sympathetic preganglionic neurons have distinct segmental localization and might project specifically to a population of non-adrenergic sympathetic postganglionic neurons in the celiac and cranial sympathetic ganglia.

Serotonin-immunoreactive axons in the cell column of sympathetic preganglionic neurons in the spinal cord of the filefish Stephanolepis cirrhifer

Serotonin-immunoreactive axonal components were observed in the central autonomic nucleus (CAN), a cell column of sympathetic preganglionic neurons in the rostral spinal cord of the filefish Stephanolepis cirrhifer. Serotonin-positive axonal varicosities were seen around neuronal perikarya through the whole rostrocaudal extent of the CAN, although their distribution pattern in the rostral CAN was different from that in the caudal CAN. Electron microscopically, serotonin-positive axonal varicosities were found to make axodendritic and axosomatic synapses on CAN neurons. Many serotonin-positive neuronal cell bodies were seen in the raphe nuclei in the lower brainstem, whereas only a few were found in the spinal cord. Thus most of serotoninergic axons within the CAN were considered to originate from the raphe nuclei in the lower brainstem.

Nitric oxide synthase in the glossopharyngeal and vagal afferent pathway of a teleost, Takifugu niphobles. The branchial vascular innervation

To examine the presence of nitric oxide synthase (NOS) in the sensory system of the glossopharyngeal and vagus nerves of teleosts, nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) activity and immunoreactivity for NOS were examined in the puffer fish Takifugu niphobles. The nitrergic sensory neurons were located in the ganglia of both the glossopharyngeal and the vagal nerves. In the vagal ganglion, positive neurons were found in the subpopulations for the branchial rami and the coelomic visceral ramus, but not for the posterior ramus or the lateral line ramus. In the medulla, nitrergic afferent terminals were found in the glossopharyngeal lobe, the vagal lobe, and the commissural nucleus. In the gill structure, the nitrergic nerve fibers were seen in the nerve bundles running along the efferent branchial artery of all three gill arches. These fibers appeared to terminate in the proximal portion of the efferent filament arteries of three gill arches. On the other hand, autonomic neurons innervating the gill arches were unstained. These results suggest that nitrergic sensory neurons in the glossopharyngeal and vagal ganglia project their peripheral processes through the branchial rami to a specific portion of the branchial arteries, and they might play a role in baroreception of this fish. A possible role for nitric oxide (NO) in baroreception is also discussed.

Microvasculature of crotaline snake pit organs: possible function as a heat exchange mechanism

The infrared sensory membranes of the pit organs of pit vipers have an extremely rich capillary vasculature, which has been noted passim in the literature, but never illustrated or studied in detail. We rendered the pit vasculature visible in various ways, namely, by microinjection of India ink, by a combination of ink and succinate dehydrogenase staining, and by making resin casts for scanning electron microscope study. We also used transmission electron microscopy for identifying the types (arterioles, venules, capillaries) of blood vessels. Then we compared the pit vasculature with that of the retina and the dermis. Good visualization of the vasculature was obtained with both ink and resin injection. Arterioles, venules, and capillaries could be distinguished with all methods used. The monolayer vasculature was denser in the pit membrane than in the retina or skin. Each loop of the network enclosed a small number of infrared receptors so that all receptors were in contact with a capillary on at least one side. The forward-looking areas of the pit had a denser network than side-looking areas. Since infrared rays cause nerve impulses by raising the temperature of individual receptors, the capillary network functions not only as a supplier of energy but also as a cooling mechanism to reduce afterimages. Thus the denser network in the forward-looking areas causes these areas to be more sensitive and have better image resolution than the rest of the membrane.

Gastrin/CCK-ergic innervation of cutaneous mucous gland by the supramedullary cells of the puffer fish Takifugu niphobles

The supramedullary cells (SMCs) are spinal neurons lying at the dorsal surface of teleosts. In the present study, we examined whether the SMCs of the puffer fish (Takifugu niphobles) might express gastrin/cholecystokinin-immunoreactivity, as observed in some other teleosts. All the SMCs were immunoreactive for gastrin/cholecystokinin. On the other hand, many immunoreactive varicose nerve fibers were also found terminating in the mucous glands in the skin. In addition, immunoreactive fibers were sparsely distributed in the epidermal layer. No neuronal cells other than the SMCs showed gastrin/cholecystokinin-immunoreactivity centrally or peripherally. The results suggest that gastrin/cholecystokinin-immunoreactive axons in the cutaneous mucous glands and epidermal layer are axons of the SMCs. In view of the present findings, the possible nature of SMCs was discussed.

NADPH-diaphorase activity in the vagal afferent pathway of the dogfish, Triakis scyllia

Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity was examined in the cranial sensory ganglia and brainstem of the banded dogfish, Triakis scyllia. Positive neurons were found in the vagal sensory ganglion projecting to the coelomic organs, but not in those projecting to the gills or the lateral line organs. Nerve terminals in the vagal lobe were also positive. No positive neurons were found in the glossopharyngeal, facial, or trigeminal sensory ganglia. These results suggest that use of nitric oxide in the vagal sensory transmission from the coelomic organs may have been maintained in the evolutionary process from fish to mammals.

Ultrastructure of the crotaline snake infrared pit receptors: SEM confirmation of TEM findings

BACKGROUND

Crotaline snakes possess a pair of infrared-sensing pit organs that aid the eyes in the detection and apprehension of prey. The morphology of the receptors in the pit organs has been studied by light and transmission electron microscopy, and the ultrastructure of the receptors has been inferred from the results of this work. But this theoretical reconstruction has never been confirmed by any kind of three-dimensional imaging.

METHODS

We treated the receptor-containing membrane of the pit organs with potassium hydroxide to remove collagen and expose the receptors, which we then viewed by scanning electron microscopy.

RESULTS

We were able to obtain three-dimensional views of all structures previously reported to exist within the receptor-containing membrane: terminal nerve masses formed from free nerve endings, supporting Schwann cells within the nerve masses, unmyelinated and myelinated nerve fibers, a capillary bed, and vacuole cells.

CONCLUSIONS

By providing the first three-dimensional views of the infrared receptors, we have confirmed that previous theoretical reconstructions of the receptors were substantially correct and have provided new evidence of the spatial arrangement of the receptors in a monolayer array.

Calcitonin gene-related peptide immunoreactivity in the trigeminal ganglion of Trimeresurus flavoviridis

Crotaline snakes, which have infrared-sensitive pit organs, provide a good model for linking neuron morphology with sensory modality. In the trigeminal ganglion of the habu, Trimeresurus flavoviridis, cells positive for calcitonin gene-related peptide-like (CGRP) immunoreactivity were found to be of two types, darkly stained and lightly stained. They were pseudo-unipolar, having an axon divided into stem, peripheral branch, and central branch, all of which were 1 micron or less in diameter. Other, CGRP-negative cells in the ganglion were also pseudo-unipolar, but much larger. In configuration, some of the positive cells were similar to the neurons with A-delta fibers, and others to the neurons with C fibers that have been reported by other workers. On the basis of their distribution and density, and physiological studies by other workers, the CGRP-positive cells were judged to be not part of the infrared-receptive system, but to be involved in the transmission of nociception in small fibers.

Somatosensory and visual correlation in the optic tectum of a python, Python regius: a horseradish peroxidase and Golgi study

In snakes with infrared receptors the optic tectum receives infrared input in addition to visual and general somatosensory inputs. In order to observe their tectal termination patterns in ball pythons, Python regius, we injected horseradish peroxidase (HRP) into the nucleus of the lateral descending trigeminal tract (LTTD) which mediates infrared information, the optic nerve, and the nucleus of the trigeminal descending tract (TTD) which relays general somatosensory information. Fibers from LTTD were found in layers 5-13 of the contralateral optic tectum, and were especially dense in layers 7a-8. Optic nerve fibers terminated in layers 7a-13 of the contralateral tectum, and mainly in layers 12-13. TTD fibers were few, and could be seen in only the rostral half of the contralateral tectum. These fibers were found in layers 5-7b, but mainly in layers 6-7a. Among various types of neurons stained by the Golgi-Cox method, we focused on six types of neurons whose dendritic arborization overlapped with the distribution of the terminals of these sensory afferents described above. It is possible that these different sensory modalities converge on a single neuron of the various types.

Nerve fibers immunoreactive for substance P and calcitonin gene-related peptide in the cervical spinal ventral roots of the mouse

We demonstrate the existence of nerve fibers possessing substance P (SP) and calcitonin gene-related peptide (CGRP) immunoreactivity in the mouse cervical ventral roots. The distribution of the SP and CGRP fibers was similar, but CGRP fibers were generally more numerous. Both types entered the ventral pia mater or formed hairpin loops, but they did not enter the spinal cord directly through these roots. SP and CGRP fibers in the ventral roots were thin and had many varicosities. We suggest that these SP and CGRP fibers are involved not only in a sensory mechanism, but also in other functions, via the release of SP and CGRP from varicosities in the ventral roots.

Use of a cortico-cancellous bone graft in the repair of a cleft palate in a dog

We report the successful use of a cortico-cancellous bone graft to repair a cleft of the secondary palate in a 6-month-old Akita dog. The cleft extended from the incisal papilla to the posterior border of the soft palate. It was 10 mm wide in the hard palate and 16 mm in the soft palate. The cleft was repaired using the "push-back" method with single-pedicled mucoperiosteal flaps to close the cleft in the soft tissues, and a free bone graft from the tibia (cortex with cancellous bone attached) to fill the defect in the hard palate. Two and one-half years after the operation the graft was indistinguishable from surrounding bone on radiographs. Maxillary growth appeared to have progressed normally, resulting in normal occlusion.

Visual and infrared input to the same dendrite in the tectum opticum of the python, Python regius: electron-microscopic evidence

In snakes with infrared receptors, the optic tectum receives input from both the visual and the infrared senses. We investigated the infrared and optic fiber terminations in the tectum with a combination of horseradish peroxidase and degeneration labeling. In addition to synapses by visual and infrared fibers onto individual neurons, we were able to observe for the first time visual and infrared synapses on one and the same dendrite.

Afferent and efferent projections of the glossopharyngeal-vagal nerve in the hagfish

Anterograde and retrograde transport of horseradish peroxidase was used to examine the afferent and efferent projections of the glossopharyngeal-vagal nerve in the hagfish Eptatretus burgeri. Anterogradely labeled ganglion cells are scattered in the glossopharyngeal-vagal nerve trunk, in the saccular ganglion, and in the brainstem. Afferent fibers of the glossopharyngeal-vagal nerve terminate in both the vagal lobe and the fasciculus communis. Close observation showed no morphological differentiation between these two structures, indicating that they are not separate entities, but a single, continuous structure that is homologous with the nucleus and tractus solitarius of other vertebrates. The median part of this structure (the commissura infima) is displaced more rostrally than the same part of the solitary nucleus in many other vertebrates. Some of the afferent fibers invade the ventral portion of the trigeminal sensory nucleus, which receives the maxillo-mandibular nerve fibers, and terminate there. Our study showed that the hagfish has only one nucleus in the vagal motor system, i.e., the vagal motor nucleus, which contains both parasympathetic and branchiomotor neurons. The dendrites of the vagal motor neurons in the hagfish are more highly developed than those in other vertebrates. This suggests that the motor reflex arc of the glossopharyngeal-vagal nerve in hagfishes may be simpler than in other vertebrates.

Organization of the primary projections of the lateral line nerves in the lamprey Lampetra japonica

The lateral line sensory system of Lampetra japonica is innervated by the anterior and posterior lateral line nerves. The anterior lateral line nerve innervates all electroreceptors throughout the body and mechanoreceptors of the head. The posterior lateral line nerve innervates trunk mechanoreceptors. The anterior lateral line nerve consists of two ganglia (anterior lateral line and intracapsular) and four major peripheral branches (superficial ophthalmic, buccal, hyomandibular, and recurrent nerves). The posterior lateral line nerve has one posterior lateral line ganglion and one peripheral branch. The location and central projection patterns of the primary sensory neurons of these branches of the lateral line nerves were studied with the aid of horseradish peroxidase labeling. The ganglion cells of the buccal nerve were found in the rostral half, and those of the hyomandibular nerve were found in the caudal half of the medial part of the anterior lateral line ganglion. The lateral part of the anterior lateral line ganglion contains ganglion cells of the recurrent nerve and the superficial ophthalmic nerve. The rostral half of the intracapsular ganglion contains ganglion cells of the recurrent, hyomandibular, and buccal nerves. The ganglion cells of the posterior lateral line nerve were found in the posterior lateral line ganglion. The buccal nerve afferents terminated mainly in the lateral part of the ipsilateral mechanoreceptive medial nucleus. The peripheral part of the electroreceptive dorsal nucleus also received several afferents. The hyomandibular afferents terminated ipsilaterally in the central part of the medial nucleus and in the dorsolateral part of the dorsal nucleus. Some afferents of the hyomandibular nerve ascended and descended in the descending nucleus of the trigeminal nerve near its dorsal margin. The ventral nucleus, the primary nucleus of the VIIIth nerve, received a few fibers of the buccal and hyomandibular nerves. In the recurrent nerve, the fibers of the lateral part of the anterior lateral line ganglion terminated throughout the entire dorsal nucleus, and the fibers of the intracapsular ganglion projected to the dorsolateral part of the nucleus. The afferents of the posterior lateral line nerve terminated in the medial part of the ipsilateral medial nucleus and in the lateral part of the contralateral medial nucleus. In the cerebellar area, afferents of the anterior lateral line nerve were located laterally to those of the posterior lateral line nerve. Several fibers terminated in some branchiomotor nuclei, the cerebellar crest, and the dorsal gray near the obex level. No efferent cell bodies were found in the place where efferent neurons of the VIIIth nerve have been previously reported.

Substance P immunoreactivity in the vagal nerve of mice

After horseradish peroxidase was applied to the main trunk of the mouse vagal nerve, anterogradely labeled cells in the vagal ganglia and fibers in the solitary complex, and retrogradely labeled cells in the dorsal motor nucleus and the ambiguous nucleus were observed. Most of the cells in the nodose ganglion were labeled, but only a few cells in the jugular ganglion were labeled. Heavily labeled nerve terminals and fibers were found in 3 areas in the solitary nucleus: i.e., the lateral half of the medial nucleus, the ventrolateral nucleus, and the commissural nucleus. There was only weak labeling in the dorsolateral nucleus, ventral nucleus, and intermediate nucleus. Substance P immunoreactive neurons in the vagal ganglia were found in the jugular ganglion and the dorsal part of the nodose ganglion, but not in the ventral part of the nodose ganglion. Substance P immunoreactivity in the solitary nucleus was moderate in the commissural nucleus and the intermediate nucleus, but was lacking or very weak in the lateral half of the medial nucleus, ventral nucleus, dorsolateral nucleus, and ventrolateral nucleus. We conclude that most substance P containing fibers in the main trunk of the vagal nerve project centrally to the commissural nucleus and peripherally to some of the thoracic viscera.

Afferent and efferent projections of the VIIIth cranial nerve in the lamprey Lampetra japonica

Anterograde and retrograde transport of horseradish peroxidase was used to examine the afferent and efferent projections of the VIIIth cranial nerve in the lamprey Lampetra japonica. Ganglion cells of the VIIIth nerve are classified into three types on the basis of their morphology. The central processes of these ganglion cells enter the medulla in two groups: the anterior group (mostly thick fibers) and the posterior group (mostly thin fibers). Afferent fibers mainly terminate within the ipsilateral ventral and octavomotor nuclei of the octavolateralis area and within the granular and molecular layer of the cerebellum. Some fibers terminate in the contralateral cerebellum, the medial and dorsal nuclei of the octavolateralis area, the descending nucleus of the trigeminal nerve, some cranial motor nuclei, and the lateral octavus nucleus, which has not been described previously. This small nucleus is located beneath the descending nucleus of the trigeminal nerve near the obex. Within the ventral nucleus, thin fibers occupy the dorsal part and thick fibers occupy the ventral part. The basic projection pattern of the primary afferents of the VIIIth nerve in the lampreys was similar to that of gnathostome fishes that have been studied to date. Cell bodies of the efferent vestibular neurons are located between the ipsilateral trigeminal motor nucleus and the facial motor nucleus. The lateral location of these cell bodies differs from that of all other fish species that have been studied.

Giant lateral-line afferent terminals in the electroreceptive dorsal nucleus of lampreys

In HRP studies of the lateral line nerve in lampreys, the dorsal nucleus of the area octavolateralis received projections mainly from the recurrent branch of the anterior lateral line nerve. Furthermore, the recurrent branch projected exclusively to the dorsal nucleus. Besides the common type (1-3 micron) of nerve terminals, a hitherto unreported type of giant (10-30 micron) nerve terminal was found aggregated at the rostral and caudal ends of the nucleus. Since the dorsal nucleus mediates electroreception in lampreys, we conclude that the giant terminals are very probably the terminals of the electroreceptive primary fibers.

Substance P-like immunoreactivity in the trigeminal sensory nuclei of an infrared-sensitive snake, Agkistrodon blomhoffi

With the peroxidase-antiperoxidase immunohistochemical method we ascertained the presence of substance P-like immunoreactivity (SPLI) in fibers and cell bodies of the trigeminal sensory system of the pit viper, Agkistrodon blomhoffi. There are a few SPLI fibers each in the principal sensory nucleus and the main neuropil of the lateral descending nucleus (i.e., the infrared sensory nucleus); a moderate number in the descending nucleus; and a large number in the caudal subnucleus, the medial edges of the interpolar subnucleus, and the marginal neuropil of the lateral descending nucleus. About 30% of the cell bodies in the ophthalmic and maxillo-mandibular ganglia show SPLI, and of the two craniocervical ganglia, the proximal ganglion has many more cells with SPLI than the distal ganglion. The SPLI distribution in the common trigeminal sensory system is similar to that of mammals, and suggests that the function of this system is also similar. In the infrared that the function of this system is also similar. In the infrared sensory system, the differing distribution in the main and marginal neuropils suggests separate functions for these two structures in the system.

Substance P-like immunoreactivity in the central retinal artery of the rabbit

Substance P-like immunoreactive nerve fibers were identified in the central retinal artery of the rabbit using the peroxidase-antiperoxidase method. The fibers were seen to encircle the central retinal artery throughout its course in the main trunk of the optic nerve. No labeled fibers were seen in the central retinal vein or in the retinal blood vessels. It appears, therefore, that the central retinal artery and the retinal blood vessels are innervated by different nerve systems: the central retinal artery by one of the peripheral nerves, and the retinal vessels by the central nervous system.

Somatotopic organization of the primary sensory trigeminal neurons in the hagfish, Eptatretus burgeri

Primary sensory trigeminal projections were investigated in the hagfish following application of horseradish peroxidase (HRP) to the sensory branches. In our control preparations we were able to distinguish five sensory ganglia and their respective nerves. HRP application confirmed the almost exclusive relation of each of these nerves to their respective ganglia, with very little overlap. In normal frontal sections of the medulla oblongata, five columns of fibers surrounded by neuronal cell bodies could be clearly distinguished, but the number is probably fortuitous, for there was no one-on-one relationship with the five trigeminal ganglia. From their peripheral connections, we surmised that columns 1 and 3 handle general cutaneous sensation, columns 2, 4, and 5 handle taste sensation, and column 5 handles general mucous cutaneous sensation conveyed by utricular ganglion cells. Dorsally located columns received projections from nerves with dorsal peripheral connections, and more ventrally located columns received projections from nerves with ventral peripheral connections. This relation is the reverse of that seen in other vertebrates.

Organization of sensory and motor nuclei of the trigeminal nerve in lampreys

Anterograde and retrograde HRP transport were used to elucidate the primary central projections of the trigeminal nerve in a lamprey, Lampetra japonica, by application to the ophthalmic, apical, basilar, suborbital, and mandibular branches of the trigeminal nerve. (1) Most of the trigeminal and a few facial ganglion cells were labeled. The ganglion cells of each nerve were distributed in separate areas within their respective ganglia. (2) Some ipsilateral medullary and spinal dorsal cells were labeled after HRP application to the ophthalmic and apical nerves, but there was no contralateral labeling. (3) Most of the neurons of the trigeminal motor nucleus were labeled, and when the apical or the basilar nerve was labeled, in each case a cluster of small motor neurons was found ventrolateral to the classic motor nucleus. (4) Miscellaneous neurons were found scattered along the course of the descending trigeminal tract and nucleus in all cases except after application to the mandibular branch. The shape, size, and distribution patterns of these neurons were varied, and several characteristics indicated that they were sensory in nature. (5) In the rostral part of the medulla, sensory fibers of each nerve showed restricted localization within the descending trigeminal tract and nucleus. When compared to the distribution of the same fibers in the hagfish Eptatretus burgeri, another member of the cyclostomes, the distribution pattern in the lampreys studied was closer to the type seen in gnathostomes.

Primary neurons of the lateral line nerves and their central projections in hagfishes

The hagfish lateral line system was studied by horseradish peroxidase transganglionic transport. The anterior lateral line nerve innervates the group of lateral line canals situated anteriorly to the eye, and the posterior lateral line nerve innervates the group of canals situated posteriorly to the eye. Although both nerves pass through the muscle fascia at the same point, each runs a different course to the brain. The anterior lateral line nerve runs near the trigeminal nerve and its ganglion is closely attached to the trigeminal ganglion, but both systems are completely independent. The posterior lateral line nerve runs independently of any other cranial nerve and makes a peculiar U-turn at the point of entry to the brain capsule. The anterior lateral line ganglion contains both cutaneous sensory cells (small to large cells) and lateral line sensory cells (small cells); from this ganglion projections run to both the trigeminal sensory nucleus (fine and thick fibers) and medial nucleus of the area acousticolateralis (fine fibers). The posterior lateral line ganglion contains only small lateral line cells that project fine fibers to the medial nucleus of the area acousticolateralis. There are no efferent components in this lateral line system, and its only afferent terminal field is the medial nucleus of the area acousticolateralis.

Organization of the trigeminal and facial motor nuclei in the hagfish, Eptatretus burgeri: a retrograde HRP study

We studied the trigeminal and facial motor nuclei of the hagfish by the retrograde HRP method. We distinguished 4 components in a single column of the motor nuclei of the trigeminal nerve and the facial nerve, viz., the pars magnocellularis of the trigeminal motor nucleus (mVm), the anterior part of the pars parvocellularis of the trigeminal motor nucleus (mVp1), the posterior part of the pars parvocellularis of the trigeminal motor nucleus (mVp2) and the facial motor nucleus (mVII). Although in Nissl preparations only the mVm could be distinguished from the rest of the nucleus, the boundaries of the other 3 components were clearly demarcated in HRP preparations. Intramuscular injections into two representative antagonistic jaw muscles revealed that there was no apparent topological organization of the neurons pertaining to the opening and closing muscles in the mVm and mVp1, but both antagonistic muscles were innervated bilaterally. Although the hagfish does possess a cartilaginous jaw, the organization pattern of the motor nuclei of the jaw muscles seems to be the most primitive of all living vertebrates.

Primary sensory ganglion cells projecting to the principal trigeminal nucleus in the mallard, Anas platyrhynchos

The trigeminal and glossopharyngeal ganglia of the adult mallard were studied following HRP injections into the principal trigeminal nucleus (PrV). The PrV consists of the principal trigeminal nucleus proper (prV) and the principal glossopharyngeal nucleus (prIX). After an injection into the prV, the labeled cells were found in the ipsilateral trigeminal ganglion. After an injection into the prIX, labeled cells were found in the ipsilateral distal glossopharyngeal ganglion, but not in the proximal ganglion of the IX and X cranial nerve (pGIX + X). In Nissl preparations, two types of ganglion cells in the trigeminal ganglion, pGIX + X, and distal ganglion of N IX could be distinguished: larger light cells and smaller dark cells. We could not determine whether the HRP-labeled cells belonged to both types or to one of them; but because all the labeled cells were over 20 microns, we concluded that the smallest cells (10-19 microns) in the trigeminal ganglion and distal ganglion of N IX did not project to the PrV. The labeling of the cells in the distal ganglion of N IX (average 34.5 microns) was uniformly moderate. In the trigeminal ganglion there were two types of labeled cells: heavily labeled cells (average 29.1 microns) and moderately labeled cells (average 35.1 l microns). These two types of labeling (moderate and heavy) may reflect two types of primary sensory neurons: cells with ascending, nonbifurcating axons, and cells with bifurcating axons. We speculate that the former are proprioceptive neurons and the latter tactile neurons. Labeled bifurcating axons in the sensory trigeminal complex gave off collaterals to all parts of the descending trigeminal nucleus except to the caudalmost laminated spinal part.

Primary vestibular projections in the hagfish, Eptatretus burgeri

The VIIIth cranial nerve projections in the hagfish, which has only one circular canal in the ear, were studied by transganglionic HRP transport. This nerve has two branches, the nervus utricularis (N. utr.) and the nervus saccularis (N. sac.), each with its own ganglion, the ganglion utriculare (G. utr.) and the ganglion sacculare (G. sac.), respectively. Although the G. sac. has uniformly small cells, the G. utr. consists of two separate cell masses, a ventral mass of large cells and a dorsal mass of small cells. The small cells were labeled in both ganglia after horseradish peroxidase (HRP) injection into the endolymphatic space. The greater part of the terminal areas of these two branches overlapped in the ventral nucleus of the area acoustico-lateralis, but the terminals of the N. sac. extended slightly further in a caudal direction. No projections to the primordial cerebellum and no retrogradely labeled cells in the brain were found. The large cells in the ventral part of the G. utr. seem to be general cutaneous neurons, and the dorsal part of the area acousticolateralis seems to receive lateral line input.

A suspected infrared-recipient nucleus in the brainstem of the vampire bat, Desmodus rotundus

We discovered in the brainstem of infrared-sensitive vampire bats, Desmodus rotundus, a specific nucleus not known in other species of bats. Because it corresponded in location and histological features to the infrared nucleus of infrared-sensitive snakes, we suggest the probability of its being part of the infrared processing system of vampire bats.

Vagal afferent C fibers projecting to the lateral descending trigeminal complex of crotaline snakes

The primary vagal axons and terminals in the lateral descending trigeminal complex (dlv-DLV complex) in crotaline snakes were studied following HRP injections into the vagal nerve. Labeled fibers and terminals were found in the marginal neuropil, which was made up entirely of unmyelinated fibers, i.e., C fibers. The general features of vagal input to the dlv-DLV complex in snakes with infrared sensitivity (Boidae and Crotalinae) are discussed.

Static response of infrared neurons of crotaline snakes--normal distribution of interspike intervals

Background discharges (static responses) of warm fibers in the pit organs (infrared receptive organs) of two species of crotaline snakes were recorded at various temperatures (water, 18-33 degrees C; air, 19-28 degrees C). Mean interspike intervals (means), standard deviations (SD), and coefficients of variation (CV) were calculated, and the goodness of fit of interspike interval histograms to a corresponding normal distribution (i.e., one having the same mean and SD) were tested. Means, SD, and CV were smallest at a certain temperature, which might be the optimum receptor temperature for the species. More than half of the histograms (22/42 for water, 7/10 for air) showed a normal distribution at a significance level of 0.01. This suggests that the spike intervals generated at the spike initiation site are constant, with some random error. Background discharges of three pure infrared secondary neurons from the lateral descending nucleus were analyzed in the same way and compared to the peripheral discharges. There were no histograms with a normal distribution in these central neurons, which might indicate that the constant interspike intervals which appear in the primary afferent fibers are not utilized for information processing at this level but occur only as part of a receptor mechanism which is still unknown. The discharge patterns of primary afferent fibers are also discussed in relation to the known discharge patterns of cold fibers in other animals.

Infrared sensory neurons in the trigeminal ganglia of crotaline snakes: transganglionic HRP transport

Trigeminal neurons were labeled by inserting HRP into holes cut in the pit receptor membranes of a crotaline snake, Agkistrodon blomhoffi brevicaudus. Neurons were labeled in the ophthalmic ganglion and the maxillary division of the maxillo-mandibular ganglion, and the HRP was further transported across the ganglia and through the lateral descending trigeminal tract (dlv) to label axon terminals exclusively in the dlv nucleus (DLV). In 6 successful preparations, 7.1-19.3% of totals of 5568-5986 cells in the maxillary division of the ganglion were labeled, but none at all were labeled in the mandibular division. Only a few or none at all were labeled in the ophthalmic ganglion. Cells in the two ganglia ranged in size from 10 to 55 micrometers, but large cells (greater than or equal to 40 micrometers) were scarce (4.9% of the total population). All HRP-labeled neurons fell in the median range of 20-39 micrometers. We concluded that these ganglion cells were infrared neurons, and were therefore the origin of the A delta fibers in the pit membrane. There were no HRP-labeled neurons above or below this range, in spite of the fact that smaller cells (less than or equal to 19 micrometers) made up 35.8% of the total population. In normal Nissl preparations we found both light- and dark-staining cells, but the size range of neither corresponded to the size range of infrared neurons.

Python pit organs analyzed as warm receptors

The infrared receptor neurons of Python reticulatus pit organs were all found to have bimodal sensitivity, responding to both infrared and touch stimuli with fairly rapid adaptation. The majority (22 of 29 neurons) had no background discharges at any temperature between 20 and 33 degrees C. The receptive areas were 150-250 micrometers in diameter and identical for both modalities. There was only one receptive area for each neuron. These facts suggest the possibility that some kinds of temperature sensitive neurons can also function as touch neurons and vice versa, not only in this species, but also in other animals.

Crotaline pit organs analyzed as warm receptors

Afferent impulses from single-fiber preparations of the trigeminal nerve in Agkistrodon blomhoffi brevicaudus were recorded during steady and dynamic temperature stimulation of the sensory membrane in the facial pit. The thermoreceptors of the pit showed high sensitivity to the rate of change in receptor temperature. Changing the heat capacity of the pit membrane (a drop of water in the pit in the case of the laser and halogen lamp, and a drop of water covered by a plastic film in the case of flowing water) changed the pattern of response. When the heat capacity of the pit membrane is increased, responses approach those obtained in other warm receptors. The spatial gradient theory of Williams, whereby a reversal of heat energy flow is supposed to produce a reverse of response, was shown to be inapplicable to the pit receptors. Reversal of heat energy flow in the pits produced neither off-silence nor depression of response, and therefore direction of heat flow is not an important component of the stimulus for these receptors.

Central Response to Infra-Red Stimulation of the Pit Receptors in a Crotaline Snake, Trimeresurus Flavoviridis

1. Both action potentials and evoked potentials were recorded from the tectum opticum of a crotaline snake, Trimeresurus flavoviridis, in response to infra-red stimulation of the facial pit organs. Action potentials from single units were recorded throughout the tectum.

2. Most units responded to contralateral stimulation, while some responded to both ipsi- and contralateral stimulation.

3. Firing patterns were tonic, phasic, or phasic-tonic, depending on the position of the stimulus and the type of unit being recorded.

4. Sensitivity to stimulus movement was observed.

5. All potentials differed from peripheral potentials in firing patterns.

6. Firing frequency was directly proportional to stimulus intensity.

7. Measurements were made of the vertical and horizontal response fields of single units.

8. Background discharge was noted in all units and its nature discussed.

9. The integrative function of the tectum in regard to infra-red perception was also discussed, as well as the possibility of stereoscopic perception.