Retinal projections in the hagfish, Eptatretus burgeri

The retinal projections of hagfish were investigated by anterograde transport of HRP and the Nauta-Gygax method⁹. The pathway coincided with the commissura postoptica of Jansen⁵ after complete crossing within the hypothalamus. Many projections were found in the contralateral ‘area pretectalis’, but there were onlya few projections in the tectum mesencephali, the pars ventralis thalami, and the n. tuberculi posterioris of Jansen⁵.     

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.     

Organization of spinal motor nuclei in the stingray, Dasyatis sabina

The Atlantic stingray, Dasyatis sabina, has enlarged pectoral fins consisting of a series of antagonist dorsal (elevator) and ventral (depressor) muscles. Each muscle is divided into superficial and deep components. The retrograde transport of horseradish peroxidase (HRP) was used to determine the organization of motoneuron pools innervating fin and epaxial muscles. HRP applied to a single peripheral nerve labeled motoneurons within a single spinal segment. Following intramuscular injection of HRP, 3 distinct cell groups were identified in the transverse plane. Motoneurons innervating elevator muscles were lateral in the ventral horn, while motoneurons innervating depressor muscles were dorsomedial. The epaxial muscles were found to be innervated by a distinct cell column along the ventral border of the ventral horn. Separate injections of the superficial and deep bundles of the elevator muscle resulted in considerable overlap in the distribution of labeled motoneurons. Soma areas for both elevator and depressor motoneurons were unimodally distributed. The mean cell diameters were 33.6 and 31.8 μm respectively. Motoneurons innervating the superficial and deep bundles of elevator muscle also had similar size distributions. The location of motoneurons innervating elevator and depressor fin muscles in the stingray supports the hypothesis that motoneurons innervating muscle derived from the dorsal premuscle mass are located laterally in the ventral horn while motoneurons innervating muscle derived from the ventral premuscle mass are located medially.     

The projection to the mesencephalon from the sensory trigeminal nuclei. An anatomical study in the cat

The terminal areas and the cells of origin of the projection from the sensory trigeminal nuclei to the mesencephalon were investigated, using the method of anterograde and retrograde transport of horseradish peroxidase or wheat germ agglutinin-horseradish peroxidase conjugate. Injection of tracer into the nucleus interpolaris or nucleus oralis (in the latter cases with involvement of the nucleus principalis) resulted in dense anterograde labeling in the deep and intermediate gray layers of the contralateral superior colliculus, extending throughout the rostrocaudal extent of the colliculus with the exception of its caudalmost part, which was not labeled. Minor projections to the intercollicular nucleus, posterior pretectal nucleus and nucleus of Darkschewitsch were found. Injection of tracer into the nucleus caudalis yielded a completely different result; terminal labeling in the midbrain was now present only in the periaqueductal gray matter, in its rostral and middle parts. The retrograde labeling observed after injection of tracer into the midbrain terminal areas showed that the cells of origin were located mainly in the alaminar spinal trigeminal nucleus, and the highest density of labeled neurons was found in the rostral part (subnucleus y) of the nucleus oralis. The retrograde labeling in the nucleus principalis was very sparse and almost exclusively involved peripherally located neurons. In the nucleus caudalis the overwhelming majority of the retrogradely labeled neurons were situated in its marginal layer. The functional implications of the above observations are discussed in relation to the findings in previous studies of the projections from the dorsal column nuclei and spinal cord to the midbrain. The combined results suggest that the trigeminal projections to the superior colliculus may be involved in the mechanisms of orientational behavior. The observation that the projection to the periaqueductal gray matter originates in the marginal layer suggests that it transmits information related to noxious stimuli.     

A qualitative investigation of the topographical representation of masticatory muscles within the motor trigeminal nucleus of the rat: a horseradish peroxidase study

The topographical representation of the masticatory muscles of the rat was investigated by studying retrograde transport of horseradish peroxidase (HRP) from individual muscles. Contrary to the classically accepted scheme, the temporalis and masseter are separately represented dorsolaterally, the pterygoids dorsomedially and the jaw-opening mylohyoid and anterior belly of digastric ventrally within the motor nucleus, corresponding to the arrangement of the muscles on the head. Phylogenetic and ontogenetic justifications for this organization are adduced.     

Is there morphological separation between the spinal cord motor nuclei which innervate the heads of a multiheaded muscle?

Horseradish peroxidase was injected into the individual heads of the pectoralis muscles of the dog or applied to the nerve which supplies each of these heads. The location and numbers of labeled motoneurons in the spinal cord were studied using light microscopy. There was longitudinal overlap of the pectoral nuclei, but no separation in their mediolateral or dorsoventral positions. The cutaneous trunci muscle motor nucleus is distinctly separate from the motor nuclei of the pectoral muscles, even though they share a common nerve supply. The methods of horseradish peroxidase application to the cut nerve or injection into the muscle are compared.     

Identification and somatotopic organization of nuclei projecting via the dorsolateral funiculus in rats: A retrograde tracing study using HRP slow-release gels

Horseradish peroxidase (HRP) in slow-release gel was unilaterally implanted in the transected dorsolateral funiculus (DLF) of either cervical, midthoracic, lumbar or sacral spinal cord levels of adult male rats. Cell mappings were made of all brain areas projecting through the DLF. Following cervical implants, dense labelling was observed within a band along the dorsolateral border of the inferior olive, locus coeruleus, the paralemniscal reticular formation, the mesencephalic central gray, the red nucleus and the paraventricular nucleus of the hypothalamus. The DLF projection from the central gray consisted of a rostrocaudal line of cells extending from the level of the mesen-/diencephalic junction to the rostral red nucleus. The somatotopic organization of labelled nuclei was assessed by comparing the pattern of filled cells following HRP implants at various cord levels. The potential role of these areas in pain modulation was discussed in light of their descending projections through the DLF of the spinal cord.     

Chromatophore motoneurons in the brain of the squid, Lolliguncula brevis: a HRP study

The location of the motoneuron somata controllingg activity of the chromatophore muslces was studied in the squid Lollinguncula brevis. Retrograde transport of horseradish peroxidase from injection sites in the skin or in the mantle muscle established that the chromatophore motoneurons are situated in the subesophageal mass of the brain while at least some of the mantle muscle motoneurones are in the stellate ganglia. Motoneurons to chromatophores in the mantle have their somata in the posterior subesophageal mass, mainly in the chromatophore or fin lobes. Motoneurons to chromatophores in the head are located in the anterior pedal lobes and those to the chromatophores in the arms project mainly from the anterior chromatophore lobes. However, some neurons in the posterior chromatophore lobes project to the head or arm regions. A few cells in both the anterior and posterior chromatophore lobes project contralaterally. Somata in other lobes of the subesophageal mass are also labelled by injections in the skin or in the mantle muscle. Evidence presented here suggests that some of the neurons labelled outside the chromatophore lobes are chromatophore motoneurons.     

Cerebellar afferents from motor nuclei of cranial nerves, the nucleus of the solitary tract, and nuclei coeruleus and parabrachialis in sheep, demonstrated with retrograde transport of horseradish peroxidase

Following HRP injections in the cerebellar cortex of the sheep (except the ventral part of the anterior lobe, the flocculus and ventral paraflocculus), labeled cells were evident in motor nuclei of cranial nerves (XII, VII, VI, III, visceromotor nucleus of X and nucleus ambiguus), in the solitary tract nucleus, the nucleus coeruleus and the parabrachial nucleus.     

Vasodilator responses following intracranial stimulation of the trigeminal, facial and glossopharyngeal nerves in the cat gingiva

The effects of electrical stimulation of the trigeminal, facial and glossopharyngeal nerves on gingival blood flow in the cat were studied. The intracranial part of these nerves was stimulated electrically, and gingival blood flow was measured by the laser Doppler technique. Electrical stimulation of the trigeminal, facial and glossopharyngeal nerves caused blood flow to increase in the ipsilateral gingiva both with the cranial nerve intact and after cutting it to the medulla. Stimulation of the distal cut ends of the facial and glossopharyngeal nerves elicited an increase in blood flow but no increase in systemic blood pressure. Pretreatment with hexamethonium reduced the increase in blood flow elicited by electrical stimulation of the facial and glossopharyngeal nerves, but had no effect on that elicited by stimulation of the trigeminal nerve. In contrast, pretreatment with tripelennamine attenuated the trigeminal nerve-stimulated blood flow increase, but not that elicited by stimulation of the facial and glossopharyngeal nerves. Atropine, propranolol and phentolamine had no effect on these responses. These results suggest that the autonomic nervous system, particularly the parasympathetic nervous system, is responsible for the blood flow increase elicited by facial and glossopharyngeal nerve stimulation, and that the trigeminal nerve-stimulated blood flow increase is induced by antidromic vasodilatation of the trigeminal sensory nerve.     

Direct amygdaloid projections to the dorsal motor nucleus of the vagus nerve: a light and electron microscopic study in the rat

The projections from the central nucleus of the amygdala to the dorsal vagal complex were examined in the rat by means of anterograde and retrograde axonal transport of wheat germ agglutinin-horseradish peroxidase and anterograde degeneration. Light microscopic findings confirmed that the amygdala projects to the dorsal motor nucleus (DMV) and the nucleus of the solitary tract. Electron microscopic experiments demonstrated degenerating axosomatic and axodendritic terminals in the DMV following electrolytic lesions in the central nucleus of the amygdala.     

Interrelations between lateral, dorsomedial and ventromedial hypothalamic nuclei in the rat. An HRP study

Afferents of the lateral (LH) and ventromedial (VMH) hypothalamic nuclei were studied with the horseradish peroxidase method. The aim was to investigate relations between these two centers presumed to be involved in the regulation of food intake. Special attempts were made to produce HRP injections limited to intranuclear dimensions, which was achieved by iontophoretic delivery of the tracer. The results indicate that LH and VMH do not maintain direct interconnections. Both nuclei, however, appear to have numerous afferents from the dorsomedial hypothalamic nucleus (DMH) in common, which led us to extend our analysis to the DMH. DMH injections of HRP resulted in retrograde labeling of somata in both LH and VMH, suggesting a reciprocal relationship of DMH with these latter nuclei. The possible significance of such a LH-DMH-VMH relationship in the food intake control circuitry is discussed. The other labeling of afferents resulting from HRP injections localized to LH, DMH and VMH is described and discussed as regards their morphological significance. A number of these connections confirm studies using anterograde transport techniques, but others have not been described before, including an extensive projection to the VMH from the mesencephalic perpendicular nucleus.     

A direct hypothalamic projection to the superior salivatory nucleus neurons in the rat. A study using anterograde autoradiographic and retrograde HRP methods

The location of the superior salivatory nucleus and terminal labelings of the hypothalamic descending fibers were demonstrated in the nucleus reticularis parvocellularis using HRP and the autoradiographic techniques, respectively. When both techniques were used in the same animals, some HRP-labeled neurons were seen among the accumulations of silver grains, suggesting pericellular terminations. The present study demonstrates that the hypothalamic efferents project directly to the superior salivatory nucleus innervating salivary and lacrimal glands.     

HRP示踪评价导管修复猫动眼神经的效果

目的HRP示踪方法评价导管修复动眼神经缺损的效果。方法用辣根过氧化物酶(HRP)标记法观察猫动眼神经横断并分别采用导管套接和神经桥接修复后,其动眼神经运动核内神经元的变化。结果两组动物均于同侧的动眼神经核内发现HRP标记的神经元,内侧纵束及对侧动眼神经核中亦见散在的阳性标记细胞。标记神经元的数量神经桥接组265±92个,右侧占72.3%;导管套接组312±81个,右侧占84.5%。桥接组标记细胞数较少,差异有显著性(P<0.05),导管套接组同侧细胞所占比例较高(P<0.05)。结论导管套接及神经桥接均能较好地修复动眼神经的小段缺损,且导管修复后可能有一定程度的趋向性再生。     

The distribution of muscle primary afferents from the masseter nerve to the trigeminal sensory nuclei

Transganglionic transport of horseradish peroxidase--wheat germ agglutinin conjugate was used to study the pattern of termination of somatic afferent fibers innervating the masseter muscle within the trigeminal sensory nuclear complex (TSNC) of the cat. The central processes of the masseteric nerve terminated in the caudal third of the pars interpolaris, and laminae I/V through the caudal two-thirds of caudalis and rostral parts of the C1 spinal cord segment. The functional significance of the masseteric afferent projections to the TSNC with a preferential pattern was discussed, particularly with respect to muscle pain.     

Primary vagal nerve projections to the lateral descending trigeminal nucleus in boidae (Python molurus andBoa constrictor)

After injections of horseradish peroxidase into several areas of the neocortex in the macaque monkey longitudinal bands of labeled cells in the basal nucleus of Meynert related to areas of cortex in the frontal lobe have been found to overlap along their long axes with the bands related to widely separated but interconnected areas of the parieto-temporal cortex. The frontal and parietal lobes are related to the anterior and posterior halves respectively of the nucleus, the temporal cortex to the postero-lateral margin of the nucleus and the occipital lobe to its upturned posterior extension.