Neurons of origin of the perforant path

Neurons of origin of the perforant path were labeled in entorhinal cortex after exposure of their injured axons to horseradish peroxidase. Almost all neurons in layer II of portions of the entorhinal cortex ipsilateral to the injury site contained diffuse and/or granular label. They included stellates, pyramids, fusiforms, and two cell types whose dendrites arose from two or three characteristic sites and divided into branches which were largely parallel or oblique to the pial surface. These two types predominated in the area lateralis, and stellates with dendrites mainly oriented perpendicular to the pia were the most numerous cells in the area medialis.     

Muscle sensory neurons in the spinal ganglia in the rat determined by the retrograde transport of horseradish peroxidase

The method of retrograde transport of horseradish peroxidase (HRP) was used to identify muscle sensory neurons in the spinal ganglia in the rat. Experiments were conducted on 25 albino rats. Injections of 0.06 to 0.08 ml 2 to 20% Sigma type VIHRP were made unilaterally into anterior tibial muscle. Cells of origin of muscle receptors and motor endings in the same area where HRP was administered were demonstrated. The labeled cells, medium to large, were found in fourth and fifth lumbar ganglia ipsilateral to the site of injection. Simultaneously, labeled neurons were also found in the ipsilateral ventral horn of the same cord segments as the labeled sensory ganglia.     

Trigeminal nerve and temporomandibular joint of the cat: A horseradish peroxidase study

The mesencephalic nucleus of the trigeminal nerve is considered to contain the cell bodies of the first-order neurons that have peripheral connections in the temporomandibular joint capsule. Through use of retrograde transport of horseradish peroxidase, this concept is challenged. The results indicate that a relatively specific region of the mandibular division of the trigeminal ganglion of the cat contains the first-order neurons innervating the temporomandibular joint capsule.     

Preganglionic innervation of the adrenal gland of the rat using horseradish peroxidase

Using the tetramethyl benzidine method for the demonstration of horseradish peroxidase, it was possible to label retrogradely spinal neurons whose axons project to the adrenal medulla in both young and adult rats. In both age groups, labeled neurons were found in the ipsilateral intermediolateral cell column of the T2 through T13 segments of the spinal cord, with most of the labeling in the T6 to T10 segments. The neurons labeled with horseradish peroxidase also demonstrated a strong acetylcholinesterase activity.     

Neurons for flight,a horseradish peroxidase study

Retrograde labeling of neurons in the medial half of lamina IX followed injection of horseradish peroxidase into the pectoral muscles. Included were the very large neurons (to 70 μm) which are found in this region. A few labeled neurons were seen in the medial half of the contralateral lamina IX, in a position corresponding to the loci of the neurons for the contralateral pectoralis muscle.     

Brain stem penetration by horseradish peroxidase from the cerebrospinal fluid spaces in the cat

Horseradish peroxidase (HRP) was used as an extracellular marker to determine the nature and time course of molecular penetration from the CSF into the brain stem parenchyma. Anesthetized cats were injected with HRP (1 or 2%) intracerebroventricularly or intracisternally. The brain was fixed in situ by vascular or ventriculocisternal perfusion with formaldehyde after 5 min to 24 h of exposure to HRP in the cerebrospinal fluid. After intraventricular injection, the widest band of penetration by HRP occurred in 5 min beneath the pial surface with radial spurs extending farther inward along perivascular and perineural sheaths. Permeation of the ependymal surface was more limited and uniform in depth even after 0.5 h. Clearing of the parenchyma was well advanced by 4 h and was essentially complete by 24 h with the exception of HRP contained in macrophages primarily along blood vessels. After intracisternal injection, distant labeling by HRP was found in the vascular endothelium of the upper brain stem parenchyma. We conclude that rapid and deep molecular penetration of the brain stem occurs from the subarachoid fluid space. Hence, effects of drugs in the cerebrospinal fluid attributed to activation of hypothetical chemoreceptors on the pial surface may actually result from actions upon structures deep in the parenchyma.     

Mesencephalic and pontine afferent fiber system to the facial neucleus in the cat: a study using the horseradish peroxidase and silver impregnation techniques.

The mesencephalic and pontine afferent fiber system to the medial or lateral part of the facial nucleus was examined in the cat by the horseradish peroxidase and the Fink-Heimer methods. The medial part of the facial nucleus was observed to receive afferent fibers mainly from the perioculomotor and the midbrain paralemniscal regions. The perioculomotor region, which included the oculomotor nucleus, the Edinger-Westphal nucleus, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch, and the ventral part of the periaqueducatal gray, sent fibers to the facial nucleus bilaterally with a slight dominance of the ipsilateral distribution. The midbrain paralemniscal region, which was just medial to the dorsal part of the medial lemniscus at caudal levels of the superior colliculus, sent numerous fibers to the contralateral facial nucleus. In contrast, the lateral part of the facial nucleus received many afferent fibers from the ventral part of the parabrachial nuclei; the parabrachiofacial fibers were distributed bilaterally with a marked predominance of the ipsilateral distribution. The existence of crossed rubrofacial fibers was confirmed. Some neurons in the ventral part of the nucleus pontis centralis oralis were found to send fibers to the facial nucleus bilaterally with a predominance of the contralateral distribution.     

A horseradish peroxidase study of the cerebellorubral pathway in the rat

The distribution and character of labeled neurons within the cerebellar nuclei of the rat were studied after injection of horseradish peroxidase into the red nucleus. Cells possessing horseradish peroxidase activity were found throughout the contralateral nucleus lateralis (dentate) and interposed complex and were absent from the nucleus medialis (fastigial). Relatively more labeled neurons were present within the anterior part of the interposed complex than in its posterior portion. Peroxidase-stained cells were characteristically large and multipolar, whereas small neurons throughout these centers were devoid of activity. An ipsilateral projection to the red nucleus was not observed.     

Distribution and morphology of sacral autonomic neurons in the cat: peroxidase labeling of efferent neurons through transected ventral roots.

The distribution and morphologic characteristics of the nucleus intermediolateralis inferior, the cell group X of Onuf, and the medial border cell group of the ventral horn, the latter two of which are also possibly autonomic in function, were investigated in the cat by means of retrograde axonal transport of horseradish peroxidase through the cut end of the transected individual sacral ventral root. The nucleus intermediolateralis inferior contributes its axons chiefly to the S2 and S3 ventral roots, and the nucleus occupies a larger triangular area of the intermediate region than that described previously. The neurons of the intermediolateral group are arranged in horizontal fashion. Cell group X contributes its axons chiefly to S1, and this is composed of longitudinally arranged, medium-size neurons having very well-developed longitudinal dendritic bundles. The medial border cells of the ventral horn, which are chiefly of medium and small size, are also labeled by bathing the S1 through C×1 roots. Their neuronal characteristics suggest that they might be also autonomic in function.     

Parabrachial nucleus neurons projecting to the lower brain stem and the spinal cord. A study in the cat by the Fink-Heimer and the horseradish peroxidase methods

Direct projections from the parabrachial nucleus (PBN) to the lower brain stem and the spinal cord were examined in the cat by the Fink-Heimer and the horseradish peroxidase (HRP) methods. After placing lesions in the PBN, many fine degenerated fibers were seen contralaterally in the ventromedial portions of the caudal pontine reticular formation, and ipsilaterally in the lateral portions of the facial nucleus, the regions around the hypoglossal nucleus, and the regions around the ambiguus nucleus; some degenerated fibers were traced ipsilaterally down to the spinal cord. Subsequently, HRP injections were attempted into these regions where many fine degenerated fibers were observed. In cats injected with HRP into the lateral portions of the facial nucleus, the regions around the hypoglossal nucleus, the regions around the ambiguus nucleus, or the first cervical cord segment, many HRP-labeled neurons were seen in the ventral portions of the PBN. The mean of the average soma diameters of the PBN neurons labeled with HRP injected into the regions around the hypoglossal nucleus or the first cervical cord segment was significantly larger than that of the PBN neurons labeled with HRP injected into the lateral portions of the facial nucleus or the regions around the ambiguus nucleus.     

Olivocerebellar connections in sheep studied with the retrograde transport of horseradish peroxidase

We describe here the morphology of the inferior olive and the localization of labeled cells after HRP injections into various lobules of vermis and hemisphere of the cerebellum of the sheep. The medial part of the caudal half of the medial accessory olive projects to a medial zone in the anterior lobe, the simple lobule, and the lobules VII and VIII. The lateral part of the medial accessory olive projects to more lateral parts of these lobules with the exception of lobule VII. The group beta projects in a differential manner to the lateral parts of the lobules VII and VIII and the medial parts of the lobules IX and X. The dorsomedial cell column projects to lobules VIII, IX, and X; the connections of the dorsal cap are restricted to lobule X. Fibers from the caudal limb of the dorsal accessory olive terminate in the B zone, the simple lobule, and in lobule VIII. The rostral half of the medial accessory olive projects to lobule IX and to the hemisphere. The other projections of the accessory olives and the principal olive to the hemisphere are similar to those reported for the cat. An accessory cell group in the sheep, located between the principal and the dorsal accessory olive, has connections with the caudal vermis and the hemisphere.     

Conjugated dimers of horseradish peroxidase as neuroanatomical tracers

Horseradish peroxidase dimer (HRP-HRP) and monomer (HRP) were compared in their ability to act as neuroanatomical tracers. Dimers exhibited less diffusion at the site of injection. At 48-72 h survival periods, there were no appreciable differences in the retrograde neuronal labeling produced by these two compounds. However, at 7 days survival, there was little retrograde labeling due to the presence of monomer while dimer labeling was still intense.     

Reciprocal connections between the amygdala and parabrachial nuclei: ultrastructural demonstration by degeneration and axonal transport of horseradish peroxidase in the cat

An ultrastructural analysis of the connections of the amygdala with the parabrachial nuclei (PBN) was carried out after electrolytic lesions or injections of horseradish peroxidase in the amygdala. Degenerating and labeled terminals originating from the amygdala formed axosomatic and axodendritic synapses in the PBN. In some instances, anterograde labeled terminals synapsed with retrogradely labeled neurons. These results demonstrate that the amygdala and PBN have close reciprocal synaptic connections.     

Localization of parabrachial nucleus neurons projecting to the thalamus or the amygdala in the cat using horseradish peroxidase.

Topographical localization of parabrachial nucleus (PBN) neurons projecting directly to the thalamus or the amygdala was examined in the cat by the horseradish peroxidase (HRP) method. After HRP injection in the central nucleus of the amygdala, PBN neurons labeled with the enzyme were seen ipsilaterally in the ventral portion of the lateral PBN as well as in the medial PBN. When the HRP injections were centered on the parvocellular portion of the posteromedial ventral nucleus of the thalamus (VPMpc), HRP-labeled neurons were observed ipsilaterally in the dorsal portion of the lateral PBN as well as in the medial PBN. Within the medial PBN, the distribution of neurons projecting to the amygdala overlapped that of neurons projecting to VPMpc; the cell bodies of the former neurons, however, tended to be more elongated than the latter, and the mean of the average soma diameters of the former was significantly larger than the latter. On the other hand, in the lateral PBN no significant differences were noted between the means of the average soma diameters of neurons projecting to VPMpc and those projecting to the amygdala. The PBN neurons in the cat were presumed to transmit gustatory and general visceral information ipsilaterally to the thalamic taste region and the limbic areas in the basal forebrain.     

Heterogeneity of neurons in the crustacean X-organ as revealed by intracellular recording and injection of horseradish peroxidase

The intracellular injection technique of HRP with simultaneous recordings of intracellular potential was applied to the crab X-organ-sinus gland peptidergic neurosecretory neurons. At least two classes of neurons were discriminated from the usual type of neurosecretory neurons morphologically as well as electrophysiologically. Possible roles of those neurons were suggested as the modulation and coordination of activities of the neurosecretory system.     

Cells of origin of long descending propriospinal fibers connecting the spinal enlargements in cat and monkey determined by horseradish peroxidase and electrophysiological techniques.

The cells of origin of the long descending propriospinal tract (LDPT) in the cervical enlargement were studied in cat and monkey by using the retrograde transport of horseradish peroxidase (HRP). Their distribution was confirmed electrophysiologically in cat by recording their antidromic action potentials. In cats and monkeys unilateral injections of HRP were made into the gray matter of the lumbosacral enlargement, but there was some spread to the contralateral side. In cats labeled somas were found in greatest numbers in lamina VIII and medial lamina VII, bilaterally. Labeled cells also were found bilaterally in laminae I, IV--VI, and X, but few were in IV and VI. Those in lamina V were usually in the lateral part of the lamina near the reticulated region. The cross-sectional areas of 20 neurons from each of laminae I and V--VIII were measured. Cells in lamina I were smallest and the largest were in VII and VIII. In cats with the spinal cord hemisected between the injection site and the cervical enlargement containing the somas, the bilaterality of the LDPT neurons in laminae VII and VIII was confirmed anatomically and physiologically. Contralaterally projecting neurons in laminae VIII and medial VII constituted a majority of LDPT cells in those laminae. The LDPT neurons in the dorsal horn appeared to project mainly ipsilaterally, but the number of labeled dorsal horn cells in these preparations was small. The distribution of antidromically localized cells of the LDPT was found to be in good agreement with the anatomical results. Their conduction velocity was 59 +/- 22 m/s (mean +/- s.d., n = 245). Histograms of the conduction velocity by laminae are given. In monkey the distribution of labeled somas was similar to that in the cat, except that the concentration of labeled somas in the ventral horn was more medially and dorsally located. Labeled somas were found bilaterally in laminae I, IV--VIII, and X, but more appeared to be ipsilateral to the side of the injection, especially in the dorsal horn. The bilaterality of the LDPT in the monkey was not tested with hemisections of the spinal cord. Neurons of the LDPT are ideally situated for conveying sensory information from the forelimb for eliciting reflexes in the hindlimb, as has been observed after stimulating afferents in the forelimb, and for coordinating, in general, motor functions between the two pairs of limbs.