Peptidergic innervation of the temporomandibular disk in the rat

Summary The peptidergic innervation of the temporomandibular disk was investigated in the postnatal young rat by using an indirect immunofluorescence method. Calcitonin gene-related peptide-containing nerve fibers were located around the blood vessels and terminated as free nerve endings in the disk. These nerve fibers may be of a sensory nature.     

An analysis of the distribution of the myelinated nerve fibers in the optic fascicle of a beagle dog

The composition of both optic fascicles of a Beagle dog was studied in topographically oriented, semithin transections of whole nerve stained with toluidine blue. About 165,000 myelinated fibers were present in each nerve, their maximum caliber reaching 11 micron; large, less densely arranged fibers occurred especially in the dorso-temporal region.     

Conditioning of depressor responses evoked by single volleys in the aortic nerve

Summary Depressor responses evoked by single volleys in the aortic nerve are more facilitated by conditioning volleys exciting C fibers in the same aortic nerve than in the contralateral one. Conditioning volleys in A fibers do not facilitate the testing depressor responses.     

An analysis of the distribution of the myelinated nerve fibers in the optic fascicle of a Beagle dog

Summary The composition of both optic fascicles of a Beagle dog was studied in topographically oriented, semithin transections of whole nerve stained with toluidine blue. About 165,000 myelinated fibers were present in each nerve, their maximum caliber reaching 11 m; large, less densely arranged fibers occurred especially in the dorso-temporal region.We are grateful to Dr D.C. Naylor, Mrs K. Schnider, Mr F. da Silva and Mr K. Traber for their aid.     

Comparative ultrastructural and cytochemical analysis of the cephalopod systemic heart and its innervation

Summary The present knowledge of the morphology of cephalopod central hearts is presented. The cytological characteristics of the epicardial, myocardial and endothelial tissue layers are reviewed. Myocardial cells are characterized as obliquely striated myocytes with a high level of oxidative metabolism. The voluminous myocardium is intensively penetrated by nerve fibers controlling the myogenic heart rhythm by different chemical transmitter systems. Catecholaminergic fluorophores and acetylcholinesterase activity could be localized by means of histochemical and cytochemical investigations. A glio-interstitial cell system is shown to be present in connection with nerve fibers and also uncombined between heart muscle cells. Its content of large different-sized inclusions is described and their function discussed.     

The conduction velocity, number, and diameter of unmyelinated fibers in Remak's nerve

Remak's nerve in the chicken was examined ultrastructurally and electrophysiologically to determine the characteristics of fibers in the nerve trunk. The ration of unmyelinated fibers to myelinated ones was 111:1. The mean number of unmyelinated fibers was 3555 plus/minus 232 (SEM, n=5) and they had a mean diameter of 0.502 plus/minus 0.034 (SEM) micron. The compound action potential consisted almost entirely of a large diphasic waveform which had a mean peak conduction velocity of 0.62 plus/minus 0.031 (SEM, n=5) m.s-1 at 37 degrees C.     

Interaction between bradykinin and voltage-sensitive sodium channels in myelinated nerve fibers

The effects of externally and internally applied bradykinin on the excitability of single myelinated nerve fibers were studied. External bradykinin (10 microM) slightly prolongs the action potential of a single myelinated nerve fiber; hence, when the fibers are stimulated by long-lasting pulses, this raises the frequency of repetitive firing in sensory fibers and evokes repetitive activity in motor fibers. Under voltage-clamp conditions, sodium channel inactivation is slowed, while sodium channel activation remains unaffected. Prolonged depolarization of the membrane leads to a maintained sodium current. The voltage dependence of the steady-state sodium current inactivation (h infinity) is shifted in the depolarized direction by approximately 10 mV. Internally applied bradykinin produces a frequency-dependent block of the sodium current. The phenomena described here imply that more than one site on the sodium channel is modified by bradykinin.     

Dantrolene: evidence for effects on Na permeability properties of the nodal membrane

The effects of dantrolene on myelinated frog nerve fibers were studied in voltage clamp experiments. Dantrolene shifted the potential-dependent parameters describing Na+ permeability towards more negative membrane potentials. The findings are interpreted as a change in the negative surface charge of the membrane.     

Role played in man by myelinated fibers of different diameters for the evocation of a nociceptive flex reflex and the accompanying pain sensation]

Using simultaneous recordings we have made in Man a comparative study of: the sural nerve afferent volley, the nociceptive flexor reflex of a muscle of the lower limb and the associated painful sensation. Two types of stimulations were used, a single short duration electric stimulus, and a train of electric shocks (100/sec). With a single stimulus, the nociceptive flexor reflex and the painful sensation develop only when A delta fibers are recruited. On the other hand, when the stimulations are given by trains the nociceptive flexor reflex and the painful sensation can develop with a stimulus sub-liminar to the threshold of A delta fibers, when A alpha fibers are recruited. When the stimulus activate both A alpha and A delta fibers, the flexion reflex and the pain disappear when a selective blockade of the A delta group is exerted by means of Lidocain.     

Effect of 5,7-dihydroxytryptamine on Auerbach's plexus in the ileum of guinea-pig

Action of 100 mg/kg of 5,7-dihydroxytryptamine on Auerbach's plexus in the ileum of the guinea-pig has been studied using Falck and Hillarp's formaldehyde condensation technique. The drug caused partial disappearance of the adrenergic nerve profiles initially but after 10 days of treatment all the lost fibers reappeared.     

Extracellular matrix and neuronal movement

Summary During brain development, both neuronal migration and axon guidance are influenced by extracellular matrix molecules present in the environment of the migrating neuronal cell bodies and nerve fibers. Glial laminin is an extracellular matrix protein which these early brain cells preferentially attach to. Extracellular glycosaminoglycans are suggested to function in restricting neuronal cell bodies and axons from certain brain areas. Since laminin is deposited along the radial glial fibers and along the developing nerve pathways in punctate form, the punctate assemblies may be one of the key factors in routing the developing neurons in vivo. This review discusses the role of laminin in neuronal movement given the present concept of the extracellular matrix molecules and their proposed interactions.     

Extracellular matrix and neuronal movement

During brain development, both neuronal migration and axon guidance are influenced by extracellular matrix molecules present in the environment of the migrating neuronal cell bodies and nerve fibers. Glial laminin is an extracellular matrix protein which these early brain cells preferentially attach to. Extracellular glycosaminoglycans are suggested to function in restricting neuronal cell bodies and axons from certain brain areas. Since laminin is deposited along the radial glial fibers and along the developing nerve pathways in punctate form, the punctate assemblies may be one of the key factors in routing the developing neurons in vivo. This review discusses the role of laminin in neuronal movement given the present concept of the extracellular matrix molecules and their proposed interactions.     

Occurrence, distribution and nature of neuropeptide Y in the rat pancreas

Significant quantities of a newly discovered peptide, neuropeptide Y, were found in the rat pancreas, where they were localized to nerves in the exocrine parenchyma and around arterial and ductal structures. Although unaffected by surgical parasympathectomy, the periarterial and periductal nerves were abolished by chemical sympathectomy, suggesting that NPY is partially costored with sympathetic transmitters in nerve fibers.     

The morphology of the Schwann cells and the unmyelinated fibers of a nerve supplying an immobilized muscle

Summary Hind limbs of cats were immobilized in the resting position for varying periods and the nerve supplying the medial head of the gastrocnemius muscle was studied while it was undergoing immobilization atrophy. Degenerative changes in the unmyelinated fibers and the Schwann, cells, followed by an abundant increase in collagen, were noticed after prolonged immobilization. Electron microscopic evidence that Schwann cells produce the collagen is discussed.     

Occurrence,distribution and nature of neuropeptide Y in the rat pancreas

Summary Significant quantities of a newly discovered peptide, neuropeptide Y, were found in the rat pancreas, where they were localized to nerves in the exocrine parenchyma and around arterial and ductal structures. Although unaffected by surgical parasympathectomy, the periarterial and periductal nerves were abolished by chemical sympathectomy, suggesting that NPY is partially costored with sympathetic transmitters in nerve fibers.     

Immunohistochemical localization of pancreatic polypeptide (PP) in the brain of the larval instar of the hoverfly,Eristalis aenus (Diptera)

Summary 2 pancreatic polypeptide (PP) immunoreactive cells were observed in each half of the protocerebrum of the last (5th), larval instar of the hoverfly,Eristalis aenus. No PP immunoreactive nerve fibers could be detected in the brain.Support by a grant from the Swedish Medical Research Council (project No. 12X-102) and by a Swedish Institute scholarship.     

Oculomotor reflex evoked by vibrassae stimulation in the cat]

The oculomotor effects of vibrissae stimulation have been studied in the "encéphale isolé" non-anaesthetized Cat. Intracellular recording of lateral rectus motoneurones showed an excitatory projection via the ipsilateral infraorbital nerve to these motoneurones. The afferent fibers are type A alpha, recuited with a low threshold (0.2-0.5 mA) and convey information about vibrissae displacement.     

The conduction velocity,number and diameter of unmyelinated fibers in Remak's nerve

Summary Remak's nerve in the chicken was examined ultrastructurally and electrophysiologically to determine the characteristics of fibers in the nerve trunk. The ratio of unmyelinated fibers to myelinated ones was 1111. The mean number of unmyelinated fibers was 3555±232 (SEM, n=5) and they had a mean diameter of 0.502±0.034 (SEM) m. The compound action potential consisted almost entirely of a large diphasic waveform which had a mean peak conduction velocity of 0.62±0.031 (SEM, n=5) m·s^–1 at 37°C.     

Effect of a dipeptide inhibiting ubiquitin-mediated protein degradation on nerve-dependent limb regeneration in the newt

The dipeptide Leu-Ala, which inhibits ubiquitin-mediated protein degradation, has been shown to act in vitro as an inhibitor of neurite outgrowth of PC12 cells (Hondermarck et al. [1992] Biochem. Biophys. Res. Commun.189: 280). Using agarose beads as vehicles, we tested, in vivo, the effect of this dipeptide (and the inactive inverse, Ala-Leu, as a control) on limb regeneration in the newt (Triturus cristatus), a nerve-dependent developmental process. Leu-Ala inhibited the growth of mid-bud blastemas without altering blastema differentiation, while Ala-Leu had no effect. Cytological observations of dipeptide-treated blastemas using Bodian staining or neurofilament antibodies showed that all the blastema tissues were unmodified except with regard to innervation. Leu-Ala-treated blastemas were devoid of nerve fibers in the epidermal cap, while the mesenchyme distal to the dipeptide impregnated bead exhibited fewer nerve fibers than did Ala-Leu-treated blastemas, which were similar to the control nontreated blastemas. Thus, Leu-Ala, in reducing blastema innervation, inhibits its growth in the same manner as surgical denervation.     

Interaction of vasoactive intestinal peptide (VIP) with cholinergic stimulation of glucagon secretion

Summary VIP-containing nerve fibers as well as cholinergic nerve fibers have a ubiquitous distribution in the body and both types of nerves have been demonstrated to innervate the pancreatic islets. The present study shows, in the intact, conscious mouse, that VIP and the cholinergic agonist carbachol stimulate glucagon secretion in a dose-dependent manner. Furthermore VIP and carbachol were found to exert potentiating interactions on glucagon secretion. These results suggest the existence of an interactive neural regulation of glucagon secretion, exerted by acetylcholine and VIP.We thank Professor V. Mutt, Karolinska Institutet, Stockholm, for giving us VIP. The skilful technical assistance of Lena K vist and Peter Okmark is gratefully acknowledged. This study was supported by grants from the Swedish Medical Research Council (14P-4289, 14X-4286) and the Medical Faculty, University of Lund, Sweden.