Concerning the ionic basis of presynaptic inhibition.

The superfused rat cuneate nucleus has been used to investigate the sensitivity of primary afferent terminals and of evoked primary afferent depolarization (PAD) to alterations in extracellular K+ and Cl- ions levels. Results indicate that PAD is caused by an efflux of Cl- from primary afferent terminals rather than by an increase in extracellular K+.     

Concerning the ionic basis of presynaptic inhibition

Summary The superfused rat cuneate nucleus has been used to investigate the sensitivity of primary afferent terminals and of evoked primary afferent depolarization (PAD) to alterations in extracellular K⁺ and Cl^– ion levels. Results indicate that PAD is caused by an efflux of Cl^– from primary afferent terminals rather than by an increase in extracellular K⁺.     

Destruction of afferent nerve terminals in the inner ear of frog by aminooxyactic acid.

The drug aminooxyacetic acid, which inhibits GABA-transaminase, destroys the afferent nerve ending in the inner ear of the frog. The efferent nerve endings and the sensory cells are not affected.     

Destruction of afferent nerve terminals in the inner ear of frog by aminooxyacetic acid

Summary The drug aminooxyacetic acid, which inhibits GABA-transaminase, destroys the afferent nerve endings in the inner ear of the frog. The efferent nerve endings and the sensory cells are not affected.     

Synkinesis in hemifacial spasm: results of recording intracranially from the facial nerve

We show evidence that the motonucleus of the facial nerve is involved in producing the synkinesis in patients with hemifacial spasm. These results were obtained by recording from the intracranial portion of the facial nerve and from the orbicularis oculi muscle in patients operated upon for hemifacial spasm during electrical stimulation of the mandibular branch of the facial nerve. Also, the electromyographic response from the same muscle was recorded when the facial nerve was electrically stimulated at a location near the brainstem. The results show that it is unlikely that the symptoms of patients with hemifacial spasm can be explained on the basis of ephaptic transmission at the site of lesion of the facial nerve.     

Synkinesis in hemifacial spasm: results of recording intracranially from the facial nerve

Summary We show evidence that the motonucleus of the facial nerve is involved in producing the synkinesis in patients with hemifacial spasm. These results were obtained by recording from the intracranial portion of the facial nerve and from the orbicularis oculi muscle in patients operated upon for hemifacial spasm during electrical stimulation of the mandibular branch of the facial nerve. Also, the electromyographic response from the same muscle was recorded when the facial nerve was electrically stimulated at a location near the brainstem. The results show that it is unlikely that the symptoms of patients with hemifacial spasm can be explained on the basis of ephaptic transmission at the site of lesion of the facial nerve.     

GABA in the caudate nucleus: A possible synaptic transmitter of interneurons

Summary Microiontophoretic application of GABA and its antagonist, picrotoxin, altered focal potentials evoked in the caudate nucleus by stimulation near the recording site to a much greater extent than potentials elicited by stimulation of afferent pathways, suggesting that GABA is a transmitter of interneurons in this nucleus.This study was supported by funds from the Veterans Administration and by NIH research grant No. 06820.We thank Kathleen Downes and Clifford Smathers for their assistance.     

Uptake and transport of exogenous peroxidase in the masticatory muscles of cats. Localization of ganglionic neurons]

Retrograde axonal transport of Horseradish peroxydase (HRP) has been used to trace the cells of origin of proprioceptive fibers in jaw-closing and jaw-opening muscles. After injection of HRP in young cats' masticatory muscles (masseteric, temporal, pterygoid, mylohyoid and digastric) labelled neurons were found in the ipsilateral semi-lunar ganglion and trigeminal mesencephalic nucleus. It is concluded that sensory endings are present in jaw-opening as in jaw-closing muscles; possibly the afferent fibers from muscle endings of the opener muscles have their somata in the mesencephalic nucleus, afferent fibers from tendinous receptors in the semi-lunar ganglion.     

Der elektrophysiologische Nachweis der propriozeptiven Muskelafferenz und des monosynaptischen Reflexbogens der inneren Kehlkopfmuskeln

Summary On excitation of the superior laryngeal nerve and the recurrent nerve with single square wave shocks in patients undergoing total exstirpation of the larynx for cancer, a reflex potential can be recorded from the vocal muscle. This potential shows the criteria characteristic of the reflex potential arising on excitation of muscle spindles or the afferents of muscle spindles (la-fibres) in limb muscles. The pathway of afferent fibres is for the main part via the sup. lar. nerve but there seems to be an indication of a small part of afferents in the recurrent nerve also.     

Neuroma formation and abnormal afferent nerve discharges after partial beak amputation (beak trimming) in poultry

Following partial amputation of the beak recordings were taken of the electrical activity from single afferent fibers of the intramandibular nerve. A total of 192 single afferent fiber units were isolated of which 47 were classified as nociceptors, with an abnormal pattern of discharge, and 89 were abnormal spontaneously active units. Following amputation neuromas were developing by 15 days after surgery and they were well formed by 20 to 30 days. The presence of neuromas together with abnormal spontaneous activity originating from them raise serious welfare questions concerning beak trimming.     

Influence of cervical sympathetic nerve stimulation on carotid sinus baroreceptor afferents

Summary In rabbits and dogs, the response of low-threshold carotid sinus baroreceptor afferent fibres to cervical sympathetic nerve stimulation at various non-pulsatile steady pressures was examined. Fibres which possessed a rhythmic bursting discharge at low pressures increased this activity during sympathetic stimulation; all other low-threshold afferents were unaffected.This work was supported by the Medical Research Council of Canada and the British Columbia Heart Foundation.     

Absence of dopamine sensitive adenylate cyclase in the A10 region, the origin of mesolimbic dopamine neurones.

Dopamine (DA) failed to stimulate the adenylate cyclase of the mesolimbic A10 DA nerve cell body area, in contrast to tis activating effect in the nigrostriatal A9 DA cell body area. The enzyme was stimulated by GMPPNP (a GTP analog) and NaF. This indicates the absence in the A 10 cell area of DA receptors with functional coupling on adenylate cyclase, in contrast to the A9 cell area where such DA receptors are believed to be located on afferent axon terminals.     

Vagal afferent innervation in regenerated rat liver

Summary The possible presence of neural sprouting in the afferent neurons of regenerated rat liver after hepatectomy was investigated bu retrograde transport of horesradish peroxidase. This experiment was carried out to see if the increase in hepatic parenchyma could provide an adequate stimulus for the sprouting precess. The study was limited to the vagal afferents, particularly the left ones, because they are the principal contributors to hepatic afferent innervation in the rat. The results show that neural sprouting does not occur in regenerated rat liver after 3 weeks In fact, the number of intensely labeled neurons in the left nodose ganglia of hepatectomized rats was significantly smaller than in controls. This could be due to a lessened availability of horseradish peroxidase to nerve terminals in hepatectomized and control animals. This could be a consequence of their possible distribution in hepatic areas not involved in the regenerative process.     

Neuroma formation and abnormal afferent nerve discharges after partial beak amputation (beak trimming) in poultry

Summary Following partial amputation of the beak recordings were taken of the electrical activity from single afferent fibers of the intramandibular nerve. A total of 192 single afferent fiber units were isolated of which 47 were classified as nociceptors, with an abnormal pattern of discharge, and 89 were abnormal spontaneously active units. Following amputation neuromas were developing by 15 days after surgery and they were well formed by 20 to 30 days. The presence of neuromas together with abnormal spontaneous activity originating from them raise serious welfare questions concerning beak trimming.Acknowledgment. We thank Louise Hunter for her technical assistance and J. B. is indebted to the AFRC and BEMB for financial support during the tenure of his studentship.     

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.     

Neuropeptides in pelvic afferent pathways

Neurochemical and pharmacological experiments have raised the possibility that several neuropeptides including, vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine amide (PHI), substance P, calcitonin gene-related peptide (CGRP), neurokinin A, cholecystokinin (CCK) and opioid peptides may be transmitters in afferent pathways to the pelvic viscera. These substances are widely distributed in: 1) nerve fibers in the pelvic organs, 2) visceral afferent neurons in the lumbosacral dorsal root ganglia and 3) at sites of afferent termination in the spinal cord. Double staining immunocytochemical techniques have shown that more than one peptide can be localized in individual visceral afferent neurons and that neuronal excitatory (VIP, substance P, CCK) and inhibitory peptides (leucine enkephalin) can coexist in the same afferent cell. Studies with the neurotoxin, capsaicin, indicate that peptidergic afferent pathways are involved in the initiation of central autonomic reflexes as well as peripheral axon reflexes which modulate smooth muscle activity, facilitate transmission in automatic ganglia and trigger local inflammatory responses.     

Neuropeptides in pelvic afferent pathways

Summary Neurochemical and pharmacological experiments have raised the possibility that several neuropeptides including, vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine amide (PHI), substance P, calcitonin gene-related peptide (CGRP), neurokinin A, cholecystokinin (CCK) and opioid peptides may be transmitters in afferent pathways to the pelvic viscera. These substances are widely distributed in: 1) nerve fibers in the pelvic organs, 2) visceral afferent neurons in the lumbosacral dorsal root ganglia and 3) at sites of afferent termination in the spinal cord. Double, staining immunocytochemical techniques have shown that more than one peptide can be localized in individual visceral afferent neurons and that neuronal excitatory (VIP, substance P, CCK) and inhibitory peptides (leucine enkephalin) can coexist in the same afferent cell. Studies with the neurotoxin, capsaicin, indicate that peptidergic afferent pathways are, involved in the initiation of central autonomic reflexes as well as peripheral axon reflexes which modulate smooth muscle activity, facilitate transmission in automatic ganglia and trigger local inflammatory responses.     

Vagal afferent innervation in regenerated rat liver

The possible presence of neural sprouting in the afferent neurons of regenerated rat liver after hepatectomy was investigated by retrograde transport of horseradish peroxidase. This experiment was carried out to see if the increase in hepatic parenchyma could provide an adequate stimulus for the sprouting process. The study was limited to the vagal afferents, particularly the left ones, because they are the principal contributors to hepatic afferent innervation in the rat. The results show that neural sprouting does not occur in regenerated rat liver after 3 weeks. In fact, the number of intensely labeled neurons in the left nodose ganglia of hepatectomized rats was significantly smaller than in controls. This could be due to a lessened availability of horseradish peroxidase to nerve terminals because of the increased non-innervated hepatic mass. There was no difference between right nodose ganglia neurons in hepatectomized and control animals. This could be a consequence of their possible distribution in hepatic areas not involved in the regenerative process.     

The fine structure of the conical-headed sperm of the crinoidAntedon bifida

Summary Scanning- and transmission electron microscopy show that the sperm head ofAntedon bifida is conical and thus different from the spherical sperm head that is typical of crinoids. The head consists of the acrosome and the nucleus. The posterior fibrogranular component of the acrosome is housed in a tubular, axial invagination running from the anterior pole almost to the posterior pole of the nucleus. The middle piece includes a mitochondrion and a pair of centrioles. One of the centrioles is a basal body, which gives rise to the tail flagellum.     

Metabolism and signaling activities of nuclear lipids

Apart from the lipids present in the nuclear envelope, the nucleus also contains lipids which are located further inside and are resistant to treatment with nonionic detergents. Evidence is being accumulated on the importance of internal nuclear lipid metabolism. Nuclear lipid metabolism gives rise to several lipid second messengers that function within the nucleus. Moreover, it is beginning to emerge that nuclear lipids not only act as precursors of bioactive second messengers but may be directly involved in regulation of nuclear structure and gene expression. Over the last 10years, especially the role of the inositol lipid cycle in nuclear signal transduction has been extensively studied. This cycle is activated following a variety of stimuli and is regulated independently from the inositide cycle located at the plasma membrane. However, the nucleus contain other lipids, such as phosphatidylcholine, sphingomyelin, fatty acids and eicosanoids. There are numerous reports which suggest that these classes of nuclear lipids may play roles in the nucleus as important as those of phosphoinositides. This review aims at highlighting the most important aspects regarding the metabolism and signaling activities of nuclear phosphatidylcholine, sphingomyelin, fatty acids and eicosanoids.Received 7 November 2003; received after revision 18 December 2003; accepted 29 December 2003