[Afferent connections of the prefrontal cerebral cortex in cats]. / Afferentnye sviazi prefrontal'noi kory bol'shogo mozga koshki.

In experiments with unilateral injections of horseradish peroxidase microdoses into the dorsal sites of external g. proreus. using the method of retrograde axonal transport, labeled neurons have been revealed ipsilaterally in the singular cortex of telencephalon, in amygdala and thalamic structures of the brain (n.medio-dorsal nucleus, anterior group of nuclei and intralaminar nuclei). The role of the direct projections discovered to the prefrontal cortex in the formation of emotional component of pain is discussed.

Spinal and trigeminal projections to the parabrachial nucleus in the rat: electron-microscopic evidence of a spino-ponto-amygdalian somatosensory pathway.

The fine structure of spinal and trigeminal projections to the parabrachial area (PB) of the rat was studied using either the anterograde transport of a lectin-peroxidase conjugate or the degeneration technique. Two morphologically different types of terminals were observed. Most labeled terminals contained round vesicles (R type) and formed asymmetrical synapses, usually with large dendrites. Others contained pleomorphic vesicles (P type) and usually made symmetrical contacts with large or medium-size dendrites. A double-labeling strategy was used, combining the retrograde labeling of PB neurons with lectin-peroxidase conjugate from the amygdala and the identification of degenerating terminals after lesions of spinal or trigeminal pathways. These experiments demonstrated that spinal and trigeminal terminals contact PB neurons that project to the central nucleus of the amygdala. The role of this spino(trigemino)-ponto-amygdalian pathway is discussed in relation to some aspects of pain.

Neurophysiology of gastrointestinal pain.

The only non-general sensation that can be evoked from the gastrointestinal (GI) tract is that of pain ranging from mild discomfort to intense pain. However, in certain regions of the gut, such as the rectum and gastro-oesophagus, the feeling of pain can be preceded by non-painful sensations of distension at lower stimulus intensities. GI pain is often dull, aching, ill-defined and badly localized. In some cases, GI pain is projected to areas of the body away from the originating viscus ('referred' pain). These properties indicate that the representation of internal organs within the central nervous system is very imprecise. Behavioural, neurophysiological and clinical evidence shows that most forms of GI pain are mediated by activity in visceral afferent fibres running in sympathetic nerves and that the afferent innervation of the gut mediated by parasympathetic nerves is not primarily concerned with the signalling and transmission of GI pain. As for the encoding mechanism of the peripheral sensory receptor in the gut, there is evidence for the existence of specific visceral nociceptors in some locations (e.g. the biliary system) and for the existence of non-specific 'intensity' type receptors in other locations (e.g. the colon). In any case, the actual number of nociceptive afferent fibres in the gut is very small and this explains why large areas of the GI tract appear to be insensitive or require considerable stimulation before giving rise to painful sensations. The few nociceptive afferents contained in sympathetic nerves can excite many second order neurones in the spinal cord which in turn generate extensive divergence within the spinal cord and brain stem, sometimes involving long supraspinal loops. Such a divergent input can activate many different systems, motor and autonomic as well as sensory, and thus trigger the general reactions that are characteristic of visceral nociception: a diffuse and ill-localized pain sometimes referred to somatic areas, and autonomic and somatic reflexes that result in prolonged motor activity.

Lectin and neuropeptide labeling of separate populations of dorsal root ganglion neurons and associated "nociceptor" thin axons in rat testis and cornea whole-mount preparations.

As part of a program to explore patterns of innervation by nociceptor-related thin sensory axons in a variety of peripheral regions, we have labeled calcitonin gene-related peptide immunoreactive (CGRP-IR) nerve fibers in whole mounts of rat testicular tunica vasculosa and cornea. Efforts were undertaken to visualize the numerically significant fluoride-resistant acid phosphatase (FRAP)-containing axon population, whose peripheral endings have heretofore remained undemonstrable due to technical limitations of currently available acid phosphatase methods. Various histochemical markers that colocalize with FRAP in dorsal root ganglion (DRG) and spinal cord were examined, and a plant lectin, Griffonia simplicifolia I-B4, has been identified that not only selectively labels FRAP(+) sensory ganglion cells and central terminals in spinal cord, but also differentially stains a large number of thin axons in testicular and corneal whole mounts. Slender lectin-labeled fibers are abundant in cornea, and are distributed throughout tunica vasculosa preparations unrelated to blood vessels. CGRP-IR axons, in contrast, maintain close adherence to vascular patterns and are more coarse and varicose in appearance. Lectin staining therefore provides the first practical and specific method for visualization of peripheral FRAP(+) axons consisting principally of sensory C fibers but possibly including a small number of unmyelinated autonomic axons. It should now be feasible, using individual whole-mount preparations from various peripheral nociceptor-innervated tissues, to examine the distributions of both peptidergic and FRAP(+) fibers, which together comprise the vast majority of thin sensory axons. It may then be possible to correlate the observed anatomical patterns with knowledge regarding properties of corresponding physiologically characterized receptive fields.

Sensorimotor mapping and oropharyngeal reflexes in goldfish, Carassius auratus.

The vagal lobe of goldfish and some carps is a laminated, specialized lobe of the midmedulla containing both primary sensory terminals and primary motor neurons. Both the sensory and motor components are represented in the lobe in a matching, orotopic fashion, i.e. the oral cavity is mapped across the surface of the lobe. Anatomical tracing studies reveal that the circuitry exists for a point-to-point reflex system in which the superficial sensory layers are mapped directly onto the underlying motor layer. The utility of this relatively direct sensorimotor coupling appears to be in terms of sorting food within the mouth according to its gustatory properties. The direct coupling between the mapped sensory layer and the similarly mapped motor layer may be a useful model in which to study the evolutionary development of less tightly coupled sensorimotor systems.

Between the retinotectal projection and directed movement: topography of a sensorimotor interface.

This article reviews some recent findings on the character of the neuronal organization lying between the optic tectum and motor pattern-generating circuitry in the case of orienting behaviors. It focuses on frogs but notes parallels to existing work on saccade control in mammals and suggests some additional ones for further exploration. In general, the map-like function of orienting does not appear to be subserved by a comparable map-like organization. It is argued that the current conceptual vocabulary for describing interface organization (sensory map, motor map, pattern-generating circuitry) is inadequate and that some additional concepts (activity-gated divergence, intermediate spatial representation) are necessary. Finally, some questions are raised about the appropriateness of the term 'motor map'.

Neural cartography: sensory and motor maps in the superior colliculus.

The sudden onset of a novel or behaviorally significant stimulus usually triggers responses that orient the eyes, external ears, head and/or body toward the source of the stimulus. As a consequence, the reception of additional signals originating from the source and the sensory guidance of appropriate limb and body movements are facilitated. Converging lines of evidence, derived from anatomical, electrophysiological and lesion experiments, indicate that the superior colliculus is an important part of the neural substrate responsible for the generation of orienting responses. This paper briefly reviews the functional organization of the mammalian superior colliculus and discusses possible linkages between the sensory and motor maps observed in this structure. The hypothesis is advanced that the sensory maps are organized in motor (not sensory) coordinates and that the maps of sensory space are dynamic, shifting with relative movements of the eyes, head and body.

Electrosensory maps form a substrate for the distributed and parallel control of behavioral responses in weakly electric fish.

Electroreceptors, distributed over the body surface of weakly electric fish, code the local amplitude and phase, or timing of zerocrossing, of the animal's electric signals. These signals are generated by rhythmic discharges of the electric organ and form a dipole-like field around the animal. This field is perturbed by interference with electric fields of other fish as well as by the appearance of objects electrically different from water. The spatial and temporal structure of such perturbations can be interpreted as the electric image of interfering fields and moving objects. This strategy of assessing the environment is called 'electrolocation', a form of 'seeing' with the body surface. Electric images are analyzed in somatotopically ordered strata of neurons within the central nervous system. Primary electrosensory afferents project to somatotopically ordered layers of higher-order neurons in the electrosensory lateral line lobe (ELL) of the hindbrain. Phase and amplitude information are processed in separate layers of the ELL. The phase of the signal in a given region of the body surface is coded by the timing of spikes of spherical cells marking the zerocrossings of the electric signal. This phase information is relayed to lamina 6 of the torus semicircularis of the midbrain. Rises and falls in local amplitude are coded by the activity of different pyramidal cell types, E- and I-units, which project to various laminae of the torus above and below lamina 6. The somatotopic organization of the torus allows for computations of spatial patterns in electrosensory information. Within lamina 6, differences in the phase of signals from different parts of the body surface are computed. Differential-phase information is then relayed to deeper laminae of the torus and remains in topographic register with amplitude information. This organization allows for joint evaluation of spatially related patterns of amplitude and phase modulations on the animal's body surface within local neuronal circuits of the torus. A topographic projection of the torus relays amplitude and differential-phase information to the optic tectum where a further joint evaluation of amplitude and phase serves to control behavioral responses. The control of a particular behavioral performance, the 'jamming avoidance response', is of a distributed nature in that the representations of individual sites on the body surface contribute cumulatively to shift the electric organ pacemaker frequency.(ABSTRACT TRUNCATED AT 400 WORDS)

Carbonic anhydrase and horseradish peroxidase: double labelling of rat dorsal root ganglion neurons innervating motor and sensory peripheral nerves.

Dorsal root ganglion neurons supplying peroneus longus, soleus and gastrocnemius medius muscles and the sural nerve of the rat were labelled with horseradish peroxidase and analysed for their carbonic anhydrase content. Staining of the sections was done either on the same or on alternate slides. Both methods led to the same results, despite a slight fading of the carbonic anhydrase reaction in double-stained sections. The data indicated that the muscles under study were supplied by approximately the same number of horseradish peroxidase-labelled cells, irrespective of their differences in size. 74.9% of these labelled neurons had diameters exceeding 30 microns and 52.4% of them also stained for carbonic anhydrase. The double-labelled cells represented 66.9% of the population of large neurons (greater than 30 microns) and comprised most of those measuring over 47.5 microns. Richness in carbonic anhydrase of the large muscle afferent neurons may be linked to their innervation of the stretch receptors, as components of an active apparatus which includes the gamma motor axons which also stain positively for carbonic anhydrase. In contrast, the ganglion cells supplying the sural nerve were almost totally devoid of carbonic anhydrase, as only 6.4% showed double labelling. This contingent possibly represents the muscle afferents of the small motoneural population which supplies, through this nerve, part of the foot musculature of the rat.

The relationship between structural features of peripheral nerves and suture methods for nerve repair.

Based on techniques for identifying and distinguishing motor, sensory, and mixed fasciculi in peripheral nerves, the authors propose guidelines for selecting suture methods for nerve repair. When many mixed fasciculi are known to exist at the nerve lesion, epineurial repair is preferable; fascicular (perineurial) repair is more suitable when pure motor and sensory fasciculi are clearly recognized. Generally, epineurial repair is indicated for more proximal injuries, with fascicular repair most appropriate for more distal sites. A greater ratio of epineurial connective tissue to intrafascicular nervous tissue implies an inclination toward fascicular repair.

1,25(OH)2 vitamin D3 sites of action in spinal cord and sensory ganglion.

Autoradiographic studies revealed concentration of 3H 1,25(OH)2 vitamin D3 in nuclei of certain neurons in the spinal cord of adult and neonatal mice, fed a normal or a vitamin D deficient diet. Nuclear uptake and retention was strongest in motor neurons in lamina IX. Nuclear concentration also existed in neurons of lamina II, lamina VIII, lamina X and intermediate nucleus of the lateral column. The results indicate that these neurons are target neurons which contain nuclear receptors for 1,25(OH)2 vitamin D3. This suggests that 1,25(OH)2 vitamin D3 has direct genomic actions on the innervation of skeletal muscle by exerting related trophic, secretory, and electrophysiological effects. In addition, these data point to direct genomic actions of 1,25(OH)2 vitamin D3 on spinal sensory perception, and on certain autonomic functions. Nuclear binding in certain neurons in the peripheral ganglion of the trigeminal nerve further suggests that sensory perception is influenced by 1,25(OH)2 vitamin D3 not only at the level of the substantia gelatinosa, but also at the level of spinal ganglia.

Sensory, motor and sympathetic neurons forming the common peroneal and tibial nerves in the macaque monkey (Macaca fascicularis).

The motoneurons, dorsal root ganglion (DRG) and sympathetic ganglion (SG) cells forming the common peroneal (CPN) and tibial (TN) nerves of young and semiadult monkeys (Macaca fascicularis) were localised by the horseradish peroxidase method of tracing neuronal connections. The motoneurons forming the CPN occur in the L4-L6 segments, appearing as 1-3 groups and occupying the retroposterolateral (rpl), posterolateral (pl) and central (c) groups of motor nuclei. The motoneurons forming the TN occur in the L4-L7 segments, appearing as 1-4 groups and occupying the rpl, pl, c and anterolateral (al) groups. The motoneurons and DRG cells forming the CPN show peak frequencies at the L5 level, and the SG cells forming the same nerve, at the L6 level in most cases. The motoneurons and DRG cells forming the TN show peak frequencies at the L6 level and the SG cells forming the same nerve, also at the L6 level in most cases. The bulk of motoneurons, DRG and SG cells forming the CPN and TN are concentrated in two segmental levels. For CPN the motoneurons measure between 14-76 micron in their average somal diameters and for TN, 16-70 micron. The majority of them (65.5% for CPN motoneurons and 72% for TN motoneurons) have average somal diameters greater than 38 micron. The size spectrum of the DRG cells forming the CPN is similar to that of DRG cells forming the TN, being 12-78 micron for CPN and 10-76 micron for TN. The sympathetic neurons forming the CPN (measuring 10-44 micron) have a larger size spectrum than those forming the TN (measuring 6-33 micron). The diameter spectrum (3-20 micron for TN and 2-19 micron for CPN) and peak frequency distributions (10 micron for both TN and CPN) of the myelinated fibres present in the CPN and TN are also similar, with the CPN fibres skewing towards a slightly larger size. Many of the fibres in the young and semi-adult monkeys are not yet myelinated.

Receptive field properties of the parabrachio-thalamic taste and mechanoreceptive neurons in rats.

Receptive fields (RFs) of 36 taste (the 22 parabrachio-thalamic relay (P-T) and 14 non-P-T) and 23 mechanoreceptive neurons (7 P-T and 16 non-P-T) were located in the oral cavity of rats. All of the taste and most of the mechanoreceptive units examined had an RF on the ipsilateral side of the tongue or palate, but some mechanoreceptive P-T and non-P-T units had RFs bilaterally. When the RFs of taste neurons were examined with the most effective of the four basic taste (the best stimulus) and non-best stimuli, no difference was noticed in the location of RFs between the P-T and non-P-T neurons. Though most of the P-T neurons (7/11) and all of the non-P-T neurons (6/6) had an RF for non-best stimuli at a region similar to that for the best stimulus, some P-T neurons (4/11) had an RFs for non-best stimulus outside the RF for the best stimulus and/or on the region separate from the RF for the best stimulus. The P-T neurons, responding vigorously to non-optimal stimuli as well as to the best stimulus, had an RF outside the RF for the best stimulus. RFs for mechanical stimulation were also examined in some taste and mechanoreceptive neurons. The mechanoreceptive P-T units rarely had an RF exclusively on the palate. Some mechanoreceptive units had an RF on the region where no taste RF has been found, e.g. the intermolar eminence and the folium of the hard palate.