Comparative study of effects of cortical nucleus of amygdala and pyriform cortex on activity of bulbar respiratory neurons in cats

Comparative microelectrophysiological study of character and peculiarities of effects of the cortical nucleus of amygdala and of the periamygdalar area of pyriform cortex on impulse activity was performed on the same single functionally identified respiratory medullar neurons. A high reactivity of bulbar respiratory neurons on stimulation is established in both studied limbic structures. There is established the qualitatively different character of their response reactions at stimulation of the cortical amygdala nucleus and the periamygdalar cortex. The cortical amygdala nucleus has been shown to produce on the activity of medullar respiratory neurons both facilitating and inhibitory action with predominance of the activating one (without topographical orderliness). The effect of periamygdalar cortex at stimulation of various parts was characterized by topographic differentiation. The suppressing reactions of neurons in the majority of cases were recorded at stimulation of the rostral area of periamygdalar cortex, whereas the excitatory reactions--at stimulation of its caudal part. Functional organization of respiratory control of the studied limbic system structures is discussed.     

Comparative study of effect of cortical nucleus of amygdala and pyriform cortex on activity of bulbar respiratory neurons in cats

Comparative microelectrophysiological study of character and peculiarities of effects of the cortical nucleus of amygdala and of the periamygdalar area of pyriform cortex on impulse activity was performed on the same single functionally identified respiratory medullar neurons. A high reactivity of bulbar respiratory neurons to stimulation is established in both studied limbic structures. There is established the qualitatively different character of their response reactions at stimulation of the cortical amygdala nucleus and the periamygdalar cortex. The cortical amygdala nucleus has been shown to produce both facilitating and inhibitory effects (with predominance of the activating one) on activity of medullar respiratory neurons (without topographical orderliness). The effect of periamygdalar cortex at stimulation of various parts was characterized by topographic differentiation. The suppressing reactions of neurons in the majority of cases were recorded at stimulation of the rostral area of periamygdalar cortex, whereas the excitatory reactions-at stimulation of its caudal part. Functional organization of respiratory control of the studied limbic system structures is discussed.     

Responses of limbic cortical neurons to stimulation of splanchnic and sciatic nerves and of the mammillary bodies

Spontaneous and evoked unit activity in the anterior limbic cortex in response to stimulation of the splanchnic and sciatic nerves and of the mammillary region of the hypothalamus were recorded extracellularly in acute experiments on cats. The study of heterogeneous transsynaptic influence on limbic cortical neurons showed that in the presence of effective sensory viscerosomatic convergence, weak convergence of influences from the central hypothalamic and peripheral sources took place. Short-latency responses of limbic cortical neurons to stimulation of the mammillary bodies consisted of orthodromic and antidromic responses, evidence of the existence of short two-way connections between the anterior limbic cortex and mammillary nuclei of the hypothalamus.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 419–426, September–October, 1979.     

Nerves and nerve plexuses of the human vertebral column

The origin, distribution, and termination pattern of nerves supplying the vertebral column and its associated structures have been studied in the human fetus by means of an acetylcholinesterase whole-mount method. The vertebral column is surrounded by ventral and dorsal nerve plexuses which are interconnected. The ventral nerve plexus consists of the nerve plexus associated with the anterior longitudinal ligament. This longitudinally oriented nerve plexus has a bilateral supply from many small branches of the sympathetic trunk, rami communicantes, and perivascular nerve plexuses of segmental arteries. In the thoracic region, the ventral nerve plexus also is connected to the nerve plexuses of costovertebral joints. The dorsal nerve plexus is made up of the nerve plexus associated with the posterior longitudinal ligament. This nerve plexus is more irregular and receives contributions only from the sinu-vertebral nerves. The sinu-vertebral nerves originate from the rami communicantes and, in the cervical region, also from the nerve plexus of the vertebral artery. Thick and thin sinu-vertebral nerves are found. Most frequently three types of thick sinu-vertebral nerves are observed, i.e., ascending, descending, or dichotomizing ones. Finally, the distribution of the branches of the ventral and dorsal nerve plexuses and of the sinu-vertebral nerves is described.     

Visceral nociception: peripheral and central aspects of visceral nociceptive systems

Discomfort and pain are the sensations most commonly evoked from viscera. Most nociceptive signals that originate from visceral organs reach the central nervous system (c.n.s.) via afferent fibres in sympathetic nerves, whereas parasympathetic nerves contain mainly those visceral afferent fibres concerned with the non-sensory aspects of visceral afferent function. Noxious stimulation of viscera activates a variety of specific and non-specific receptors, the vast majority of which are connected to unmyelinated afferent fibres. Studies on the mechanisms of visceral sensation can thus provide information on the more general functions of unmyelinated afferent fibres. Specific visceral nociceptors have been found in the heart, lungs, testes and biliary system, whereas noxious stimulation of the gastro-intestinal tract appears to be detected mainly by non-specific visceral receptors that use an intensity-encoding mechanism. Visceral nociceptive messages are conveyed to the spinal cord by relatively few visceral afferent fibres which activate many central neurons by extensive functional divergence through polysynaptic pathways. Impulses in visceral afferent fibres excite spinal cord neurons also driven by somatic inputs from the corresponding dermatome (viscero-somatic neurons). Noxious intensities of visceral stimulation are needed to activate viscero-somatic neurons, most of which can also be excited by noxious stimulation of their somatic receptive fields. The visceral input to some viscero-somatic neurons in the spinal cord can be mediated via long supraspinal loops. Pathways of projection of viscero-somatic neurons include the spino-reticular and spino-thalamic tracts. All these findings give experimental support to the 'convergence-projection' theory of referred visceral pain. Visceral pain is the consequence of the diffuse activation of somato-sensory nociceptive systems in a manner that prevents accurate spatial discrimination or localization of the stimuli. Noxious stimulation of visceral receptors triggers general reactions of alertness and arousal and evokes unpleasant and poorly localized sensory experiences. This type of response may be a feature of sensory systems dominated by unmyelinated afferent inputs.     

Organization of the Viscerosomatic Afferent Projections to Fields 24 and 25 of the Cingulate Gyrus of the Cat Brain Cortex

We studied evoked potentials (EP) and responses of single neurons in fields 24 and 25 of the cingulate gyrus of the cat brain cortex. The responses were elicited by stimulations of a parasympathetic, a sympathetic, and a somatic nerve (the pelvic, splanchnic, and sciatic nerves). The configuration and amplitude/temporal characteristics of both EP and neuronal responses showed that the organization of the visceral and somatic afferent inputs to the cortical fields under study is to a great extent similar. Localization of the foci of maximum activity for EP within field 24 and their overlapping, the higher responsiveness of the neurons of this field to afferent volleys as compared with that in field 25, the dominance of short-latency neuronal responses in field 24, and the presence of polysensory neurons with modally specific opposite responses in this field allow us to conclude that field 24 (compared with field 25) plays a more significant role in the perception and analysis of viscerosomatic afferent information. Taking into account earlier published data that the zones of concentration of the efferent neurons (forming a descending limbico-sympathetic discharge in the L2-L3 white connective branches and a limbico-parasympathetic discharge in the pelvic nerve) are localized within field 25 and overlap each other, we discuss the functional roles of fields 24 and 25 of the cingulate gyrus in viscerosensory and visceromotor control.     

Conducting pathways of the rabbit lumbar sympathetic ganglia

Conducting pathways of ganglia from the lumbar portion (L₃–L₅) of the sympathetic trunk in rabbits were studied by recording action potentials from nerves of the ganglia evoked by stimulation of other nerves of these ganglia, and by intracellular recording from single neurons. Besides the well-known system of descending preganglionic fibers, which enter the trunk through white rami communicantes and, as they pass through the ganglia, form synapses on ganglionic neurons, some preganglionic fibers were shown to enter the sympathetic chain through gray rami communicantes and to run in both ascending and descending directions, forming synaptic connections with neurons of the lumbar ganglia.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 247–254, March–April, 1984.     

Effectiveness of ascending synaptic influences from various spinal funiculi on reticulospinal neurons in cats

Activity of reticulospinal neurons evoked by stimulation of the ventral, ventrolateral, dorsolateral, and dorsal funiculi of the spinal cord was recorded extracellularly in cats anesthetized with chloralose. Responses of 57 reticulospinal neurons, of which 22 projected into the ventral funiculus, 20 into the ventrolateral, and 15 into the dorsolateral, were studied. The functional properties (conduction velocity and refractory period) and the location of the neurons of the above-mentioned groups in the medulla did not differ appreciably. The most effective synaptic activation of all neurons was observed during stimulation of the dorsal and dorsolateral funiculi. Responses to stimulation of the dorsal funiculus had the lowest threshold. These responses arose in reticulospinal neurons of the ventral and ventrolateral funiculi after the shortest latent period. The effectiveness of synaptic influences from the dorsal and dorsolateral funiculi was identical in the group of neurons of the dorsolateral funiculus. Correlation between activity evoked by stimulation of the dorsal funiculus in reticulospinal neurons and peripheral nerves indicated that the responses appeared in these cells to stimulation of muscular (groups I and II) and cutaneous (group II) afferent fibers. The results indicate that impulses from low-threshold muscular and cutaneous afferents, which effectively activate reticulospinal neurons, are transmitted along ascending pathways of the dorsal funiculi.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 11, No. 3, pp. 254–263, May–June, 1979.     

Apnea-Induced Cortical BOLD-fMRI and Peripheral Sympathoneural Firing Response Patterns of Awake Healthy Humans

End-expiratory breath-holds (BH) and Mueller manoeuvres (MM) elicit large increases in muscle sympathetic nerve activity (MSNA). In 16 healthy humans (9♀, 35±4 years) we used functional magnetic resonance imaging with blood oxygen level-dependent (BOLD) contrast to determine the cortical network associated with such sympathoexcitation. We hypothesized that increases in MSNA evoked by these simulated apneas are accompanied by BOLD contrast changes in the insular cortex, thalamus and limbic cortex. A series of 150 whole-brain images were collected during 3 randomly performed 16-second end-expiratory BHs and MMs (-30 mmHg). The identical protocol was repeated separately with MSNA recorded from the fibular nerve. The time course of the sympathoexcitatory response to both breathing tasks were correlated with whole-brain BOLD signal changes. Brain sites demonstrating both positive (activation) and negative (deactivation) correlations with the MSNA time course were identified. Sympathetic burst incidence increased (p<0.001) from 29±6 (rest) to 49±6 (BH) and 47±6 bursts/100 heartbeats (MM). Increased neural activity (Z-scores) was identified in the right posterior and anterior insular cortices (3.74, 3.64), dorsal anterior cingulate (3.42), fastigial and dentate cerebellar nuclei (3.02, 3.34). Signal intensity decreased in the left posterior insula (3.28) and ventral anterior cingulate (3.01). Apnea both activates and inhibits elements of a cortical network involved in the generation of sympathetic outflow. These findings identify a neuroanatomical substrate to guide future investigations into central mechanisms contributing to disorders characterized by elevated basal MSNA and exaggerated sympathetic responses to simulated apneas such as sleep apnea and heart failure.     

Activation of slowly conducting medullary raphe-spinal neurons, including serotonergic neurons, increases cutaneous sympathetic vasomotor discharge in rabbit

Neurons in the rostral medullary raphe/parapyramidal region regulate cutaneous sympathetic nerve discharge. Using focal electrical stimulation at different dorsoventral raphe/parapyramidal sites in anesthetized rabbits, we have now demonstrated that increases in ear pinna cutaneous sympathetic nerve discharge can be elicited only from sites within 1 mm of the ventral surface of the medulla. By comparing the latency to sympathetic discharge following stimulation at the ventral raphe site with the corresponding latency following stimulation of the spinal cord [third thoracic (T3) dorsolateral funiculus] we determined that the axonal conduction velocity of raphe-spinal neurons exciting ear pinna sympathetic vasomotor nerves is 0.8 +/- 0.1 m/s (n = 6, range 0.6-1.1 m/s). Applications of the 5-hydroxytryptamine (HT)(2A) antagonist trans-4-((3Z)3-[(2-dimethylaminoethyl)oxyimino]-3-(2-fluorophenyl)propen-1-yl)-phenol, hemifumarate (SR-46349B, 80 microg/kg in 0.8 ml) to the cerebrospinal fluid above thoracic spinal cord (T1-T7), but not the lumbar spinal cord (L2-L4), reduced raphe-evoked increases in ear pinna sympathetic vasomotor discharge from 43 +/- 9 to 16 +/- 6% (P < 0.01, n = 8). Subsequent application of the excitatory amino acid (EAA) antagonist kynurenic acid (25 micromol in 0.5 ml) substantially reduced the remaining evoked discharge (22 +/- 8 to 6 +/- 6%, P < 0.05, n = 5). Our conduction velocity data demonstrate that only slowly conducting raphe-spinal axons, in the unmyelinated range, contribute to sympathetic cutaneous vasomotor discharge evoked by electrical stimulation of the medullary raphe/parapyramidal region. Our pharmacological data provide evidence that raphe-spinal neurons using 5-HT as a neurotransmitter contribute to excitation of sympathetic preganglionic neurons regulating cutaneous vasomotor discharge. Raphe-spinal neurons using an EAA, perhaps glutamate, make a substantial contribution to the ear sympathetic nerve discharge evoked by raphe stimulation.     

Possible mechanisms of the anterior limbic cortex influence on the neuron activity of the vago-solitary complex

In ananesthetized cats, neurons of the nucleus of the tractus solitarius (NTS) and the dorsal motor nucleus of the vagus nerve (DMNV) revealed phasic excitatory responses to separate single vagal and cortical stimuli. Stimulation of the anterior limbic cortex combined with vagal stimulation resulted in inhibitory or excitatory modification of the vagal induced responses of the NTS and DMNV neurons. The data obtained suggest that complete inhibitory effects are related to general cortical mechanisms of control of the functional state of the brain stem visceral neurons. Selective inhibition of the vagal induced responses by limbic cortex stimulation is due to particular cortical mechanisms of the visceral sensory transmission control via the NTS neurons.     

Projections of the posterior area of the hypothalamus to its medial,anterior, and lateral areas

The effect of stimulation of the lateral and medial supramammillary areas of the posterior hypothalamus on spontaneous single unit activity in the anterior, lateral, medial dorsal, and medial ventral areas of the hypothalamus was investigated in acute experiments on rabbits. Single stimulation of the medial area of the posterior hypothalamus evoked responses of 44% of neurons, whereas stimulation of the lateral area did so in only 35% of all neurons recorded. Repetitive stimulation led to an increase in the number of responding neurons (to 57% during stimulation of the lateral and 74% during stimulation of the medial supramammillary area). In response to repetitive stimulation of the medial supramammillary area, activating influences became predominant in all areas, whereas in response to stimulation of the lateral area, they became predominant in the medial, ventral, and lateral areas. The results are assessed from the standpoint of the role of the posterior hypothalamus in the regulation of adenohypophyseal functions.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 9, No. 4, pp. 377–381, July–August, 1977.     

Modulation by arginine vasopressin of glutamate excitation in the ventral septal area of the rat brain

Arginine vasopressin is hypothesized to act as a neurotransmitter or neuromodulator in the ventral septal area of the rat brain. To examine this role of vasopressin further, it was applied by microiontophoresis or micropressure from multiple-barrelled micropipettes onto spontaneously active or glutamate-activated neurons. Applied in this manner, vasopressin reduced glutamate-evoked excitation in 32 of the 47 cells studied. Further, micropressure application of the vasopressin antagonist d(CH2)5Tyr(Me)AVP reversed the vasopressin effects. In contrast, administration of vasopressin had no effect on excitations evoked by acetylcholine iontophoresis or on the spontaneous activity of the majority of the ventral septal neurons studied. These observations suggest that vasopressin may be acting on a V1-like receptor on specific neurons in the ventral septal area as a modulator of glutamate actions. Evoked responses were also obtained in the same population of ventral septal cells following stimulation of a variety of limbic areas. Inhibitory input onto most of the vasopressin responsive neurons studied was obtained following electrical stimulation of the paraventricular nucleus and bed nucleus of the stria terminalis, two cell groupings that are potential sources of vasopressin to the ventral septal area. Thus, the similarity in action of exogenously applied vasopressin and the evoked responses following paraventricular nucleus and bed nucleus stimulation suggests that vasopressin may be a neurotransmitter in this pathway.     

Depletions in the cervical and thoracolumbar sympathetic system following removal of neural crest from the embryo of Chelydra serpentina

Neural crest and dorsal neural tube of cervical and thoracolumbar levels were removed from embryos of Chelydra serpentina at stages ranging from 8 to 18 somites. Extirpation extended from the levels of the last four somites posteriorly around the neurenteric canal. Deficiencies in sensory and sympathetic ganglia occurred. Motor roots of the associated spinal nerves differentiated. In the absence of postganglionic neurons, the preganglionic fibers form a neuron-free plexus in the thoracolumbar region. Some observations in the cervical region indicate that the postganglionic neurons depend on preganglionic fibers for their differentiation. The cortex of the adrenal gland formed without related medulla in appropriate experiments. The normal morphology of the sympathetic trunks is illustrated. Superficial and deep cervical sympathetic trunks are described. The latter ascends the neck in a paravertebral position. Along its course are segmental ganglia and rami communicantes; it terminates by joining the medial branch of the superficial sympathetic trunk rostral to the ninth cranial nerve.     

Modulation of cerebral acetylcholine metabolism by the dorsal diencephalic conduction system in the rat

We investigated the effects of interruption of the impulse flow in the habenulopeduncular pathways by local infusion of tetrodotoxin on the acetylcholine and choline content in selected dopamine rich regions in the forebrain and midbrain in rats. The tetrodotoxin infusion caused a marked increase in acetylcholine content in the medial frontal cortex, striatum and ventral tegmental area+interpeduncular nucleus, but not in the limbic area or the substantia nigra, whereas choline content was reduced only in both the striatum and ventral tegmental area+interpeduncular nucleus. There was an increase in 3,4-dihydroxyphenylacetic acid content in the striatum after the manipulation. These findings suggest that the dorsal diencephalic conduction system may be involved in the integration of the activity of cholinergic neurons in the forebrain and midbrain regions and striatal dopanine neurons may play a role in the modulation of cholinergic neurons.     

Innervation of the dermatomes in the neck of the mouse

The dorsal rami of the cervical and thoracic spinal nerves were investigated using both the in situ cholinesterase staining technique and cholinesterase staining on serial sections of plastic-embedded embryos. In most cases only the dorsal rami of the 2nd to 5th cervical spinal nerve possess cutaneous branches. The area innervated by the cutaneous branch of the dorsal ramus of the 5th spinal nerve borders on an area innervated by the cutaneous branch of the dorsal ramus of the 1st thoracic spinal nerve. The dorsal rami of the cervical spinal nerves 6-8 show no cutaneous branches. Therefore the gap in the series of the dorsal cutaneous branches is due only to the middle part of the nerves of the brachial plexus, which range from the 5th cervical nerve to the 1st thoracic nerve.     

Mechanisms of reflex bladder activation by pudendal afferents

Activation of pudendal afferents can evoke bladder contraction or relaxation dependent on the frequency of stimulation, but the mechanisms of reflex bladder excitation evoked by pudendal afferent stimulation are unknown. The objective of this study was to determine the contributions of sympathetic and parasympathetic mechanisms to bladder contractions evoked by stimulation of the dorsal nerve of the penis (DNP) in α-chloralose anesthetized adult male cats. Bladder contractions were evoked by DNP stimulation only above a bladder volume threshold equal to 73 ± 12% of the distension-evoked reflex contraction volume threshold. Bilateral hypogastric nerve transection (to eliminate sympathetic innervation of the bladder) or administration of propranolol (a β-adrenergic antagonist) decreased the stimulation-evoked and distension-evoked volume thresholds by -25% to -39%. Neither hypogastric nerve transection nor propranolol affected contraction magnitude, and robust bladder contractions were still evoked by stimulation at volume thresholds below the distension-evoked volume threshold. As well, inhibition of distention-evoked reflex bladder contractions by 10 Hz stimulation of the DNP was preserved following bilateral hypogastric nerve transection. Administration of phentolamine (an α-adrenergic antagonist) increased stimulation-evoked and distension-evoked volume thresholds by 18%, but again, robust contractions were still evoked by stimulation at volumes below the distension-evoked threshold. These results indicate that sympathetic mechanisms contribute to establishing the volume dependence of reflex contractions but are not critical to the excitatory pudendal to bladder reflex. A strong correlation between the magnitude of stimulation-evoked bladder contractions and bladder volume supports that convergence of pelvic afferents and pudendal afferents is responsible for bladder excitation evoked by pudendal afferents. Further, abolition of stimulation-evoked bladder contractions following administration of hexamethonium bromide confirmed that contractions were generated by pelvic efferent activation via the pelvic ganglion. These findings indicate that pudendal afferent stimulation evokes bladder contractions through convergence with pelvic afferents to increase pelvic efferent activity.     

Unit responses in area 5b of the suprasylvian gyrus to stimulation of the ventral posterolateral thalamic nucleus

Unanesthetized cats were immobilized with D-tubocurarine. Single unit responses in area 5b of the suprasylvian gyrus to stimulation of the ventral posterolateral thalamic nucleus were recorded extracellularly. Of the total number of neurons tested, 32% were excited and 3% inhibited. In 65% of neurons the responses were mixed, most of them being predominantly excitatory. Repetitive stimulation of the ventral posterolateral nucleus (6–9/sec) frequently intensified the excitatory component of the responses. Sometimes inhibition, present in the response to a single stimulus, was replaced by increased excitation. However, the same response as to a single stimulus frequently appeared in response to each consecutive stimulus of a series. Stimulation of the ventral posterolateral nucleus had a mainly excitatory effect on neurons in area 5b. Stimulation of the dorsal lateral nucleus, on the other hand, inhibited their activity. This antagonism could also be observed on the same neuron. It was concluded from the short latent periods of the orthodromic responses (3–6 msec) and from the antidromic responses of the cortical neurons to stimulation of the ventral posterolateral nucleus that this nucleus has direct two-way connections with the cortex of area 5b.     

Review of spino-occipital and spinal nerves in Tetraodontiformes,with special reference to pectoral and pelvic fin muscle innervation

The spino-occipital nerve (SO) and ventral rami of the spinal nerves (SV) in 10 tetraodontiform families and 5 outgroup taxa were examined, with special reference to pectoral and pelvic fin muscle innervation. Compared with the outgroup taxa, tetraodontiforms were characteristic in having SO3 + SV1 (SO3 in tetraodontids) that gave off several lateral subbranches to the pectoral fin base and SO participation in infracarinalis anterior innervation. SO and SV1 were connected with one another (6 patterns) before entering the pectoral fin muscles in most species, including the outgroup taxa, resulting in the participation of SV1 in the innervation of almost all of the pectoral fin muscles. SO3 + SV1 was present in all tetraodontiforms (except in 2 tetraodontids having only SO3) and the outgroup taxa, an upper dorsal branch uniformly extending dorsally into the pectoral fin base. The pectoral fin base also received a branch ventrally, but its identity differed (participation or nonparticipation of SV2). SV1 alone constituting the branch was a derived condition occurring in Aracanidae, Ostraciidae, Tetraodontidae, Diodontidae, and Molidae. No strong characters supporting a tetraodontiform sister group were recognized among the spino-occipital nerve and ventral rami of spinal nerves.     

Glyoxylic acid induced fluorescence in the nervous system of Gyratrix hermaphroditus (Kalyptorhynchia,Polycystididae)

Catecholamines (CAs) are found in the neuropile of the brain, in 3 pairs of longitudinal nerve cords, in the transverse ventral commissure, in anterior ventral and dorsal nerves, in two pharyngeal nerve rings and in 24 neurons in the nervous system of Gyratrix hermaphroditus. The CA distribution pattern in compared with those of other neuroactive substances. Homology of neurons in the family of Polycystididae and in Plathelminthes in general is discussed.