Stimulation Of Greater Splanchnic Nerve Research Articles

Increasing Blood Pressure by Greater Splanchnic Nerve Stimulation: a Feasibility Study.

The splanchnic vascular compartment is the major reservoir for intravascular blood volume, and dysregulation of the compartment was implicated in a series of cardiovascular conditions. We explored feasibility and effectiveness of an implantable cuff system on the greater splanchnic nerve (GSN) in healthy canines for short- and long-term neuromodulation to affect the circulation. Five mongrel hounds underwent minimally invasive right-sided unilateral GSN cuff placement. All animals underwent same day GSN stimulation and repeat stimulation at 9-30 days. Stimulation parameter optimization was conducted both acutely and chronically. Parameters ranged from 1-250 Hz, 0.25 mA-35 mA, 0.1-0.5 ms, and 30-s pulse duration. Two animals were survived for 9 days and 3 animals for 30 days. Stimulation of the right GSN increased mean arterial blood pressure by 36.9 mmHg ± 13.4 (p < 0.0001), central venous pressure by 6.9 mmHg ± 1.7 (p < 0.0001), and mean pulmonary arterial pressure by 6.3 mmHg ± 2.0 (p < 0.0001). Peak effects were observed within 30 s, and magnitude of effects was comparable between stimulation cycles (p = 0.4). Stimulation-induced changes in hemodynamics were independent of afferent nerve fibers (pain response) or the adrenal gland. Necropsy showed no evidence of nerve damage on histologic studies up to 30 days after implantation. GSN stimulation via an implanted nerve cuff provided a reproducible and rapid method to increase arterial, central venous, and pulmonary arterial pressures. The neuromodulation cuff was well tolerated and elicited a response up to 30 days after implantation. The clinical application of GSN stimulation as a tool to change central and peripheral cardiovascular hemodynamics needs to be explored.

Effects of abdominal or cardiopulmonary sympathetic afferents on upper cervical inspiratory neurons.

Responses of upper cervical inspiratory neurons (UCINs) to abdominal visceral or cardiopulmonary sympathetic stimulation were studied using extracellular recordings from 213 UCINs in 54 pentobarbital sodium-anesthetized and paralyzed rats. Phrenic nerve activity was used to assess inspiration. The UCINs discharging during inspiration only were mainly in the C(1) segment, whereas phase-spanning UCINs were mostly in the C(2) segment. Phase-spanning activity was typically retained after overventilation or vagotomy. When greater splanchnic nerve (GSN) or cardiopulmonary sympathetic afferent (CPSA) fibers were electrically stimulated, augmented UCIN activity was observed in 65% of cells responding to CPSA stimulation but in only 17% of cells responding to GSN. Response latencies were 10.7 +/- 0.5 and 20.6 +/- 1.5 (SE) ms, respectively. Many augmented responses to CPSA stimulation (64%) and all augmented responses to GSN stimulation were followed by suppression of UCIN discharge (biphasic response). Phrenic nerve activity was suppressed by both GSN and CPSA stimulation, but with shorter latency for the latter (29 +/- 0.7 vs. 14.0 +/- 0.7 ms). Excitation of UCINs using CPSA stimulation occurs more often and by a more direct pathway than for GSN input.

Morphological characteristics and electrophysiological responses of visceral nociceptive neurons in somatosensory cerebral cortex of cat

The morphology of intracellular neurobiotin-labeled cortical neurons activated by noxious visceral stimuli in cat was reported. The electrophysiologic properties of 851 neurons and structure of 52 neurons of representative area of the greater splanchnic nerve (GSN) in the primary somatosensory cortex were described. The neurons responding to stimulation of GSN with strong intensity were referred to as viscero-nociceptive neurons (VNNs). Patterns of the responses of VNNs in SI area were excitatory, inhibitory and mixed. According to latency of discharge clusters in response, the VNNs could be classified into two kinds. The neurons only showing long latency were called specific VNNs; those having discharge clusters with both long and short latency induced by stimulus were nonspecific VNNs. Following acquisition of electrophysiological data, neurobiotin was injected into some cells by electrophoresis and their structure and location in the cerebral cortex were studied. The results provided some findings about morphological and electrophysiological characteristics of VNNs in SI area. It is thought that VNNs have more complicated morphology in the dendritic construction and axon distribution than nonvisceral nociceptive neurons (NVNNs). Most of the excitatory VNNs showed pyramidal shape and most of the inhibitory VNNs had stellate shape in camera lucida drawing. The architecture of the nonspecific VNNs might be different from specific VNNs in dendritic distribution.

The central effect of electro-acupuncture analgesia on visceral pain of rats: a study using the [3H] 2-deoxyglucose method.

This study had the objective to understand the central effect of electro-acupuncture analgesia (EAA) on visceral pain of rats. We used the method of Sokoloff's 2-deoxyglucose (2-DG) auto-radiographic quantitative analysis to observe the changes of local cerebral metabolic rate of glucose (LCMRG) in rats given electrical stimulation of greater splanchnic nerve (GSN) followed by electro-acupuncture. From the results of this study, we found that the LCMRG had a significant difference between EAA group and pain group at some structures, such as the spinal thoracic and lumbar dorsal horns (segments T6-T8, L1-L3), locus coeruleus (lc), nucleus raphe magnus (rm), nucleus reticular gigantocellularis (rgi), periaqueductal gray (PAG) and habenulae lateralis (hl) of thalanum. The results combining reports by other investigators, suggest that these local cerebral structures might be the key nuclei in EAA on visceral pain.

Processing of splanchnic and somatic input in thoracic spinal cord of the rat

To better understand the spinal transmission of visceral afferent information, we conducted neurophysiological studies of single spinal neurons that receive input from the greater splanchnic nerve (GSN). Extracellular single-neuron recordings were made in the thoracic spinal cord of chloralose-anesthetized, paralyzed, and artificially ventilated rats, some of which had undergone acute spinal transection at C1. Neurons were divided into four classes according to their responses to GSN stimulation: one-burst excitatory, two-burst excitatory, biphasic, and inhibited. We then studied the characteristics of the convergent somatic input to each class of neurons using either natural somatic stimuli or electrical stimulation of the iliohypogastric nerve (IHN). Most splanchnic input was mediated by unmyelinated fibers, whereas somatic input was mediated by both unmyelinated and small myelinated fibers. Most of the neurons exhibited somatic receptive fields, and the majority responded to both innocuous and noxious somatic stimuli. However, a small number could be excited only by GSN stimulation. Although a careful analysis of response characteristics indicated that there was a tendency for neurons to exhibit similar responses to electrical stimulation of the GSN and the IHN, we observed many combinations of somatic and visceral responses. We suggest that visceral afferent activity, in addition to being processed via convergent somatovisceral pathways, may be processed by neurons that convey only visceral information or by neurons in which visceral and somatic information is differentially coded.

Splanchnic and somatic afferent convergence on cervical spinal neurons of the rat

The rostral cervical spinal cord is increasingly being considered the source of important propriospinal regulation. To better understand the substrate for this function, we investigated the effects of stimulation of the greater splanchnic nerve (GSN) and both thoracic and cervical somatic afferents on the activity of cervical spinal neurons. Extracellular single-neuron recordings were made in the C2-C5 spinal segments of chloralose-anesthetized, paralyzed, and artificially ventilated rats. Neurons were classified according to their responses to GSN stimulation. Neurons were inhibited by this stimulation as frequently as they were excited. We then studied the characteristics of cervical and thoracic convergent somatic input to each class of neurons. Although all cervical neurons that responded to GSN stimulation responded to electrical stimulation of the iliohypogastric nerve (IHN), only the few neurons that exhibited whole body receptive fields (RF) responded to natural thoracic somatic stimuli. Responses to electrical stimulation of the GSN and IHN were similar for most neurons; most exhibited nociceptive cutaneous RFs in cervical dermatomes. These data indicate that input from cervical somatic afferents and from both thoracic visceral and thoracic somatic afferents converge on individual splanchnic-receptive cervical neurons. Although these neurons exhibited the predicted cervical somatic RFs, responses from thoracic levels did not exhibit discrete RFs, requiring instead more synchronous or more spatially convergent input.

Pharmacological properties of a slow C-fiber response induced by stimulation of greater splanchnic nerve in an isolated spinal cord-nerve preparation of the newborn rat

Pharmacological properties of a slow C-fiber response induced by stimulation of greater splanchnic nerve in an isolated spinal cord-nerve preparation of the newborn rat

Pharmacological properties of a slow C-fiber response induced by stimulation of greater splanchnic nerve in an isolated spinal cord-nerve preparation of the newborn rat

Pharmacological properties of a slow C-fiber response induced by stimulation of greater splanchnic nerve in an isolated spinal cord-nerve preparation of the newborn rat

Parabrachial nucleus: neuronal evoked responses to gastric vagal and greater splanchnic nerve stimulation

Unitary responses were recorded extracellularly in the parabrachial nucleus (PBN) in anesthetized cats during electrical stimulation of the 1) gastric branches of the ventral and dorsal vagal trunks which serve the proximal stomach, and 2) left greater splanchnic nerve. The gastric vagally evoked parabrachial responses consisted of phasic single and multiple spike orthodromic discharges, which were bilaterally distributed, with a mean latency of 349 ms (S.D. ± 38.5). The parabrachial-evoked splanchnic unitary responses had a much shorter latency with a bimodal distribution (mean latencies, 53 and 128 ms, respectively). Convergence of gastric vagal input from the proximal stomach and the left greater splanchnic nerve upon single neurons in the PBN was electrophysiologically demonstrated in 132 units. Eighty-seven percent of the gastric vagally evoked parabrachial unitary responses were inhibited by simultaneous electrical stimulation of the splanchnic nerve. The condition-test paradigm was used to evaluate the time course of the splanchnic inhibition of the gastric vagally evoked parabrachial response. Reciprocal connections between neuronal populations in the nucleus tractus solitarius (NTS) which received gastric vagal input and the PBN were also identified electrophysiologically by direct microstimulation of the former structure. The density and characteristics of the gastric vagal and greater splanchnic input to the PBN suggested that this nucleus receives and processes a substantial amount of visceral afferent input. The PBN may serve as an important site for integrating visceral information governing the proximal stomach and ingestive processes.

Time course of renal responses to greater splanchnic nerve stimulation

The objective of the present study was to describe the time courses of renal responses during renal sympathetic stimulation and to determine whether the kidney can provide a sustained response to sympathetic stimulation for 3 h. In four pentobarbital sodium-anesthetized dogs, stimulation (3.3 Hz) of a greater splanchnic nerve (GSN) on one side caused reductions in renal blood flow (RBF) and sodium excretion (UNaV) of both stimulated and contralateral-denervated kidneys, plus an increase in plasma renin activity (PRA). During continued stimulation, RBF partially recovered, but UNaV fell to less than 5% of control and PRA rose and remained at least eight times above control. In nine dogs, a single GSN was stimulated after ipsilateral adrenal medullectomy and ligation of the splanchnic circulation. The acute response to GSN stimulation was now confined to the ipsilateral kidney. Ipsilateral RBF fell by 32 +/- 10% but returned to 85 +/- 5% of control values by the end of the stimulation period. Contralateral RBF fell slowly by approximately 10%. Ipsilateral and contralateral UNaV fell to 34 +/- 10 and 43 +/- 11% of control values, respectively. PRA increased rapidly at the onset of GSN stimulation and remained at least 2.8 times control levels. After stimulation, RBF, UNaV, and PRA returned toward control levels. These results confirm the findings of others that the response of the renal vasculature to sympathetic stimulation is mainly transient. However, they additionally demonstrate a strong and sustained decrease in UNaV lasting for the total 3-h period of sympathetic stimulation.

Pharmacological properties of a c-fiber response evoked by stimulation of greater splanchnic nerve in an isolated spinal cord-nerve preparation of the newborn rat

Pharmacological properties of a c-fiber response evoked by stimulation of greater splanchnic nerve in an isolated spinal cord-nerve preparation of the newborn rat

Splanchnic input to thoracic spinal neurons and its supraspinal modulation in the rat

The unitary responses of 62 T 8–T 11 spinal neurons were recorded extracellularly following electrical stimulation of the greater splanchnic nerve (GSN) in chloralose-anesthetized rats. Recorded neurons were found inboth the dorsal and ventral horns. Fifty-seven neurons increased their firing rate in response to GSN stimulation; 8 of these exhibited biphasic responses consisting of excitations followed by inhibitions. Excitatory responses to GSN stimulation consisted of either one or two bursts with latencies consistent with activation by either Aδ or C fibers. GSN stimulation inhibited 5 neurons. The effects of reversible spinalization on spontaneous activity and on both synchronous and non-synchronous (afterdischarge) GSN-evoked responses were investigated using a cooling probe on the spinal cord between C 1 and C 2. Of 29 neurons tested in this way, 9 exhibited opposite directional changes in their spontaneous activities and their GSN-evoked responses upon spinalization. Differential effects of cold-block on first and second bursts, or on Aδ- and C-fiber mediated responses, were not usually observed. However, differential effects of cold-block on synchronous and non-synchronous portions of the overall GSN-evoked response were often observed in that their magnitudes often changed independently of one another. Supraspinal pathways contributed to GSN-evoked responses of several neurons because their responses were diminished during cooling while spontaneous activity was increased or unchanged. These decreases in the magnitude of the GSN-evoked response were not always accounted for by decreases in the synchronous portions of the responses. However, most neurons did exhibit decreases in the number of non-synchronous responses, or afterdischarges, during spinal cooling, exhibiting in some cases biphasic responses. This study provides evidence for strong supraspinal regulation of splanchnic afferent input to the spinal cord of the rat. Further, this regulation exhibits some specificity toward different portions of splanchnic-evoked responses in spinal neurons.

Extrinsic innervation of the canine abdominal vena cava and the origin of cholinergic vasoconstrictor nerves.

1. The effects of electrical stimulation of the greater splanchnic nerve and the vagus nerve on the middle segment of the inferior vena cava (i.v.c.) were studied in anaesthetized and unilaterally or bilaterally adrenalectomized dogs. The vascular response of the segment was measured as the change in pressure of an intravascular cuff inserted into the lumen of the segment.2. Electrical stimulation of the greater splanchnic nerve of either side caused an increase in the tension of the vein with a delay of less than 3 sec. The tension increased with frequency of stimulation until it reached a maximum at the frequency of 32 Hz. The maximum tension development was consistently larger, by a factor of about two, when the right greater splanchnic nerve was stimulated than when the left was. It seems that the right greater splanchnic nerve supplies more sympathetic nerve fibres to the middle segment of the i.v.c. than does the left.3. The response to electrical stimulation of the right or left greater splanchnic nerve was markedly reduced by phentolamine or hexamethonium. The response remaining after treatment with phentolamine or hexamethonium was augmented by neostigmine and diminished by atropine.4. The electrical stimulation of the vagus nerve elicited no response of the vein before and after treatment with neostigmine.5. The effects of electrical stimulation of the right greater splanchnic nerve were further confirmed by a preparation in which the middle segment of the i.v.c. was perfused with Krebs solution in situ. The relation between the frequency of stimulation and the magnitude of the response was almost the same as in the in vivo experiments.6. It was also confirmed in the perfused preparation that the response to electrical stimulation of the right greater splanchnic nerve was reduced by phentolamine and the remaining response was augmented by neostigmine and abolished by atropine.7. Our data show that the middle segment of the canine i.v.c. receives both adrenergic and cholinergic excitatory innervation, preferentially via the right greater splanchnic nerve.8. The infrarenal segment of the i.v.c. was also examined in the in vivo experiment, in which it was shown that this segment received much clearer dominant innervation of the right greater splanchnic nerve.9. The infrarenal segment of the i.v.c. is also supplied with excitatory adrenergic fibres and, in some cases, with the cholinergic ones from the right greater splanchnic nerve.