Character of evoked responses of the dorsomedial thalamic nucleus to stimulation of the periamygdalar cortex and area amygdaloidea anterior in rats

Characteristics of focal potentials and single unit responses of the dorsomedial nucleus of the thalamus to electrical stimulation of the anterior periamygdalar cortex (APC) and area amygdaloidea anterior (AAA) were compared in acute experiments on rats. Differences were found in the parameters, dynamics, and duration of the recovery cycle of focal potentials in response to stimulation of APC and AAA. Stimulation of APC and AAA was accompanied by changes in the discharges of 26.9 and 19.2% of neurons studied respectively. Four types of unit responses are described: activating (64.3% of responding cells), biphasic activating (14.3%), inhibitory or inhibitory-activating (14.3%), and complex (7.1%). Spontaneous activity was exhibited by 25% of reacting cells. Stimulation of APC was shown to give rise to both shortlatency (12–18 msec) and long-latency (23–66 msec) phasic activating responses of the neurons whereas the latent periods of the analogous responses to stimulation of AAA exceeded 20 msec (from 21 to 136 msec). Unit responses of the second type consisted of a principal phasic response of three or four spikes with mean latent periods of 9–19.1 msec, preceded by a single short-latency (2.9–4.1 msec) spike. Responses of the first two types were characteristic of 92.9 and 64.3% of neurons responding to stimulation of APC and AAA respectively.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 6, pp. 604–611, November–December, 1981.     

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.     

Swallowing reflex and brain stem neurons activated by superior laryngeal nerve stimulation in the mouse

The purpose of the present study was to identify vagal subnuclei that participate in reflex swallowing in response to electrical stimulation of the left superior laryngeal nerve (SLN). SLN stimulation at 10 Hz evoked primary peristalsis, including oropharyngeal and esophageal peristalsis, and LES relaxation. It also induced c-fos expression in interneurons in the interstitial (SolI), intermediate (SolIM), central (SolCe), dorsomedial (SolDM) and commissural (SolC) solitary subnuclei. Neurons in parvicellular reticular nucleus (PCRt) and area postrema (AP) and motoneurons in the semicompact (NAsc), loose (NAl), and compact (NAc) formations of the nucleus ambiguus and both rostral (DMVr) and caudal (DMVc) parts of the dorsal motor nucleus of vagus were also activated. The activated neurons represent all neurons concerned with afferent SLN-mediated reflexes, including the swallowing-related neurons. SLN stimulation at 5 Hz elicited oropharyngeal and LES but not esophageal responses and evoked c-fos expression in neurons in SolI, SolIM, SolDM, PCRt, AP, NAsc, NAl, and DMVc but not in SolCe, NAc, or DMVr. These data are consistent with the role of SolI, SolIM, SolDM, NAsc, NAl, and DMVc circuit in oropharyngeal peristalsis and LES relaxation and SolCe, NAc, DMVc, and DMVr in esophageal peristalsis and LES responses.     

The influence of damage to the septum pellucidum on the effects of electrical stimulation of the hypothalamus in rabbits]

In chronic experiments the influences of septal lesions on the behavioural emotional effects of electrical stimulation of various hypothalamic nuclei were investigated. The total ablation of the septum caused irreversible increase of the lateral hypothalamus self-stimulation and reversal of the negative emotional responses (escape--avoidance) to the medial hypothalamus stimulation into the positive self-stimulation behaviour. When the septal ablation was only partial, involving mainly the medial nucleus, effects were weaker and lasted only 2-3 days after the surgery. The role of the septum in the septohippocampal behavioural inhibition system (J. Gray) is discussed.     

Functional identification of central pressor pathways originating in the subfornical organ

The functional projections from pressor sites in the subfornical organ (SFO) were identified using the 2-deoxyglucose (2-DG) autoradiographic method in urethane-anesthetized, sinoaortic-denervated rats. Autoradiographs of brain and spinal cord sections taken from rats whose SFO was continuously stimulated electrically for 45 min with stereotaxically placed monopolar electrodes (150 microA, 1.5-ms pulse duration, 15 Hz) following injection of tritiated 2-DG were compared with control rats that received intravenous infusions of pressor doses of phenylephrine to mimic the increase in arterial pressure observed during SFO stimulation. Comparisons were also made to autoradiographs from rats in which the ventral fornical commissure (CFV), just dorsal to the SFO, was electrically stimulated. The pressor responses during either electrical stimulation of the SFO or intravenous infusion of phenylephrine were similar in magnitude. On the other hand, stimulation of the CFV did not elicit a significant pressor response. Electrical stimulation of the SFO increased 2-DG uptake, in comparison to the phenylephrine-infused rats, in the nucleus triangularis, septofimbrial nucleus, lateral septal nucleus, nucleus accumbens, bed nucleus of the stria terminalis, dorsal and ventral nucleus medianus (median preoptic nucleus), paraventricular nucleus of the thalamus, hippocampus, supraoptic nucleus, suprachiasmatic nucleus, paraventricular nucleus of the hypothalamus, and the intermediolateral nucleus of and central autonomic area of the thoracic spinal cord. In contrast, in rats whose CFV was stimulated, these nuclei did not demonstrate changes in 2-DG uptake compared with control animals that received pressor doses of phenylephrine. These data have demonstrated some of the components of the neural circuitry likely involved in mediating the pressor responses to stimulation of the SFO and the corrective responses to activation of the SFO by disturbances to circulatory and fluid balance homeostasis.     

电刺激大鼠尾核头部镇痛的中枢效应—[^3H]—2脱氧...

Sokoloff's 2-deoxyglucose (2-DG) autoradiographic technique was used to identify changes of glucose metabolic rate in the rat brain following unilateral stimulation of the head of the caudate nucleus. The results were as follows. The local glucose metabolic rate after noxious stimulation was increased in the somatosensory cortex, cingulate cortex, ventroposterior and parafascicular nucleus of the thalamus, septal area, habenular nucleus, head of caudate nucleus, periaqueductal gray (PAG) and dorsal raphe nucleus (P < 0.05). After stimulating the head of the caudate nucleus, the local glucose metabolic rate of nucleus raphe magnus (rm) and nucleus paragigantocellularis (pgcl) was increased significantly and that of the PAG and dorsal raphe nucleus had a tendency to increase, while stimulation of the head of caudate nucleus could partially abolish the increased glucose metabolic rate in the somatosensory cortex, cingulate cortex, ventroposterior and parafascicular nucleus of the thalamus, septal area and habenular nucleus as induced by noxious stimulation. These results suggest that caudate stimulation is able to depress the activation of some brain structures related to nociception and to activate those related to antinociception. The pgcl, rm, PAG and dorsal raphe nucleus might be the key structures participating in the caudate stimulation produced analgesia.     

Septal nuclei in the regulation of vago-sensitive neurons activity of the solitary nucleus in cats

The descending influences of the septal nuclei (lateral nucleus--LSN and bed nucleus stria terminalis--BNST) on activity of viscero-sensory neurons of the nucleus of tractus solitarius (NTS) identified by stimulation of cervical part of the n. vagus were investigated in the cat anaesthetised by chloraloze-nembutal combination. It was found that out of 70 units recorded in the NTS area 50 were identified as those of primary and secondary input vagal neurons. Influence of single, paired and frequency stimulation on the septal structures was studied on these neurons. It was revealed that 30% (15 un) reacted by phase-specific response to the single stimulation of the septal nuclei. The latent period of initial excitation was in the range 5-25 ms. During the paired stimulation these neurons were not able to react to the second stimulus for the equal 10-300 ms. It was revealed that 34% (17 un) of the identified vagal neurons reacted by a tonic change of their spontaneous activity. The increase of frequency stimulation to 20 Hz evoked different changes of the rhythmical activity of the vagal neurons (increase, diminishing or inhibition). The study of interaction between central and peripheral signals in the solitary neurons induced blocking influence of descending septal discharge on the vagal test response. It is possible that the septal downward impulses reach the vago-sensitive solitary neurons indirectly through other structures of the limbic brain (amygdala, hypothalamus) and participate in modulation of the spontaneous activity of these neurons.     

Septal nuclei in the mechanisms of lateral hypothalamic self stimulation in rabbits

Unilateral lesions of medial septal nucleus and lateral septal nuclei (dorsalis, intermedius, ventralis) decreased ipsilateral hypothalamic self-stimulation; the lesions of n. dorsalis, n. medialis and lateral septal nuclei (intermedius and ventralis) has the opposite effect on contralateral self-stimulation. The inhibition of ipsilateral self-stimulation was neither total nor permanent; 25-32% decrease in stimulation rate was seen, but behaviour returned to near-normal levels over a period of few days. In contrast, the augmentation of contralateral self-stimulation showed no significant change over the same period; in this case the 35-40% shift in stimulation rate was immediate and permanent. Bilateral lesions of septal nuclei had no effect if the initial level of self-stimulation rate was high and significantly increased self-stimulation.     

Effect of electrical stimulation of the septum on subicular neurons with different kinds of spontaneous activity in rabbits

The effect of electrical stimulation of the medial nucleus of the septum and of hippocampal area CA₁ on subicular neurons with three different types of spontaneous activity (with theta-modulation, with delta-modulation and complex spikes, and with irregular single-spike activity) was studied in unanesthetized rabbits by extracellular recording of unit activity. Cells with theta-activity were found to respond in a distinctive functional manner to stimulation of the medial nucleus of the septum: Their reactivity was higher but latent periods of their responses were much shorter than those of cells with delta-activity and irregular discharges. Stability of modulation of theta-cell activity increased both during and after stimulation of the medial septal nucleus. Electrical stimulation of hippocampal area CA₁, on the other hand, led to disappearance of rhythm modulation. Average response latencies of all three types of cells to stimulation of area CA₁ were equal. The results indicate special properties of the septal input to subicular cells with theta-modulation.Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. Translated from Neirofiziologiya, Vol. 17, No. 3, pp. 326–333, May–June, 1985.     

The functional role of the pedunculopontine nucleus in the regulation of the electrical activity of entopeduncular neurons in the rat

The purpose of this study was to investigate the influence of the pedunculopontine nucleus (PPN) on the electrical activity of entopeduncular nucleus (EP) in the rat and to analyze the influence of the subthalamic nucleus (STN) on the PPN-evoked responses of EP cells. Most of the EP neurons recorded (65.1%) were identified electrophysiologically as output cells projecting to the lateral habenula while only a minority (3.8%) were output cells to the PPN. Stimulation of the PPN in intact rats caused a short-latency (2.5 +/- 2.0, S.D. ms) activation in 22.6% and suppression of activity in 8.5% of EP neurons recorded. The mean impulse rate of EP neurons in intact rats was 27.0 +/- 5.5, S.D. imp./s and the overall mean interspike interval 36.8 +/- 7.1, S.D. ms. In rats where the PPN had been destroyed 10-12 days before recording by a local microinjection of kainic acid only a few EP neurons were still responsive to stimulation of the PPN showing suppression of activity. In these rats the kainate lesion slowed the impulse spontaneous activity to 14.3 +/- 6.3, S.D. imp./s and markedly altered the distribution of interspike intervals in 62.5% of the EP neurons recorded. The overall mean interspike interval in this group of deregulated neurons was 68.2 +/- 20.1, S.D. ms. A small kainate lesion of the STN placed 4-5 days before recording, on the other hand, did not affect the spontaneous activity of EP cells but increased the percentage of cells which were activated (43.6%) by stimulating the PPN. The present data demonstrate a predominant activatory influence of the PPN on EP cells and suggest that destruction of the STN may affect the responsiveness of entopeduncular cells to stimulation of the PPN possibly through the removal of a tonic inhibitory STN influence on the EP.     

The topography and dynamics of cholinergic transmission in the myenteric plexus-smooth muscle preparation of the guinea-pig ileum; the effect of ketocyclazocine, a kappa opiate ligand

Output of acetylcholine (ACh), neurogenic electromyogram (NEMG) and contractions of guinea-pig ileum preparations were studied during stimulation by high-frequency trains of impulses. Under control conditions the output of ACh per impulse after 2nd to 4th impulses during train stimulation (30 Hz) was higher by 20-40% than the level of ACh output during the first impulse. In the presence of ketocyclazocine (KTZ, 80 nmol x l-1) the output of ACh evoked by the first impulse was more effectively inhibited than that after impulses 2 to 4 so that the increase was higher (80-170%). NEMG, a direct consequence of the localized action of released transmitter (ACh), was recorded in the longitudinal muscle 4 and 10 mm aborally from the focal stimulation site. The incidence of NEMG responses was higher at the proximal than at the distal site and was proportional to the number of impulses in a train (100 Hz). At the distal site KTZ suppressed the appearance of NEMG responses to single impulses whereas at the proximal site its effect was much less; and so was its effect at either site during train stimulation. It is concluded that in the course of train stimulation, sites of transmission more distant from the stimulation focus were recruited, and consequently the secretion of ACh in succeeding impulses was enhanced. KTZ might preferentially inhibit the propagation of excitation by the very first impulse.     

Bronchomotor vagal preganglionic cell bodies in the dog: an anatomic and functional study.

A previous study in our laboratory demonstrated that the stimulation with microinjection of DL-homocysteic acid of cell bodies in the rostral portion of the external formation of the nucleus ambiguus (Aext) increased total lung resistance in dogs. In the present study anatomic experiments were conducted in dogs to determine if the rostral Aext contains vagal preganglionic cell bodies that give rise to axons in the pulmonary branches of the vagus nerve. The application of horseradish peroxidase (HRP) to either the pulmonary branches or the vagus at a point between the pulmonary branches and the cardiac branches resulted in retrograde labeling of cell bodies in both rostral Aext and the dorsal motor nucleus of the vagus (DMN). On the other hand, application of HRP to the vagus at a point below the pulmonary branches did not result in any retrogradely labeled cell bodies in rostral Aext but did result in labeled cell bodies in DMN. In another series of experiments DL-homocysteic acid (2.5 nmol in 25 nl) was microinjected at sites in rostral Aext and DMN. As we previously reported the injection of DL-homocysteic acid in rostral Aext increased total lung resistance. In contrast, in the same animals, the injection of DL-homocysteic acid in DMN did not change total lung resistance. We conclude that bronchomotor vagal preganglionic cell bodies are located in rostral Aext but not in DMN. The functional significance of vagal preganglionic cell bodies in DMN whose axons contribute to the pulmonary branches of the vagus nerve remains to be determined.     

Activation of central adenosine A(2A) receptors enhances superior laryngeal nerve stimulation-induced apnea in piglets via a GABAergic pathway.

Activation of the laryngeal mucosa results in apnea that is mediated through, and can be elicited via electrical stimulation of, the superior laryngeal nerve (SLN). This potent inhibitory reflex has been suggested to play a role in the pathogenesis of apnea of prematurity and sudden infant death syndrome, and it is attenuated by theophylline and blockade of GABA(A) receptors. However, the interaction between GABA and adenosine in the production of SLN stimulation-induced apnea has not been previously examined. We hypothesized that activation of adenosine A(2A) receptors will enhance apnea induced by SLN stimulation while subsequent blockade of GABA(A) receptors will reverse the effect of A(2A) receptor activation. The phrenic nerve responses to increasing levels of SLN stimulation were measured before and after sequential intracisternal administration of the adenosine A(2A) receptor agonist CGS (n = 10) and GABA(A) receptor blocker bicuculline (n = 7) in ventilated, vagotomized, decerebrate, and paralyzed newborn piglets. Increasing levels of SLN stimulation caused progressive inhibition of phrenic activity and lead to apnea during higher levels of stimulation. CGS caused inhibition of baseline phrenic activity, hypotension, and enhancement of apnea induced by SLN stimulation. Subsequent bicuculline administration reversed the effects of CGS and prevented the production of apnea compared with control at higher SLN stimulation levels. We conclude that activation of adenosine A(2A) receptors enhances SLN stimulation-induced apnea probably via a GABAergic pathway. We speculate that SLN stimulation causes endogenous release of adenosine that activates A(2A) receptors on GABAergic neurons, resulting in the release of GABA at inspiratory neurons and subsequent respiratory inhibition.     

Effect of doublet impulse sequences in the crayfish claw opener muscles and the computer-simulated neuromuscular synapse

The effects of doublet impulse sequences of the excitatory motor axon on the movement of the claw opener muscles in the crayfish were examined. The excitatory motor axon was stimulated electrically with various patterns of doublet impulse sequences generated by a digital computer. Doublet impulse sequences of stimulation produced a larger sustained movement than an uniform impulse sequences at the same mean rate of stimulation. The movement was largest when the interval between the impulses of a doublet was about 5 ms. This interval generated a movement amplitude 25% greater than that for the uniform impulse sequence. A simple model was formulated to stimulate the neuromuscular synapse of the claw opener muscle. The relationship between stimulation sequences with alternating long and short intervals and responses (firing probabilities) of the neuromuscular synapse at the same mean rate was investigated. The responses was classified into two typical types which are noneffective Type I and effective Type II to the absolute refractory period (ARP). The characteristics which are larger responses with short intervals in Type I and reduction of responses in the ARP region of Type II formed a plateau peak of the experimental results. By incorporating the reduction of end-plate potential (EPP) as a property of nonlinear rule for temporal summation into the model, it was shown that Type I response is maximal with a plateau peak at short interval, agreeing well with the experimental results from the claw opener muscles.     

Effect of damage of the nigro-neostriatal dopaminergic system by MPTP on the transmission of corticofugal impulses to the neurons of the caudate nucleus

It is shown in acute experiments on cats (males) that the induced responses as action potentials (AP) by the latent period (LP) less than 8.0 ms in the caudate nucleus neurons (CN) to a single stimulation of the motor zone of the cortex (MI) are more frequently inhibited than facilitated after specifying single stimulation of the compact part of the black substance (BS) in the intervals between stimuli 10-100 ms. As a result of system multiple injection of MPTP neurotoxin during 5 days per 5 mg/kg the number of CN neurons responding to stimulation of MI, AP, LP less than 8.0 Usec and to stimulation of BS-LP less than 10.0 ms reliably decreases. A conclusion is made that dopaminergic nigro-striatum system exerts a protective action on the impulse transfer on monosynaptic connections from the cortex to striatum.     

Quantitation and characterization of thyrotropin-releasing hormone in vagal nuclei and other regions of the medulla oblongata of the rat

Abstract: Since evidence is now available to support a nonendocrine autonomic function for thyrotropin-releasing hormone (TRH), quantitative measurements of TRH were made in nuclei of the vagal complex and other areas of the caudal medulla oblongata of the rat. Regions containing the dorsal motor nucleus of the vagus (DMN), nucleus tractus solitarius (NTS), hypoglossal nucleus, dorsal column nuclei, descending nucleus V (DNV), nucleus ambiguus (NA), raphe nuclei (MR) dorsomedial and ventromedial reticular formation, and inferior olivary nuclei were isolated from 300-μm-thick frozen sections of medulla by the micropunch technique. Each region was pooled bilaterally, homogenized in 0.1 M HCl, and vacuum-dried. Extracts were assayed for TRH by specific radioimmunoassay (RIA). TRH levels varied 100-fold among medulla nuclei. Highest content (ng/mg protein ± SEM) was found in DMN (14 ± 1.38) and NTS (4.7 ± 0.68), whereas lowest levels occurred in the DNV and MR (0.13, 0.06). Nearly 65% of the total medullary TRH was localized in nuclei associated with vagal complex (DMN, NTS, NA). Characterization of tissue immunoreactivity (TRHi) in these regions suggests the presence of TRH, since (1) medullary tissue extracts competed with ¹²⁵I-TRH for antibody binding sites with the same affinity as authentic TRH; (2) TRHi in tissue extracts co-migrated with synthetic TRH when subjected to reverse-phase high performance liquid chromatography and Sephadex G-10 chromatography; and (3) rat serum TRH peptidases degraded TRHi and authentic TRH at similar rates. Another group of rats was subjected to unilateral (right side) vagotomy. At 33 weeks post-vagotomy, the vagal preganglionic cell population in the ipsilateral DMN was depleted 50–75%, while the contralateral side was unaffected. Interestingly, the content of TRH in the ipsilateral (right) DMN remained unchanged, whereas TRH in the contralateral DMN increased by 50%. In contrast, TRH was significantly elevated in the NA on the ipsilateral side of the lesion. TRH in both ipsi- and contralateral NTS was unchanged when compared with sham-operated controls. These results indicate that (1) TRH is present in several specific loci of the medulla; (2) very high levels are found in the vagal complex; and (3) vagotomy may alter TRH in the contralateral DMN and ipsilateral NA.     

Particle motion is broadly represented in the vestibular medulla of the bullfrog across larval development

In their shallow-water habitats, bullfrog (Rana catesbeiana) tadpoles are exposed to both underwater and airborne sources of acoustic stimulation. We probed the representation of underwater particle motion throughout the tadpole’s dorsal medulla to determine its spatial extent over larval life. Using neurobiotin-filled micropipettes, we recorded neural activity to z-axis particle motion (frequencies of 40–200 Hz) in the medial vestibular nucleus, lateral vestibular nucleus, dorsal medullary nucleus (DMN), and along the dorsal arcuate pathway. Sensitivity was comparable in the medial and lateral vestibular nuclei, with estimated thresholds between 0.016 and 12.5 μm displacement. Neither best responding frequency nor estimated threshold varied significantly over larval stage. Transport of neurobiotin from active recording sites was also stable over development. The DMN responded poorly to z-axis particle motion, but did respond to low-frequency pressure stimulation. These data suggest that particle motion is represented widely and stably in the tadpole’s vestibular medulla. This is in marked contrast to the representation of pressure stimulation in the auditory midbrain, where a transient “deaf period” of non-responsiveness and decreased connectivity occurs immediately prior to metamorphic climax. We suggest that, in bullfrogs, sensitivity to particle motion and to pressure follows different developmental trajectories.     

The modelling of theta rhythm regulation by an increasing afferent inflow in septal slices in vitro

The aim of the work was the modelling in vitro of the condition of increased afferent inflow, which in the intact septum results in an increase of population of theta-bursting units, their synchronization and shift to a higher frequency of the bursts, with corresponding changes in the hippocampal electrical activity. Neuronal activity was recorded extracellularly in the medial septal nucleus and vertical limb of the nucleus of diagonal band (MS-DB) in guinea pig septal slices. Electrical stimulation in the medial part of horizontal limb of DB evokes initial period of suppression of spontaneous activity in 85% of the neurones. This low-threshold, rapid inhibition has variable duration (20-280 ms) in different units at low intensities of the stimulating current. With increased intensities of stimulation this inhibitory phase in majority of units is gradually or by steps shortened, though in some units with initial short inhibition it is not changed. As a result the variability of initial inhibitory period between units is decreased and centered around 30-60 ms. Many units with single-spike background activity developed postinhibitory burst responses at various levels of stimulating current. The spontaneously bursting MS-DB units always responded by resetting of their background bursts. In total 58% of all recorded neurones generated evoked bursts under condition of increased afferent inflow.     

Central GABAergic mechanisms are involved in apnea induced by SLN stimulation in piglets.

Stimulation of the superior laryngeal nerve (SLN) results in apnea in animals of different species, the mechanism of which is not known. We studied the effect of the GABA(A) receptor blocker bicuculline, given intravenously and intracisternally, on apnea induced by SLN stimulation. Eighteen 5- to 10-day-old piglets were studied: bicuculline was administered intravenously to nine animals and intracisternally to nine animals. The animals were anesthetized and then decerebrated, vagotomized, ventilated, and paralyzed. The phrenic nerve responses to four levels of electrical SLN stimulation were measured before and after bicuculline. SLN stimulation caused a significant decrease in phrenic nerve amplitude, phrenic nerve frequency, minute phrenic activity, and inspiratory time (P < 0.01) that was proportional to the level of electrical stimulation. Increased levels of stimulation were more likely to induce apnea during stimulation that often persisted beyond cessation of the stimulus. Bicuculline, administered intravenously or intracisternally, decreased the SLN stimulation-induced decrease in phrenic nerve amplitude, minute phrenic activity, and phrenic nerve frequency (P < 0.05). Bicuculline also reduced SLN-induced apnea and duration of poststimulation apnea (P < 0.05). We conclude that centrally mediated GABAergic pathways are involved in laryngeal stimulation-induced apnea.     

电刺激大鼠尾核头部镇痛的中枢效应——〔~3H〕-2脱氧葡萄糖放射自显影研究

本文利用[~3H]-2脱氧葡萄糖定量放射自显影方法,研究了电刺激大鼠尾核头部镇痛时中枢神经系统有关结构的葡萄糖代谢率变化。结果表明,痛刺激后,皮层躯体感觉Ⅰ,Ⅱ区、扣带回皮质、丘脑束旁核、丘脑中央中核、丘脑腹后核、尾核、外侧缰核、外侧隔核、中缝背核及中脑导水管周围灰质等结等的葡萄糖代谢率均明显升高(P<0.05)。电刺激大鼠尾核头部后,中缝大核及延髓旁巨细胞网状外侧核的葡萄糖代谢率显著升高,中脑导水管周围灰质和中缝背核的葡萄糖代谢率亦有升高趋势。电刺激大鼠尾核头部可部份降低痛刺激引起的有关结构葡萄糖代谢率升高(如皮层躯体感觉Ⅰ、Ⅱ区、扣带回皮质、丘脑束旁核、丘脑中央中核、丘脑腹后核、外侧隔核及外侧缰核等)。上述结果提示,电刺激大鼠尾核头部镇痛时抑制了与痛感觉有关的结构,同时激活了与镇痛有关的结构。中缝大核、中缝背核、中脑导水管周围灰质及延髓旁巨细胞网状外侧核等结构是实现尾核镇痛的重要环节。