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Author(s): Tianwen Huang [sup.1] [sup.2] , Shing-Hong Lin [sup.1] [sup.2] , Nathalie M. Malewicz [sup.3] , Yan Zhang [sup.1] [sup.4] [sup.5] , Ying Zhang [sup.1] [sup.6] , Martyn Goulding [sup.7] [...], Animals and humans display two types of response to noxious stimuli. The first includes reflexive defensive responses that prevent or limit injury; a well-known example of these responses is the quick withdrawal of one's hand upon touching a hot object. When the first-line response fails to prevent tissue damage (for example, a finger is burnt), the resulting pain invokes a second-line coping response--such as licking the injured area to soothe suffering. However, the underlying neural circuits that drive these two strings of behaviour remain poorly understood. Here we show in mice that spinal neurons marked by coexpression of TAC1.sup.Cre and LBX1.sup.Flpo drive coping responses associated with pain. Ablation of these spinal neurons led to the loss of both persistent licking and conditioned aversion evoked by stimuli (including skin pinching and burn injury) that--in humans--produce sustained pain, without affecting any of the reflexive defensive reactions that we tested. This selective indifference to sustained pain resembles the phenotype seen in humans with lesions of medial thalamic nuclei.sup.1-3. Consistently, spinal TAC1-lineage neurons are connected to medial thalamic nuclei by direct projections and via indirect routes through the superior lateral parabrachial nuclei. Furthermore, the anatomical and functional segregation observed at the spinal level also applies to primary sensory neurons. For example, in response to noxious mechanical stimuli, MRGPRD- and TRPV1-positive nociceptors are required to elicit reflexive and coping responses, respectively. Our study therefore reveals a fundamental subdivision within the cutaneous somatosensory system, and challenges the validity of using reflexive defensive responses to measure sustained pain.In mice, the ablation of spinal neurons that co-express TAC1 and LBX1 leads to the loss of coping responses to sustained pain without affecting reflexive defensive reactions to external threats.

We defined the sensory-motor characteristics of the lower esophageal sphincter relaxation (LESR) (stimulus threshold volume, response onset, and relaxation period, relaxation magnitude, nadir) during maturation in human neonates. We hypothesized that LESR kinetics differs during maturation and with peristaltic reflex type. Basal and adaptive esophageal motility testing was performed (N = 20 premature neonates) at 34.7 and 39.1 wk (time 1 and time 2). Effects of midesophageal provocation with graded stimuli (N = 1,267 stimuli, air and liquids) on LESR kinetics during esophagodeglutition response (EDR) and secondary peristalsis (SP) were analyzed by mixed models. Frequency of LESR with basal primary peristalsis were different during maturation (P = 0.03). During adaptive responses with maturation, 1) the frequencies of peristaltic reflexes and LESR were similar; 2) liquid stimuli resulted in a shorter LESR response latency and LESR nadir and greater LESR magnitude (all P < 0.05); 3) media differences were noted with LESR response latency (air vs. liquids, P < 0.02); and 4) infusion flow rate-LESR were different (P < 0.01 for air and liquids). Mechanistically, 1) frequency of LESR was greater during peristaltic reflexes at both times (vs. none, P < 0.0001); 2) LESR response latency, duration, and time to complete LESR were longer with EDR (all P < 0.05, vs. SP at time 2); and 3) graded stimulus volume LESR were different for air and liquids (P < 0.01). In conclusion, sensory-motor characteristics of LESR depend on the mechanosensitive properties of the stimulus (media, volume, flow), type of peristaltic reflex, and postnatal maturation. Maturation modulates an increased recruitment of inhibitory pathways that favor LESR. gastroesophageal reflux; neonate; primary peristalsis; secondary peristalsis doi: 10.1152/ajpgi.00289.2010.

[[alpha].sub.1]-Adrenergic receptor subtypes are widely distributed in the central nervous system and are involved in autonomic functions such as micturition. We investigated the presence and the role of supraspinal and/or spinal [[alpha].sub.1]-adrenergic receptors in modulating the micturition reflex in conscious female Wistar rats. The expression of [[alpha].sub.1]-adrenergic receptor subtypes in rat brain and lumbosacral spinal cord was studied using RT-PCR. Continuous-infusion cystometrograms were obtained in conscious rats, and [[alpha].sub.1]-adrenergic receptor antagonists were administered via intracerebroventricular or intrathecal routes. The mRNA expression of [[alpha].sub.1A]-, [[alpha].sub.1B]-, and [[alpha].sub.1D]-adrenergic receptors was detected in rat brain (midbrain and pons) and lumbosacral spinal cord (dorsal and ventral parts of spinal cord). In addition, intracerebroventricular injection of the [[alpha].sub.1]-adrenergic receptor antagonist tamsulosin (1-10 [micro]g), the selective [[alpha].sub.1A]-adrenergic receptor antagonist silodosin (1-10 [micro]g), and the selective [[alpha].sub.1D]-adrenergic receptor antagonist BMY 7378 (1-10 [micro]g) significantly prolonged the intercontraction interval (ICI) but did not alter maximum voiding pressure (MVP). Although intrathecal injection of BMY 7378 (0.0001-10 [micro]g) did not affect ICI, tamsulosin and silodosin prolonged ICI in a dose-dependent manner. MVP was significantly reduced by intrathecal injection of tamsulosin (10 [micro]g) but not by silodosin or BMY 7378 (0.0001-10 [micro]g). Supraspinal [[alpha].sub.1A]- and [[alpha].sub.1D]-adrenergic receptors are apparently important for the regulation of reflex-bladder activity in conscious rats. Noradrenergic projection from the brain stem to the lumbosacral spinal cord may promote the afferent limb rather than the efferent limb of the micturition reflex pathway via [[alpha].sub.1A]-adrenergic receptors. cystometrogram; intracerebroventricular and intrathecal injections; tamsulosin; silodosin; BMY 7378 doi: 10.1152/ajprenal.00553.2009.

Inhibition of Return (IOR, slower reaction times to previously cued or inspected locations) is observed both when eye movements are prohibited, and when the eyes move to the peripheral location and back to the centre before the target appears. It has been postulated that both effects are generated by a common mechanism, the activation of the oculomotor system. In strong support of this claim, IOR is not observed when attention is oriented endogenously and covertly, but it has been observed when eye movements are endogenously prepared, even when not executed. Here, we aimed to replicate and extend the finding that endogenous saccade preparation produces IOR. In five experiments using different paradigms, IOR was not observed when participants endogenously prepared an eye movement. These results lead us to conclude that endogenous saccade preparation is not sufficient to produce IOR. Keywords: inhibition of return, oculomotor activation, endogenous saccade preparation DOI: 10.1037/a0019951

Am J Physiol Heart Circ Physiol 298: H245-H250, 2010. First published November 6, 2009; doi: 10.1152/ajpheart.00909.2009.--Muscle metaboreflex activation during submaximai dynamic exercise in normal subjects elicits a pressor response primarily due to increased cardiac output (CO). However, when the ability to increase CO is limited, such as in heart failure or during maximal exercise, the muscle metaboreflex-induced increases in arterial pressure occur via peripheral vasoconstriction. How the mechanisms of this pressor response are altered is unknown. We tested the hypothesis that this change in metaboreflex function is dependent on the level of CO. The muscle metaboreflex was activated in dogs during mild dynamic exercise (3.2 km/h) via a partial reduction of hindlimb blood flow. Muscle metaboreflex activation increased CO and arterial pressure, whereas vascular conductance of all areas other than the hindlimbs did not change. CO was then reduced to the same level observed during exercise before the muscle metaboreflex activation via partial occlusion of the inferior and superior vena cavae. Arterial pressure dropped rapidly with the reduction in CO but, subsequently, nearly completely recovered. With the removal of the muscle metaboreflex-induced rise in CO, substantial peripheral vasoconstriction occurred that maintained arterial pressure at the same levels as before CO reduction. Therefore, the muscle metaboreflex function is nearly instantaneously shifted from increased CO to increased vasoconstriction when the muscle metaboreflex-induced rise in CO is removed. We conclude that whether vasoconstriction occurs with muscle metaboreflex depends on whether CO rises. integrative cardiovascular regulation; exercise reflexes; peripheral vascular regulation

Accommodation of the stomach consists of a vagally mediated relaxation of the proximal stomach, providing the meal with a reservoir. Our aim was to study whether, similar to other vagally mediated processes, the accommodation reflex is also determined by cephalic, oropharyngeal, gastric, and intestinal phases. Eleven healthy subjects underwent in randomized order five gastric barostat studies and two satiety drinking tests. In all studies, isobaric tone measurements (at minimal distending pressure + 2 mmHg) were performed 20 min before and 20 min after a nutrient stimulus. The stimuli included only visual and olfactory exposure to a meal (cephalic stimulation), taking liquid nutrient in the mouth without swallowing (sham feeding), ingestion of a 200-ml 300-kcal nutrient meal with blocked outflow to the pylorus (gastric retention), and meal infusion through a nasointestinal tube (duodenal instillation), or normal ingestion (control). During satiety testing, subjects ingested liquid nutrient at a fixed rate of 15 ml/min until maximum satiety, with an inflated or deflated intrapyloric balloon assembly. Progressively bigger gastric relaxatory responses were seen with cephalic stimulation (18 [+ or -] 19 ml), sham feeding (54 [+ or -] 21 ml), gastric retention (95 [+ or -] 47), duodenal instillation (144 [+ or -] 33), and control (232 [+ or -] 33 ml). The amount of nutrient ingested at maximum satiety was significantly lower with an inflated intrapyloric balloon (1,223 [+ or -] 103 vs. 1,392 [+ or -] 124 ml, P < 0.05). The accommodation reflex in humans lacks a cephalic phase, but it can be activated from the oropharynx, the stomach, and the duodenum. Blocking passage to the duodenum significantly decreases the amplitude of the accommodation reflex and induces early satiety. stomach; barostat; relaxation doi: 10.1152/ajpgi.00046.2009.

Cyclin-dependent kinase-5 (Cdk5), a proline-directed serine/threonine kinase, may alter pain-related neuronal plasticity by regulating extracellular signal-related kinase-1/2 (ERK1/2) activation. This study investigated whether Cdk5-dependent ERK activation underlies the estrogen-elicited facilitation on the repetitive stimulation-induced spinal reflex potentiaton (SRP) that is presumed to be involved in postinflammatory/neuropathic hyperalgesia and allodynia. Reflex activity of the external urethra sphincter electromyogram evoked by pelvic afferent nerve test stimulation (TS; 1 stimulation/30 s for 10 min) and repetitive stimulation (RS; 1 stimulation/1 s for 10 min) was recorded in anesthetized rats. TS evoked a baseline reflex activity, whereas RS produced SRP. Intrathecal (it) [beta]-estradiol facilitated the repetitive stimulation-induced SRP that was reversed by pretreatment with the estrogen receptor anatogonist ICI 182,780 (10 nM, 10 [micro]l it), Cdk5 inhibitor roscovitine (100 nM, 10 [micro]l it), ERK inhibitor (U-0126; 100 [micro]M, 10 [micro]l it) and N-methyl-D-aspartate (NMDA) NR2B subunit antagonist (Co-101244; 100 nM, 10 [micro]l it). Moreover, ER[alpha] (propylpyrazoletriol; 100 nM, 10 [micro]l it) and ER[beta] (diarylpropionitrile; 100 [micro]M, 10 [micro]l it) agonists both facilitated the SRP, similar to results with a [beta]-estradiol injection. In association with the facilitated RS-induced SRP, an intrathecal [beta]-estradiol injection elicited ERK1/2 and NR2B subunit phosphorylation that were both reversed by intrathecal roscovitine and U-0126. These results indicated that the Cdk/ERK cascade, which is activated by ER[alpha] and ER[beta], may subsequently phosphorylate the NR2B subunit to develop NMDA-dependent postinflammatory hyperalgesia and allodynia to maintain the protective mechanisms of the body. estradiol; cyclin-dependent kinase-5; NR2B; extracellular signal-related kinase; pelvic pain; spinal reflex potentiaton; hyperalgesia

The medullary 5-HT system has potent effects on heart rate and breathing in adults. We asked whether this system mitigates the respiratory instability and bradycardias frequently occurring during the neonatal period. 5,7-Dihydroxytryptamine (5,7-DHT) or vehicle was administered to rat pups at postnatal day 2 (P2), and we then compared the magnitude of bradycardias occurring with disruptions to eupnea in treated and vehicle control littermates at P5-6 and P10-12. We then used a novel method that would allow accurate assessment of the ventilatory and heart rate responses to near square-wave challenges of hypoxia (10% [O.sub.2]), hypercapnia (5 and 8% C[O.sub.2] in normoxia and hyperoxia), and asphyxia (8% C[O.sub.2]-10% [O.sub.2]), and to the induction of the Hering-Breuer inflation reflex (HBR), a potent, apnea-inducing reflex in newborns. The number of 5-HT-positive neurons was reduced ~80% by drug treatment. At both ages, lesioned animals had considerably larger bradycardias during brief apnea; at P5-6, average and severe events were ~50% and 70% greater, respectively, in lesioned animals (P = 0.002), whereas at P10-12, events were ~ 23% and 50% greater (P = 0.018). However, lesioning had no effect on the HR responses to sudden gas challenge or the HBR. At P5-6, lesioned animals had reduced breathing frequency and ventilation ([V.sub.E]), but normal [V.sub.E] relative to metabolic rate (VE/[Vo.sub.2]). At P10-12, lesioned animals had a more unstable breathing pattern (P = 0.04) and an enhanced VE response to moderate hypercapnia (P = 0.007). Within the first two postnatal weeks, the medullary 5-HT system plays an important role in cardiorespiratory control, mitigating spontaneous bradycardia, stabilizing the breathing pattern, and dampening the hypercapnic VE response. neonate; C[O.sub.2]; breathing; SIDS; Hering-Breuer; chemoreflex

In heart failure (HF) , sympathetic nerve activity is increased. Measurements in HF patients of cardiac norepinephrine spillover, reflecting cardiac sympathetic nerve activity (CSNA), indicate that it is increased earlier and to a greater extent than sympathetic activity to other organs. This has important consequences because it worsens prognosis, provoking arrhythmias and sudden death. To elucidate the mechanisms responsible for the activation of CSNA in HF, we made simultaneous direct neural recordings of CSNA and renal SNA (RSNA) in two groups of conscious sheep: normal animals and animals in HF induced by chronic, rapid ventricular pacing. In normal animals, the level of activity, measured as burst incidence (bursts of pulse related activity/100 heart beats), was significantly lower for CSNA (30 [+ or -] 5%) than for RSNA (94 [+ or -] 2%). Furthermore, the resting level of CSNA, relative to its maximum achieved while baroreceptors were unloaded by reducing arterial pressure, was set at a much lower percentage than RSNA. In HF, burst incidence of CSNA increased from 30 to 91%, whereas burst incidence of RSNA remained unaltered at 95%. The sensitivity of the control of both CSNA and RSNA by the arterial baroreflex remained unchanged in HF. These data show that, in the normal state, the resting level of CSNA is set at a lower level than RSNA, but in HF, the resting levels of SNA to both organs are close to their maxima. This finding provides an explanation for the preferential increase in cardiac norepinephrine spillover observed in HF. arterial baroreflex | renal sympathetic nerve activity | sheep

Intraoral infusions of bitter tastants activate expression of the immediate-early gene c-Fos in neurons located in the medial third of the rostral nucleus of the solitary tract (rNST). The distribution of these neurons is distinct from that activated by sour or sweet stimuli. Bitter stimuli are also distinctive because of their potency for eliciting gaping, an oral reflex that functions to actively reject potentially toxic substances. Glossopharyngeal nerve transection profoundly reduces, whereas decerebration spares, the bitter-evoked Fos-like immunoreactivity (FLI) pattern and gaping, implicating the medial rNST as a substrate for the sensory limb of oral rejection. The present experiment tested this hypothesis using microstimulation (100 Hz, 0.2 ms, 5-40 [micro]A) to activate the rNST in awake rats. NST microstimulation elicited licking and gaping, and gaping was evoked from a restricted rNST region. The results indicated some topographic organization in sites effective for evoking gaping, but, in direct conflict with the hypothesis, lateral sites farther from bitter-evoked FLI were more effective than medial sites centered closer to FLI-expressing neurons. The gape-effective sites resemble locations of bitter-responsive neurons recently observed in neurophysiological recordings. These results indicate that bitter-responsive rNST neurons critical for triggering gaping may not express FLI and imply an alternate function for bitter-responsive neurons that do. oromotor reflexes; taste reactivity; chemotopy; bitter Fos

Quantitative analysis of innervation to dorsal motor nucleus of the vagus (DMV) fundus-projecting neurons indicates that ~17% of input neurons are noradrenergic. To determine whether this small percentage of neurons innervating DMV output to the stomach is physiologically relevant, we evaluated the role of norepinephrine at the DMV in mediating a vagovagal reflex controlling the fundus. A strain gauge was sutured onto the fundus of isoflurane-anesthetized rats to monitor changes in tone evoked by esophageal distension (ED). ED produced a decrease in fundus tone of 0.31 [+ or -] 0.02 g (P < 0.05), which could be reproduced after a 30-min interval between distensions. Bilateral cervical vagotomy and/or pretreatment with intravenous atropine methylbromide prevented the reflex-induced fundus relaxation. In contrast, intravenous [N.sup.G]-nitro-L-arginine methyl ester had no effect. Bilateral microinjection of [[alpha].sub.2]-adrenoreceptor antagonists (yohimbine and RS-79948) into the DMV also prevented the response. Before microinjection of [[alpha].sub.2]-adrenoreceptor antagonists, ED decreased fundus tone by 0.33 [+ or -] 0.05 g (P < 0.05). After antagonist microinjection, ED decreased fundus tone by only 0.05 [+ or -] 0.06 g (P > 0.05). Bilateral microinjection of prazosin into the DMV had no effect on the response. Microinjection of norepinephrine into the DMV mimicked the effect of ED and was also prevented by prior microinjection of an [[alpha].sub.2]-adrenoreceptor antagonist. Our results indicate that noradrenergic innervation of DMV fundus-projecting neurons is physiologically important and suggest that norepinephrine released at the DMV acts on [[alpha].sub.2]-adrenoreceptors to inhibit activity in a cholinergic-cholinergic excitatory pathway to the fundus. gastric tone; norepinephrine; rat

Stimulation of capsaicin receptors results in an increase in afferent renal nerve activity (ARNA), but it is unclear how capsaicin contributes to sensory activation intrarenally. Here, we studied the relationships between capsaicin receptor activation, substance P (SP) release, and the sensory response in the rat renal pelvis. Immunoblots showed that one of the capsaicin receptors, transient receptor potential vanilloid type 1 channel (TRPV1), was found in various renal tissues and was especially abundant in the renal pelvis, where most sensory nerve fibers originate. Interestingly, immunolabeling showed colocalization of TRPV1, SP, and the panneuronal marker PGP9.5 in the renal pelvis. Electrophysiological recordings showed that SP and capsaicin activated the same mechanosensitive ARNA in a single-unit preparation. Intrapelvic administration of capsaicin or a specific TRPV1 agonist, resiniferatoxin, resulted in a dose-dependent increase in multi-unit ARNA and SP release, and these effects were blocked by the TRVP1 blocker capsazepine. Inhibition of the SP receptor by L-703,606 largely prevented capsaicin- or resiniferatoxin-induced ARNA. Capsazepine also prevented intrapelvic pressure (IPP)-dependent ARNA activation and contralateral diuresis/natriuresis in the renorenal reflex at an IPP of 20 mmHg, but had no effect at an IPP of 50 mmHg. These data indicate that TRPV1, a low-pressure baroreceptor, is present in the renal pelvis and exclusively regulates neuropeptide release from primary renal afferent C-fibers in response to mechanostimulation. neurokinin-1 receptor; renorenal reflex; capsaicin receptor; intrapelvic pressure

Calcium/calmodulin--protein kinase (CaMK)-dependent nitric oxide (NO) and the downstream intracellular messenger cGMP, which is activated by soluble guanylate cyclase (sGC), are believed to induce long-term changes in efficacy of synapses through the activation of protein kinase G (PKG). The aim of this study was to examine the involvement of the CaMKII-dependent NO/sGC/PKG pathway in a novel form of repetitive stimulation-induced spinal reflex potentiation (SRP). A single-pulse test stimulation (TS; 1/30 Hz) on the afferent nerve evoked a single action potential, while repetitive stimulation (RS; 1 Hz) induced a long-lasting SRP that was abolished by a selective [Ca.sup.2+]/CaMKII inhibitor, autocamtide 2-related inhibitory peptide (AIP). Such an inhibitory effect was reversed by a relative excess of nitric oxide synthase (NOS) substrate, L-arginine. In addition, the RS-induced SRP was abolished by pretreatment with the NOS inhibitor, [N.sup.G]-nitro-L-arginine-methyl ester (L-NAME). The sGC activator, protoporphyrin IX (PPIX), reversed the blocking effect caused by L-NAME. On the other hand, a sGC blocker, 1H-J1, 2, 4]oxadiazolo[4, 3-[alpha]]quinoxalin-l-one (ODQ), abolished the RS-induced SRP. Intrathecal applications of the membrane-permeable cGMP analog, 8-bromoguanosine 3',5'-cyclic monophosphate sodium salt monohydrate (8-Br-cGMP), reversed the blocking effect on the RS-induced SRP elicited by the ODQ. Our findings suggest that a CaMKII-dependent NO/sGC/PKG pathway is involved in the RSinduced SRP, which has pathological relevance to hyperalgesia and allodynia. spinal reflex potentiation; soluble guanylate cyclase; cyclic monophosphate sodium salt monohydrate; spinal cord; windup

Intentional binding refers to a temporal attraction in the perceived times of actions and effects. So far, it has solely been investigated using judgments of the perceived time of actions or their effects. The authors report 3 experiments using an alternative method: the estimation of a time interval between a voluntary action and its subsequent effect. Interval estimates were obtained for intervals bounded by different kinds of actions and effects: The actions were either performed by the participants themselves or by the experimenter. The effects, in turn, were movements either applied to the body of the participant or to the experimenter. First, the results validated interval estimation as a method for exploring action awareness. Second, intentional binding was stronger for self-generated compared with observed actions, indicating that private information about the action contributes to action awareness. In contrast, intentional binding did not depend on whether a somatic effect was applied to the participant's or to another person's body. Third, for self-generated actions, external events gave rise to a stronger intentional binding than did somatic effects. This finding indicates that intentional binding especially links actions with their consequences in the external world. Keywords: self, other, interval estimation, agency

The purpose of this research was to identify the number of sessions required for a new investigator to become proficient at evoking an H-reflex in the flexor carpi radialis (FCR), in comparison to an experienced investigator. 31 students from Brock University in the greater Niagara region (16 women M age = 32.2, SD = 8.9 yr.; 15 men M age-27.8, SD = 7.8 yr.) with no known neurological disorders volunteered and completed two test sessions performed by either an experienced or a novice investigator. In randomized order, both investigators stimulated each subject's median nerve 10 times, once every 15 sec. Each session included the measurement of the subject's flexor carpi radialis maximal M-wave amplitude and H-reflex amplitude and latency with surface electromyographic electrodes. The intraclass correlation coefficients (ICC) indicated an adequate corrdation between investigators for both M-wave maximal amplitude and H-reflex at 5% of the M-wave maximal amplitude (.84 and .70, respectively). However, there was a low correlation (.38) between the latency values obtained by the two investigators. The peak-to-peak amplitudes of the H-reflex and M-wave do not appear to be influenced by experience of the tester. The latency of the response, however, appears to have an associated learning curve, improving in consistency with increasing practice of tester.

It has long been known that the esophageal distension produced by swallowing elicits a powerful proximal gastric relaxation. Gastroinhibitory control by the esophagus involves neural pathways from esophageal distension-sensitive neurons in the nucleus tractus solitarius centralis (cNTS) with connections to virtually all levels of the dorsal motor nucleus of the vagus (DMV). We have shown recently that cNTS responses are excitatory and primarily involve tyrosine hydroxylase-immunoreactive cells, whereas the DMV response involves both an [[alpha].sub.1] excitatory and an [[alpha].sub.2] inhibitory response. In the present study, using an esophageal balloon distension to evoke gastric relaxation (esophageal-gastric reflex, EGR), we investigated the peripheral pharmacological basis responsible for this reflex. Systemic administration of atropine methyl nitrate reduced the amplitude of the gastric relaxation to 52.0 [+ or -] 4.4% of the original EGR, whereas [N.sup.G]-nitro-L-arginine methyl ester (L-NAME) reduced it to 26.3 [+ or -] 7.2% of the original EGR. Concomitant administration of atropine methyl nitrate and L-NAME reduced the amplitude of the gastric relaxation to 4.0 [+ or -] 2.5% of control. This reduction in the amplitude of induced EGR is quite comparable (4.3 [+ or -] 2.6%) to that seen when the animal was pretreated with the nicotinic ganglionic blocker hexamethonium. In the presence of bethanechol, the amplitude of the esophageal distension-induced gastric relaxation was increased to 177.0 [+ or -] 10.0% of control; administration of L-NAME reduced this amplitude to 19.9 [+ or -] 9.5%. Our data provide a clear demonstration that the gastroinhibitory control by the esophagus is mediated via a dual vagal innervation consisting of inhibitory nitrergic and excitatory cholinergic transmission. receptive relaxation reflex; nonadrenergic; noncholinergic; vagovagal reflex

Studies on the behavior of the vestibulo-ocular reflex (VOR) reveal that the monocular reflex gain is adjusted according to target position relative to each eye. In this paper, we present a nonlinear approach in modeling the viewing-context dependency of the slow-phase angular VOR. We show that including appropriate nonlinearities in the responses of premotor neurons in the brainstem is sufficient to account for the online modulation of the VOR with target position. This approach allows very complex behaviors in response to sensory patterns without resorting to currently assumed cortical computations. A local premotor topology with nonlinear properties has repercussions in the study of all ocular reflexes, since it implies context dependent dynamics in all behavioral responses (pursuit, optokinetic, VOR, saccades, etc.) that share this network. Local nonlinearities in spinal circuits could similarly influence the context dependence of other motor systems (such as stretch reflex modulation during rhythmic walking). Index Terms--Eye movement, neural topology, reflex modulation, sensory-motor mapping, vestibulo-ocular reflex.

Elucidation of the interaction between the muscle mechanoreflex and the arterial baroreflex is essential for better understanding of sympathetic regulation during exercise. We characterized the effects of these two reflexes on sympathetic nerve activity (SNA) in anesthetized rabbits (n = 7). Under open-loop baroreflex conditions, we recorded renal SNA at carotid sinus pressure (CSP) of 40, 80, 120, or 160 mmHg while passively stretching the hindlimb muscle at muscle tension (MT) of 0, 2, 4, or 6 kg. The MT-SNA relationship at CSP of 40 mmHg approximated a straight line. Increase in CSP from 40 to 120 and 160 mmHg shifted the MT-SNA relationship downward and reduced the response range (the difference between maximum and minimum SNA) to 43 [+ or -] 10% and 19 [+ or -] 6%, respectively (P < 0.01). The CSP-SNA relationship at MT of 0 kg approximated a sigmoid curve. Increase in MT from 0 to 2, 4, and 6 kg shifted the CSP-SNA relationship upward and extended the response range to 133 [+ or -] 8%, 156 [+ or -] 14%, and 178 [+ or -] 15%, respectively (P < 0.01). A model of algebraic summation, i.e., parallel shift, with a threshold of SNA functionally reproduced the interaction of the two reflexes (y = 1.00x - 0.01; [r.sup.2] = 0.991, root mean square = 2.6% between estimated and measured SNA). In conclusion, the response ranges of SNA to baroreceptor and muscle mechanoreceptor input changed in a manner that could be explained by a parallel shift with threshold. muscle stretch; exercise pressor reflex; exercise; subliminal fringe

Distension-evoked reflex of rectorectal (R-R) contractions and rectointernal anal sphincter (R-IAS) relaxations can be generated in guinea pigs through an extrinsic sacral excitatory neural pathway (pelvic nerves) as well as intrinsic cholinergic excitatory and nitrergic inhibitory pathways. The aim of the present study was to create intrinsic R-R and R-IAS reflex models by pithing (destruction of the lumbar and sacral cords; PITH) and to evaluate whether the prokinetic benzamide mosapride, a 5-[HT.sub.4] receptor agonist, enhances these reflexes. The mechanical activities of the R-R and R-IAS were recorded in the anesthetized guinea pig on days 2-9 after PITH. Although the basal rectal pressure at distension after PITH was significantly lower than control, the reflex indexes of R-R contractions and synchronous R-IAS relaxations were unchanged between days 4 and 9 after PITH. The frequency of spontaneous rectal and IAS motility were also unchanged. Immunohistochemical studies revealed that the distribution of myenteric and intramuscular interstitial cells of Cajal (ICC) were not altered after PITH. Mosapride (0.1-1.0 mg/kg iv) dose-dependently increased both intrinsic R-R (maximum: 1.82) and R-IAS reflex indexes (maximum: 2,76) from control (1.0) 6-9 days after PITH. The 5-[HT.sub.4] receptor antagonist, GR-113808 (1.0 mg/kg iv) decreased the R-R and R-IAS reflex indexes by ~50% and antagonized the effect of mosapride (1.0 mg/kg iv). The present results indicate that mosapride moderately enhanced intrinsic R-R and R-IAS reflexes functionally compensated after deprivation of extrinsic nerves, mediated through endogenously active intrinsic 5-[HT.sub.4] receptors. extrinsic reflex; internal anal sphincter; intrinsic reflex; rectum

Nitric oxide (NO) relaxes the internal anal sphincter (IAS), but its enzymatic source(s) remains unknown; neuronal (nNOS) and endothelial (eNOS) NO synthase (NOS) isoforms could be involved. Also, interstitial cells of Cajal (ICC) may be involved in IAS relaxation. We studied the relative roles of nNOS, eNOS, and c-Kit-expressing ICC for IAS relaxation using genetic murine models. The basal IAS tone and the rectoanal inhibitory reflex (RAIR) were assessed in vivo by a purpose-built solid-state manometric probe and by using wild-type, nNOS-deficient ([nNOS.sup.-/-]), eNOS-deficient ([eNOS.sup.-/-]), and W/[W.sup.v] mice (lacking certain c-Kit-expressing ICC) with or without L-arginine or [N.sup.[omega]]-nitro-L-arginine methyl ester (L-NAME) treatment. Moreover, the basal tone and response to electrical field stimulation (EFS) were studied in organ bath using wild-type and mutant IAS. In vivo, the basal tone of [eNOS.sup.-/-] was higher and W/Wv was lower than wild-type and [nNOS.sup.-/-] mice. L-Arginine administered rectally, but not intravenously, decreased the basal tone in wild-type, [nNOS.sup.-/-], and W/[W.sup.v] mice. However, neither L-arginine nor L-NAME affected basal tone in [eNOS.sup.-/-] mice. In vitro, L-arginine decreased basal tone in wild-type and [nNOS.sup.-/-] IAS but not in [eNOS.sup.-/-] or wild-type IAS without mucosa. The in vivo RAIR was intact in wild-type, [eNOS.sup.-/-], and W/[W.sup.v] mice but absent in all [nNOS.sup.-/-] mice. EFS-induced IAS relaxation was also reduced in [nNOS.sup.-/-] IAS. Thus the basal IAS tone is largely controlled by eNOS in the mucosa, whereas the RAIR is controlled by nNOS. c-Kit-expressing ICC may not be essential for the RAIR. basal internal anal sphincter tone; electrical field stimulation; internal anal sphincter; nitric oxide synthases; rectoanal inhibitory reflex

The authors examined the incremental validity of the reaction time (RT) measure beyond that of skin conductance response (SCR) in the detection of concealed information. Participants performed a Stroop-like task in which they named the color of critical and neutral words. Results show that the SCR highly differentiated between the relevant and neutral words. However, the RT demonstrated a significant differentiation only when the critical words denoted personally significant items (e.g., one's own name) and not when they denoted crime-relevant items related to a simulated crime. In both cases, combining the 2 measures yielded no advantage over the use of SCR alone. Thus, although behavioral measures may differentiate between relevant and neutral information in some cases, their practical use is questionable.

Byline: B. V. Chernyshev (1), Ya. A. Panasyuk (1), I. I. Semikopnaya (1), N. O. Timofeeva (1) Keywords: basal magnocellular nucleus; neuron; acetylcholine; cholinergic activation; operant conditioned reflex; EEG; rabbit Abstract: Spike activity was studied in 95 neurons in the basal magnocellular nucleus in rabbits during spontaneous behavior and during performance of a conditioned operant response. Nearly half the neurons (48.4%) showed significant (p &lt 0.05) negative correlations between spontaneous discharges and the power of the frontal lobe EEG delta rhythm most of these cells could be identified as cholinergic projection neurons. Neurons of this group had predominantly excitatory responses to the conditioned stimulus during performance of the operant task, while the responses to the conditioned stimulus of presumptively non-cholinergic neurons, not projecting to the cortex, were mainly inhibitory. The activatory responses of neurons in the basal magnocellular nucleus to the conditioned stimulus were markedly stronger while the animals performed the operant response as compared with performances in which there was no response to the conditioned stimulus. These results provide evidence that the basal magnocellular nucleus supports the level of waking and attending required for performance of operant conditioned reflex activity. Author Affiliation: (1) Department of Higher Nervous Activity, M. V. Lomonosov Moscow State University, U.S.A. Article History: Registration Date: 29/12/2004

Keywords: c-Fos; contextual and conditioned reflex freezing; motor cortex; cingulate cortex; heterogeneity Article History: Registration Date: 07/10/2004

It has been suggested that the midbrain periaqueductal gray (PAG) is a neural integrating site for the interaction between the muscle pressor reflex and the arterial baroreceptor reflex. The underlying mechanisms are poorly understood. The purpose of this study was to examine the roles of GABA and nitric oxide (NO) in modulating the PAG integration of both reflexes. To activate muscle afferents, static contraction of the triceps surae muscle was evoked by electrical stimulation of the [L.sub.7] and [S.sub.1] ventral roots of 18 anesthetized cats. In the first group of experiments (n = 6), the pressor response to muscle contraction was attenuated by bilateral microinjection of muscimol (a GABA receptor agonist) into the lateral PAG [change in mean arterial pressure ([DELTA]MAP) = 24 [+ or -] 5 vs. 46 [+ or -] 8 mmHg in control]. Conversely, the pressor response was significantly augmented by 0.1 mM bicuculline, a GAB[A.sub.A] receptor antagonist ([DELTA]MAP = 65 [+ or -] 10 mmHg). In addition, the effect of GAB[A.sub.A] receptor blockade on the reflex response was significantly blunted after sinoaortic denervation and vagotomy (n = 4). In the second group of experiments (n = 8), the pressor response to contraction was significantly attenuated by microinjection of L-arginine into the lateral PAG ([DELTA]MAP = 26 [+ or -] 4 mmHg after L-arginine injection vs. 45 [+ or -] 7 mmHg in control). The effect of NO attenuation was antagonized by bicuculline and was reduced after denervation. These data demonstrate that GABA and NO within the PAG modulate the pressor response to muscle contraction and that NO attenuation of the muscle pressor reflex is mediated via arterial baroreflex-engaged GABA increase. The results suggest that the PAG plays an important role in modulating cardiovascular responses when muscle afferents are activated. blood pressure: exercise pressor reflex

Within the postmodern and critical managerial communication and pedagogical literature, reflexivity has traditionally been conceptualized as an epistemological practice that emphasizes intellectual critique. Little attention has been given to how managers act reflexively in conversation with other organizational members. This study sampled managers who were trained from a communication perspective that emphasizes reflexive practice. The results suggest managers adopt a more relationally responsive approach to reflexivity within their conversational practice, which incorporates elements of intellectual critique. Three implications of a relationally responsive approach to reflexivity within managerial practice are highlighted: (1) reflexive practice should be viewed as a relational activity that highlights issues of situated judgment, timing, and rhythm within conversation, (2) reflexive practice emphasizes inclusive, respectful, and safe communication, and (3) reflexive practice is connected to empowerment. Keywords: Reflexivity; Management; Story; Affirmation; Multivocality

Byline: N. G. Starosel'tseva (1), G. A. Ivanichev (1) Keywords: spinobulbospinal reflex; CNS pathology Abstract: Data from 25 years of studies of the spinobulbospinal (SBS) reflex in normal conditions and in a variety of nervous system diseases with lesions of the afferent and efferent systems, subcortical brain formations, and musculature (contracture of the expressive muscles, myofascial pain syndrome) are presented. The instability of many characteristics of the reflex (latency, amplitude, duration of response, presence) is shown to characterize this reflex in normal conditions. These measures become more stable in central nervous system pathology, which is evidence for impairment of programs which construct and execute movements. Lesions of the peripheral neuromotor apparatus produced no significant changes in the characteristics of the SBS reflex. Author Affiliation: (1) Department of Neurology and Reflex Therapy, Kazan' Medical Academy, Russia Article History: Registration Date: 12/10/2004

Byline: I. I. Kozlovskii (1), N. D. Danchev (1) Keywords: conditioned active avoidance reflex; neuropeptides; learning; memory Abstract: The actions of the synthetic heptapeptide preparation Selank on learning and memory processes in rats with initially low levels of learning ability were compared with those in normal rats, using a method based on acquisition of a conditioned active avoidance reflex, with repeated administration of peptide 15 min before the start of training sessions for four days. The effects of Selank (300 ug/kg) were compared with the effects of the nootrope piracetam (400 mg/kg). These experiments showed that Selank significantly activated the learning process in rats with initially poor learning ability, with effects apparent after first dose on training day 1. The effect progressively increased on repeated administration of Selank: the total number of correct solutions increased and the number of errors decreased (p &lt 0.05). The maximum optimizing activity of Selank on learning in normal rats was seen on day 3 of repeated administration and training, i.e., after formation of the initial consolidation phase. The dynamic features of the development of the activating action of Selank and piracetam were described. Comparison of the results obtained here with data on the anti-anxiety actions of Selank suggested potential for its use in optimizing mnestic functions in conditions of elevated emotional tension. Author Affiliation: (1) Science Research Institute of Pharmacology, Russian Academy of Medical Sciences, Moscow Article History: Registration Date: 12/10/2004

Byline: T. Kh. Gainutdinova (1), V. V. Andrianov (1), Kh. L. Gainutdinov (1) Keywords: conditioned reflex; excitability; membrane potential; threshold potential; serotonin; 5,6-dihydroxytryptamine Abstract: The role of serotonin in the membrane properties of identified neurons was studied during acquisition of a conditioned defensive reflex. Serotonin deficiency was created using the neurotoxic serotonin analog 5,6-dihydroxytryptamine (5,6-DHT). Injection of 5,6-DHT was found to prevent decreases in the membrane and threshold potentials of command neurons during acquisition of the conditioned reflex as compared with snails given 5,6-DHT without training. Common snails recovered the ability to acquire the conditioned reflex two weeks after a second 5,6-DHT injection. Author Affiliation: (1) Biophysics Laboratory, Kazan', Physical-Technical Institute, Russian Academy of Sciences, 10/7 Sibirskii Trakt, 420029, Kazan'-29, Russia Article History: Registration Date: 12/10/2004

Byline: V. M. Storozhuk (1), V. I. Khorevin (1), N. N. Razumna (1), I. V. Tetko (2), A. P. Villa (2) Abstract: Changes in conditioned reflex spike activity of neurons in the sensorimotor cortex were studied during microiontophoretic application of agonists and antagonists of glutamate and GABAergic transmission. The results of these experiments showed that the glutamate ionotropic receptors (AMPA and NMDA) of neurons in the sensorimotor cortex were intensely activated by the arrival of a conditioned signal in the cortex. This response included not only large pyramidal neurons of the deep cortical layers, but also the surrounding inhibitory interneurons. The existence of constant tonic inhibitory regulation of the activity of large pyramidal neurons by the surrounding inhibitory cells was demonstrated, along with the active involvement of this inhibition in organizing the excitatory responses of neurons in the sensorimotor cortex during a conditioned reflex. Author Affiliation: (1) A. A. Bogomolets Institute of Physiology, Ukrainian National Academy of Sciences, Kiev, Ukraine (2) Institute of Physiology, Lausanne University, Lausanne, Switzerland Article History: Registration Date: 12/10/2004

Byline: N. Yu. Ivlieva (1), N. O. Timofeeva (1) Abstract: The activity of 109 neurons in the compact and diffuse zones of the pedunculopontine nucleus was studied in freely mobile rabbits during the acquisition and performance of a defensive operant conditioned reflex. A total of 47% of the neurons recorded showed responsive properties to the conditioned stimulus, which is evidence for the involvement of the pedunculopontine nucleus in operant learning. A significant predominance of excitatory conditioned reflex responses to the conditioned stimulus was demonstrated, showing that the nature of the influence of the pedunculopontine nucleus on projection structures during learning is mostly excitatory. The main patterns of cell responses to the conditioned stimulus were identified, these reflecting the nature of the influence of the conditioned stimulus on neuron activity, the structure of the behavioral act, and the properties of the reinforcement, suggesting a relationship between the pedunculopontine nucleus and the processes of attention, motor learning, and reinforcement. A significant decrease in the reactivity of neurons in the pedunculopontine nucleus to the conditioned stimulus as a result of specialization due to learning was demonstrated. Differences in the associative reactive properties of the compact and diffuse zones of the pedunculopontine nucleus to the conditioned stimulus were identified, which is evidence for the functional heterogeneity of this formation and suggests a leading role for the cholinergic compact zone in operant defensive behavior. Author Affiliation: (1) Department of Higher Nervous Activity, M. V. Lomonosov Moscow State University, Russia Article History: Registration Date: 12/10/2004

Postural reflex activity during unperceived perturbation of standing was investigated in 38 elderly subjects (70-96 years old) and 10 younger adults (19-48 years old), and it was related in the elderly group to a history of unexplained falling in the 12 months prior to testing. Ankle torque (T) and ankle angle (A) were recorded during unperceived forward pulls to obtain the ankle stiffness ([DELTA]T/[DELTA]A), providing a measure of postural reflex activity at the ankle. Elderly nonfallers and younger adults had similar ranges of normalized ankle reflex stiffness. High ankle stiffness was significantly more common in elderly multiple fallers than in elderly nonfallers (p = .018). Furthermore, a majority of unstable elderly subjects who had reported a single unexplained fall also had unusually high ankle stiffness (p = .004). Multiple fallers and unstable subjects tended to overshoot backward on pull release in comparison with nonfallers (p = .003), which is suggestive of an overactive reflex response that might contribute to postural instability.

Abstract: A concept of the orientating reflex is presented, based on the principle of vector coding of cognitive and executive processes. The orientating reflex is a complex of orientating reactions of motor, autonomic, and subjective types, accentuating new and significant stimuli. Two main systems form the orientating reflex: the 'targeting reaction' and the 'searchlight of attention.' In the visual system, the targeting reaction ensures that the image of the object falls onto the fovea this is mediated by involvement of premotor neurons which are excited by saccade command neurons in the superior colliculi. The 'searchlight of attention' is activated as a result of resonance within the gamma frequency range, selectively enhancing cortical detectors and involving the reticular nucleus of the thalamus. Novelty signals arise in novelty neurons of the hippocampus. The synaptic weightings of neocortical detectors for hippocampal novelty neurons is initially characterized by high efficiency, which assigns a significant level of excitation of these neurons to the new stimulus. During repeated stimulation, the synaptic weightings of all the detectors representing a given stimulus decrease, with the result that the novelty signal becomes weaker. When the stimulus changes, it acts on other detectors, whose weightings for novelty neurons remain high, which strengthens the novelty signal. Decreases in the synaptic weightings on repetition of a standard stimulus form a trace of this stimulus in the novelty neurons -- this is the 'neural model of the stimulus.' The novelty signal is determined by the non-concordance of the new stimulus with this 'neural model,' which is formed under the influence of the standard stimulus. The greater the difference between the new stimulus and the previously formed neural model, the stronger the novelty signal. Article History: Registration Date: 10/10/2004

Byline: A. A. Azarashvili (1) Author Affiliation: (1) Metabolic Biophysics Laboratory, Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino Article History: Registration Date: 10/10/2004

Byline: N. S. Sapronov (1), Yu. O. Fedotova (1) Abstract: The effects of L-tryptophan on conditioned reflex learning and behavior were studied in male rats with deficient and excess thyroid hormones levels. The learning process was studied using a model consisting of a conditioned active avoidance response animal behavior was assessed in an open field test. These studies showed that in conditions of thyroid hormone deficiency, L-tryptophan had positive effects on the acquisition and reproduction of the active avoidance reflex, restoring the ability of the animals to learn actively L-tryptophan increased investigative activity in the open field test. In conditions of increased thyroid hormone levels, L-tryptophan reversed the mild stimulating effects of thyroid hormones on the processes of developing and performing the active avoidance habit, and increased investigative activity, but decreased the amount of grooming. Author Affiliation: (1) S. V. Anichkov Department of Neuropharmacology, Science Research Institute of Experimental Medicine, Russian Academy of Medical Sciences, St. Petersburg Article History: Registration Date: 10/10/2004

Byline: V. V. Fanardzhyan (1), E. V. Papoyan (1), V. I. Pogosyan (1), O. V. Gevorkyan (1) Keywords: ventrolateral nucleus of the thalamus; operant reflexes; switching of descending influences; rats Abstract: Studies on rats showed that the facilitating influence of preliminary transection of the rubrospinal tract on recovery of motor activity and operant reflexes disrupted by lesioning of the red nucleus was more apparent when lesioning was chemical than when lesioning was electrolytic. This is due to the survival of cerebellothalamic fibers to the ventrolateral nucleus of the thalamus after chemical lesioning of the red nucleus with quinolinic acid. It was also shown that preliminary lesioning of the ventrolateral thalamic nucleus strongly hindered the switching of motor activity under the control of the corticospinal tract in rats subjected to section of the rubrospinal tract and lesioning of the red nucleus. Author Affiliation: (1) Laboratory for Central Nervous System Physiology, L. A. Orbeli Institute of Physiology, Armenian National Academy of Sciences, 22 Orbeli Brothers Street, 375028, Erevan, Armenia Article History: Registration Date: 10/10/2004

Byline: I. N. Pleshchinskii (1), R. Kh. Bikmullina (1), N. A. Shamshurina (1), R. Yu. Iskhakova (1) Abstract: The influence of cutaneous afferents of the medial plantar and sural nerves on the reflex excitability of thesoleusmuscle motoneurons and on reciprocal and nonreciprocal interactions between the gastrocnemius medialis, tibialis anterior, and soleusmuscles was studied in healthy volunteers by testing H-reflexes. Cutaneous afferents influenced reflex excitability of the soleusmotoneurons. Stimulation of cutaneous afferents changed the effects produced earlier by isolated stimulation of synergist and antagonist afferents. This confirms convergence of cutaneomuscular afferents on common interneurons. The authors postulate the existence of parallel 'cutaneous' channels (including those with an alternative influence), whose hierarchy is determined by the situation and, probably, by some other individual features. Author Affiliation: (1) Kazan State University, Kazan, Russia Article History: Registration Date: 16/10/2004

Byline: A. S. Bazyan (1), V. M. Getsova (1), N. V. Orlova (1) Keywords: pharmacological reminder; emotional state; retrieval from memory; convulsions; amnesia; pentylenetetrazole; haloperidol Abstract: The experiments reported here show that animals with different levels of acquisition of a conditioned passive avoidance reflex retrieved the reflex differently on systematic testing over a period of 28 days. Animals with the highest and high levels of training reproduced the reflex stably. Animals with an intermediate level of training reproduced the reflex with significant variation. Convulsions induced by pentylenetetrazole (75 and 50 mg/kg, i.p.) resulted in amnesia. The amnestic effect of pentylenetetrazole convulsions depended on the ratio of the intensity of training and the intensity of the induction of convulsions. Reminding, provided by presentation of an unconditioned stimulus, removed the amnestic effect of the convulsive state. Training led to significant decreases in the parameters determining the severity of the convulsive state. The convulsive state was a dissociative state, as subconvulsive doses of pentylenetetrazole (30 mg/kg, i.p.) removed the amnestic effect of convulsive doses. The dissociated state was reproduced by pharmacological reminding of the state of anxiety and fear which was formed during training. A subcataleptic dose of haloperidol (0.25 mg/kg, i.p.) induced a state of fear and removed the amnestic effect of the convulsive state. The same dose of haloperidol improved retrieval of the reflex in animals with low levels of training, i.e., those in which retrieval hardly occurred in normal conditions. Author Affiliation: (1) Laboratory of the Neurochemical Mechanisms of Learning and Memory, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, 5A Butlerov Street, 117865, Moscow, Russia Article History: Registration Date: 08/10/2004

Keywords: suprachiasmatic nuclei; hippocampus Abstract: Electrolytic destruction of the dorsal hippocampus prevented the acquisition of a conditioned reflex to time regardless of the volume of brain damage. A similar effect was obtained in rats with combined lesions consisting of damage to the suprachiasmatic nuclei of the hypothalamus and hippocampectomy (in the same animal). Denucleation (without hippocampectomy), conversely, accelerated the acquisition of this type of time-related behavior. Lesions to the hippocampus had no effect on the recovery of the conditioned reflex to time when this had been fixed before surgery in denucleated rats. It is proposed that the suprachiasmatic nuclei and hippocampus have simultaneous roles in organizing the endogenous counting of short time periods. Article History: Registration Date: 08/10/2004

Byline: V. N. Khokhlova (1), G. Kh. Merzhanova (1), E. E. Dolbakyan (1) Abstract: Experiments on cats showed that lesions affecting retrieval of an operant food-procuring reflex, occurring on a background of systemic administration of the centrally-acting muscarinic cholinoceptor blocker scopolamine (a non-selective M-cholinoceptor blocker) and trihexyphenidyl (a relatively selective M1-cholinoceptor blocker), might be associated with the central and peripheral side effects of these blockers, preventing performance of the conditioned reflex. It was established that when no side effects were present (low doses of trihexyphenidyl, 1 mg/kg), blockade of M1-cholinoceptors led to selective loss of the motor operant reflex while contextual behavior and other conditioned responses were retained or led to errors in performance of the reflex this appears to be evidence that derangement of launching and performing the motor program is the most important component of the conditioned reflex. Systemic administration of trihexyphenidyl at a dose of 10 mg/kg, scopolamine at doses of 0.03 and 0.06 mg/kg, and the peripherally-acting non-selective blocker methylscopolamine at a dose of 0.03 mg/kg led to changes in the general functional state (disturbances in the emotional-motivational sphere), the extent of which depended on the individual sensitivity of the animal to the anticholinergic agents. The presence of side effects led to complete cessation of conditioned reflex activity, though this appeared not to be associated with memory impairment. Author Affiliation: (1) Russian Academy of Sciences, Institute of Higher Nervous Activity and Neurophysiology, Moscow Article History: Registration Date: 08/10/2004

Byline: G. I. Shul'gina (1) Abstract: Administration of the NO-generating substance sodium nitrite to conscious non-immobilized rabbits at a dose of 11 mg/kg (s.c.) decreased the intensity and duration of the short-latency 'modality-specific' components of the responses of neurons in the visual cortex (to flashes of light) and sensorimotor cortex (to pain reinforcement). Decreases in neuron activation in the visual cortex in response to flashes of light occurred independently of their biological significance, i.e., as the signal for a defensive reflex and on the background of conditioned inhibition. The long-latency activatory components of the response of sensorimotor and visual cortex neurons to pain reinforcement, the inhibitory pause in the responses of visual cortex neurons to flashes of light, and the disinhibitory effect of pain reinforcement showed smaller changes after sodium nitrite. The results obtained here support the suggestion that different neuromediators are involved in transmitting 'modality-specific' and 'modality-non-specific' influences to neocortical neurons during learning, and provide the basis for suggesting that sodium nitrite has a neurotropic action when given systemically. Author Affiliation: (1) Russian Academy of Sciences, Institute of Higher Nervous Activity and Neurophysiology, Moscow Article History: Registration Date: 08/10/2004

Little is known of the functionality of the vestibulo-collic reflex (VCR) and cervico-collic reflex (CCR) during head and neck movements caused by perturbations of the trunk. Previously, we formulated mathematical expressions for these neck reflexes and incorporated them into a model of horizontal plane head movements. The formalism of this neuromechanical model allowed us to examine separately the main components of head movement control. In the present study, we examine selected parameters within the main components of the model, and associate variations of these parameters with disease processes affecting head and neck movements, such as loss of sensory input or modification in central or motor function. Our simulations led us to several conclusions. First, the probable use of the VCR and CCR in yaw plane had movements is to tune the head response. In the time domain, they diminish natural head oscillations (head wobble) related to head mechanics. Equivalently, in the frequency domain, they reduce the amplitude of head wobble (resonances) around 2 hz. Second, our simulations suggest that the VCR is about ten times stronger than the CCR in normal humans. Moreover, this disproportion is associated with only very minor contributions from the CCR in yaw. Third, head oscillations (or instability) can be generated by mechanical or neural changes in the head and neck system. Finally, readjustments of central nervous system dynamic operations could provide mechanisms to compensate for sensory and motor dysfunction caused by disease. Index Terms: Head, model, neck, reflex, vestibular

Research was conducted to examine the hypothesis that naloxone reverses the inhibitory effect of electroacupuncture (EA) on sympathetic cardiovascular reflex responses. The percutaneous EA was utilized in the feline model of repeatable, reversible, reflex-induced myocardial ischemia before and after the administration of an opioid antagonist, naloxone, either by microinjection or intravenously into the paragigantocellularis lateralis. Results suggest that the inhibitory influence of EA on the bradykinin-induced pressor response and the consequent improvement of ischemic dysfunction depends on the activation of opioid receptors.