Multisynaptic Projections Research Articles

A multisynaptic pathway from the ventral midbrain toward spinal motoneurons in monkeys.

Motivation boosts motor performance. Activity of the ventral midbrain (VM), consisting of the ventral tegmental area (VTA), the substantia nigra pars compacta (SNc) and the retrorubral field (RRF), plays an important role in processing motivation. However, little is known about the neural substrate bridging the VM and the spinal motor output. We hypothesized that the VM might exert a modulatory influence over the descending motor pathways. By retrograde transneuronal labelling with rabies virus, we demonstrated the existence of multisynaptic projections from the VM to the cervical enlargement in monkeys. The distribution pattern of spinal projection neurons in the VM exhibited a caudorostral gradient, in that the RRF and the caudal part of the SNc contained more retrogradely labelled neurons than the VTA and the rostral part of the SNc. Electrical stimulation of the VM induced muscle responses in the contralateral forelimb with a delay of a few milliseconds following the responses of the ipsilateral primary motor cortex (M1). The magnitude and number of evoked muscle responses were associated with the stimulus intensity and number of pulses. The muscle responses were diminished during M1 inactivation. Thus, the present study has identified a multisynaptic VM–spinal pathway that is mediated, at least in part, by the M1 and might play a pivotal role in modulatory control of the spinal motor output.Key points Motivation to obtain reward is thought to boost motor performance, and activity in the ventral midbrain is important to the motivational process.Little is known about a neural substrate bridging the ventral midbrain and the spinal motor output.Retrograde trans‐synaptic experiments revealed that the ventral midbrain projects multisynaptically to the spinal cord in macaque monkeys.Ventral midbrain activation by electrical stimulation generated cortical activity in the motor cortex and forelimb muscle activity.A multisynaptic ventral midbrain–spinal pathway most probably plays a pivotal role in modulatory control of the spinal motor output.

Multisynaptic Projections from the Amygdala to the Ventral Premotor Cortex in Macaque Monkeys: Anatomical Substrate for Feeding Behavior.

The amygdala codes the visual-gustatory/somatosensory valence for feeding behavior. On the other hand, the ventral premotor cortex (PMv) plays a central role in reaching and grasping movements prerequisite for feeding behavior. This implies that object valence signals derived from the amygdala may be crucial for feeding-related motor actions exerted by PMv. However, since no direct connectivity between the amygdala and PMv has been reported, the structural basis of their functional interactions still remains elusive. In the present study, we employed retrograde transneuronal labeling with rabies virus to identify the amygdalar origin and possible route of multisynaptic projections to PMv in macaque monkeys. Histological analysis of the distribution pattern of labeled neurons has found that PMv receives disynaptic input primarily from the basal nucleus, especially from its intermediate subdivision. It has also been revealed that the medial (e.g., the cingulate motor areas, CMA) and lateral (e.g., the insular cortices) cortical areas, and the cholinergic cell group 4 in the basal forebrain probably mediate the projections from the amygdala to PMv. Such multisynaptic pathways might represent amygdalar influences on PMv functions for feeding behavior.

PS49. Shifted Circadian Phase in Manic Episode was Returned to Normal after Treatment in Bipolar Disorder

EBioMedicine 11 (2016) 285–295 Contents lists available at ScienceDirect EBioMedicine journal homepage: www.ebiomedicine.com Research Paper Advanced Circadian Phase in Mania and Delayed Circadian Phase in Mixed Mania and Depression Returned to Normal after Treatment of Bipolar Disorder Joung-Ho Moon M.S. a,b,1 , Chul-Hyun Cho M.D., Ph.D. a,1 , Gi Hoon Son Ph.D. c , Dongho Geum Ph.D. b , Sooyoung Chung Ph.D. d , Hyun Kim M.D., Ph.D. e , Seung-Gul Kang M.D., Ph.D. f , Young-Min Park M.D., Ph.D. g , Ho-Kyoung Yoon M.D., Ph.D. a , Leen Kim M.D., Ph.D. a , Hee-Jung Jee M.S. h , Hyonggin An Ph.D. h , Daniel.F. Kripke M.D. i , Heon-Jeong Lee M.D., Ph.D. a,b, ⁎ a Dept. of Psychiatry, Korea Univ. College of Medicine, Seoul, South Korea Dept. of Biomedical Sciences, Korea Univ. College of Medicine, Seoul, South Korea Dept. of Legal Medicine, Korea Univ. College of Medicine, South Korea d Dept. of Brain and Cognitive Science, Ewha Womans Univ., Seoul, South Korea e Dept. of Anatomy, Korea Univ. College of Medicine, Seoul, South Korea f Dept. of Psychiatry, School of Medicine, Gachon Univ., Incheon, South Korea g Dept. of Psychiatry, Inje Univ. College of Medicine, Ilsan, South Korea h Dept. of Biostatistics, Korea Univ. College of Medicine, Seoul, South Korea i Dept. of Psychiatry, University of California, San Diego, CA, USA b c a r t i c l e i n f o Article history: Received 18 July 2016 Received in revised form 11 August 2016 Accepted 12 August 2016 Available online 13 August 2016 Keywords: Circadian rhythm Bipolar disorders Phase shift Circadian dysregulation a b s t r a c t Disturbances in circadian rhythms have been suggested as a possible cause of bipolar disorder (BD). Included in this study were 31 mood episodes of 26 BD patients, and 18 controls. Circadian rhythms of BD were evaluated at admission, at 2-week intervals during hospitalization, and at discharge. All participants wore wrist actigraphs during the studies. Saliva and buccal cells were obtained at 8:00, 11:00, 15:00, 19:00, and 23:00 for two consecutive days. Collected saliva and buccal cells were used for analysis of the cortisol and gene circadian rhythm, respectively. Circadian rhythms had different phases during acute mood episodes of BD compared to recovered states. In 23 acute manic episodes, circadian phases were ~7 hour advanced (equivalent to ~17 hour delayed). Phases of 21 out of these 23 cases returned to normal by ~ 7 hour delay along with treatment, but two out of 23 cases returned to normal by ~17 hour advance. In three cases of mixed manic episodes, the phases were ~ 6–7 hour delayed. For five cases of depressive episodes, circadian rhythms phases were ~ 4–5 hour delayed. After treatment, circadian phases resembled those of healthy controls. Circadian misalignment due to circadian rhythm phase shifts might be a pathophysiological mechanism of BD. © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 1. Introduction Bipolar disorder (BD) is a common mental disorder characterized by episodic mood symptoms of mania or depression. Episodic relapses of BD are very common, and therefore BD is one of the major leading causes of disability around the world (Goldberg and Harrow, 2004). Numerous etiologies for BD have been proposed, but there is no conclusive evidence. Humans exhibit an orchestration of circadian rhythmicity with respect to the light-dark cycle (Reppert and Weaver, 2002), involving regulation of physiological processes such as the autonomic nervous ⁎ Corresponding author at: Department of Psychiatry, Anam Hospital, Korea University College of Medicine, Anam-dong 5-ga, Seongbuk-gu, Seoul 136-705, South Korea. E-mail address: leehjeong@korea.ac.kr (H.-J. Lee). These authors contributed equally to this work. system, hormone secretion, and sleep-wake cycles (Dijk and Czeisler, 1995). Circadian rhythms can be entrained by both photic and nonphotic stimuli, however light plays the primary role in the entrainment of the human circadian pacemaker to the environment (Lavie, 2001). The hypothalamic suprachiasmatic nuclei (SCN) are a master clock for the orchestration of circadian rhythmicity. The SCN synchronize peripheral oscillators to ensure temporally coordinated physiology, while the peripheral oscillators interact among themselves and communicate back to the SCN (Schibler and Sassone-Corsi, 2002). The endogenous circadian rhythmicity affects timing for sleep-wake cycles and biochem- ical rhythms. The circadian regulation of the sleep-wake cycle is thought to be mediated by multisynaptic projections from the SCN to sleep-wake centers of the brain (Deurveilher and Semba, 2005; Saper et al., 2005). Biochemical rhythms such as cortisol concentrations are also thought to be affected by endogenous circadian timing systems (Bremner et al., http://dx.doi.org/10.1016/j.ebiom.2016.08.019 2352-3964/© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Origins of multisynaptic projections from the basal ganglia to the forelimb region of the ventral premotor cortex in macaque monkeys.

The ventral premotor cortex (PMv), occupying the ventral aspect of area 6 in the frontal lobe, has been implicated in action planning and execution based on visual signals. Although the PMv has been characterized by cortico-cortical connections with specific subregions of the parietal and prefrontal cortical areas, a topographical input/output organization between the PMv and the basal ganglia (BG) still remains elusive. In the present study, retrograde transneuronal labelling with the rabies virus was employed to identify the origins of multisynaptic projections from the BG to the PMv. The virus was injected into the forelimb region of the PMv, identified in the ventral aspect of the genu of the arcuate sulcus, in macaque monkeys. The survival time after the virus injection was set to allow either the second- or third-order neuron labelling across two or three synapses. The second-order neurons were observed in the ventral portion (primary motor territory) and the caudodorsal portion (higher-order motor territory) of the internal segment of the globus pallidus. Subsequently, the third-order neurons were distributed in the putamen caudal to the anterior commissure, including both the primary and the higher-order motor territories, and in the ventral striatum (limbic territory). In addition, they were found in the dorsolateral portion (motor territory) and ventromedial portion (limbic territory) of the subthalamic nucleus, and in the external segment of the globus pallidus including both the limbic and motor territories. These findings indicate that the PMv receives diverse signals from the primary motor, higher-order motor and limbic territories of the BG.

Multisynaptic projections from the ventrolateral prefrontal cortex to hand and mouth representations of the monkey primary motor cortex

Different sectors of the prefrontal cortex have distinct neuronal connections with higher-order sensory areas and/or limbic structures and are related to diverse aspects of cognitive functions, such as visual working memory and reward-based decision-making. Recent studies have revealed that the prefrontal cortex (PF), especially the lateral PF, is also involved in motor control. Hence, different sectors of the PF may contribute to motor behaviors with distinct body parts. To test this hypothesis anatomically, we examined the patterns of multisynaptic projections from the PF to regions of the primary motor cortex (MI) that represent the arm, hand, and mouth, using retrograde transsynaptic transport of rabies virus. Four days after rabies injections into the hand or mouth region, particularly dense neuron labeling was observed in the ventrolateral PF, including the convexity part of ventral area 46. After the rabies injections into the mouth region, another dense cluster of labeled neurons was seen in the orbitofrontal cortex (area 13). By contrast, rabies labeling of PF neurons was rather sparse in the arm-injection cases. The present results suggest that the PF-MI multisynaptic projections may be organized such that the MI hand and mouth regions preferentially receive cognitive information for execution of elaborate motor actions.

Chondroitinase ABC combined with neurotrophin NT-3 secretion and NR2D expression promotes axonal plasticity and functional recovery in rats with lateral hemisection of the spinal cord.

Elevating spinal levels of neurotrophin NT-3 (NT3) while increasing expression of the NR2D subunit of the NMDA receptor using a HSV viral construct promotes formation of novel multisynaptic projections from lateral white matter (LWM) axons to motoneurons in neonates. However, this treatment is ineffective after postnatal day 10. Because chondroitinase ABC (ChABC) treatment restores plasticity in the adult CNS, we have added ChABC to this treatment and applied the combination to adult rats receiving a left lateral hemisection (Hx) at T8. All hemisected animals initially dragged the ipsilateral hindpaw and displayed abnormal gait. Rats treated with ChABC or NT3/HSV-NR2D recovered partial hindlimb locomotor function, but animals receiving combined therapy displayed the most improved body stability and interlimb coordination [Basso-Beattie-Bresnahan (BBB) locomotor scale and gait analysis]. Electrical stimulation of the left LWM at T6 did not evoke any synaptic response in ipsilateral L5 motoneurons of control hemisected animals, indicating interruption of the white matter. Only animals with the full combination treatment recovered consistent multisynaptic responses in these motoneurons indicating formation of a detour pathway around the Hx. These physiological findings were supported by the observation of increased branching of both cut and intact LWM axons into the gray matter near the injury. ChABC-treated animals displayed more sprouting than control animals and those receiving NT3/HSV-NR2D; animals receiving the combination of all three treatments showed the most sprouting. Our results indicate that therapies aimed at increasing plasticity, promoting axon growth and modulating synaptic function have synergistic effects and promote better functional recovery than if applied individually.

Origins of multisynaptic projections from the basal ganglia to rostrocaudally distinct sectors of the dorsal premotor area in macaques

We examined the organization of multisynaptic projections from the basal ganglia (BG) to the dorsal premotor area in macaques. After injection of the rabies virus into the rostral sector of the caudal aspect of the dorsal premotor area (F2r) and the caudal sector of the caudal aspect of the dorsal premotor area (F2c), second-order neuron labeling occurred in the internal segment of the globus pallidus (GPi) and the substantia nigra pars reticulata (SNr). Labeled GPi neurons were found in the caudoventral portion after F2c injection, and in the dorsal portion at the rostrocaudal middle level after F2r injection. In the SNr, F2c and F2r injections led to labeling in the caudal or rostral part, respectively. Subsequently, third-order neuron labeling was observed in the external segment of the globus pallidus (GPe), the subthalamic nucleus (STN), and the striatum. After F2c injection, labeled neurons were observed over a broad territory in the GPe, whereas after F2r injection, labeled neurons tended to be restricted to the rostral and dorsal portions. In the STN, F2c injection resulted in extensive labeling over the nucleus, whereas F2r injection resulted in labeling in the ventral portion only. After both F2r and F2c injections, labeled neurons in the striatum were widely observed in the striatal cell bridge region and neighboring areas, as well as in the ventral striatum. The present results revealed that the origins of multisynaptic projections to F2c and F2r in the BG are segregated in the output stations of the BG, whereas intermingling rather than segregation is evident with respect to their input station.

Disruption of GABAergic tone in the dorsomedial hypothalamus attenuates responses in a subset of serotonergic neurons in the dorsal raphe nucleus following lactate-induced panic.

Panic patients are vulnerable to induction of panic attacks by sub-threshold interoceptive stimuli such as intravenous (i.v.) sodium lactate infusions. Facilitation of serotonergic signaling with selective serotonin reuptake inhibitors can suppress anxiety and panic-like responses, but the mechanisms involved are not clearly defined. We investigated the effects of i.v. 0.5 M sodium lactate or saline, in control and panic-prone rats on c-Fos expression in serotonergic neurons within subdivisions of the midbrain/pontine raphe nuclei. Rats were chronically infused with either the GABA synthesis inhibitor l-allylglycine into the dorsomedial hypo thalamus to make them panic-prone, or the enantiomer d-allylglycine (d-AG) in controls. Lactate increased c-Fos expression in serotonergic neurons located in the ventrolateral part of the dorsal raphe nucleus (DRVL) and ventrolateral periaqueductal gray (VLPAG) of control, but not panic-prone, rats. The distribution of lactate-sensitive serotonergic neurons in d-AG-treated rats is virtually identical to previously defined pre-sympathomotor serotonergic neurons with multisynaptic projections to peripheral organs mediating 'fight-or-flight'-related autonomic and motor responses. We hypothesized that serotonergic neurons within the DRVL/VLPAG region represent a 'sympathomotor control system' that normally limits autonomic/behavioral responses to innocuous interoceptive and exteroceptive stimuli, and that dysfunction of this serotonergic system contributes to an anxiety-like state and increases vulnerability to panic in animals and humans.

Hypothalamic neurons innervating fat tissue in the pig express leptin receptor immunoreactivity

While leptin receptors have been found in both the autonomic ganglion neurons and the hypothalamic nuclei, studies dealing with the projections from the central nervous system to the adipose tissue have been conducted mainly in laboratory animals. Therefore, the purpose of our study was to establish whether hypothalamic neurons are transsynaptically connected to adipose tissue depots in the pig, and if these neurons express leptin receptor immunoreactivity. Pseudorabies virus (PRV; Bartha's K strain) was introduced in perirenal or subcutaneous adipose tissue depots in domestic pigs. On day 9, animals were euthanized and hypothalami were collected and processed immunohistochemically with primary antisera against PRV and leptin receptor (OBR). PRV-labeled neurons were localized in paraventricular nucleus, supraoptic nucleus and arcuate nucleus following injections in both the perirenal and the subcutaneous adipose tissue depots. Ventromedial nucleus, dorsomedial nucleus and preoptic area-labeled neurons were observed after injection of the PRV into the perirenal adipose tissue, while in the lateral hypothalamic area-labeled neurons projected only to the subcutaneous adipose tissue. The majority of the PRV-labeled neurons simultaneously expressed OBR-immunoreactivity. Our results provide the morphological data on multisynaptic projections from hypothalamus to the fat tissue in the pig and demonstrate that these neurons, located in areas involved in reproductive processes and feeding behavior, may regulate fat tissue metabolism.

Somatotopically arranged inputs from putamen and subthalamic nucleus to primary motor cortex

Employing retrograde transsynaptic transport of rabies virus, we investigated the organization of basal ganglia inputs to hindlimb, proximal and distal forelimb, and orofacial representations of the macaque primary motor cortex (MI). Four days after rabies injections into these MI regions, neuronal labeling occurred in the striatum and the subthalamic nucleus (STN) through the cortico-basal ganglia loop circuits. In the striatum, two distinct sets of the labeling were observed: one in the dorsal putamen, and the other in the ventral striatum (ventromedial putamen and nucleus accumbens). The dorsal striatal labeling was somatotopically arranged and its distribution pattern was in good accordance with that of the corticostriatal inputs, such that the hindlimb, orofacial, or forelimb area was located in the dorsal, ventral, or intermediate zone of the putamen, respectively. The distribution pattern of the ventral striatal labeling was essentially the same in all cases. In the STN, the somatotopic arrangement of labeled neurons was in register with that of corticosubthalamic inputs. The present results suggest that the cortico-basal ganglia motor circuits involving the dorsal putamen and the STN may constitute separate closed loops based on the somatotopy, while the ventral striatum provides common multisynaptic projections to all body-part representations in the MI.

Imaging of acute versus pathological pain in humans

Pain subserves different functions. Acute pain from the intact body alerts the victim to immediately react and withdraw from the bodily threat, ideally before an injury happens. However, during manifest injury and tissue inflammation, withdrawal and flight are no longer adaptive. Instead, sparing the affected body part to promote healing requires heightened awareness and avoidance behaviour over longer periods of time. Quality and time scales of behavioural adaptations are therefore substantially different between pain during normal compared to abnormal tissue states. Given these functional differences we postulated that the two phenomena also recruit different forebrain systems. We used positron emission tomography (PET) and subtracted scans obtained during painful heating of normal skin from scans during equally intense but normally non-painful heating of capsaicin-treated skin. This comparison reveals the specific activation of a medial thalamic pathway to limbic forebrain structures such as anterior insula, perigenual anterior cingulate, ventral striatum, and prefrontal cortex during pain originating in the chemically sensitised skin. It is possible that the unique forebrain recruitment by pain under a patho-physiological tissue status is caused by a significantly greater facilitation of the multi-synaptic projections from the spino-parabrachial tract of the superficial dorsal horn to the medial thalamus compared to deeper and direct lateral thalamic projections from the spino-thalamic tract.

Expression of c-fos protein in rat brain elicited by electrical and chemical stimulation of the hypothalamic paraventricular nucleus.

The functional connectivity of the paraventricular nucleus of the hypothalamus (PVN) was studied by assessing the expression of the immediate early gene, c-fos, after unilateral stimulation of this structure in urethane-anesthetized rats. Electrical stimulation for 1 h (10 s on, 10 s off; 15-40 microA at 20 Hz) was accompanied by increases in mean arterial pressure (13-29 mm Hg). In these animals, ipsilateral increases in numbers of neurons with Fos-like immunoreactivity (FLI) were immunohistochemically demonstrated in the insular cortex, lateral septum, medial amygdala, hypothalamus, lateral division of the parabrachial nucleus (PBN) of the pons and the nucleus of the tractus solitarius (NTS) and ventrolateral medulla (VLM). Numbers of cells with FLI were quantitated in five areas known for their roles in autonomic function: arcuate nucleus, ventromedial hypothalamus, lateral PBN, NTS (at three levels) and VLM (caudal and rostral). In each case, stimulation of the PVN led to significant differences in number of neurons with FLI on the side ipsilateral to the stimulation compared to the contralateral side. To eliminate effects associated with stimulation of fibers of passage in the vicinity of the PVN, the results after electrical stimulation were compared to those obtained in animals in which the PVN was chemically stimulated unilaterally with the excitatory amino acid L-glutamate (5 one-minute infusions of 50 nl, 0.5 M glutamate over 1 h). Mean arterial pressure was increased after each injection (7-13 mm Hg), and significant differences in numbers of neurons with FLI between sides were maintained in all five areas except the NTS caudal to, and at, the level of the area postrema. An increase in neurons with FLI in the piriform cortex of all animals including controls may be due to injury-induced activation of target neurons from the PVN. These data illustrate that electrical and chemical stimulation of the PVN leads to simultaneous activation of neurons in many targets. All of the target areas studied receive direct projections from the PVN, although multisynaptic projections may also contribute to activation of target neurons.

Lesions of the retrosplenial cortex produce deficits in reversal learning of the rabbit nictitating membrane response: implications for potential interactions between hippocampal and cerebellar brain systems.

The effect of bilateral lesions of the retrosplenial cortex on discrimination reversal learning of the rabbit nictitating membrane response was examined. Results showed that animals with such lesions were not impaired in their ability to acquire a cross-modality discrimination, but were severely impaired in their ability to reverse the discrimination once it was learned. All animals failed at the reversal phase of the task because they displayed high levels of conditioned responding to both the CS+ and the CS-. Thus bilateral damage to the retrosplenial cortex results in deficits in reversal learning that are highly similar to those observed after bilateral hippocampectomy. These findings are interpreted within a conceptual framework that characterizes multisynaptic projections from the hippocampus to the retrosplenial cortex, and ultimately to the cerebellum, as responsible for the behavioral expression of learning-related changes in hippocampal pyramidal cell activity.