Hiroshi Ushiro

Neural circuits and functional organization of the striatum

Abstract The basal ganglia and motor thalamic nuclei are functionally and anatomically divided into the sensorimotor, supplementary motor, premotor, associative and limbic territories. There exist both primary segregated basal ganglia-thalamocortical loops and convergence of functionally related information from different cortical areas onto these cortical basal gaglia-thalamocortical loops. The basal ganglia-thalamocortical loop arising from the sensorimotor area, supplementary motor area (SMA), premotor area and cingulate motor area provides distinct segregated subloops through the functionally distict stritial, pallidal and thalamic regions with partial overlap. The subthalamic nucleus (STN) is also topographically organized. The ventrolateral part of the caudal 2/3 levels of the medial pallidal segment (GPi) projects to the primary motor area via the oral part of the ventral lateral thalamic nucleus (VLo) (Voa, Vop by Hasslers nomenclature). The thalamic relay nuclei of the GPi projection to SMA are identified in the transitional zoe of the VApc (parvicellular part of the anterior ventral nucleus)-VLo and in the rostromedical part of the VLo. The thalamic nuclei relaying the cingulate subloop are not yet clearly defined. The supplementary motor subloop appears to be divided into the pre-SMA and SMA proper subloops. The premotor area is also divided into the dorsal premotor area subloop and the ventral premotor area subloop. It is suggested that the limbic loop consists of a number of subloops in the monkey as indicated by Haber et al. [67] and in rats [64]. We review here the microcircuitry of the striatum, as well as the convergence and integration between the functionally segregated loops. Finally, we discuss the functional implications of stritial connections.

A novel cDNA clone encoding a prolactin-like protein that lacks the two C-terminal cysteine residues isolated from bovine placenta

A new prolactin-like cDNA clone, bPLP-IV, was isolated from a bovine placental cDNA library and the complete nucleotide sequence was determined. The bPLP-IV encodes a protein consisting of 237 amino acids, which is related to, but different from seven other known bovine prolactin-like proteins including two placental lactogens. The predicted amino acid sequence of the bPLP-IV shows over 52% identity to other known members of bovine prolactin-like proteins, 48% to bovine prolactin, 40% to both two bovine placental lactogens and only 22% to bovine growth hormone. The bPLP-IV protein has a unique feature in its primary structure, lacking the two C-terminal cysteine residues which are completely conserved in all other known members of prolactin-growth hormone-placental lactogen gene family. The expression of bPLP-IV in developing bovine placenta was apparently stage-specific, being maximal in the full-term placenta.

The Basal Ganglia-Thalamo-Cortical Connections with Special Reference to Output Neuronal Distributions in Macaque Monkeys

The thalamic subdivisions that receive basal ganglia inputs gain access to wide regions of the frontal lobe. Five parallel basal ganglia-thalamo-cortical loops have been identified (Alexander et al., 1986). The individual output channels in the medial pallidal segment (GPm) are concerned with different aspects of behavior. Recently, the motor related cortical areas such as cingulate motor area, supplementary motor area (SMA) and premotor area, have been divided into several subareas morphologically and functionally. The striatum, especially the ventral striatum, is also heterogeneous, both neurochemically and functionally. Much attention has been given to the concept of parallel processing of information through the functionally distinct multiple channels, instead of the classical concept of a general funneling of cortical inputs from widespread cortical areas.

Distribution of Pontomesencephalic Neurons Projecting to the Medullary Reticular Areas and Spinal Cord in Relation to the Pedunculopontine Nucleus in the Monkey

The pedunculopontine tegmental nucleus (PPN) is located in the mesopontine tegmentum lateral to the decussation of the superior cerebellar peduncle, at the levels from the caudal pole of the red nucleus to the ponto-mesencephalic junction, and innervated by descending projections from the motor outflow of the basal ganglia. It is interconnected with the substantia nigra (SN), the internal segment of pallidum (GPi) and the subthalamic nucleus (STN), and is an important interface between the basal ganglia and the brainstem motor system (Jackson and Crossman, 1983; Garcia-Rilli et al., 1991; Rye et al., 1996; Winn et al., 1997). It also receives cortical afferents mainly from the primary motor cortex, and afferents from the nucleus accumbens directly or indirectly via its output stations, such as the ventral pallidum, lateral hypothalamic area, and the ventral tegmental area (VTA) (Garcia-Rill et al., 1983c). The PPN transfers limbic information concerned with motivation reinforcement from the ventral striatum to the basal ganglia thalamo-cortical loops and to the ponto-medullary systems (limbic-motor integration). The PPN could be involved in locomotion and a variety of behavioral functions, such as the control of sleep and wake, learning and reinforcement processes, and autonomic functions. It is also involved in response choice to interrupt ongoing behavior; either to switch to a new response or simply to cease the current response (Winn et al., 1997).

Superficial and Deep Thalamo-Cortical Projections from the Oral Part of RHE Ventral Lateral Thalamic Nucleus (VLo) Receiving Inputs to the Internal Pallidal Segment (GPi) and Cerebellar Dentate Nucleus in the Macaque Monkey

Superficial thalamo-cortical (T-C) responses were recorded in the lateral motor area and dorsal premotor area (PMd) following stimulation of the cerebellar dentate nucleus in monkeys (Sasaki, 1979). These responses were also recorded in the motor area following pallidal stimulation (Nambu et al., 1988; 1991). An anatomical study was also carried out on the T-C projections from the motor thalamic subdivisions in monkeys using autoradiography (Nakano et al., 1992). The latter fmdings demonstrated that the basal ganglia territories of the motor thalamic subdivisions give rise to superficial T-C projections, whereas the cerebellar territories give rise only to deep T-C projections. Recent studies, using modem axonal tracing techniques, have reported a possible overlap of basal ganglia and cerebellar inputs in the thalamic subdivisions (Rouiller et al., 1994; Sakai et al., 1996). We have reported that the lateral parts of the nucleus ventralis lateralis pars oralis (VLo) receive cerebellar afferents from the ventral part of the dentate nucleus (Nakano et al., 1996).

Characterization of Ste20-related protein kinase PASK

The major PKG substrates found in the vascular smooth muscle, GO (2 15 250-kDa) and GI (120 I40-kDa), were compared with type I IP3 receptor (IP3R, 240-kDa) and myosin-binding subunit (MBS, 138-kDa) of myosin light chain phosphatase, PKG substrates which we identified in vascular smooth muscle as those implicated in the cGMP-induced relaxation of vascular smooth muscle. To identify molecular nature of GO and GI, microsomal GO and GI were thiophosphorylated with [y-“S]ATP, and then subjected to immunoprecipitation with affinity-purified antibodies (Abs) specific to IP3R and MBS. Immunoprecipitation with an anti-MBS Ab resulted in removal of a minor portion of GI, while an antiIP3R Ab precipitated GO completely. Unexpectedly, the anti-IP3R Ab co-precipitated a large part of Gl, which could not be recognized on Western blotting by anti-MB& anti-IP3R or anti-plasma membrane Ca’*-pump Abs. Furthermore, just like IP3R, GO was found to bind calmodulin-column in a Ca*‘-dependent manner. GI was also co-purified with GO in the column chromatography. These results suggested that GO is identical to type 1 IP3R, and that GI consists of several polypeptides in which MBS represents a minor component, and the protein associated with IP3R is a major component.

616 Localization and characterization of a novel Ste20-related protein kinase

Tomonari Tsutsumi, Hiroshi Ushiro, Tetsuro Kayahara, Katsuma Nakano We have cloned a novel protein kinase cDNA from rat brain. The deduced amino acid sequence of the catalytic domain indicates that it belongs to the Ste20-related protein kinase family, the members of which have been reported to act upstream of MAP kinase pathways. The distribution of the kinase in rat organs was examined with a rabbit polyclonal antibody against the C-terminal non-catalytic region. Immunoblot analysis demonstrated ubiquitous expression of the enzyme, except in liver and skeletal muscle where no immunoreactive band was detected. Immunohistochemical analysis revealed cell type specific distribution of the enzyme. In the brain, the most prominent immunoreactivity was found in epithelial cells of choroid plexus. A moderate immunoreactivity was seen in large neurons such as motor neurons in brainstem, cerebellar Purkinje cells and pyramidal cells of cerebral cortex.

704 Molecular cloning of a novel protein kinase cDNA from rat brain

Merkel cells are mechano-receptor cells in the skin that form synaptic contact with primary sensory nerve fibers. Culturing of these cells in vitro has not been successful. We report here that an almost pure culture of Merkel cells in chemically-defined media was achieved, and that these cells underwent apoptosis during culture in these media. In order to obtained Merkel cells, we dissected cores of hair follicles located in the upper-lips of the rat under binocular microscope, and then, they were digested with collagenase in L-15 medium. Merkel cells were isolated from the cores by pippeting, and were platted on poly-L -lysine-coated plastic dishes. Merkel cells were identified by staining with a fluorescence marking dye, quinacrine. During culture in the medium, population of the Merkel cells reduced quickly in time. Addition of serum (5 %) or actinomycin D (2 nM) in the medium prevented the reduction in the cell population. Furthermore, nuclei of many Merkel cells were well stained with TUNEL-method. We thus concluded that the loss of Merkel cells during culture in the serum-free medium was due to the programmed cell death.

1612 Cerebello-thalamic projections in monkeys with special reference to the rostral regions of motor thalamic nuclei

A number of questions still persist with regard to the cerebellar projections to the rostra1 regions of motor thalamic nuclei. Attempts were made to confirm the existence of these projections, and to determine their cells of origin in the cerebellar nuclei in macaque monkeys using axonai transport techniques. Biotinylated dextran amine (BDA) was injected into the various parts of distinct cerebellar nuclei in one group, and wheatgerm agglutinin-horseradish peroxidase (WGA-HRP) injected in the subdivisions of motor thalamic nuclei in the other group. Our data indicates following major findings: The nucleus ventralis lateralis pars oralis (VLo) received cerebellar afferents mainly from the ventromedial portion of nucleus dentatus (NL). These cerebellar projections terminated in the lateral region of VLo. The nucleus ventralis posterolatemlis pars oralis (VPLo) received afferents from all crebellar nuclei. The major VPLo input arose from the nucleus interpositus anterior (NIA) and the dorsal to medial parts of the nucleus interpositus posterior (NIP). A second heavy input arose from the dorsal half of rostra1 NL, and sparser input was present from the nucleus fastigii (NM). Area X received cerebellar afferents from the NIP, NM and whole parts of the caudal NL as well as the ventral intermediate part of middle NL. Cerebellar projections to the nucleus lateralis posterior (LP) were also traced from NIA. No terminal labeling was seen in the centromedian nucleus.