Which of the following basal ganglia nucleus is primarily glutaminergic
B i.e. Subthalamic Nucleus - Basal ganglia consists of - caudate nucleusQ, putamen, globus pallidus, subthalmic nucleus, and substantia nigraQ. Striatum (term derived from the striated appearance of these nuclei) refers to the caudate nucleus and putamen. Whereas the combination of putamen and globus pallidus is often referred to as lentiform nucleus - Efferent fiber bundle of substantia nigra (pars compacta) transmit dopaminergic fibers to corpus striatum/ striatum (dopaminergic nigro striatal projection). - Subthalamic nucleus (a diencephalic grey matter pa of basal ganglia) is the only nucleus of basal ganglia that actually produce excitatory neurotransmitter glutamate. Subthalamic nucleus receives inhibitory (GABA - nergic) imput from globus pallidus external segment (GPe) and has excitatory (glutaminergic) projections to both GPe and GPi (globus pallidus internal segment). Subthalamic nucleus plays an impoant role in stimulation of indirect SNpc-GPi (substantia nigra - pars compacta - globus pallidus internal segment) pathway. - Although the majority of striatal neurons are GABA nergic medium spiny neurons, the highest density of glutamate receptors in basal ganglia is found in corpus striatum (putamen + caudate nucleus)Q, which receives 2 main inputs (both of which are excitatory glutaminergic) from cerebral coex (coico striatal pathway) and from intralaminar nuclei of thalamus (thalamostriatal pathway). Structural Organization Major Connections of Basal Ganglia * Basal ganglia is composed of 5 interactive structures on each side of brain including * Afferents: 2 main inputs to basal ganglia, both of which are excitatory (glutamate) terminate in striatum. They - Caudate nucleus, putamen and globus pallidus (= 3 large nuclear originate from layer V of most regions of coex (except masses underlying the coical mantle) and primary visual & auditory coices) with an impoant - Subthalamic nucleus of diencephalon and substantia nigra of component originating in motor coex (coicostriatal midbrain pathway) and from intralaminar nuclei of thalamus * The term striatum (or corpus striatum) is applied to caudate nucleus & (thalamostriatal pathway). putamen because of the striated appearance of these nuclei. The striations * Efferents : 2 main outputs of basal ganglia, both of which are produced by fiber bundles formed by the anterior limb of internal are inhibitory (GABA ergic); arise from GPi and SNIT capsule as it seperates the caudate nucleus and putamen and project to thalamus. Thalamic neuron inturn give * The putamen and globus pallidus collectively form lenticular nucleus. excitatory (glutamate?) projections to prefrontal and * Globus pallidus has two pas GPi and GPe. Substantia nigra pretnotor coex thereby, completing a full coical - basal (substance black d/t melanin) has 2 pas SNpc and SNeR ganglia-thalamic - coical loop. Neurotransmitters * Connections within basal ganglia include * Globus pallidus has 2 pas, an internal and an external segments (GPi & GPe); both containing inhibitory GABA ergic neuron - Dopaminergic (both excitatory & inhibitory) * Substantia nigra (= black substance) derives its name from its content of melanin pigment. It is divided into pars compacta which uses dopamine nigrostriatal projection from substantia nigra pars compacta (SNpc) to striatum and an inhibitory GABA neurotransmitter (& melanin; a by product of dopamine synthesis) and ergic reverse projection from striatum to SNPR (pars pars reticulate (SNoR) which uses GABA as neurotransmitter. reticulata) * Striatum contains at least 4 types of neurons: 95% are medium spiny - Inhibitory GABA ergic projections from stritum to neurons using GABA as neurotransmitter. Remaining 5% are all Aspiny both GPi and GPe. interneurons differing in size and neurotransmitters : small (GABA), medium (somatostatin) and large (acetyl choline). - Subthalamic nucleus receives an inhibitory (GABA) * Several thalamic nuclei including ventral anterior (VA) and ventral input/afferent from GPe and project excitatory lateral (VL) nuclei and intralaminar complex are associated with basal ganglia. (glutamate) output/ efferent to both GPi and GPe. * GABA is always inhibitory neurotransmitter forming negative feed back loops. Dopamine is mostly inhibitory and sometimes stabilizer. Glutamate is always excitatory balancing out inhibitory signals from GABA, dopamine & serotonin inhibitory transmitters. * Dopamine neurotransmitter of SNpc in nigrostriatal pathway has an excitatory action on direct pathway has an excitatory action on direct pathway & an inhibitory action on indirect pathway. This difference in action of dopamine (modulatory effect) is d/t different types of dopamine receptors expressed by spiny striatal cells. - ie dopamine is causing its action by altering the striatal cells response to other transmitters (& not by generating post synaptic potentials). Dopamine is a neuromodulator that acts on DI. and D2 receptors on striatal neuron cells paicipating in direct and indirect pathways (respectively) by projecting to GPi and GPe respectively Direct & Indirect Pathways and spinal cord * Excitatory coical input to striatum influences output from GPi and SNPR a direct and indirect pathway. * The overall effect of direct pathway is to enhance motor activity, whereas indirect pathway reduces the activity of motor neurons in cerebral coex. Subdivision of Striatum * On the basis of NTs, it can be divided into striosome (to which limbic system projects) and matrix (to which coical projections related to motor control end). Striosome synapse in SNpc to influence dopaminergic nigrostriatal pathway. * Striatal neurons disoharge before movement occurs suggesting their role in selecting the probable movements. Putamen is related to body movement and caudate nucleus to eye movement.
Putamen
Subthalamic Nucleus
Globus pallidus
Substantial Nigra