Detailed anatomy of the motor and sensory roots of the trigeminal nerve and their neurovascular relationships: a magnetic resonance imaging study.

OBJECT: The trigeminal nerve conducts both sensory and motor impulses. Separate superior and inferior motor roots typically emerge from the pons just anterosuperomedial to the entry point of the sensory root, but to date these two motor roots have not been adequately displayed on magnetic resonance (MR) images. The specific aims of this study, therefore, were to identify the superior and inferior motor roots, to describe their exact relationship to the sensory root, and to assess the neurovascular relationships among all three roots of the trigeminal nerve. METHODS: Thirty-three patients and seven cadaveric specimens (80 sides) were studied using three-dimensional (3D) Fourier transform constructive interference in steady-state (CISS) imaging. The 33 patients were also studied by obtaining complementary time-of-flight (TOF) MR angiography sequences with and without contrast enhancement. At least one motor root was identified in all sides examined: in 51.2% of the sides a single motor root, in 37.5% two motor roots, and in 11.2% three motor roots. The superior cerebellar artery (SCA) and the anterior inferior cerebellar artery (AICA) contacted the sensory root in 45.5% of patients and 42.9% of specimens. The SCA often contacted the superior motor root (48.5% of patients and 50% of specimens) and less frequently the inferior motor root (26.5% of patients and 20% of specimens). CONCLUSIONS: Three-dimensional CISS and complementary 3D TOF MR angiography sequences reliably display sensory, superior motor, and inferior motor roots of the trigeminal nerve and their relationships to the SCA and AICA.

Applications of neuroreceptor imaging to psychiatry research.

Over the past two decades, there have been significant advances in the ability to study the neurochemistry of the living brain using neuroreceptor radiotracers with Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) imaging modalities. The greater availability of radiotracers for neurotransmitter synthesis/metabolism, enzymes, transporters and receptors, as well as neuromodulators and second messengers has enabled the evaluation of hypotheses regarding neurotransmitter function and regulation that are generated from basic neuroscience studies in animals, and the investigation of the neurochemical substrates of psychiatric disorders and the mechanism of action of psychotropic medications. This review will focus on the status of radiotracer development, on the clinical and methodological considerations regarding neurochemical brain imaging study design and data interpretation. The applications of neurochemical brain imaging methods to the study of specific psychiatric disorders, including schizophrenia, anxiety disorders, depression and Alzheimer's Disease, will be reviewed and potential future directions of research in these areas identified. Finally, the studies of the neurochemical substrates of personality traits will be reviewed. Thus far, fundamental observations have been made with respect to 1). detecting abnormalities in the availability of neurotransmitter transporter and receptor sites in psychiatric patients; 2). evaluating the relationship of these neurochemical measures to symptomatology; and 3). assessing the magnitude of occupancy of the initial target sites of action of psychotropic medication relative to treatment response and drug concentrations. Further advances in instrumentation and radiotracer chemistry will enable investigators to conduct pre-clinical and clinical mechanistic studies focused on other neurotransmitters and neuromodulators. These data will provide important insights into the neurochemical substrates of treatment response variability in psychiatric disorders that will have important implications for the refinement of pharmacotherapy.

Nervous control of blood flow microkinetics in the infrared organs of pit vipers.

The pit organ of pit vipers contains a membrane which serves as an infrared retina, processing infrared information by the degree to which the temperature of trigeminal nerve receptors (terminal nerve masses) is raised. The receptors are arranged in a monolayer array within the pit membrane and irrigated by a capillary network which both supplies energy to the terminal nerve masses and serves as a heat exchange mechanism. This mechanism maintains the receptors at a stable temperature level to increase or decrease their sensitivity and to reduce to a minimum the afterimage effect of a moving stimulus. We used a Doppler laser blood flow meter to measure the local changes in blood flow in response to a point heat source (a small soldering iron) and to direct stimuli (red and infrared lasers). Resection of any one of the trigeminal A-delta fiber trunks innervating the pit membrane abolished blood flow response in the area innervated, but resection of the main trunk between the primary neurons and the medulla left the response intact. In addition to the A-delta fibers the pit membrane contains autonomic and sensory C-fiber innervation, but preganglionic resection of parasympathetic neurons, and chemical blocking of postganglionic fibers with atropine and capsaicin had no influence on the blood flow changes. Therefore, on the basis of the rapid response time and the similarity of the blood flow curves to electrophysiological recordings from the receptors, we surmised that all blood flow changes were due to a vasomotor reaction, modulated by the terminal nerve masses directly, resulting in a change in local heat capacity that cools the stimulated receptors back to a basal temperature.

Ultrastructure of the capillary pericytes and the expression of smooth muscle alpha-actin and desmin in the snake infrared sensory organs.

The infrared sensory membranes of pit organs of pit vipers have an extremely rich capillary vasculature that forms many vascular loops, each serving a small number of infrared nerve terminals. We clarified the ultrastructure of capillary pericytes in the pit membranes by scanning and transmission electron microscopy, and examined the immunoreactivity in their cytoplasm to two contractile proteins: smooth muscle alpha-actin (SM alpha-actin) and desmin. The capillary pericytes had two major cytoplasmic processes: thickened primary processes that radiate to embrace the endothelial tube and flattened secondary processes that are distributed widely on the endothelium. Coexpression of SM alpha-actin and desmin was observed in the pericytes of entire capillary segments, and SM alpha-actin was characterized by prominent filament bundles directed mainly at right angles to the capillary long axis. This expression pattern was different from that of capillary pericytes of the scales, where SM alpha-actin was expressed diffusely in the cytoplasm. In a series of electron microscopic sections, we often observed the pericyte processes depressing the endothelial wall. We also observed a close relationship of the pericytes with inter-endothelial cell junctions, and pericyte processes connected with the endothelial cells via gap junctions. From these findings, we surmised that capillary pericytes in the pit membrane have a close functional relationship with the endothelium, and through their contractile and relaxing activity regulate capillary bloodflow to stabilize production of infrared nerve impulses.

[The sensitive nerve endings of the clitoris of the sow (Sus scrofa domesticus)]. / Sur les terminaisons nerveuses sensitives du clitoris chez la Truie (Sus scrofa domesticus).

Neural receptors of the porcine clitoris were examined using light and electron microscopy. Perfusion with ink allowed study of the unique vascular arrangement associated with the genital corpuscles. Sensory nerve-endings were generally rounded and formed a morphologically and structurally characteristic unit. They were composed of a network of primarily non-myelinated nerve fibers and flat cells. Between these structures, isolated small blood vessels were embedded amongst collagen fibers and amorphous material. An external capsule of variable thickness always surrounded the structures. A complex arrangement of vessels in the center of the capsule was formed by a subpapillary mesh. The same arrangement was seen in the morphologically comparable penile genital corpuscles of the same species. Based on the particular arrangement of blood vessels and nerve fibers in the genital corpuscles, some authors postulate the presence of a neuro-vascular glomerulus.

[Formation of the vascular-receptor connections in the human forearm muscles]. / Stanovlenie sosudisto-retseptornykh otnoshenii v myshtsakh predplech'ia cheloveka.

The data on formation and construction principles of the blood supply system in the terminal sensitive apparatuses of the human forearm muscles during embryogenesis and early postnatal period are presented. During the intrauterine development, the formation of the vascular-receptor relations takes place in the sequence corresponding to the anlage of the receptors. The first blood vessels appear in the area of the nonencapsulated sensitive terminals and only after in the encapsulated receptors. The latter have their own blood supply system which is formed by the vessels of the intramuscular neural fasciculi and the surrounding muscular tissue. Around the sensitive terminals thick microvascular networks are formed, they often tightly adhere the external receptor capsule. The intrareceptor capillaries are situated in the mass of the neural terminals and sometimes form capillary loops in them.

Intraepithelial blood vessels in the vomeronasal neuroepithelium of the rat. A light and electron microscopic study.

Epithelial-vascular relationships are established during the development of the vomeronasal neuroepithelium of the rat. Special attention is given to the fine structure of the endothelial wall of intra-epithelial vessels, to ultrastructural aspects of the neuronal-vascular relationships, and to the appearance of inclusion bodies in the neuronal cells adjacent to these vessels. The neuronal perikarya surrounding the blood vessels are filled with highly developed smooth endoplasmic reticulum. Possible functional implications of the vascularization of the neuroepithelium of the vomeronasal organ in mediating olfacto-endocrine relationship are discussed. It is suggested that the intra-epithelial blood vessels are at least supportive and nutritive in nature, while their implication in an olfacto-endocrine connection remains obscure.