Vladimir Karpitskiy

Central command neurons of the sympathetic nervous system: basis of the fight-or-flight response.

During stress, the activity of the sympathetic nervous system is changed in a global fashion, leading to an increase in cardiovascular function and a release of adrenal catecholamines. This response is thought to be regulated by a common set of brain neurons that provide a dual input to the sympathetic preganglionic neurons regulating cardiac and adrenal medullary functions. By using a double-virus transneuronal labeling technique, the existence of such a set of central autonomic neurons in the hypothalamus and brainstem was demonstrated. These neurons innervate both of the sympathetic outflow systems and likely function in circumstances where parallel sympathetic processing occurs, such as in the fight-or-flight response.

Suprachiasmatic nucleus: a central autonomic clock.

Circadian rhythms are daily changes in behavior and physiology produced by the suprachiasmatic nucleus (SCN) even in the absence of external stimuli, although photic input from the retina to the SCN entrains these changes to a 24-hour cycle. The SCN modulates autonomic and neuroendocrine function to prepare for diurnal or nocturnal changes in behavior, but its precise connections to the autonomic nervous system are unknown. We used viral transneuronal labeling to demonstrate extensive connections of the SCN with diverse types of sympathetic as well as parasympathetic motor systems. Double-virus transneuronal tracing showed connections of single SCN neurons to multiple autonomic systems. However, targets of SCN modulation seem limited to those that operate continuously under tonic, rather than phasic, control.

Coordinate Regulation of T Cell Activation by CD2 and CD28

T cell activation requires co-engagement of the TCR with accessory and costimulatory molecules. However, the exact mechanism of costimulatory function is unknown. Mice lacking CD2 or CD28 show only mild deficits, demonstrating that neither protein is essential for T cell activation. In this paper we have generated mice lacking both CD2 and CD28. T cells from the double-deficient mice have a profound defect in activation by soluble anti-CD3 Ab and Ag, yet remain responsive to immobilized anti-CD3. This suggests that CD2 and CD28 may function together to facilitate interactions of the T cell and APC, allowing for efficient signal transduction through the TCR.

Intravenous Valproate Sodium in the Treatment of Daily Headache

Background.—Treatment of chronic daily headache/transformed migraine is challenging, especially when it is complicated by overuse of analgesics, triptans, or both. One common approach involves the use of repetitive intravenous dihydroergotamine. We investigated the use of intravenous valproate sodium in the treatment of chronic daily headache/transformed migraine in patients who had contraindications to the use of or had failed treatment with dihydroergotamine.

CNS neurons with links to both mood-related cortex and sympathetic nervous system.

Cardiovascular changes occur during mental stress and in certain types of mood disorders. The neural basis for this phenomenon is unknown but it may be dependent on CNS neurons that provide branched projections to affective processing regions of the brain, such as the medial prefrontal cortex, and to the sympathetic outflow system. Because these putative neurons may be connected to these two target sites by chains of neurons, we performed double virus transneuronal tracing experiments and show here that a select subset of neurons in the medial preoptic nucleus (MPN), lateral hypothalamic area (LHA), and nucleus tractus solitarius (NTS) are co-linked to these two sites. Neurotensin MPN, orexin-containing LHA, and catecholamine NTS neurons were the major phenotypes involved in these projections. This novel class of neurons may coordinate cardiovascular changes seen in different emotional states.

Astroglial distribution of neurokinin-2 receptor immunoreactivity in the rat spinal cord

Two mouse monoclonal antibodies, 11H9.1 and 1G7.10, raised against the COOH-terminus peptide (359-390) of the rat neurokinin-2 receptor, were used to visualize by light and electron microscope immunocytochemistry the distribution of this receptor in adult rat spinal cord. At all spinal levels, immunoreactivity was mainly observed in two narrow crescentic zones bordering the gray matter of the dorsal and ventral horns, and around the central canal. In the light microscope, this labelling was the densest within the outer part of lamina I facing the dorsal column, where it took the form of minute dots and streaks scattered in the neuropil. In the electron microscope, such a localization was exclusively astrocytic and essentially involved astrocytic leaflets, as indicated by the size and irregular shape of the immunostained processes, their location between and around neuronal profiles, and their occasional display of glial filaments. The diaminobenzidine reaction product showed some predilection for the plasma membrane and was occasionally seen at gap junctions of these labelled processes. Many labelled astrocytic leaflets were observed in the immediate vicinity of axon terminals containing large dense-cored vesicles, and around fibres morphologically identifiable as primary afferent, unmyelinated C-fibres. These observations suggest that astrocytic neurokinin-2 receptors could define the effective sphere of neurokinin A neuromodulation in rat spinal cord, via alterations in the regulation of the extracellular environment and glutamate uptake by astrocytes and/or the release of putative astroglial mediators. The astrocyte neurokinin-2 receptors, activated by extrasynaptic neurokinin A, might thus co-operate with neurokinin-1 and neurokinin-3 neuronal receptors in the modulation of nociceptive information.

Immunoelectron microscopic localization of NK-3 receptor in the rat spinal cord

THE immunocytochemical localization of tachykinin NK-3 receptor (NK-3R) was studied in rat spinal cord using a mouse monoclonal antibody directed against the C-terminus peptide (434-465) of the human NK-3R. Light microscopic labeling prevailed in lamina II and lamina X. Under the electron microscope, the immuno-labeling in lamina II involved mainly dendritic spines inside glomeruli, preterminal axons and axon terminals. This suggests that neurokinin B can modulate primary afferent, sensory information, both post-and pre-synaptically. These actions are likely to involve extrasynaptic diffusion of the peptide, since NK-3R immunoreactivity was not found in association with postjunctional differentiations.

THE NEOSTRIATAL MOSAIC : BASIS FOR THE CHANGING DISTRIBUTION OF NEUROKININ-1 RECEPTOR IMMUNOREACTIVITY DURING DEVELOPMENT

The pattern of neurokinin‐1 receptor‐like immunoreactivity (NK‐1Rir) was mapped in perinatal and adult mouse striatum by using a new polyclonal antiserum. NK‐1Rir was detected in the differentiating regions of the ganglionic eminences on embryonic day 12.5 (E12.5). NK‐1Rir structures were enriched in the striatal patch compartment between E16.5 and approximately postnatal day 3 (P3); distributed more uniformly, within portions of both the patch and matrix compartments on P7; and enriched in the matrix compartment in the adult. Analysis of the phenotype of NK‐1Rir cells on P2, P7, and in the adult suggested that cholinergic cells accounted for the majority of NK‐1Rir cells early postnatally, with increasing contributions from somatostatinergic cells later postnatally. In the adult, approximately half of NK‐1Rir cells were cholinergic and half were somatostatinergic. The transient enrichment of NK‐1R‐bearing cells and processes in the patch compartment which contains cells that express substance P (SP), a putative ligand for the NK‐1R, may be a consequence of compartment formation or may be functionally important for compartment development.

Characterization of Tachykinin Receptors

The mammalian tachykinin peptides are a family of neuropeptides characterized by a common C‐terminal amino acid sequence of the form Phe‐X‐Gly‐Leu‐Met‐NH2, where X is either Phe or Val. Tachykinin peptides have various biological activities, including excitation of both peripheral and central neurons, stimulation of smooth muscle contraction, stimulation of exocrine and endocrine gland secretion, and involvement in immune and inflammatory responses. This unit presents basic methods for the characterization of tachykinin receptors by radioligand binding assay. The protocols detail methods for three major classes of tachykinin receptors and techniques for the generation of high specific activity iodinated radioligands.