The research I conduct is focused on acquiring an understanding of the cellular and molecular mechanisms that regulate neuronal function and signaling under physiological and pathophysiological conditions, and how these mechanisms are modulated by endogenous and therapeutic pharmacological agents.   The properties of biologically active chemical compounds and their interactions with living neuronal systems are investigated using a variety of state-of-the-art techniques, such as patch-clamp electrophysiology, confocal microscopy, fluorescent Ca 2+ and Na + imaging and immunohistochemistry.   The electrical activity of neurons, the factors that regulate intracellular concentrations of Ca 2+ and Na + ions, the biophysical properties of synaptic neurotransmission and underlying voltage- and ligand-gated ion channels are being investigated in conjunction with the morphological properties of neurons and the anatomy of brain regions of interest.

   Specifically, my research is driven by both academic and clinical rationales, as it investigates the effects of elevated levels of endogenous and therapeutic cholinergic agents on neuronal function and signaling in the hypothalamus and the brainstem: brain regions involved with the regulation of important cognitive and visceral functions.   Understanding the effects of activation and desensitization of post- and pre-synaptic nicotinic and muscarinic acetylcholine (ACh) receptors on the function of hypothalamic and brainstem neurons provides researchers and clinicians with a powerful tool to optimize treatments of attention and sleep disorders, cognitive deficits, cardiac dysfunction and nicotine dependency.

Nicotine
   Nicotine exhibits pharmacological properties atypical for endogenous nicotinic agents, such as choline and ACh.   Therefore, I am specifically interested in investigating what pharmacological properties make nicotine , but not choline or ACh, addictive; and what may account for the behavioral effects of tobacco alkaloids associated with tobacco use.   Equally interested would be obtaining an understanding of what pharmacological properties of nicotine and other tobacco alkaloids made those compounds inadequate for the role of endogenous nicotinic agents currently played by choline and ACh.   One hypothesis is that addictive non-physiological effects of tobacco alkaloids are determined by their: 1) slow rates of unbinding (relative to choline or ACh); 2) high lipophilicity, which promotes accumulation of alkaloids in the brain tissue; and 3) profound desensitization, which reduces responsiveness of nicotinic ACh receptors to other cholinergic stimuli, including endogenous.

The Hypothalamus
   Neurons of the tuberomammillary (TM) nucleus of the posterior hypothalamus represent the major source of brain histamine and project their axons to most brain regions to control attention and arousal, as evidenced by the sedation caused by anti-histamines.   Alpha-bungarotoxin-sensitive nicotinic acetylcholine receptors (nAChRs), whose kinetics and pharmacology are similar to those of highly Ca 2+ -permeable homomeric a 7 nAChRs, are the only functional nAChRs expressed in TM neurons in high densities.   Activation of TM nAChRs does not significantly elevate cytosolic Ca 2+ concentrations ([Ca 2+ ] i ) in TM somata in the absence of voltage-gated Ca 2+ channels (VGCCs).   Therefore, the kinetic of a 7-like nAChRs and functional links among a 7-like nAChRs and other TM Ca 2+ sources become the key factors determining the impact of a 7-like nAChR activation on [Ca 2+ ] i .   This implication is important, because the physiological role of a 7 nAChRs remains unknown, and may involve cytoprotection and regulation of TM histaminergic function by endogenous and therapeutic nicotinic agents, such as choline and nicotine, respectively.

   This research direction tests the hypothesis that a 7-like nAChRs regulate TM [Ca 2+ ] i indirectly, via functional links to key Ca 2+ sources: VGCCs; Ca 2+ stores; and Na + -Ca 2+ exchangers.   We employ the confocal microscopy and fluorescent Ca 2+ imaging combined with patch-clamp electrophysiology, reverse transcription polymerase chain reaction, Western blot and immunohistochemistry to determine the nature of a 7-like nAChRs, the mechanisms of [Ca 2+ ] i regulation, and, the links among a 7-like nAChRs and other key Ca 2+ sources in histaminergic TM neurons.   This study will provide important information regarding the function of a 7-like nAChRs in histaminergic TM neurons, and a 7-like nAChR-driven mechanisms of regulation of Ca 2+ homeostasis .   Intriguingly, the behavioral and cognitive effects of nicotine and histamine are similar: both agents are anti-nociceptive, improve attention, promote alertness and arousal, and inhibit food intake.   Some of these effects of nicotine and therapeutic nicotinic agents may arise from their ability to modulate histaminergic function.

The Brainstem
   The nucleus of the solitary tract (NTS) of the brainstem is a heterogeneous group of neurons representing the key integrating relay in the processing of visceral sensory and gustatory information.   The caudal portion of NTS (i.e., cNTS) receives baroreceptor and chemoreceptor afferents from the heart (e.g., aortic arch) and blood vessels (e.g., carotid body and sinus) via glossopharyngeal nerve IX and vagal nerve X to provide a rapid control of cardiac output (i.e., baroreflex).   The NTS also receives visceral afferents from various regions of the gastrointestinal (GI) tract and the second-order neurons of the dorsal horn and other components of the central autonomic system such as respiratory afferents.   The rostral portion of NTS (i.e., rNTS) receives mostly gustatory information directly from the oral cavity via cranial nerves VII, IX and X.

   The presence of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) immunostaining in the NTS suggests that ACh is involved in processing and modulation of visceral sensory and gustatory information.   In the rNTS region, the position of cholinergic neurons is consistent with the distribution of preganglionic parasympathetic neurons labeled by horseradish peroxidase (HRP) applied to the chorda tympani branch of the VIIth nerve and the lingual-tonsillar branch of the IXth nerve.   Furthermore, both low- and high-affinity nicotinic binding sites have been demonstrated in the NTS; and our electrophysiological recordings from the NTS in brainstem slices revealed a heterogeneous population of functional nicotinic (nAChRs) and muscarinic (mAChRs) ACh receptors.   However, for the most part, nAChRs and mAChRs were expressed by different cells.

   In most recent experiments, we have determined that activation of pre-synaptic nAChRs by nicotine facilitates release of glutamate in ~ 20% of NTS neurons tested.   We refer to these neurons as "effect-positive".   At this point, the exact reason why only ~20% of NTS neurons exhibit such facilitation is unknown.   A number of hypotheses are currently being tested.   This modulation of glutamate release by pre-synaptic nAChRs in the NTS region has not been previously described and may represent an important component of cholinergic regulation of the visceral sensory (e.g., cardioreflex) and gustatory information processing.

Selected Publications:

Uteshev V.V. and Smith D.V.   Cholinergic modulation of neurons in the gustatory region of the nucleus of the solitary tract.   Brain Research (2006) 1084(1): 38-53.

Uteshev V.V. and Knot H.J. Somatic Ca2+ dynamics in response to choline-mediated excitation in histaminergic tuberomammillary neurons. Neuroscience (2005), 134 (1): 133-143.

Uteshev V.V., Meyer E.M. and Papke R.L. Regulation of neuronal function by choline and 4OH-GTS-21 through alpha7 nicotinic receptors . Journal of Neurophysiology (2003) 89 (4): 1797-1806

Uteshev VV and Pennefather PS. A mathematical description of mPSC generation at central synapses. Biophysical Journal 7:1256-1266 (1996).

Uteshev V., Stevens D.R. and Haas H.L. A persistent sodium current in acutely isolated histaminergic neurons from rat hypothalamus. Neuroscience (1995), 66: 143-149.