Responsiveness to nicotine of neurons of the caudal nucleus of the solitary tract correlates with the neuronal projection target.

The caudal nucleus of the solitary tract (NTS) is the key integrating center of visceral sensory-motor signaling supporting autonomic homeostasis. Two key projections of this nucleus are the parabrachial nucleus (PbN) and the dorsal motor nucleus of the vagus (DMV). The PbN integrates and relays viscerosensory information primarily to the forebrain, supporting behavioral, emotional, and endocrine responses to visceral events, while the DMV contains parasympathetic preganglionic cholinergic motoneurons that support primarily gastrointestinal reflexes.

Mechanisms of facilitation of synaptic glutamate release by nicotinic agonists in the nucleus of the solitary tract.

The nucleus of the solitary tract (NTS) is the principal integrating relay in the processing of visceral sensory information. Functional nicotinic acetylcholine receptors (nAChRs) have been found on presynaptic glutamatergic terminals in subsets of caudal NTS neurons. Activation of these receptors has been shown to enhance synaptic release of glutamate and thus may modulate autonomic sensory-motor integration and visceral reflexes.

Activation of functional α7-containing nAChRs in hippocampal CA1 pyramidal neurons by physiological levels of choline in the presence of PNU-120596.

Background: The level of expression of functional α7-containing nicotinic acetylcholine receptors (nAChRs) in hippocampal CA1 pyramidal neurons is believed to be very low compared to hippocampal CA1 interneurons, and for many years this expression was largely overlooked. However, high densities of expression of functional α7-containing nAChRs in CA1 pyramidal neurons may not be necessary for triggering important cellular and network functions, especially if activation of α7-containing nAChRs occurs in the presence of positive allosteric modulators such as PNU-120596.

Methodology/principal Findings: An approach previously developed for α7-containing nAChRs expressed in tuberomammillary neurons was applied to investigate functional CA1 pyramidal α7-containing nAChRs using rat coronal hippocampal slices and patch-clamp electrophysiology.

Physiological concentrations of choline activate native alpha7-containing nicotinic acetylcholine receptors in the presence of PNU-120596 [1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-methylisoxazol-3-yl)-urea].

The use of PNU-120596 [1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-methylisoxazol-3-yl)-urea], a positive allosteric modulator of alpha7 nicotinic acetylcholine receptor (nAChR), may be beneficial for enhancing cholinergic therapies. However, the effects of PNU-120596 on activation of native alpha7-containing nAChRs by physiological concentrations of choline are not known and were investigated in this study using patch-clamp electrophysiology and histaminergic tuberomammillary neurons in hypothalamic slices. In the presence of PNU-120596, subthreshold (i.

The impact of an LGNd impulse on the awake visual cortex: synaptic dynamics and the sustained/transient distinction.

We used spike-triggered current source-density analysis to examine axonal and postsynaptic currents generated in the visual cortex of awake rabbits by spontaneous spikes of individual sustained and transient dorsal lateral geniculate nucleus (LGNd) neurons. Using these data, we asked whether sustained/transient sensory responses are related to short-term synaptic dynamics at the thalamocortical synapse. Most sustained (34 of 40) and transient (24 of 25) neurons generated axonal and monosynaptic responses in layer 4 and/or 6 of the aligned cortical domain, with input from transient neurons arriving approximately 0.

Dendritic backpropagation and the state of the awake neocortex.

The spread of somatic spikes into dendritic trees has become central to models of dendritic integrative properties and synaptic plasticity. However, backpropagating action potentials (BPAPs) have been studied mainly in slices, in which they are highly sensitive to multiple factors such as firing frequency and membrane conductance, raising doubts about their effectiveness in the awake behaving brain. Here, we examine the spatiotemporal characteristics of BPAPs in layer 5 pyramidal neurons in the visual cortex of adult, awake rabbits, in which EEG-defined brain states ranged from alert vigilance to drowsy/inattention, and, in some cases, to light sleep.

The impact of a corticotectal impulse on the awake superior colliculus.

Corticotectal (CTect) neurons of layer 5 are large and prominent elements of mammalian visual cortex, with thick apical dendrites that ascend to layer 1, "intrinsically bursting" membrane properties, and fast-conducting descending axons that terminate in multiple subcortical domains. These neurons comprise a major output pathway of primary visual cortex, but virtually nothing is known about the synaptic influence of single CTect impulses on the superior colliculus (SC). Here, we examine the distribution of monosynaptic currents generated in the superficial SC by spontaneous impulses of single CTect neurons.

Spike timing and synaptic dynamics at the awake thalamocortical synapse.

Thalamocortical (TC) neurons form only a small percentage of the synapses onto neurons of cortical layer 4, but the response properties of these cortical neurons are arguably dominated by thalamic input. This discrepancy is explained, in part, by studies showing that TC synapses are of high efficacy. However, TC synapses display activity-dependent depression.

Activation of a cortical column by a thalamocortical impulse.

Thalamocortical (TC) impulses potently influence the sensory neocortex, but the functional impact of individual TC neurons throughout the layers of the cortex has proved difficult to assess. Here we examine, in awake rabbits, the vertical distribution of monosynaptic currents generated in a somatosensory cortical "barrel" column by spontaneous impulses of single, topographically aligned TC neurons. We show that closely neighboring TC neurons generate widely differing patterns of monosynaptic activation within layers 4 and 6 of their aligned column.