Occurrence, co-occurrence and topographic distribution of choline acetyl transferase, Met-enkephalin and neurotensin in the stellate ganglion of the cat

Autonomic neural control of intrathoracic airways

Autonomic neural control of the intrathoracic airways aids in optimizing air flow and gas exchange. In addition, and perhaps more importantly, the autonomic nervous system contributes to host defense of the respiratory tract. These functions are accomplished by tightly regulating airway caliber, blood flow, and secretions. Although both the sympathetic and parasympathetic branches of the autonomic nervous system innervate the airways, it is the later that dominates, especially with respect to control of airway smooth muscle and secretions. Parasympathetic tone in the airways is regulated by reflex activity often initiated by activation of airway stretch receptors and polymodal nociceptors. This review discusses the preganglionic, ganglionic, and postganglionic mechanisms of airway autonomic innervation. Additionally, it provides a brief overview of how dysregulation of the airway autonomic nervous system may contribute to respiratory diseases.

Neurotransmitter segregation: functional and plastic implications

Synaptic cotransmission is the ability of neurons to use more than one transmitter to convey synaptic signals. Cotransmission was originally described as the presence of a classic transmitter, which conveys main signal, along one or more cotransmitters that modulate transmission, later on, it was found cotransmission of classic transmitters. It has been generally accepted that neurons store and release the same set of transmitters in all their synaptic processes. However, some findings that show axon endings of individual neurons storing and releasing different sets of transmitters, are not in accordance with this assumption, and give support to the hypothesis that neurons can segregate transmitters to different synapses. Here, we review the studies showing segregation of transmitters in invertebrate and mammalian central nervous system neurons, and correlate them with our results obtained in sympathetic neurons. Our data show that these neurons segregate even classic transmitters to separated axons. Based on our data we suggest that segregation is a plastic phenomenon and responds to functional synaptic requirements, and to 'environmental' cues such as neurotrophins. We propose that neurons have the machinery to guide the different molecules required in synaptic transmission through axons and sort them to different axon endings. We believe that transmitter segregation improves neuron interactions during cotransmission and gives them selective and better control of synaptic plasticity.

Segregation of the classical transmitters norepinephrine and acetylcholine and the neuropeptide Y in sympathetic neurons: modulation by ciliary neurotrophic factor or prolonged growth in culture

Recent evidence has demonstrated that cotransmission from mammalian neurons is not uniquely achieved by costorage and corelease of transmitters and cotransmitters from single varicosities, but also by the concurrent release of mediators segregated in separate synapses of individual neurons. An important question to be addressed is whether neurons show defined patterns of segregation or whether this is a plastic feature. We addressed this question by exploring the segregation pattern of the classical sympathetic transmitters norepinephrine (NE) and acetylcholine (ACh) and the cotransmitter neuropeptide Y (NPY) in sympathetic ganglionic neurons cocultured with cardiac myocytes. Using antibodies against NPY and the vesicular NE and ACh transporters VMAT2 and vesicular acetylcholine transporter (VAChT), we investigated the effect of ciliary neurotrophic factor (CNTF) or long (three weeks) culture periods on the segregation of VMAT2, VAChT, and NPY to separate varicosities. We found that although ganglionic neurons showed cell body coexpression of all the markers examined after three days, VMAT2 was segregated from VAChT in 43% of the VAChT-positive varicosities. In contrast, VMAT2 was only segregated from NPY in 16.3% of the NPY-positive varicosities. Cotransmitter segregation and VAChT expression was potentiated by both CNTF and longer times in culture. We also found two types of varicosities: one was smaller and located further from neuronal somata, and the other was larger, proximal to neuronal somata and had a higher level of segregation. These data demonstrate segregation of classical transmitters in sympathetic neurons and plasticity of neurotransmitter segregation. Finally, we discuss a possible functional correlate of segregation in sympathetic neurons.

Segregation of met-enkephalin from vesicular acetylcholine transporter and choline acetyltransferase in sympathetic preganglionic varicosities mostly lacking synaptophysin and synaptotagmin

Sympathetic preganglionic neurons (SPN) coexpress the acetylcholine (ACh)-synthesizing enzyme choline acetyltransferase and different peptides in their cell bodies, but can express them independently in separate varicosities, indicating that SPN segregate transmitters to different synapses. Consequently, there are populations of preganglionic varicosities (peptidergic and noncholinergic) that store peptides but not ACh. We studied in the cell bodies and axon processes of the rat SPN the expression and the proportional coexpression of the vesicular ACh transporter-like immunoreactivity (VAChT), a specific marker of cholinergic synaptic vesicles or ChAT-like immunoreactivity (ChAT), and the peptide methionine enkephalin-like immunoreactivity (mENK), and confirmed the presence of a population of SPN peptidergic, noncholinergic varicosities. We characterized these varicosities by exploring the occurrence of synaptophysin-like immunoreactivity (Syn), a marker of small clear vesicles, and synaptotagmin-like immunoreactivity (Syt), a preferential marker of large dense core vesicles. We found that (i) VAChT and mENK, like ChAT-mENK, were coexpressed in only 59% of the mENK-containing varicosities, although they colocalized in the SPN cell bodies; and (ii) almost 60% of the population of mENK-containing varicosities did not express Syn or Syt, and over 80% of the mENK-containing varicosities negative for VAChT also lacked Syn. These data prove that SPN segregate mENK from VAChT and ChAT, and show that most of the subset of mENKergic varicosities negative for VAChT also does not express Syn, suggesting the presence of a different vesicular pattern in these sympathetic preganglionic varicosities.

Choline acetyl transferase and neuropeptide immunoreactivities are colocalized in somata, but preferentially localized in distinct axon fibers and boutons of cat sympathetic preganglionic neurons

Cholinergic sympathetic preganglionic neurons (SPN) coexpress the biosynthetic enzyme for acetylcholine, choline acetyl-transferase (ChAT), and neuropeptides such as enkephalin (ENK) in their cell bodies. However, it is not clear whether they also coexpress ChAT and neuropeptides in axon fibers and boutons. To explore coexpression of ChAT and neuropeptides in somata and axon processes of SPN, we investigated, using immunohistochemistry, retrograde labeling, confocal analysis, and tridimensional reconstruction, whether ChAT and the peptides neurotensin, methionine-ENK, somatostatin, calcitonin gene-related peptide, and vasoactive intestinal peptide colocalize in somata, axons fibers, and boutons of cat SPN. Practically, complete colocalization for these peptides and ChAT was observed in SPN somata. Conversely, in most instances we observed independent localization of immunoreactivity (IR) for ChAT and the peptides in axon fibers and boutons. The minor colocalization between ChAT- and peptide-IR in preganglionic fibers could correspond to a sequential axonal transport of ChAT and peptides, since we observed coexistence of these transmitters after blocking axonal transport. Contrary to Dale's principle, our results suggest that SPN can synthesize ChAT and peptides in their cell bodies and route them to distinct axon boutons or terminals in sympathetic ganglia. Presence of axon boutons containing either ChAT or neuropeptides lead us to suggest a new neurochemical pattern of cotransmission in sympathetic ganglia based on the concurrent release of transmitters and cotransmitters from distinct presynaptic boutons, rather than in the corelease of these mediators from the same axon process. The possibility that cellular segregation could be transient and depend on functional requirements is considered.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).