Biomedical subjects

C A Doyle

Publications and source records attributed to C A Doyle.

At least 19 recordsLinked to original sources

PubMed1999

Substance P receptor (neurokinin-1)-expressing neurons in lamina I of the spinal cord encode for the intensity of noxious stimulation: a c-Fos study in rat.

The substance P receptor neurokinin-1 is expressed by a subset of neurons in the rat spinal cord. We have combined immunostaining for Fos, a marker of noxious peripheral stimulation, and neurokinin-1 to examine whether nociceptive signals from particular peripheral tissues (skin, muscle or knee joint) or activity generated by nerve injury or formalin-induced inflammation are preferentially modulated by substance P. Our results indicate that superficial and deep spinal neurokinin-1-positive neurons process nociceptive information in markedly different ways. In lamina I, the number of double-labelled neurons was positively correlated with the intensity of the stimulus (defined by the total Fos count) and was not directly related to any particular peripheral target. However, in the deeper layers of the spinal cord (V-X), there was no such correlation, and stimulation of joint nociceptors and formalin-induced inflammation produced the greatest proportion of Fos/neurokinin-1 co-localization, suggesting a particular role for substance P in the mediation of joint pain and inflammatory hyperalgesia. Thus, lamina I neurokinin-1 receptor-bearing neurons appear to be involved in intensity discriminative aspects of pain, whereas the deep neurokinin-1 cells are involved in spatial localization or the detection of particular nociceptive submodalities.

Animals↗

PubMed1999

Brain tissue oxygenation during hemorrhagic shock, resuscitation, and alterations in ventilation.

OBJECTIVES: Recently developed polarographic microelectrodes permit continuous, reliable monitoring of oxygen tension in brain tissue (PbrO2). The aim of this study was to investigate the feasibility and utility of directly monitoring PbrO2 in cerebral tissue during changes in oxygenation or ventilation and during hemorrhagic shock and resuscitation. We also sought to develop a model in which treatment protocols could be evaluated using PbrO2 as an end point. METHODS: Licox Clark-type polarographic probes were inserted in the brain tissue of 16 swine to monitor PbrO2. In eight swine, changes in PbrO2 were observed over a range of fractional concentrations of inspired O2 (FiO2) as well as during periods of hyperventilation and hypoventilation. In eight other swine, PbrO2 was monitored during a graded hemorrhage of up to 70% estimated blood volume and during the resuscitation period. RESULTS: When FiO2 was elevated to 100%, PbrO2 increased from a baseline of 15+/-2 mm Hg to 36+/-11 mm Hg. Hyperventilation while breathing 100% oxygen resulted in a 40% decrease in PbrO2 (p < 0.05), whereas hypoventilation increased PbrO2 to 88 mm Hg (p < 0.01). A graded hemorrhage to 50% estimated blood volume significantly reduced PbrO2, mean arterial pressure, and intracranial pressure (p < 0.01). Continued hemorrhage to 70% estimated blood volume resulted in a PbrO2 of 2.9+/-1.5 mm Hg. After resuscitation, PbrO2 was significantly elevated, reaching 65+/-13 mm Hg (p < 0.01), whereas mean arterial pressure and cerebral perfusion pressure simply returned to baseline. CONCLUSION: Directly measured PbrO2 was highly responsive to changes in FiO2, ventilatory rate, and blood volume in this experimental model. In particular, hypoventilation significantly increased PbrO2, whereas hyperventilation had the opposite effect. The postresuscitation increase in PbrO2 may reflect changes in both O2 delivery and O2 metabolism. These experiments set the stage for future investigations of a variety of resuscitation protocols in both normal and injured brain.

Animals↗

PubMed1998

Altered nociception, analgesia and aggression in mice lacking the receptor for substance P.

The peptide neurotransmitter substance P modulates sensitivity to pain by activating the neurokinin-1 (NK-1) receptor, which is expressed by discrete populations of neurons throughout the central nervous system. Substance P is synthesized by small-diameter sensory 'pain' fibres, and release of the peptide into the dorsal horn of the spinal cord following intense peripheral stimulation promotes central hyperexcitability and increased sensitivity to pain. However, despite the availability of specific NK-1 antagonists, the function of substance P in the perception of pain remains unclear. Here we investigate the effect of disrupting the gene encoding the NK-1 receptor in mice. We found that the mutant mice were healthy and fertile, but the characteristic amplification ('wind up') and intensity coding of nociceptive reflexes was absent. Although substance P did not mediate the signalling of acute pain or hyperalgesia, it was essential for the full development of stress-induced analgesia and for an aggressive response to territorial challenge, demonstrating that the peptide plays an unexpected role in the adaptive response to stress.

Aggression↗

PubMed1998

Abnormal persistence of cerebellar serotonin-1A receptors in schizophrenia suggests failure to regress in neonates.

This study investigated the neurodevelopmental basis of schizophrenia by examining an early transient population of serotonin-1A (5-HT1A) receptors using quantitative [3H]8-OH-DPAT autoradiography on sections of frozen postmortem cerebellum. Production of an ontogenetic map showed that human neonatal cerebellum acquired dense 5-HT1A receptors, most of which were eliminated by early childhood. Autoradiographic measurements on cerebellar vermis from 16 control adult subjects confirmed sparse 5-HT1A receptor binding. The data show a persistence of some vermal 5-HT1A receptors in brains from 19 adults with chronic schizophrenia in whom there may have been a slowed or arrested postnatal regression of vermal 5-HT1A receptors. Alternatively, some 5-HT1A receptors may have been re-expressed prior to, or subsequent to, the onset of the disease symptoms. The findings are not obviously explained by drug treatment and there are no data to explain how neuroleptics might promote expression of cerebellar 5-HT1A receptors. We propose that the study has identified a neurotransmitter receptor population which, in schizophrenia, undergoes misdirected reshaping during brain development. The findings support neurodevelopmental hypotheses of the disease.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1998

Differential time course of neuronal and glial apoptosis in neonatal rat dorsal root ganglia after sciatic nerve axotomy.

Sensory neurons in neonatal rat lumbar dorsal root ganglia die after sciatic nerve axotomy, and previous studies have estimated the total cell loss to be 40-95%. We have used the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) technique, combined with immunohistochemistry, to investigate the contribution of apoptosis to the cell loss that occurs after unilaterally transecting the sciatic nerve of new-born rats. TUNEL-positive cells were detected 1 day post-lesion, and their number peaked 3 days after the injury. Combining TUNEL labelling with immunohistochemistry, for neuron-specific neurofilament 150 kDa, or glial-specific S-100beta, enabled us to identify dying neurons and dying glia. One day after axotomy, most of the TUNEL-positive cells (58%) were neurons, whereas 3 days post-injury, only a small number of dying cells (6%) were neuronal. This lower incidence was due to a decrease in neuronal death and an increase in glial death. The glia in the dorsal root ganglia therefore die subsequent to the neurons. The apoptotic nature of the cell death was confirmed by electron microscopy, with fine structural features of apoptotic cell death, e.g. chromatin compaction and membrane blebbing, being observed in both glia and neurons. Our results confirm that extensive apoptosis occurs in the neonatal lumbar dorsal root ganglia after sciatic nerve section, and show that neurons and glial cells die with different time-courses. The results suggest a neuron-glia trophic interdependence in the dorsal root ganglia.

Animals↗

PubMed1997

Reduced nuclear factor kappaB (p65) expression in rat primary sensory neurons after peripheral nerve injury.

The activated form (p65) of nuclear factor kappa B (NF-kappa B) was found to be expressed in a sub-population (32%) of mixed diameter rat sensory neurons in L4 and L5 dorsal root ganglia, indicating that this transcription factor is involved in intracellular signalling in sensory neurons under physiological conditions. Four hours after crushing the sciatic nerve, ipsilateral p65 staining was abolished in a subgroup (60-70%) of these neurons. The contralateral side was unaffected by the injury and loss of NF-kappa B activity was not observed following sham surgery. Within 24 h of sciatic injury, ipsilateral p65 staining had recovered to control levels. We suggest that the decline in p65 after nerve injury was due to failure of retrograde axonal transport of trophic factor(s). Since neurotrophins and cytokines promote the survival of non-neuronal cells by activation of NF-kappa B, we believe that p65 may be critical for the resistance to apoptosis shown by adult sensory neurons.

Animals↗

PubMed1997

Characterization of liquid chromatographic stationary phases by Raman spectroscopy. Effect of ligand type.

This study represents the first Raman spectroscopic characterization of conventional chemically-bonded liquid chromatographic (LC) stationary phases under typical flow-rate and pressure conditions. Raman spectra were obtained for amino propyl (NH2), cyano propyl (CN), phenyl (Ph), octadecyl (C18), octyl (C8), and methyl (C1) chemically-bonded silica-based stationary phases in 100% aqueous mobile phases. The present experimental set-up has allowed Raman spectra of various stationary phase ligands, present in sub-monolayer coverages on the siliceous supports, to be obtained. This study: (1) demonstrates that conventional Raman spectroscopic techniques can be used to study LC stationary phases; (2) presents the experimental set-up, conditions, and approaches utilized to obtain Raman spectra of conventional stationary phases; (3) examines the spectroscopic differences observed for a variety of different types of bonded ligands that are typically used in reversed-phase (RPLC) and normal-phase (NPLC) liquid chromatographic separations; and (4) considers other future studies that are possible with this experimental approach, including mobile phase composition and temperature studies.

Chromatography, Liquid↗

PubMed1997

Localization of neuronal and endothelial nitric oxide synthase isoforms in human hippocampus.

The aim of the study was to use immunohistochemistry to identify, in the hippocampal region of human brain. the distribution of neuronal and endothelial isoforms of the enzyme nitric oxide synthase. Numerous pyramidal neurons and small, presumed GABAergic interneurons throughout the pyramidal cell layer of CA1-CA3 exhibited neuronal nitric oxide synthase-like immunoreactivity. Comparable immunopositive cells were seen in the granule cell and polymorphic layers of the dentate gyrus and in the stratum oriens. A dense plexus of immunopositive fibres was seen in the granule cell layer of the dentate gyrus. In contrast, endothelial nitric oxide synthase-like immunoreactivity was localized specifically, and with a pronounced punctate distribution, to the cell bodies of CA1 pyramidal neurons. The endothelial isoform was also present in blood vessels and in cells which resembled astroglia. These latter cells had a similar appearance and distribution to astroglia identified by their positive reaction to glial fibrillary acidic protein. The most frequently used method for identifying nitric oxide synthase-containing cells in brain, the NADPH-diaphorase reaction, was also applied to hippocampal sections. Only occasional NADPH-diaphorase-positive cells were seen in the hippocampus where, in contrast to their nitric oxide synthase-like immunoreactivity, the pyramidal cells did not stain for NADPH-diaphorase. Similarly, only occasional NADPH-diaphorase-reactive varicose axons were found in the hippocampus in these experiments. This study is the first to identify mostly separate populations of cells containing neuronal and endothelial nitric oxide synthase isoforms in human hippocampus. The data show that NADPH-diaphorase histochemistry, which is frequently used to show the presence of nitric oxide synthase, greatly underestimates the potential for hippocampal cells to produce nitric oxide. The fact that human hippocampus has a great many nitric oxide synthase-containing cells implies that nitric oxide has a role in human hippocampal functions although, at the present time, these actions are not clear. Whether those stimuli known to produce nitric oxide, such as activation of glutamate N-methyl-D-aspartate receptors, cause both enzyme isoforms in CA1 pyramidal cells to produce nitric oxide remains to be determined.

Aged↗

PubMed1997

Low-frequency stimulation induces homosynaptic depotentiation but not long-term depression of synaptic transmission in the adult anaesthetized and awake rat hippocampus in vivo.

The induction of homosynaptic long-term depression and depotentiation of previously established long-term potentiation was investigated in the CA1 hippocampal region of anaesthetized and awake adult rats following prolonged ipsilateral low-frequency stimulation of the Schaffer collateral/ commissural pathway. Prolonged low-frequency stimulation at 1-10 Hz failed to induce long-term depression of field excitatory postsynaptic potentials in the anaesthetized or awake adult rat. However, prolonged low-frequency stimulation at 5 and 10 Hz, although not at 1 or 2 Hz, did induce depotentiation of previously established long-term potentiation in anaesthetized animals. Thus, in the anaesthetized animals, 900 pulses at 10 Hz induced a depotentiation of 68%, 59% and 66% when given 10, 30 and 40 min following long-term potentiation induction. Depotentiation could also be induced at much longer times following the induction of long-term potentiation. Thus, in anaesthetized rats, depotentiation measuring 34% was induced by 10-Hz stimulation 4 h following long-term potentiation induction, and depotentiation measuring 60% was induced in two sets of experiments 24 h after long-term potentiation induction in awake animals. The results of the present study show that homosynaptic long-term depression was not induced in the adult hippocampus in vivo using stimulation protocols which are effective in hippocampal slices. However, erasure of long-term potentiation by the process of depotentiation has been shown to occur in the adult hippocampus in vivo, both at short times and at prolonged times after the induction of long-term potentiation.

Anesthesia↗

PubMed1997

Amphiphysin heterodimers: potential role in clathrin-mediated endocytosis.

Amphiphysin (Amph) is a src homology 3 domain-containing protein that has been implicated in synaptic vesicle endocytosis as a result of its interaction with dynamin. In a screen for novel members of the amphiphysin family, we identified Amph2, an isoform 49% identical to the previously characterized Amph1 protein. The subcellular distribution of this isoform parallels Amph1, both being enriched in nerve terminals. Like Amph1, a role in endocytosis at the nerve terminal is supported by the rapid dephosphorylation of Amph2 on depolarization. Importantly, the two isoforms can be coimmunoprecipitated from the brain as an equimolar complex, suggesting that the two isoforms act in concert. As determined by cross-linking of brain extracts, the Amph1-Amph2 complex is a 220- to 250-kDa heterodimer. COS cells transfected with either Amph1 or Amph2 show greatly reduced transferrin uptake, but coexpression of the two proteins rescues this defect, supporting a role for the heterodimer in clathrin-mediated endocytosis. Although the src homology 3 domains of both isoforms interact with dynamin, the heterodimer can associate with multiple dynamin molecules in vitro and activates dynamin's GTPase activity. We propose that it is an amphiphysin heterodimer that drives the recruitment of dynamin to clathrin-coated pits in endocytosing nerve terminals.

Amino Acid Sequence↗

PubMed1997

Use of tissue oxygen tension measurements during resuscitation from hemorrhagic shock.

BACKGROUND: Tissue oxygen tension can be measured directly in selected organ beds, and these measurements may be more sensitive in assessing the adequacy of resuscitation than global physiologic parameters. We hypothesized that heart tissue oxygen tension would be an important marker for the severity of ischemic insult to the heart during hemorrhagic shock. We further hypothesized that gut oxygen tension measured in the jejunum would prove to be a better measure of splanchnic hypoperfusion than intramucosal pH (pHi). METHODS: Tissue oxygen probes were inserted directly into the myocardium of the left ventricle and into the lumen of the proximal jejunum in 10 anesthetized swine. A pHi catheter was introduced into the stomach. The animals were subjected to a controlled hemorrhage of 50% of estimated blood volume. Gut and cardiac oxygen were monitored continuously during hemorrhage and resuscitation, which was performed with shed blood and crystalloid. RESULTS: While gut O2 and pHi trended together, we were unable to establish a correlation between changes in these two variables during hemorrhage and resuscitation. Heart PO2 decreased significantly during hemorrhage, but surpassed baseline values after resuscitation, a finding not seen in gut PO2. No standard physiologic variables reliably predicted changes in heart PO2 during these experiments. CONCLUSIONS: Tissue oxygen tensions measurements are highly responsive to changes induced during graded hemorrhagic shock and resuscitation. Gut PO2 and pHi appear to be measuring different physiologic processes in the gastrointestinal tract. The compensatory ability of the heart far exceeds that of the gut after ischemic insult. This hemorrhagic shock model appears feasible for the study of various methods of resuscitation.

Animals↗

PubMed1997

Frequency and natural history of rhinovirus infections in adults during autumn.

Human rhinovirus (HRV) accounts for a significant portion of common-cold illness, with the peak incidence being in the early fall. Three hundred forty-six adults who had self-diagnosed colds of 48 h or less were enrolled in a study during September and October 1994 to determine the frequency and clinical course of HRV infections. Nasal wash specimens for viral culture and reverse transcription-PCR (RT-PCR) for HRV RNA and human coronavirus OC43 and 229E RNA detection were collected on enrollment, and participants recorded their symptoms twice daily for 14 days. Middle ear pressure (MEP) was measured with a digital tympanometer on days 1 and 7. Picornaviruses (224 HRV and 7 enterovirus isolates) were detected by culture in 67% (231 of 346) of the subjects. Among 114 samples negative by culture, HRV was detected by RT-PCR in 52 (46%) for an overall picornavirus infection rate of 82% (283 of 346 subjects). Among the remaining 62 negative samples, human coronavirus RNA was detected by RT-PCR in 5 patients, so that 288 (83%) of patients had documented viral infection. The first symptom noticed most often was sore throat (40%) in HRV culture- or PCR-positive patients and stuffy nose in HRV-negative patients (27%). No differences in symptom scores over time or in the presence of individual symptoms were noted between groups. The median duration of the cold episodes was 11 days in HRV culture-positive patients, 9.5 days in HRV RT-PCR-positive patients, and 11.5 days in HRV-negative patients. On enrollment, abnormal MEPs (< or = -100 or > or = +100 mm of H2O) were found for 21% of HRV culture-positive patients, 14% of HRV RT-PCR-positive patients, and 10% of HRV-negative patients. No important differences in the clinical course of HRV culture-positive, HRV culture-negative and RT-PCR-positive, or HRV-negative colds were found. These results represent the highest frequency of virologically confirmed natural colds to date and document the importance of rhinoviruses as the cause of colds during fall months.

Adolescent↗

PubMed1995

Application of [3H]L-N(G)-nitro-arginine labelling to measure cerebellar nitric oxide synthase in patients with schizophrenia.

Brains from patients with schizophrenia have been reported to contain deficient and dysplastic forebrain neurons containing nitric oxide synthase (NOS). As part of a study of NOS in schizophrenia, we decided to investigate the cerebellum, which has particularly high levels of NOS. We used an autoradiographic method to measure the density and distribution of NOS. Sections of frozen cerebellum removed at autopsy were labelled with the selective NOS inhibitor [3H]L-NG-nitro-arginine. NOS levels were visualized in sagittal sections of vermis from 16 control subjects and 21 schizophrenia patients, and measurements were taken from the three groups of developmentally-distinct lobules I-V, VI-VII and VIII-X. The highest NOS density was in the Purkinje/molecular layer of cerebellar cortex, although there was some NOS in the granule cell layer. There were no differences in Purkinje/molecular or granule cell layer NOS levels between the two groups of subjects. The mild structural faults in cerebellar vermis observed in some patients with schizophrenia probably do not involve reductions in NOS-containing cells.

Aged↗

PubMed1995

Use of MRI for measuring structures in frozen postmortem brain.

A method was developed for magnetic resonance imaging (MRI) of human autopsy brains stored long-term at -70 degrees C. Scanning brains at temperatures between -70 and -8 degrees C gave minimal MRI signals consistent with protons having limited freedom of movement at low temperature. Raising brain temperature improved the signal such that scanning at -1 degree C generated images with good in-plane resolution, grey/white matter contrast, and fine detail of cortical sulcal/gyral patterns. To validate the method, volume and area measurements were made using computerized image analysis on stored digital images of 14 brains from adult subjects of both genders and various ages. The data confirmed that brain volume was inversely correlated with age, and female subjects had smaller brains. This is a valuable new method for acquiring morphometric data from previously unscanned pathologic brains that are to be used for neurochemical and molecular investigations.

Analysis of Variance↗

PubMed1994

Relationships between spinocervical tract neurons and descending catecholamine-containing axons in the cat.

Lumbosacral (L6-S1) spinal cord neurons in the cat were retrogradely labelled after uptake of horseradish peroxidase by their severed axons in the upper cervical (C3-C4) dorsolateral funiculus. Sections of L6-S1 containing labelled neurons were then processed immunocytochemically using antibodies against dopamine-beta-hydroxylase or tyrosine hydroxylase, two enzymes responsible for the synthesis of catecholamines. Two hundred and ninety eight retrogradely-labelled cells within laminae III-V of the dorsal horn were examined under high power (x 1000) with the light microscope. In Triton X-100-treated material, only 13% of these cells had catecholamine-containing varicosities closely apposed to their somata and proximal dendrites, which suggests that in comparison with the postsynaptic dorsal column pathway, spinocervical tract neurons are only sparsely innervated by descending catecholaminergic axons.

Animals↗

PubMed1994

Light- and electron-microscopic analysis of neuropeptide Y-immunoreactive profiles in the cat spinal dorsal horn.

The organization of neuropeptide Y-containing profiles in the dorsal horn of cat lumbosacral spinal cord was examined in an immunocytochemical study employing a specific antiserum against neuropeptide Y. Light-microscopic inspection revealed heavy concentrations of immunoreactive axons and varicosities within the superficial layers of the dorsal horn (laminae I and II) and only low to moderate numbers of positive terminals in the deeper layers (laminae III-VI). Neuropeptide-Y immunoreactivity in the superficial laminae occurred primarily as single punctate terminals, although in sagittal sections long rostrocaudally orientated fibres were also found. Immunoreactive fibres in the deeper layers were usually long and beaded. Two-hundred and eight neuropeptide Y-immunoreactive profiles throughout laminae I-VI were examined through serial sections with the electron microscope, and the overwhelming majority (n = 194) was confirmed to be axon terminals, most of which (95%) formed synaptic junctions. These terminals were packed with small irregularly shaped agranular vesicles, together with a number of large dense-core vesicles. Immunoreactivity was homogeneously scattered throughout the cytoplasm, and was also associated with the dense-core vesicles. A few neuropeptide Y-containing profiles (n = 14) were difficult to classify but they could have been vesicle-containing dendrites. The postsynaptic targets of neuropeptide Y-positive terminals were similar throughout each dorsal horn lamina. Most frequently, neuropeptide Y-positive boutons formed axodendritic and axosomatic synaptic junctions (range = 64% of synapses in laminae V/VI to 83% in lamina III). A smaller proportion of synapses were found upon other axon terminals and in laminae I-III the postsynaptic axon terminals were sometimes the central boutons of glomeruli. A number of terminals, especially those in lamina II, formed multiple synapses which often comprised a triadic arrangement. These findings suggest that neuropeptide Y regulates spinal sensory transmission through both a postsynaptic action upon dorsal horn neurons and a presynaptic action upon primary afferent terminals.

Animals↗

PubMed1994

Catecholaminergic innervation of the lateral cervical nucleus: a correlated light and electron microscopic analysis of tyrosine hydroxylase-immunoreactive axons in the cat.

The organization of catecholamine-containing axons in the cat lateral cervical nucleus was examined by immunocytochemical methods using a specific tyrosine hydroxylase antiserum. Light microscopic examination revealed numerous tyrosine hydroxylase-immunoreactive axons and varicosities throughout this nucleus, and some of these structures were found in contact with neuronal cell bodies. Correlated ultrastructural analysis showed that these varicosities were synaptic boutons which formed symmetric synaptic junctions with dendrites and somata. This evidence suggests that catecholamines exert a postsynaptic action upon neurons within the lateral cervical nucleus.

Animals↗

PubMed1993

Direct catecholaminergic innervation of spinal dorsal horn neurons with axons ascending the dorsal columns in cat.

Previous ultrastructural studies have shown that catecholamine-containing nerve terminals in the spinal dorsal horn form synaptic junctions with dendrites and somata, but the identity of the neurons giving rise to these structures is largely unknown. In this study we have investigated the possibility that spinomedullary neurons, which project through the dorsal columns to the dorsal column nuclei, are synaptic targets for descending catecholaminergic axons. Neurons with axons ascending the dorsal columns were retrogradely labelled after uptake of horseradish peroxidase by their severed axons in the thoracic (T10-T12) or cervical (C2-C3) dorsal columns. After the retrogradely labelled neurons were visualized, the tissue was immunocytochemically stained with antisera raised against tyrosine hydroxylase or dopamine-beta-hydroxylase. Three hundred forty-three retrogradely labelled neurons within laminae III-V of the lumbosacral dorsal horn were examined under high power with the light microscope. In Triton X-100 treated material, over 60% of cells were found to have dopamine-beta-hydroxylase-immunoreactive varicosities closely apposed to their somata and proximal dendrites. The number of contacts per cell varied from 1 to 22, with a mean number of 4.5. Fewer cells (34%) received contacts from axons immunoreactive for tyrosine hydroxylase as a consequence of the weaker immunoreaction produced by this antiserum. Correlated light and electron microscopic analysis confirmed that many of these contacts were regions of synaptic specialization and that immunostained boutons contained pleomorphic (round to oval) agranular vesicles together with several dense core vesicles. These observations suggest that catecholamines regulate sensory transmission through this spinomedullary pathway by a direct postsynaptic action upon its cells of origin. Such an action would be predicted to suppress transmission generally through this pathway.

Afferent Pathways↗