A quantitative and morphological study of projection neurons in lamina I of the rat lumbar spinal cord

Spike, Rosemary C.; Puskár, Zita; Andrew, David P.; Todd, Andrew J.

doi:10.1046/j.1460-9568.2003.02981.x

Cited by 215 publications

(295 citation statements)

References 52 publications

(127 reference statements)

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“…In adult rat SDH neurons this current is thought to underlie "gap firing," a form of AP discharge characteristic of projection neurons (Ruscheweyh et al 2004). Because 5-10% of lamina I neurons are projection neurons (Spike et al 2003) and some labeling studies show that projection neurons can in fact lie in lamina II (Al-Khater et al 2008;Bice and Beal 1997), it is possible that some of our I As -expressing neurons were projection neurons. If this is so, then the maturation of this important neuronal population that relays SDH output to higher brain centers is not complete until at least P10.…”

Section: Ap Discharge Categories and Subthreshold Whole Cell Currentsmentioning

confidence: 99%

Evidence for a Critical Period in the Development of Excitability and Potassium Currents in Mouse Lumbar Superficial Dorsal Horn Neurons

Walsh

Graham²,

Brichta³

et al. 2009

Journal of Neurophysiology

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Walsh MA, Graham BA, Brichta AM, Callister RJ. Evidence for a critical period in the development of excitability and potassium currents in mouse lumbar superficial dorsal horn neurons. J Neurophysiol 101: 1800 -1812, 2009. First published January 28, 2009 doi:10.1152/jn.90755.2008. The output of superficial dorsal horn (SDH; laminae I-II) neurons is critical for processing nociceptive, thermal, and tactile information. Like other neurons, the combined effects of synaptic inputs and intrinsic membrane properties determine their output. It is well established that peripheral synaptic inputs to SDH neurons undergo extensive reorganization during preand postnatal development. It is unclear, however, how membrane properties or the subthreshold whole cell currents that shape SDH neuron output change during this period. Here we assess the intrinsic membrane properties and whole cell currents in mouse SDH neurons during late embryonic and early postnatal development (E15-P25). Transverse slices were prepared from lumbar spinal cord and whole cell recordings were obtained at 32°C. During this developmental period resting membrane potential (RMP) became more hyperpolarized (by ϳ10 mV, E15-E17 vs. P21-P25) and input resistance decreased (1,074 Ϯ 78 vs. 420 Ϯ 27 M⍀). In addition, action potential (AP) amplitude and AP afterhyperpolarization increased, whereas AP half-width decreased. Before and after birth (E15-P10), AP discharge evoked by intracellular current injection was limited to a single AP at depolarization onset in many neurons (Ͼ41%). In older animals (P11-P25) this changed, with AP discharge consisting of brief bursts at current onset (ϳ46% of neurons). Investigation of major subthreshold whole cell currents showed the rapid A-type potassium current (I Ar ) dominated at all ages examined (90% of neurons at E15-E17, decreasing to Ͼ50% after P10). I Ar expression levels, based on peak current amplitude, increased during development. Steady-state inactivation and activation for I Ar were slightly less potent in E15-E17 versus P21-P25 neurons at potentials near RMP (Ϫ55 mV). Together, our data indicate that intrinsic properties and I Ar expression change dramatically in SDH neurons during development, with the greatest alterations occurring on either side of a critical period, P6 -P10.

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Section: Ap Discharge Categories and Subthreshold Whole Cell Currentsmentioning

confidence: 99%

Evidence for a Critical Period in the Development of Excitability and Potassium Currents in Mouse Lumbar Superficial Dorsal Horn Neurons

Walsh

Graham²,

Brichta³

et al. 2009

Journal of Neurophysiology

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“…Nociceptive neurons in the superficial laminae project to the contralateral side directly at the spinal segmental level although some cells seem to project bilaterally (Spike et al, 2003). The neurons in lamina I have relatively small receptive fields and, at least in the cat and monkey, can be divided functionally as well as morphologically into three different classes.…”

Section: Structural Components In Nociceptive Processing Via the Spinmentioning

confidence: 99%

Estrogenic influences in pain processing

Amandusson

Blomqvist

2013

Frontiers in Neuroendocrinology

108

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Gonadal hormones not only play a pivotal role in reproductive behavior and sexual differentiation, they also contribute to thermoregulation, feeding, memory, neuronal survival, and the perception of somatosensory stimuli. Numerous studies on both animals and human subjects have also demonstrated the potential effects of gonadal hormones, such as estrogens, on pain transmission. These effects most likely involve multiple neuroanatomical circuits as well as diverse neurochemical systems and they therefore need to be evaluated specifically to determine the localization and intrinsic characteristics of the neurons engaged. The aim of this review is to summarize the morphological as well as biochemical evidence in support for gonadal hormone modulation of nociceptive processing, with particular focus on estrogens and spinal cord mechanisms.

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“…Finally, information is relayed to cortical centers where the discriminative and affective components of pain are established (Craig 2003a,b;Ohara et al 2005). At the level of the spinal cord, this view is convenient but simplistic and overlooks the fact that most SDH neurons (certainly Ͼ95%) are local circuit interneurons and not projection neurons (Polgar et al 2004;Spike et al 2003;Willis and Coggeshall 2004). These interneurons can be excitatory or inhibitory and receive inputs from higher brain centers and other local interneurons in addition to those from the periphery.…”

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confidence: 99%

Moving From an Averaged to Specific View of Spinal Cord Pain Processing Circuits

Graham

Brichta²,

Callister³

2007

Journal of Neurophysiology

103

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Graham BA, Brichta AM, Callister RJ. Moving from an averaged to specific view of spinal cord pain processing circuits. J Neurophysiol 98: [1057][1058][1059][1060][1061][1062][1063] 2007. First published June 13, 2007; doi:10.1152/jn.00581.2007. Neurons in the superficial dorsal horn (SDH) of the spinal cord play a critical role in processing potentially painful or noxious signals from skin, muscle, and viscera. Many acute pain therapies are based on the notion that altering the excitability of SDH neurons can block or gate these signals and reduce pain. This same notion also underlies treatments for certain chronic pain states. Basic scientists are now beginning to identify a number of potential molecular targets for spinal cord-based pain therapies with a focus on ion channels and receptors that can alter neuronal excitability. The current challenge in pain research is to identify which are the most promising targets and how their manipulation alters pain processing. In this review, we propose that our understanding of spinal pain processing mechanisms and translation of these discoveries into pain therapies could be improved by 1) better appreciating and understanding neuronal heterogeneity in the SDH; 2) establishing connectivity patterns among SDH neuron types; and 3) testing and extending findings made in vitro to intact (in vivo) animal models. As this information becomes available, it will be possible to determine the precise distribution of potential therapeutic targets on various SDH neuron types within specific circuits known to be functionally important in spinal pain processing. I N T R O D U C T I O NThe exact details of how the CNS processes noxious stimuli under normal and pathological conditions into a pain percept are complex and still poorly understood (Craig 2003b;Millan 1999;Willis and Coggeshall 2004). The classic ascending pain-processing pathway is characterized by collections of neurons located in anatomically discrete locations, or processing nodes, along the neuroaxis. These nodes include regions like the spinal cord dorsal horn, midline brain stem centers, and the thalamus. The aim of current pain therapies is to alter neuronal excitability and thus ultimately affect signal processing at various nodes in this pathway (Fields and Basbaum 1999; Gebhart 2004;Mason 2005;Sandkuhler 1996). Therefore efforts have focused on examining how neurotransmitters, receptors, and ion channels can alter the excitability of neurons located in processing nodes. Because the superficial dorsal horn (SDH; laminae I-II) is the first central node in the pain pathway, it has received considerable attention, both as a site for understanding pain processing mechanisms and subsequent development of pain therapies.The SDH is the major spinal target for small diameter (A␦ and C-fiber) primary afferents carrying noxious, thermal, itch, and innocuous tactile information (Christensen and Perl 1970;Sugiura et al. 1986; Tuckett and Wei 1987a,b;Vallbo et al. 1999). Evidence suggests that each of these modalities ascend...

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A quantitative and morphological study of projection neurons in lamina I of the rat lumbar spinal cord

Cited by 215 publications

References 52 publications

Evidence for a Critical Period in the Development of Excitability and Potassium Currents in Mouse Lumbar Superficial Dorsal Horn Neurons

Evidence for a Critical Period in the Development of Excitability and Potassium Currents in Mouse Lumbar Superficial Dorsal Horn Neurons

Estrogenic influences in pain processing

Moving From an Averaged to Specific View of Spinal Cord Pain Processing Circuits

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