Publisher Summary This chapter summarizes recent efforts on the design of anatomical and physiological experiments that are capable of bridging the gap between cellular-membrane studies of locus ceruleus-norepinephrine (LC-NE) attributes and more global hypotheses regarding the impact of the LC projection system on sensory neural network function. Recent studies using fluorescent retrograde tracers have shown that LC efferents to target structures along the trigeminal somatosensory pathway in rat exhibit an orderly projection with respect to the crossed trajectory of this ascending sensory system. It has been also found that LC projection neurons to somatosensory structures are organized into overlapping subsets within the nucleus, thus raising the possibility that a significant proportion of these cells may project to multiple, common somatosensory targets via axon collaterals. These studies show that the LC exhibits an internal organization and efferent projection pattern that is consistent with the idea that LC outputs can selectively and coordinately modulate the flow of somatosensory information through forebrain circuits. These findings indicate that NE can augment membrane responses to GABA via a β -receptor-linked/ cyclic adenosine monophosphate (cAMP) cascade of events. As such, these noradrenergic influences on putative transmitter-induced conductance changes are consistent with previously observed effects of iontophoretic NE on single-unit responses to GABA in anesthetized and awake, behaving animals. The results reported here continue to support and refine the idea that the LC efferent system exhibits a high degree of anatomical and physiological specificity with respect to its potential impact on target neuronal circuits. Overall, these advances in the understanding of the organizational principles and physiological specificity of the LC-NE efferent system provide new insights into the role of this monoamine-containing brain-stem nucleus in behavior.
[1]
B. Waterhouse,et al.
Noradrenergic enhancement of GABA-induced input resistance changes in layer V regular spiking pyramidal neurons of rat somatosensory cortex
,
1995,
Brain Research.
[2]
F. Bloom,et al.
Nucleus locus ceruleus: new evidence of anatomical and physiological specificity.
,
1983,
Physiological reviews.
[3]
R C Lin,et al.
Lateralization and functional organization of the locus coeruleus projection to the trigeminal somatosensory pathway in rat
,
1997,
The Journal of comparative neurology.
[4]
Donald J. Woodward,et al.
Modulation of rat cortical area 17 neuronal responses to moving visual stimuli during norepinephrine and serotonin microiontophoresis
,
1990,
Brain Research.
[5]
D. Woodward,et al.
Noradrenergic modulation of somatosensory cortical neuronal responses to lontophoretically applied putative neurotransmitters
,
1980,
Experimental Neurology.