What the heck is the noradrenergic system for and how do we know? I know it has something to do with arousal and attention. It's not central to the system underlying Intercranial Self Stimulation. Destruction of 80-97% of these neurons in different nuclei dont diminish ICS.
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A step up in specificity from wholesale destruction of neural tissue by electrolytic lesions is chemical lesions. Chemical lesions target neurons or axons with certain neurotransmitter receptors. For example 6-hydroxydopamine (6-OHDA) is a selective catecholaminergic neurotoxin.
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I wonder what deep electrode stimulation of the hippocampus feels like. There are many sites that trigger Intercranial Self-Stimulation but not all ICS is the same. The nucleus accumbens and the septal area trigger very different behaviors and subjective reports.
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Theres a bundle of noradrenergic fibers connecting the hippocampus and the medial forebrain bundle. This is one terminus. This bundle running through the MFB originates in the locus coeruleus in the dor pons. I want to remember these facts. NEUROANATOMY
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It was an early hypothesis that Intracranial Self-stimulation was a 'unitary reward system'. ICS could be obtained through electrodes placed along the noradrenergic pathway and noreadrenaline was thought to be the main neurotransmitter responsible for supporting ICS.
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Tying it together, selectively destroying noradrenergic fibers with 6-OHDA DID NOT attenuate Intracranial Self Stimulation. An abundance of negative evidence of this kind Torpedoed the Noreadrenergic hypothesis of a 'unitary brain reward system'.
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This book dive while successful at ruling out the noradrenergic basis of ICS did not answer my opening question. I had to run to wikipedia to satisfy my curiously since the book was obviously done with the topic. What I found:
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The noradrenergic system is the CNS's sympathetic component. It's about preparing for deliberate action which is why it's unifies from the cerebrum where movement lives, through the medial forebrain bundle and hypothalamus (v. simplified involved in expectation), and cortex.
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Would be very interested to figure out the over lap of noradrenergic, dopaminergic, and sertonergic (5-HT) systems. They have anatomical overlap with NE systems being the broadest, DA systems being the narrowest, and 5-HT in the middle.
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NE systems reach their lowest output during sleep and spike on waking, but I'll have to check if they lead or lag. I wonder if a anthropomorphic rendering would be 'energy'. I also wonder what the relationship between NE and autonomic behaviors is, mainly yawning.
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I'll be looking for experiments with microinjections, broad injections, and blocking of NE. I'll also be looking at what happens when NE systems are neurochemically lesioned. NE systems are so broad so I'm maybe expecting it to be hard to find clean delineations.
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I followed up on a hunch that melatonin and norepinephrine would have biochemical coupling. "In vertebrates, melatonin secretion is regulated by activation of the beta-1 adrenergic receptor by norepinephrine." Happy I'm finally using my biochem training.
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Dopamine is the precursor for norepinephrine synthesis and I just found melatonin's precursor is serotonin. From a systems biology perspective these relationship set up dynamic systems. Put another way, these are chemical circuits.
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"Nasty little Buddhist"
Seeking via neuroscience and psychology informed dharma.