The Anatomical and Neurochemical Basis of Atropine-Resistant Hippocampal Rhythmical Slow Activity
Hippocampal slow wave activity was recorded together with neocortical activity in many of the experiments described in Chapter 5. In most respects, atropine-resistant hippocampal rhythmical slow activity appeared to operate in parallel with atropine-resistant neocortical activation. Thus, like the corresponding neocortical wave pattern, atropine-resistant hippocampal rhythmical slow activity was not directly affected by dopaminergic or noradrenergic synaptic blockade, by lesions of the substantia nigra or the locus coeruleus, by blockade of the synthesis of catecholamines by α-methyl p-tyrosine, by intraventricular injection of 6-hydroxydopamine or by such serotonergic antagonists as methysergide or metergoline. Neuroleptic drugs (blocking dopamine receptors) produced a striking reduction in the occurrence of atropine-resistant hippocampal rhythmical slow activity but did not alter its correlation with Type 1 movement: the movement and the hippocampal wave form always occurred together even though both occurred much less frequently than under normal conditions. Conversely, the occurrence of the atropine-resistant hippocampal waveform and the associated Type 1 behavior (mainly walking, rearing, and head movement) were greatly increased by the administration of a moderate dose of d-amphetamine. These observations suggest that atropine-resistant inputs to both the hippocampus and the neocortex are brought into action by a dopaminergic mechanism.
KeywordsEntorhinal Cortex Dorsal Raphe Nucleus Lateral Hypothalamic Area Atropine Sulfate Septal Nucleus
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Notes on Chapter 6
- 2.During this period several other notable discoveries were made. Terry showed that the higher frequency hippocampal rhythmical slow activity associated with the muscular twitches of active sleep was resistant to atropine while the lower frequency activity appearing during the inter-twitch intervals was sensitive to atropine [Robinson, T.E., Kramis, R.C. and Vanderwolf, C.H. (1977). Two types of cerebral activation during active sleep: relations to behavior. Brain Research, 124: 544–549]. We also discovered that anesthetic doses of urethane do not abolish atropine-resistant low voltage fast activity even though they do abolish atropine-resistant hippocampal rhythmical slow activity [Vanderwolf, C.H., Kramis, R. and Robinson, T.E. (1978). Hippocampal electrical activity during waking behaviour and sleep: analyses using centrally acting drugs. Functions of the septo-hippocampal system, Ciba Foundation Symposium. 1158(new series),Amsterdam; Elsevier, pp. 199–226]. The basis of this selectivity is completely unknown.Google Scholar
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