Recent immunohistochemical and radioimmunochemical observations have demonstrated a differential distribution of immunoreactive dynorphin (DYN) in rat brain. The presence of DYN immunoreactivity in a major intrinsic fiber pathway within the rat hippocampus (the mossy fiber system) has led us to evaluate the possible role of DYN and other closely related peptides in this structure. Single cell activity and hippocampal field potentials have been recorded from the CA1-CA3 cellular fields in halothane or urethane anesthetized rats. DYN, DYN1-13, DYN1-8, and alpha-neo-endorphin had an excitatory effect on most CA1-CA3 neurons encountered as has been previously observed for opiates and other opioid peptides. This response could be blocked by naloxone or by co-administration of Mg++ ion suggesting an indirect (synaptic) mechanism of excitation similar to that hypothetized for enkephalin. A significant number of CA3 neurons, however, exhibited a non-naloxone sensitive inhibitory response to DYN, related opioid peptides, and the kappa agonist WIN 35-197 (ethylketocyclazocine). Field potential analysis of CA1-CA3 neuronal responses to mossy fiber activation also indicated an excitatory, Mg++ reversible, action of iontophoretically applied DYN. These observations support our cytochemical and assay studies indicating diverse opioid systems within the rat hippocampus. In addition, these functional studies are congruent with other evidence suggesting multiple opioid mechanisms in this structure.

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PubMedDate not supplied

Internal temperature variations during the sleep-wake cycle in the rat.

This study attempted to explain the variations of internal (brain and subcutaneous) temperature in the rat as a function of sleeping and waking. Temperature variations in cerebellum and hypothalamus were related to the changes in local cerebral blood flow (CBF) measured chronically with a thermal clearance method. CBF was stable and at a high level during slow wave sleep (SWS), decreased at the beginning of each wake (W) and paradoxical sleep (PS) phase, but tended to overshoot at the end of the PS phase. Subcutaneous temperature was related to the whole body thermogenesis (VO2) and to the sensible heat loss by radiation, convection and conduction. VO2 increased during W, decreased and plateaued during SWS, and was at a minimum level during PS. Sensible heat loss decreased during W, increased during SWS, and generally rose abruptly during PS. These variations in body and brain heat gain and heat loss are in agreement with the local temperature variations during sleeping and waking. The concomitant variations in vigilance states and internal temperature led to an apparent close relationship between the circadian rhythms of these variables, although their exact degree of liaison was not established.

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PubMedDate not supplied

An automatic sleep classifier for laboratory rodents.

Two successive main steps are usually performed in automatic sleep classification: a) a periodic quantification of the EEG signal by a set of indices featuring each polygraphic epoch by a point in a multidimensional space, b) a stage decision to determine the cluster that includes the representative point for a given epoch (discriminant analysis). As solid state logic comparators simulate linear discriminant functions, this article describes an improved classifier for automatic sleep scoring in laboratory rodents. Four indices were found to be discriminant on both rats and mice: F(the energy in the EEG theta band relative to that in the delta band), Z(number of EEG zero-crossings), D(variability of the EEG amplitude) and M(integrated EMG). They are measured by analog techniques for 30 sec epochs from an EEG and an EMG lead per animal. At the end of each epoch, the logic results of their respective comparators serves as an input to a hardwired modifiable truthtable where a sleep stage decision is elaborated. The outputs of 4 multiplexed classifiers are controlled by microprocessor and may be used for chart or digital recordings on various peripherals. The overall agreement with visual scoring is more than 95% for both rats and mice.

Animals↗