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T L Stanton

Publications and source records attributed to T L Stanton.

26 records · Page 2Linked to original sources
PubMed1982

Seasonal variation in thyrotropin-releasing hormone (TRH) content of different brain regions and the pineal in the mammalian hibernator, Citellus lateralis.

We have measured the endogenous TRH concentration in the pineal and 9 brain regions of a seasonal hibernator, the golden-mantled ground squirrel, during euthermia and hibernation in order to investigate the possibility that changes in TRH concentration might occur in association with naturally-occurring changes in CNS-mediated physiological and behavioral processes. Regional TRH content was assessed by radioimmunoassay in adult animals that were killed during euthermia in the mid-portion of each season and during hibernation in mid-winter. No significant changes in TRH concentration related to season or to hibernation versus euthermic state were noted in the hippocampus, brainstem, or cerebellum. In the olfactory bulb, preoptic area, and pineal, seasonal variation within euthermic groups was evident. During hibernation, statistically significant decreases in TRH content occurred in the forebrain, olfactory bulb, hypothalamus, septum, preoptic area, and midbrain. Significant fluctuations during hibernation were also observed in the pineal. In this structure, TRH concentration varied in relation to the phase of the hibernation bout. TRH content in the last quarter of the bout was three times greater when compared to values observed in the first quarter of the bout. These results suggest that TRH may be involved in the control processes attributed to these regions and support a role for TRH in the neural control of hibernation.

Animals↗
PubMed1981

Thyrotropin-releasing hormone effects in the central nervous system: dependence on arousal state.

Thyrotropin-releasing hormone was microinjected into the dorsal hippocampus of ground squirrels (Citellus lateralis) when they were at different levels of arousal, as assessed by electrophysiological and behavioral criteria. When administered to the awake animal, thyrotropin-releasing hormone produced dose-dependent decreases in body temperature accompanied by behavioral quieting and reductions in metabolic rate and electromyographic activity. The magnitude of these effects was greater when the peptide was microinjected during a period of behavioral activation. In contrast, administration of the peptide during slow wave sleep produced increased thermogenesis, an increase in electromyographic activity, and an increase in the amount of electroencephalographic desynchronization.

Animals↗
PubMed1981

Physical dependence on morphine fails to develop during the hibernating state.

Physical dependence on morphine occurs in a typical fashion during the active state of the mammalian hibernator Citellus lateralis, but does not occur when morphine exposure is confined to the hibernating state. Morphine exposure during hibernation can produce stereotyped behavior, thus demonstrating partial responsiveness of the central nervous system to opioids during this natural state.

Animals↗
PubMed1976

Characterization of midbrain component of the trigger for arousal from hibernation.

The ability of the midbrain reticular formation (MRF) to trigger arousal from hibernation and to change body temperature (Tb) during euthermia was tested in golden-mantled ground squirrels (Citellus lateralis). During hibernation (ambient temperature 5-6 degrees C) microinjections of cholinomimetic compounds (acetylcholine and carbachol) triggered full arousal or produced transient increases in Tb in 15 out of 19 tests; MRF microinjections of norepinephrine (NE) and 5-hydroxytryptamine (5-HT), at the same concentrations that produced full arousal when microinjected into the preoptic/anterior hypothalamus (PO/AH) area in previous experiments, has no effect on Tb in 13 out of 16 tests. In experiments on euthermic ground squirrels tested at an ambient temperature of 25 degrees C, MRF microinjections of acetylcholine raised Tb, whereas the monoamines had no significant effects. These results show that cholinoceptive neurons in the MRF can trigger arousal from hibernation and increase Tb during euthermia. The failure of NE and 5-HT to produce any significant effects at the same doses that were reported to be effective in the PO/AH indicates that the functional organization of the MRF portion of the arousal mechanism is different from that reported for the PO/AH.

Acetylcholine↗
PubMed1976

Inhibition of the CNA trigger process for arousal from hibernation.

Ground squirrels (Citellus lateralis) produced three distinct types of thermogenic response during hibernation. These responses were evoked spontaneously as well as after stimulation produced by brief handling, or after microinjection of acetylcholine into the midbrain reticular formation. Type I responses were characterized by small magnitude and a slow (mean rate, 0.03 degrees C/min), variable rising phase. Type II responses were characterized by a smooth, rapid rising phase with a mean rate of increase of 0.11 degrees C/min and by an abrupt reversal of the rising phase within a restricted ceiling temperature band with a mean value of 9.4 degrees C. The third type of response, full arousal, was characterized by a return of body temperature to euthermic (nonhibernating) levels and by an early rising phase that was indistinguishable from the rising phase of type II responses. This indicates that the rising phase of type II responses and the duplicate portion of full arousals are produced by a common neuronal mechanism that functions as the trigger for arousal from hibernation, and that this mechanism can be spontaneously inhibited when increasing internal temperature reaches a hibernation ceiling level.

Acetylcholine↗
PubMed1976

Changes in CNS responsiveness during hibernation.

The ability of the midbrain reticular formation (MRF) to produce thermogenic responses and to trigger arousal from hibernation was tested during successive quarters of individual hibernation bouts. Golden-mantled ground squirrels (Citellus lateralis) were implanted with bilateral cannula guides into the MRF. Single, bilateral, 1-mul injections of acetylcholine (ACh) at concentrations of 50, 100, or 200 mug/mul were delivered in each quarter of the same bout or in selected quarters of different bouts. The results show that the magnitude of thermogenic responses evoked by ACh stimulation of the MRF was depressed during the early portion of the bout and increased as time in the bout elapsed. Furthermore, the magnitude of responses evoked during hibernation was depressed in comparison to those evoked during euthermia, indicating the influence of inhibition on the responsiveness of the CNS during hibernation. We suggest that during hibernation, a progressive change in responsiveness of the CNS, perhpas focused in the MRF, controls the duration of each hibernation bout.

Acetylcholine↗