Effect of adrenalectomy on the circadian rhythm of LTP

Dana, Richard C.; Martinez, Joe L.

doi:10.1016/0006-8993(84)91086-2

Cited by 64 publications

(39 citation statements)

References 20 publications

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“…The present data support a diurnal modulation of hippocampal neurotransmission [2,4,7,14], and demonstrate a dynamic daytime-dependence in the spike afterpotentials and postsynaptic HVA Ca 21 currents of CA3 pyramidal neurons. Depolarization-induced excitability exhibited daytime-dependent alterations, possibly related to changes in HVA Ca 21 -amplitudes.…”

supporting

confidence: 79%

“…Consistent with the idea of a biphasic regulation, our data show a U-shaped relationship between the time-of-daydependent measurements of CA3 neuronal HVA Ca 21 -amplitudes and circulating corticosterone concentrations. Interestingly, removal of the adrenal glands, eliminating the main source of corticosterone, reverses the circadian rhythm of hippocampal LTP induction [7]. Voltage recordings during the dark phase showed a suppression of the mAHP but no change in the sAHP.…”

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confidence: 97%

“…Some of these¯uc-tuations occur independently of light cues, the most important`zeitgeber' [4]. Diurnal rhythms have also been reported for the strength of synaptic connections within the dentate gyrus and the induction of long-term potentiation (LTP) in the CA1 region of the hippocampal formation [2,7,14], which even persist in in vitro preparations [14]. We hypothesized that the daytime-dependent modulation of hippocampal neurotransmission may depend on changes in the in¯ux of Ca 21 , which is an important element of hippocampal synaptic plasticity, of postsynaptic excitability, and of neurotransmitter release [9,10,16,17].…”

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confidence: 99%

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High-voltage-activated Ca2+ currents and the excitability of pyramidal neurons in the hippocampal CA3 subfield in rats depend on corticosterone and time of day

Kole

Koolhaas

Luiten

et al. 2001

Neuroscience Letters

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High-voltage-activated Ca2+ currents and the excitability of pyramidal neurons in the hippocampal CA3 subfield in rats depend on corticosterone and time of day Kole, MHP; Koolhaas, JM; Luiten, PGM; Fuchs, E Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractThis study tested the time-of-day dependence of the intrinsic postsynaptic properties of hippocampal CA3 pyramidal neurons. High-voltage-activated Ca 21 currents and the Ca 21 -and voltage-dependent afterhyperpolarizations were examined in slices of rat brains obtained at four distinct time periods. Just after onset of the dark phase, the steady-state amplitude of the Ca 21 current (21.24^0.11 nA) was signi®cantly greater (P , 0:03) than that of the light phase (20.84^0.06 nA). Over the entire time range, the amplitude of the Ca 21 current correlated with plasma corticosterone levels in a U-shaped function. Furthermore, depolarization-induced excitability during the dark phase exhibited an increased spike after depolarization (3.1^0.1 mV) and a slower adaptation of the ®ring frequency (146^18%). These ®ndings point to a dynamic time-of-day dependence of the CA3 neuronal properties and postsynaptic Ca 21 currents. q

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confidence: 79%

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confidence: 97%

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confidence: 99%

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High-voltage-activated Ca2+ currents and the excitability of pyramidal neurons in the hippocampal CA3 subfield in rats depend on corticosterone and time of day

Kole

Koolhaas

Luiten

et al. 2001

Neuroscience Letters

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“…First, they reversibly and biphasically modulate the excitability of hippocampal neurons and influence the magnitude of long-term potentiation, as well as producing long-term depression (27,63,(109)(110)(111)(112). These effects may be involved in biphasic effects of adrenal secretion on excitability and cognitive 53 STRESS AND THE AGING HIPPOCAMPUS function and memory during the diurnal rhythm and after stress (8,24,31,34). In particular, acute nonpainful novelty stress inhibits primed-burst potentiation and memory (32,33).…”

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confidence: 99%

Stress and the Aging Hippocampus

McEwen

1999

Frontiers in Neuroendocrinology

208

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The ''glucocorticoid cascade hypothesis'' of hippocampal aging has stimulated a great deal of research into the neuroendocrine aspects of aging and the role of glucocorticoids, in particular. Besides strengthening the methods for investigating the aging brain, this research has revealed that the interactions between glucocorticoids and hippocampal neurons are far more complicated than originally envisioned and involve the participation of neurotransmitter systems, particularly the excitatory amino acids, as well as calcium ions and neurotrophins. New information has provided insights into the role of early experience in determining individual differences in brain and body aging by setting the reactivity of the hypothalamopituitary-adrenal axis and the autonomic nervous system. As a result of this research and advances in neuroscience and the study of aging, we now have a far more sophisticated view of the interactions among genes, early development, and environmental influences, as well as a greater appreciation of events at the cellular and molecular levels which protect neurons, and a greater appreciation of pathways of neuronal damage and destruction. While documenting the ultimate vulnerability of the brain to stressful challenges and to the aging process, the net result of this research has highlighted the resilience of the brain and offered new hope for treatment strategies for promoting the health of the aging brain. KEY WORDS: stress; hippocampal aging; glucocorticoid cascade hypothesis. 1999 Academic Press INTRODUCTIONThe hippocampus is a particularly vulnerable and sensitive region of the brain that is also very important for declarative and spatial learning and memory (36). Hippocampal neurons are vulnerable to seizures, strokes, and head trauma, as well as responding to stressful experiences (27,92,130). At the same time they show remarkable plasticity, involving long-term synaptic potentiation and depression, dendritic remodeling, synaptic turnover, and neurogenesis in the case of the dentate gyrus (Fig 1) (17,27,92).The work of aus der Muhlen and Ockenfels (3) first drew attention to potentially toxic actions of adrenal steroids. The reported darkly stained neurons in the hippocampus of guinea pigs exposed to high levels of glucocorticoids, an observation that has been confirmed and extended to repeated stress in subsequent studies (41,100), although there are still some doubts as to whether ''dark neurons'' may be artifacts of tissue trauma (18). In 1968, we discovered receptors for adrenal steroids in hippocampus (95), and it is now known that two types of adrenal steroid receptors exist in the hippocampus and other brain regions and mediate a variety of adrenal steroid effects on excitability, neurochemistry, and structure (27). Landfield (68) and then Sapolsky (127,128) provided evidence for a role of adrenal steroids in neuronal aging in the hippocampus, leading to the formulation of the ''glucocorticoid cascade hypothesis '' (130). This hypothesis states that glucocorticoids participate in a ...

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“…We were prompted to initiate thex studies by anecdotal observations on the phenomenon of jet ! ;ig and by studies which showed that the electrical activity of the llippocampus shows a diurnal variation (1)(2)(3), with an increase in !lie electrical field potential of the dentate gyrus during the actliity phase of the diurnal cyclc of rats and squirrel monkeys (1) l h a and Martinez (2) found an adrcnal influence on synaptic efhcy in the dentate gyrus, such that intact rats experienccd the W i h synaptic efficacy during their waking phase while adrenalectoinired (ADX) rats showed a peak synaptic efficacy during the s1ei.p phase. The diurnal cycle of glucocorticoid secretion parallels thi\ increase in synaptic activity, with the onset of the glucocorticoid rise occurring just prior to waking and reaching a peak approximately 4 h following wakefulness (4).…”

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confidence: 99%

Diurnal Differences and Adrenal Involvement in Calmodulin Stimulation of Hippocampal Adenylate Cyclase Activity

Gannon¹,

Brinton²,

Sakai³

et al. 1991

J Neuroendocrinology

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Calclum/calmodulin-dependent processes a r e altered by manipulations of the hypothalamic-pituitary-adrenal axis, and a r e associated 'with changes in synaptic efficacy in t h e hippocampus, s u c h as long-term potentiation. Recent evidence indicates that there are tliurnal variations in t h e threshold for long-term potentiation, as well as diverse effects of the adrenals and of adrenal steroids on e:octrical activity related to long-term potentiation. In order to probe possible mechanisms underlying these observations, we inve::tigated the effects of the diurnal cycle, as well as adrenalectomy (ADX) and adrenal demedullation on adenylate cyclase activ::y. In hippocampal, but not cortical, membranes the adenylate cyclase response.to calmodulin w a s higher during the beginning of thi: dark phase of the cycle, when endogenous corticosterone levels a r e high. Basal and forskolin-stimulated adenylate cyclase activity did not exhibit diurnal variation in either brain region. ADX (6 and 14 days) depressed the adenylate cyclase response to calni<)dulin in hippocampal membranes, and abolished the diurnal difference. ADX had smaller effects on this response in cortical menibranes. ADX also attenuated basal and forskolin-stimulated adenylate cyclase activity, but these changes were less striking than effects on calmodulin-stimulated activity. Demedullation (14 days), generating corticosterone levels in the low physiological ran:;!?, mirrored the effects of ADX on hippocampal adenylate cyclase activity. Corticosterone (20 to 25 pghnl in the drinking water) did riot consistently prevent ADX effects on adenylate cyclase activity. These results demonstrate that adrenal effects on adenylate -e activity a r e regionally spectfic within the brain, and they suggest that other adrenal secretions besides glucocorticoids ma) b e involved in the feedback of the diurnal rhythm on the hippocampus. Taken together with our recent finding that chronic stre -3 or corticosterone injection selectively attenuated the adenylate cyclase response to calmodulin in cortical, but not hippocampal inembranes our findings provide further support for a role of the pituitary-adrenal axis in modulating neural calmodulindep,:ndent adenylate cyclase activity.Out interest in neurochemical and hormonal factors involved in neu1.d processes underlying cognitive function has led us to expi:m the biochemical differences between the active waking stat', and the sleep state of the rat. We were prompted to initiate thex studies by anecdotal observations on the phenomenon of jet !;ig and by studies which showed that the electrical activity of the llippocampus shows a diurnal variation (1-3), with an increase in !lie electrical field potential of the dentate gyrus during the actliity phase of the diurnal cyclc of rats and squirrel monkeys(1) l h a and Martinez (2) found an adrcnal influence on synaptic efhcy in the dentate gyrus, such that intact rats experienccd the W i h synaptic efficacy during their waking phase while adrenalectoinired (ADX) rats sho...

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Effect of adrenalectomy on the circadian rhythm of LTP

Cited by 64 publications

References 20 publications

High-voltage-activated Ca2+ currents and the excitability of pyramidal neurons in the hippocampal CA3 subfield in rats depend on corticosterone and time of day

High-voltage-activated Ca2+ currents and the excitability of pyramidal neurons in the hippocampal CA3 subfield in rats depend on corticosterone and time of day

Stress and the Aging Hippocampus

Diurnal Differences and Adrenal Involvement in Calmodulin Stimulation of Hippocampal Adenylate Cyclase Activity

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