Loss of dynorphin-mediated inhibition of voltage-dependent Ca2+ currents in hippocampal granule cells isolated from epilepsy patients is associated with mossy fiber sprouting

doi:10.1016/S0306-4522(99)00249-3

Neuroscience

Volume 94, Issue 2, September 1999, Pages 465-471

https://doi.org/10.1016/S0306-4522(99)00249-3 Get rights and content

Abstract

The endogenous κ receptor selective opioid peptide dynorphin has been shown to inhibit glutamate receptor-mediated neurotransmission and voltage-dependent Ca²⁺ channels. It is thought that dynorphin can be released from hippocampal dentate granule cells in an activity-dependent manner. Since actions of dynorphin may be important in limiting excitability in human epilepsy, we have investigated its effects on voltage-dependent Ca²⁺ channels in dentate granule cells isolated from hippocampi removed during epilepsy surgery. One group of patients showed classical Ammon's horn sclerosis characterized by segmental neuronal cell loss and astrogliosis. Prominent dynorphin-immunoreactive axon terminals were present in the inner molecular layer of the dentate gyrus, indicating pronounced recurrent mossy fiber sprouting. A second group displayed lesions in the temporal lobe that did not involve the hipppocampus proper. All except one of these specimens showed a normal pattern of dynorphin immunoreactivity confined to dentate granule cell somata and their mossy fiber terminals in the hilus and CA3 region. In patients without mossy fiber sprouting the application of the κ receptor selective opioid agonist dynorphin A ([D-Arg⁶]1–13, 1 μM) caused a reversible and dose-dependent depression of voltage-dependent Ca²⁺ channels in most granule cells. These effects could be antagonized by the non-selective opioid antagonist naloxone (1 μM). In contrast, significantly less dentate granule cells displayed inhibition of Ca²⁺ channels by dynorphin A in patients with mossy fiber sprouting (Chi-square test, P<0.0005).

The lack of dynorphin A effects in patients showing mossy fiber sprouting compares well to the loss of κ receptors on granule cells in Ammon's horn sclerosis but not lesion-associated epilepsy. Our data suggest that a protective mechanism exerted by dynorphin release and activation of κ receptors may be lost in hippocampi with recurrent mossy fiber sprouting.

Section snippets

Patient data

Surgical specimens from 14 patients with pharmaco-resistant TLE were obtained for electrophysiological analysis (see Table 1; average age at surgery 33.5±10.9 years). The mean duration of TLE in the patients was 19.2±11.7 years (mean±S.E.M.) and the mean age at the onset of seizures was 14.3±9.0 years. All patients suffered from complex partial seizures, with additional simple partial seizures in 11 patients and additional secondary generalized seizures in nine patients. One patient also

Dynorphin immunohistochemistry

Dynorphin immunohistochemistry was performed on 13/14 specimens investigated electrophysiologically (see Table 1, no dynorphin staining could be obtained for patient A6). In all tested specimens dynorphin immunoreactivity was observed within granule cell bodies with some intercellular variation (Fig. 1). In addition, mossy fiber terminals appeared as clusters of immunoreaction product near cell bodies and proximal dendrites of hilar neurons in the CA4 region and of pyramidal cells in the CA3

Discussion

The mossy fiber bundle is composed of the axons of dentate granule cells which form glutamatergic synapses on dendrites of CA3 pyramidal neurons and interneurons in the CA3 and hilar region of the hippocampus. In addition to glutamate, mossy fibers contain and co-release dynorphin, enkephalins and zinc.5., 20., 21., 28. These substances may exert modulatory effects on NMDA receptors, GABA receptors and VDCCs.

In human epilepsy, sprouting and reorganization of the mossy fiber bundle is one of the

Conclusion

We conclude that dynorphin inhibits VDCCs in granule cells from patients with lesion-associated epilepsy without mossy fiber sprouting. Thus, in these patients, release of dynorphin from granule cell dendrites¹¹ may lead to inhibition of VDCCs. Such inhibition may markedly attenuate the propagation of excitatory postsynaptic potentials towards the soma. In contrast, dynorphin fails to inhibit VDCCs in granule cells of hippocampi with recurrent mossy fiber sprouting, even though it is present in

Acknowledgements

This research was supported by a University of Bonn Center grant BONFOR 111/2, the Sonderforschungsbereich SFB 400 of the Deutsche Forschungsgemeinschaft, DFG EL 122/7-1 and the joint German-Israeli research program. We thank Prof. Schramm, Dr Behrens and Dr van Roost for providing neurosurgical specimens and M. Reitze and D. Langendörfer for expert technical assistance.

References (37)

T.L. Babb et al.
Synaptic reorganization by mossy fibers in human epileptic fascia dentata
Neuroscience
(1991)
N.C. DeLanerolle et al.
Dynorphin and the kappa 1 ligand (³H)U69,593 binding in the human epileptogenic hippocampus
Epilepsy Res.
(1997)
J. Douglass et al.
Systemic administration of kainic acid differentially regulates the levels of prodynorphin and proenkephalin mRNA and peptides in the rat hippocampus
Molec. Brain Res.
(1991)
C. Gall et al.
Seizures, neuropeptide regulation, and mRNA expression in the hippocampus
Prog. Brain Res.
(1990)
B. Przewlocka et al.
The effect of various opiate receptor agonists on the seizure threshold in the rat. Is dynorphin an endogenous anticonvulsant?
Life Sci.
(1983)
F.J. Sigworth et al.
Design of the EPC-9, a computer-controlled patch-clamp amplifier. 2 Software
J. Neurosci. Meth.
(1995)
D.M. Terrian et al.
Glutamate and dynorphin release from a subcellular fraction enriched in hippocampal mossy fiber synaptosomes
Brain Res. Bull.
(1988)
F.C. Tortella
Endogenous opioid peptides and epilepsy: quieting the seizing brain
Trends pharmac. Sci.
(1988)
A.R. Wyler et al.
A grading system for mesial temporal pathology (hippocampal sclerosis) from anterior temporal lobectomy
J. Epilepsy
(1992)
J.-Z. Xiang et al.
The kappa-opiate agonist U50488H decreases the entry of ⁴⁵Ca into rat cortical synaptosomes by inhibiting N- but not L-type calcium channels
Neuropharmacology
(1990)

P.H. Barry et al.

Liquid junction potentials and small cell effects in patch-clamp analysis

J. Membr. Biol.

(1991)

B.P. Bean

Neurotransmitter inhibition of neuronal calcium currents by changes in channel voltage dependence

Nature

(1989)

H. Beck et al.

Properties of voltage-activated calcium currents in acutely dissociated human hippocampal granule cells

J. Neurophysiol.

(1998)

E.H. Buhl et al.

Zinc-induced collapse of augmented inhibition by GABA in temporal lobe epilepsy model

Science

(1996)

C. Chavkin et al.

Dynorphin is a specific endogenous ligand of the kappa opioid receptor

Science

(1982)

L. Chen et al.

The opioid peptide dynorphin directly blocks NMDA receptor channels in the rat

J. Physiol., Lond.

(1995)

L. Chen et al.

The mechanism of action for the block of NMDA receptor channels by the opioid peptide dynorphin

J. Neurosci.

(1995)

C.T. Drake et al.

Dynorphin opioids present in dentate granule cells may function as retrograde inhibitory neurotransmitters

J. Neurosci.

(1994)

Cited by (25)

Short-term withdrawal from repeated exposure to cocaine during adolescence modulates dynorphin mRNA levels and BDNF signaling in the rat nucleus accumbens
2019, Drug and Alcohol Dependence
Citation Excerpt :
These data suggest that the herein shown changes in pDYN mRNA levels may be due to the withdrawal condition and/or to the period of life of exposure (adolescence vs. adulthood). The reduction of pDYN gene expression here reported, after a short abstinence from developmental chronic cocaine exposure, might facilitate the increase of glutamate release since, at hippocampal level, the dynorphinergic system modulates transmission at all excitatory synapses (Wagner et al., 1993; Jeub et al., 1999; Terman et al., 2000; Drake et al., 2007). Actually, a recent report analyzed the consequences of chronic cocaine intoxication identifying seizures as one of major negative effects (Rolland et al., 2011).
Early-life stressful events affect the neurobiological maturation of cerebral circuitries including the endogenous opioid system and the effects elicited by adolescent cocaine exposure on this system have been poorly investigated. Here, we evaluated whether cocaine exposure during adolescence causes short- or long-term alterations in mRNAs codifying for selected elements belonging to the opioid system. Moreover, since brain-derived neurotrophic factor (BDNF) may undergo simultaneous alterations with the opioid peptide dynorphin, we also evaluated its signaling pathway as well.
Adolescent male rats were exposed to cocaine (20 mg/kg/day) from post-natal day (PND) 28 to PND42, approximately corresponding to human adolescence. After short- (PND45) or long-term (PND90) abstinence, prodynorphin-κ-opioid receptor (pDYN-KOP) and pronociceptin-nociceptin receptor (pN/OFQ-NOP) gene expression were evaluated in the nucleus accumbens (NAc) and hippocampus (Hip) together with the analysis of BDNF signaling pathways.
In the NAc of PND45 rats, pDYN mRNA levels were up-regulated, an effect paralled by increased BDNF signaling. Differently from NAc, pDYN mRNA levels were down-regulated in the Hip of PND45 rats without significant changes of BDNF pathway. At variance from PND45 rats, we did not find any significant alteration of the investigated parameters either in NAc and Hip of PND90 rats.
Our results indicate that the short-term withdrawal from adolescent cocaine exposure is characterized by a parallel pDYN mRNA and BDNF signaling increase in the NAc. Given the depressive-like state experienced during short abstinence in humans, we hypothesize that such changes may contribute to promote the risk of cocaine abuse escalation and relapse.
30 years of dynorphins - New insights on their functions in neuropsychiatric diseases
2009, Pharmacology and Therapeutics
Since the first description of their opioid properties three decades ago, dynorphins have increasingly been thought to play a regulatory role in numerous functional pathways of the brain. Dynorphins are members of the opioid peptide family and preferentially bind to kappa opioid receptors. In line with their localization in the hippocampus, amygdala, hypothalamus, striatum and spinal cord, their functions are related to learning and memory, emotional control, stress response and pain. Pathophysiological mechanisms that may involve dynorphins/kappa opioid receptors include epilepsy, addiction, depression and schizophrenia. Most of these functions were proposed in the 1980s and 1990s following histochemical, pharmacological and electrophysiological experiments using kappa receptor-specific or general opioid receptor agonists and antagonists in animal models. However, at that time, we had little information on the functional relevance of endogenous dynorphins. This was mainly due to the complexity of the opioid system. Besides actions of peptides from all three classical opioid precursors (proenkephalin, prodynorphin, proopiomelanocortin) on the three classical opioid receptors (delta, mu and kappa), dynorphins were also shown to exert non-opioid effects mainly through direct effects on NMDA receptors. Moreover, discrepancies between the distribution of opioid receptor binding sites and dynorphin immunoreactivity contributed to the difficulties in interpretation. In recent years, the generation of prodynorphin- and opioid receptor-deficient mice has provided the tools to investigate open questions on network effects of endogenous dynorphins.
This article examines the physiological, pathophysiological and pharmacological implications of dynorphins in the light of new insights in part obtained from genetically modified animals.
Mossy fiber synaptic transmission: communication from the dentate gyrus to area CA3
2007, Progress in Brain Research
Citation Excerpt :
Dynorphin significantly inhibits MF responses in the hamster, mouse, and in Long-Evans rats (Salin et al., 1995). Interestingly, hippocampal opioid peptides are upregulated after seizure activity (McGinty et al., 1983; Gall, 1988; Gall et al., 1990), whereas a decrease in κ receptors has been observed in epileptic human cells (Jeub et al., 1999). Thus, opioid peptides are localized in the MF, presumably for effective control of neurotransmitter release (Weisskopf et al., 1993; Castillo et al., 1996; Drake et al., 1996; Simmons and Chavkin, 1996).
Communication between the dentate gyrus (DG) and area CA3 of the hippocampus proper is transmitted via axons of granule cells — the mossy fiber (MF) pathway. In this review we discuss and compare the properties of transmitter release from the MFs onto pyramidal neurons and interneurons. An examination of the anatomical connectivity from DG to CA3 reveals a surprising interplay between excitation and inhibition for this circuit. In this respect it is particularly relevant that the major targets of the MFs are interneurons and that the consequence of MF input into CA3 may be inhibitory or excitatory, conditionally dependent on the frequency of input and modulatory regulation. This is further complicated by the properties of transmitter release from the MFs where a large number of co-localized transmitters, including GABAergic inhibitory transmitter release, and the effects of presynaptic modulation finely tune transmitter release. A picture emerges that extends beyond the hypothesis that the MFs are simply “detonators” of CA3 pyramidal neurons; the properties of synaptic information flow from the DG have more subtle and complex influences on the CA3 network.
New facets of the neuropathology and molecular profile of human temporal lobe epilepsy
2005, Epilepsy and Behavior
This review summarizes the salient features of the anatomical and molecular neuropathology of the hippocampus from patients with intractable temporal lobe epilepsy (TLE). It argues that sclerotic hippocampus is essential for seizure expression and that sclerosis is not a consequence of seizures, but is related to the epileptogenicity of the seizure focus. While neurons in sclerotic hippocampus may contribute to hippocampal hyperexcitability, this role is perhaps less important than that of the astrocytes. The astrocytes in sclerotic hippocampus may directly influence excitability through altered water homeostasis and K⁺ buffering by redistribution of AQP4 transporters on their plasma membrane. It is proposed that they contribute to a high extracellular glutamate level through reduced glutamine synthetase, and activation through pro-inflammatory factors that release chemokines and cytokines, which enhance calcium-dependent glutamate release. Such a focal pool of glutamate may diffuse to surrounding neuron-rich areas to generate seizure activity in TLE.
Altered expression of voltage-dependent calcium channel α<inf>1</inf> subunits in temporal lobe epilepsy with Ammon's horn sclerosis
2002, Neuroscience
Voltage-dependent calcium channels, the initial components in the calcium signalling cascade, are increasingly being recognised as relevant factors in the pathology of epilepsy. To further characterise their role in temporal lobe epilepsy associated with Ammon’s horn sclerosis, we investigated the immunohistochemical distribution of five different voltage-dependent calcium channel α₁ subunits (α_1A, α_1B, α_1C, α_1D, α_1E) in 14 hippocampal specimens of patients with Ammon’s horn sclerosis in comparison with eight autopsy control cases. In epilepsy specimens an increased immunoreactivity was observed for α_1A, α_1B, α_1D and α_1E in the neuropil of the dentate gyrus molecular layer. Dentate gyrus granule cells and residual CA3 pyramidal neurones showed enhanced immunoreactivity for α_1A, while labelling of these neurones was decreased for α_1C. Astrocytes in Ammon’s horn sclerosis specimens were strongly immunoreactive for the α_1C subunit contrasting with an absent astrocytic α_1C labelling in controls.
Our results suggest that the expression of calcium channels in neurones and glial cells is dynamically regulated in temporal lobe epilepsy, supporting the relevance of calcium signalling pathways for this disease.
Endogenous opiates: 1999
2000, Peptides
This paper is the twenty-second installment of the annual review of research concerning the opiate system. It summarizes papers published during 1999 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurologic disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunologic responses.

View all citing articles on Scopus

View full text

Loss of dynorphin-mediated inhibition of voltage-dependent Ca2+ currents in hippocampal granule cells isolated from epilepsy patients is associated with mossy fiber sprouting

Abstract

Section snippets

Patient data

Dynorphin immunohistochemistry

Discussion

Conclusion

Acknowledgements

Neuroscience

Epilepsy Res.

Molec. Brain Res.

Prog. Brain Res.

Life Sci.

J. Neurosci. Meth.

Brain Res. Bull.

Trends pharmac. Sci.

J. Epilepsy

Neuropharmacology

Liquid junction potentials and small cell effects in patch-clamp analysis

J. Membr. Biol.

Neurotransmitter inhibition of neuronal calcium currents by changes in channel voltage dependence

Nature

Properties of voltage-activated calcium currents in acutely dissociated human hippocampal granule cells

J. Neurophysiol.

Zinc-induced collapse of augmented inhibition by GABA in temporal lobe epilepsy model

Science

Dynorphin is a specific endogenous ligand of the kappa opioid receptor

Science

The opioid peptide dynorphin directly blocks NMDA receptor channels in the rat

J. Physiol., Lond.

The mechanism of action for the block of NMDA receptor channels by the opioid peptide dynorphin

J. Neurosci.

Dynorphin opioids present in dentate granule cells may function as retrograde inhibitory neurotransmitters

J. Neurosci.

Loss of dynorphin-mediated inhibition of voltage-dependent Ca²⁺ currents in hippocampal granule cells isolated from epilepsy patients is associated with mossy fiber sprouting