A study on opioid peptides in CSF of patients with epilepsy

Methadone's effects on pentylenetetrazole-induced seizure threshold in mice: NMDA/opioid receptors and nitric oxide signaling

Methadone is a synthetic opioid used to treat opiate withdrawal and addiction. Studies have demonstrated the impact of methadone on seizure susceptibility. This study investigated the modulatory impacts of acute and subchronic (three times daily for 5 days) intraperitoneal methadone treatment on pentylenetetrazole-induced clonic seizure threshold (CST) in mice, as well as the involvement of the nitric oxide, N-methyl-d-aspartate (NMDA), and µ-opioid pathways. Acute administration of different doses of methadone (0.1, 0.3, 1, and 3 mg/kg) 45 min before CST significantly decreased the seizure threshold. Additionally, pretreatment with noneffective doses of an opioid receptor antagonist (naltrexone) and NMDA receptor antagonists (ketamine and MK-801) inhibited methadone's proconvulsive activity in the acute phase, while l-NAME (a nonspecific nitric oxide synthase (NOS) inhibitor) did not affect that activity. In the subchronic phase, methadone (3 mg/kg) demonstrated an anticonvulsive effect. Although subchronic pretreatment with noneffective doses of l-NAME and 7-nitroindazole (a specific neuronal NOS inhibitor) reversed methadone's anticonvulsive activity, aminoguanidine (a specific inducible NOS inhibitor), naltrexone, MK-801, and ketamine did not change methadone's anticonvulsive characteristic. Our results suggest that NMDA and µ-opioid receptors may be involved in methadone's proconvulsive activity in the acute phase, while methadone's anticonvulsive activity may be modulated by neuronal NOS in the subchronic phase.

The mu-opioid receptor-selective peptide antagonists, antanal-1 and antanal-2, produce anticonvulsant effects in mice

The activation of the mu-opioid receptors (MOR) in the central nervous system has a proconvulsant effect and seizures are a common side effect of high doses of short acting opioids, like morphine or fentanyl. However, the correct assessment of the role of MOR blockade in the initiation and propagation of epilepsy was hampered by the lack of potent and selective MOR antagonists. In this study we aimed at characterizing the effect of MOR blockade on the seizure threshold in mice using recently developed selective antagonists antanal-1 and antanal-2 and a classical MOR antagonist, β-funaltrexamine (β-FNA). The effect of the centrally administered MOR antagonists was characterized in the maximal electroshock seizure threshold (MEST), the 6 Hz psychomotor seizure threshold and the intravenous pentylenetetrazole (PTZ) seizure threshold test in mice. The acute effect of the studied compounds on skeletal muscular strength in mice was quantified in the grip-strength test. Antanal-1 and antanal-2 (30 and 50 nmol/mouse, i.c.v.), but not β-FNA significantly increased the seizure threshold in the MEST test in mice. In the 6-Hz test, all tested MOR antagonists significantly increased the psychomotor seizure threshold and the most potent anticonvulsant effect was observed for antanal-2 (2, 10 and 30 nmol/mouse, i.c.v.). The i.c.v. administration of β-FNA (10 and 30 nmol/mouse, i.c.v.), antanal-1 and antanal-2 (both 30, 50 and 100 nmol/mouse, i.c.v.) did not produce any significant effect on PTZ seizure threshold, the generalized clonus or the forelimbs tonus. All tested compounds did not affect muscle strength, as determined in the grip strength test. Our study demonstrated that the novel MOR-selective antagonists antanal-1 and antanal-2 displayed a potent and dose-dependent anticonvulsant action involving non-GABA-ergic, but some other pathways and mechanisms in animal models of epileptic seizures. We suggest that antanals are promising drug templates for future therapeutics, which may be used in the treatment of epilepsy in humans.

Anesthetic management of the patient with epilepsy or prior seizures

PURPOSE OF REVIEW

Epilepsy is a clinical disorder of paroxysmal recurring seizures, the diagnosis excluding alcohol or drug withdrawal seizures or such recurring exogenous events as repeated insulin-induced hypoglycemia. Epilepsy has a profound impact on each individual diagnosed with this disease.

RECENT FINDINGS

New antiepileptic drugs (AEDs) have been a major change in the approach to management of patients with epilepsy. These drugs tend to have fewer significant drug interactions and less severe side effects. Nonetheless, first-generation AEDs are still widely used. Propofol and desflurane have reliable anticonvulsant effects, whereas remifentanil in larger doses and sevoflurane appear to support epileptiform activity, although the clinical significance of these observations is unclear.

SUMMARY

The primary concerns for providing anesthesia to the patient with epilepsy are the capacity of anesthetics to modulate or potentiate seizure activity and the interaction of anesthetic drugs with AEDs. Proconvulsant and anticonvulsant properties have been reported for virtually every anesthetic such that these properties become elements of the anesthetic plan in the patient with epilepsy. Moreover, AEDs have many physiologic and pharmacologic effects that can have an impact on an anesthetic.

Temporal lobe epilepsy causes selective changes in mu opioid and nociceptin receptor binding and functional coupling to G-proteins in human temporal neocortex

There is no information concerning signal transduction mechanisms downstream of the opioid/nociceptin receptors in the human epileptic brain. The aim of this work was to evaluate the level of G-proteins activation mediated by DAMGO (a mu receptor selective peptide) and nociceptin, and the binding to mu and nociceptin (NOP) receptors and adenylyl cyclase (AC) in neocortex of patients with pharmacoresistant temporal lobe epilepsy. Patients with temporal lobe epilepsy associated with mesial sclerosis (MTLE) or secondary to tumor or vascular lesion showed enhanced [3H]DAMGO and [3H]forskolin binding, lower DAMGO-stimulated [35S]GTPgammaS binding and no significant changes in nociceptin-stimulated G-protein. [3H]Nociceptin binding was lower in patients with MTLE. Age of seizure onset correlated positively with [3H]DAMGO binding and DAMGO-stimulated [35S]GTPgammaS binding, whereas epilepsy duration correlated negatively with [3H]DAMGO and [3H]nociceptin binding, and positively with [3H]forskolin binding. In conclusion, our present data obtained from neocortex of epileptic patients provide strong evidence that a) temporal lobe epilepsy is associated with alterations in mu opioid and NOP receptor binding and signal transduction mechanisms downstream of these receptors, and b) clinical aspects may play an important role on these receptor changes.

Kainic acid modifies mu-receptor binding in young, adult, and elderly rat brain

Mu-receptor binding changes were evaluated following the kainic acid (KA)-induced status epilepticus (SE) in young, adult, and elderly animals. Male Wistar rats were used as follows: young rats (15 days old) were treated with KA (7 mg/kg) and sacrificed 72 h (YKA3d) or 35 days (YKA35d) after SE; adult (90 days old) (AKA1d and AKA40d) and elderly rats (1-year-old) (EKA1d and EKA40d) were injected with KA (10 mg/kg) and then sacrificed 24 h or 40 days following SE. Their brains were processed for an autoradiography assay for mu-receptors. The YKA3d group showed increased values in dentate gyrus (39%) and a decrease in substantia nigra (26%); YKA35d animals had a reduction in caudate putamen (29%) and in substantia nigra (20%). The AKA1d group exhibited increased mu-receptors in caudate putamen (49%), cingulate (415%), frontal (52%), and temporal (53%) cortices: substantia nigra (56%), dentate gyrus (48%). and CA2 field of hippocampus (53%). The AKA40d group showed increased values in sensorimotor cortex (45%), anterior (39%), medial (65%), basolateral (202%), and central (32%) amygdaloid nuclei; dentate gyrus (80%) as well as CA2 (80%) and CA3 (49%) fields of hippocampus. The EKA1d group presented decreased mu-receptor binding in piriform (16%) and enthorinal (22%) cortices as well as in anterior amygdala nucleus (17%). The EKA40d group showed reduced values in sensorimotor cortex (14%) and substantia nigra (27%). The present results indicate that the mu-binding changes following SE depend on the rate of brain maturation.

Evaluation of opioid peptide and muscarinic receptors in human epileptogenic neocortex: an autoradiography study

PURPOSE

The main goal of the present study was to evaluate possible alterations in opioid peptide and muscarinic receptors in human neocortical epileptic focus and the surrounding area removed from patients with pharmacologically resistant epilepsy and epilepsy secondary to cerebral lesion by tumor or other causes.

METHODS

In vitro quantitative autoradiography experiments were carried out to label mu, delta, and muscarinic receptors of neocortical epileptic focus and surrounding area obtained from patients with pharmacologically resistant primary epilepsy and epilepsy caused by tumors and angioma cavernosa, and compared with neocortex obtained from patients with dementia and tumors without epilepsy.

RESULTS

The mu receptor levels were lower in surrounding areas (-46%). The delta receptor binding was reduced in epileptic focus obtained from patients with epilepsy secondary to cerebral lesion (-25%) and surrounding areas (-31%). In contrast, muscarinic receptor levels were higher in the focus from patients with primary epilepsy (layers I-II, 52%; layers III-IV, 44%; layers V-VI, 36%).

CONCLUSIONS

It is suggested that the increased muscarinic receptors in the epileptic focus and the decreased mu and delta receptors in the surrounding area are associated with the initiation and propagation of seizure activity in human epileptogenic neocortex.

Isolation and structural and genetic analysis of the mouse enkephalin gene and its d(AC/TG)n repeats

Enkephalins, the endogenous opioids, mediate a wide variety of intercellular communications through ontogeny and their involvement has been suggested in drug addiction and alcohol abuse as well as in various neuropsychiatric disorders. In order to generate a genetic model, we have isolated the mouse enkephalin (mENK) gene, analyzed its regulatory region and compared its structure to the well characterized rat ENK (rENK) gene. We analyzed 2600 bp and found 3 highly homologous regions: The highest level (98%) of positional and sequence homology between mice and rats was in the TATA/proximal regulatory region. This region contains all the inducible regulatory elements (enkCRE1, NF1, AP-2, NFkappaB, etc.) and also an octamer-like element at -543 bp. This high homology is interrupted in both mice and rats by the typically polymorphic d(AC/TG)n and d(TC/GA)n dinucleotide repeats positioned between nucleotides -670 and -950. The position and orientation of these repetitive elements differ substantially in the two species. Genomic PCR analysis of the d(AC/TG)n repeat in various mouse strains, including aberrant behavioral or neurological phenotypes, showed lack of polymorphism at this repeat. The positional and sequence homologies between the rat and the mouse ENK genes decrease in more upstream regions due to the presence of nonhomologues repetititve DNA sequences.

Opioid peptide pharmacology and immunocytochemistry in an animal model of self-sustaining status epilepticus

In a model of self-sustaining status epilepticus induced in rats by 30 min intermittent stimulation of the perforant path through chronically implanted electrodes, a decrease in dynorphin-like immunoreactivity in the dentate gyrus and CA3 was observed 3 h and 24 h after the induction of status epilepticus. Enkephalin-like immunoreactivity decreased 3 h but not 24 h after perforant path stimulation. Injection into the hilus of the dentate gyrus 10 min prior to stimulation of the kappa-receptor agonist dynorphin-A(1-13), the delta-receptor antagonists ICI-174864 and naltrindole, as well as i.p. injection of naloxone prevented the development of status epilepticus. Perihilar administration of the delta-agonist [D-Ser2]Leu-enkephalin-Thr6 or the kappa-antagonist nor-Binaltorphimine, but not of the mu-agonist [D-Ala2,N-Me-Phe4,Gly-ol5]-Enkephalin, facilitated the establishment of self-sustaining status epilepticus. Injection into the hilus of dynorphin-A(1-13) after the end of perforant path stimulation, stopped established status epilepticus, while administration of naloxone, naltrindole and ICI-174864 were ineffective. We conclude that kappa-opioids in the hippocampus counteract initiation and maintenance of status epilepticus, while delta-opioids promote initiation, but not maintenance of seizure activity. These data are important for the understanding the mechanisms which underlie initiation and maintenance of status epilepticus and for the development of new approaches for its effective management.

Focal cortical release of endogenous opioids during reading-induced seizures

BACKGROUND

Studies in animals implicate endogenous release of opioid peptides as a mechanism for terminating partial and generalised seizures. To localise dynamic changes in opioid neurotransmission associated with partial seizures and higher cognitive function, we investigated the release of endogenous opioids in patients with reading-induced seizures compared with healthy controls.

METHODS

Five patients who had reading epilepsy and six controls had 11C-diprenorphine (DPN) positron-emission-tomography (PET) scans while reading a string of symbols (baseline) or a scientific paper (activation). Statistical parametric mapping was used to find areas with differences in opioid-receptor binding.

FINDINGS

On activation scans mean 11C-DPN binding to opioid receptors was significantly lower (p<0.05 corrected for multiple non-independent comparisons) in the left parieto-temporo-occipital cortex (Brodmann area 37) in reading-epilepsy patients compared with controls.

INTERPRETATION

These findings suggest that opioid-like substances are involved in the termination of reading-induced seizures.

Long-term pharmacological kindling increases in vitro release of IR-Met and IR-Leu-enkephalin from amygdala

Met-enkephalin release is increased from amygdala and striatum 1 and 15 days after pharmacological kindling with pentylenetetrazol, following potassium-induced depolarization in vitro via a Ca2+ dependent mechanism. Leu-enkephalin release was only enhanced in amygdala and striatum 1 day after the last seizure. IR-Met-enkephalin amygdala tissue content enhanced 1 and 15 days after seizure. In striatum, we found an IR-Met-enkephalin decrease 35 days after the last stimulus. IR-Leu-enkephalin amygdala tissue content enhanced 1 day after the last seizure, and no significant increases were found in striatum 1, 15 and 35 days after the last seizure. In this paper, we show that opioid peptides release is differentially enhanced in rat brain for several days after the last seizure, thus suggesting that opioid peptides may have a protective action against seizure activity.

Diurnal variations of opioid peptides and synenkephalin in vitro release in the amygdala of kindled rats

Pentylenetetrazol (PTZ) kindling was induced in male Wistar rats (250-300 g) by daily intraperitoneal injections of 35 mg/kg of the convulsant agent. Immunoreactive (IR)-Met-enkephalin (IR-ME), IR-Leu-enkephalin (IR-LE), IR-heptapeptide (IR-HE), IR-octapeptide (IR-OC) and IR-synenkephalin (IR-Syn) in vitro release was measured from amygdala slices 24 h after the last stimulus, in groups of eight rats, every 4 h beginning at 08:00 h. Opioid peptides in vitro release displayed diurnal variations. IR-ME and IR-Syn showed maximal levels before the onset of darkness (16:00 h). IR-LE and IR-OC release was enhanced 4 h later (20:00 h), no changes were detected for IR-HE. These results show that endogenous opioid system (EOS) release displays diurnal variations. The peak for the analysed peptides was reached before and during the dark phase. It is suggested that EOS release enhancement in PTZ-kindled rats, seems to be due to a compensatory mechanism against the excitation induced by the blockade of the GABAergic transmission.

Anxiogenic-like consequences in animal models of complex partial seizures

Several kinds of psychiatric symptoms (anxiety, depression, schizophrenia) have been associated with epilepsies, and clinical data suggest that patients with seizures involving limbic structures are the most prone to develop behavioural disorders between the seizures (i.e. interictally). Studying the neurobiological mechanisms that underlie these symptoms is difficult in humans because of different interfering factors (e.g. psychosocial difficulties, pharmacological side-effects, lesions), which can be avoided in animal models. Using repetitive electrical stimulations (kindling) or local applications of a neuroexcitotoxin in limbic structures (mainly the amygdala and hippocampus), several authors have reported lasting changes of emotional reactivity in cats and rats. These changes appear as anxiety-related reactions expressed as a hyperdefensiveness in the cat, or a reduction of spontaneous exploration in tests predictive of anxiogenic effects in the rat. Some neuroplasticity processes known to develop during epileptogenesis (neuronal-hyperexcitability, modulation of GABA/benzodiazepine transmission) may participate in these lasting changes of behaviour, especially in structures involved in the control of fear-promoted reactions (amygdala, periaqueductal grey matter). In addition, endogenous control systems may also play a critical role in the occurrence of interictal behavioural disorders.

Imaging of delta- and mu-opioid receptors in temporal lobe epilepsy by positron emission tomography

The involvement of opioid neurotransmitter systems in seizure mechanisms is well documented. In previous positron emission tomography (PET) studies in patients with unilateral temporal lobe epilepsy, we have found evidence for differential regulation of the opioid-receptor subtypes. The present study extends our previous observations to delta-opioid receptors by using the delta-receptor-selective antagonist [11C]methylnaltrindole ([11C]MeNTI). Paired measurements of delta- and mu-opioid receptor binding and metabolic activity were performed with PET using [11C]MeNTI and [11C]carfentanil ([11C]CFN) and [18F]fluorodeoxyglucose ([18F]FDG), respectively. Binding of [11C]MeNTI and [11C]CFN increased and [18F]FDG uptake decreased in the temporal cortex (TC) ipsilateral to the focus. Decreases in [18F]FDG uptake were more widespread regionally than were increases in opioid receptors. Increases in the delta- and mu-receptor binding showed different regional patterns. Increases in mu-receptor binding were confined to the middle aspect of the inferior TC, whereas binding of delta receptors increased in the mid-inferior TC and anterior aspect of the middle and superior TC. The increase in delta receptors suggests their anticonvulsant action, as previously shown for the delta-receptor subtype, whereas the different regional pattern of receptor alterations suggest the distinct roles of different opioid-receptor subtypes in seizure phenomena.

Dynorphin and epilepsy

Studies on dynorphin involvement in epilepsy are summarised in this review. Electrophysiological, biochemical and pharmacological data support the hypothesis that dynorphin is implicated in specific types of seizures. There is clear evidence that this is true for complex partial (limbic) seizures, i.e. those characteristic of temporal lobe epilepsy, because; (1) dynorphin is highly expressed in various parts of the limbic system, and particularly in the granule cells of the hippocampus; (2) dynorphin appears to be released in the hippocampus (and in other brain areas) during complex partial seizures; (3) released dynorphin inhibits excitatory neurotransmission at multiple synapses in the hippocampus via activation of kappa opioid receptors; (4) kappa opioid receptor agonists are highly effective against limbic seizures. Data on generalised tonic-clonic seizures are less straightforward. Dynorphin release appears to occur after ECS seizures and kappa agonists exert a clear anticonvulsant effect in this model. However, more uncertain biochemical data and lack of efficacy of kappa agonists in other generalised tonic-clonic seizure models argue that the involvement of dynorphin in this seizure type may not be paramount. Finally, an involvement of dynorphin in generalised absence seizures appears unlikely on the basis of available data. This may not be surprising, given the presumed origin of absence seizures in alterations of the thalamo-cortical circuit and the low representation of dynorphin in the thalamus. In conclusion, it may be suggested that dynorphin plays a role as an endogenous anticonvulsant in complex partial seizures and in some cases of tonic-clonic seizures, but most likely not in generalised absence. This pattern of effects may coincide with the antiseizure spectrum of selective kappa agonists.

Opioid peptides content in the rat brain during the ictal phase and after pentylenetetrazol-kindled rats

We determine the opioid peptide content in the rat brain during the ictal phase and postictal depression after pentylenetetrazol kindling rats. Radioimmunoassays with highly specific antisera risen for Met-enkephalin, Leu-enkephalin and octapeptide, were carried out during the ictal phase, and 15, 30 and 60 min after seizures. We always found an initial IR-Met-enkephalin decrease during the postictal depression content, followed by a reduction in IR-Leu-enkephalin and IR-octapeptide tissular concentration. We suggest a functional and differential release of the opioid peptides, during the postictal depression time-course.

Penicillin-G induced interictal activity increases both opioid peptide tissue content and in vitro release in the rat brain

Penicillin-G has been used as a common agent to produce epileptic foci and interictal activity. The development of the interictal spikes has been associated with enhanced inhibitory effects. There is evidence that the opioid peptides play an important role in the production of some transient postictal behaviors. In order to test whether enkephalins are involved during the interictal activity, we analyzed immunoreactive met- and leu-enkephalin content and their release in vitro, after the injection of 50 IU of penicillin-G into the left amygdala. Male Wistar rats were injected once daily for 5 days, and sacrificed by decapitation (15 min after the penicillin-G infusion) on the fifth day. The rats were divided into two groups: 1. In one group we analyzed the tissue content of enkephalins in hypothalamus, hippocampus, amygdala, striatum and cerebral cortext. 2. The second group was used for the assessment of the in vitro release of enkephalins from amygdala slices. In the amygdala, the drug treatment produced an increase in the tissue content of IR-ME. No changes occurred in the other structures. The content of IR-Leu-enkephalin increased in all structures analyzed except the cerebral cortex. In vitro release of both enkephalins increased in drug treated animals. These results suggest that the enkephalins could be involved in postictal mechanisms, as a result of repetitive interictal spiking.

Benzodiazepine receptor binding following chronic treatment with naloxone, morphine and met-enkephalin in normal rats

The effects of chronic administration of naloxone, morphine and met-enkephalin on benzodiazepine (BDZ) receptor binding in rat brain were determined 2 and 50 days after treatments were accomplished. Two days after naloxone treatment (75 micrograms/h s.c. for 14 days), enhanced BDZ receptor binding was observed in cingulate, frontal, piriform, entorhinal and sensorimotor cortices; amygdala complex, hippocampus, substantia nigra and central gray. Two days after morphine treatment (20 mg/kg i.p. daily for 6 days), increased BDZ receptor binding was detected in cingulate, frontal, piriform, entorhinal and sensorimotor cortices; amygdala complex, hippocampus and substantia nigra. Two days after met-enkephalin treatment (10 micrograms/h i.c.v. for 6 days) enhanced BDZ receptor binding was shown only in sensorimotor cortex. No significant changes were observed 50 days after the treatments were completed. These data indicate an important interaction between GABAergic and opioid peptide systems.

Characterization of mu opioid receptor binding during amygdala kindling in rats and effects of chronic naloxone pretreatment: an autoradiographic study

Using in vitro autoradiography, mu receptor binding in rat brain was characterized at different amygdala kindling stages and in amygdaloid kindled animals pretreated chronically with naloxone. Male Sprague-Dawley rats implanted with bipolar electrodes in the right amygdala received one of the following pretreatments s.c. for 14 days via osmotic minipumps: normal saline solution, 0.5 microliters/h, or naloxone HCl, 75 micrograms/h. Two days after treatments were accomplished animals were stimulated daily. Our data showed different patterns of mu receptor binding during the normal kindling process: during stage II-III, pronounced binding increase was detected in cingulate, temporal and entorhinal cortices, anterior amygdala, caudate putamen, thalamic nuclei, ventrolateral and dorsolateral portions of central gray, substantia nigra pars compacta and pars reticulata. Twenty-four hours after the last stage V kindled seizure, enhanced binding was observed in cingulate and frontoparietal cortices, anterior amygdala, caudate putamen and ventromedial thalamic nucleus. Twenty-eight days after the last stage V kindled seizure, binding augmentation was noticed in cingulate and frontoparietal cortices, whereas decreased binding was detected in amygdala complex, substantia nigra pars reticulata, piriform, perirhinal, parietal, temporal and entorhinal cortices. Mu receptor binding in kindled rats chronically pretreated with naloxone was significantly higher in several structures when compared with control and normal kindled groups. Our data indicate different regional selective patterns of mu receptor binding during amygdala kindling which may depend on epileptogenesis and long-term changes induced by this process. In addition, even higher mu receptor binding results from chronic naloxone administration prior to kindling.

Effects of chronic naloxone pretreatment on amygdaloid kindling in rats

Effects of chronic naloxone pretreatment (75 or 270 micrograms/h for 14 days) on the development of amygdaloid kindling in rats were evaluated. The acquisition of seizure activity was modified in the naloxone pretreated animals, depending on the nucleus stimulated: facilitation of stages IV and V occurred in 37%, variability of electrographic and behavioral responses to electrical stimulation during the kindling development in 33%, and facilitation of stages IV and V followed by long periods of seizure suppression in 29%. Enhancement of postictal seizure suppression during a recycling paradigm was observed in all the naloxone pretreated rats. It was concluded that the chronic administration of naloxone (known to induce opioid binding upregulation and supersensitivity), in association with the enduring changes in opioid mechanisms provoked by kindled seizures, were responsible for the facilitation and suppression of epileptic activity. These findings support bidirectional modulatory effects of opioid peptides on epileptic seizures as well as the view that epileptic seizures can induce enduring alterations in opioid mechanisms.

Quantification of mu and non-mu opiate receptors in temporal lobe epilepsy using positron emission tomography

Alterations in a variety of neurotransmitter systems have been identified in experimental models of epilepsy and in brain tissue from patients with intractable temporal lobe seizures. The availability of new high-affinity radioligands permits the study of some neuroreceptors in vivo with positron emission tomography (PET). We previously characterized the in vivo binding of 11C-carfentanil, a potent and selective mu opiate receptor agonist, and described increases in 11C-carfentanil binding in the temporal neocortex of patients with unilateral temporal lobe epilepsy. These studies have been extended to 11C-diprenorphine, which labels mu, kappa, and delta opiate receptor subtypes. Paired measurements of opiate receptor binding were performed with PET using 11C-carfentanil and 11C-diprenorphine in patients with unilateral temporal lobe seizures. Carfentanil binding, reflecting changes in mu opiate receptors, was increased in the temporal neocortex and decreased in the amygdala on the side of the epileptic focus. Diprenorphine binding, reflecting mu as well as non-mu opiate subtypes, was not significantly different among regions in the focus and nonfocus temporal lobes. Regional glucose metabolism, measured using 18F-2-fluoro-2-deoxyglucose, was decreased in the mesial and lateral aspects of the temporal lobe ipsilateral to the epileptogenic focus. The variation in pattern of carfentanil and diprenorphine binding supports a differential regulation of opiate subtypes in unilateral temporal lobe epilepsy.