Increased levels of substance P and cholecystokinin in rat cerebral cortex following repeated electroconvulsive shock and subchronic treatment with a serotonin uptake inhibitor

Molecular Targets of Cannabinoids Associated with Depression

Novel therapeutic strategies are needed to address depression, a major neurological disorder affecting hundreds of millions of people worldwide. Cannabinoids and their synthetic derivatives have demonstrated numerous neurological activities and may potentially be developed into new treatments for depression. This review highlights cannabinoid (CB) receptors, monoamine oxidase (MAO), N-methyl-D-aspartate (NMDA) receptor, gamma-aminobutyric acid (GABA) receptor, and cholecystokinin (CCK) receptor as key molecular targets of cannabinoids that are associated with depression. The anti-depressant activity of cannabinoids and their binding modes with cannabinoid receptors are discussed, providing insights into rational design and discovery of new cannabinoids or cannabimimetic agents with improved druggable properties.

The role of cholecystokinin in the induction of aggressive behavior: a focus on the available experimental data (review)

Cholecystokinin (CCK) is a neuropeptide that is (among others) reportedly involved in the pathophysiology of psychiatric disorders. The excitatory role of CCK in negative affective emotions as well as in aversive reactions, antisocial behaviors and memories, has been indicated by numerous electrophysiological, neurochemical and behavioral methodologies on both animal models for anxiety and human studies. The current review article summarizes the existing experimental evidence with regards to the role of CCK in the induction of aggressive behavior, and: (a) synopsizes the anatomical circuits through which it could potentially mediate all types of aggressive behavior, as well as (b) highlights the potential use of these experimental evidence in the current research quest for the clinical treatment of mood and anxiety disorders.

Concurrent modulation of extracellular levels of noradrenaline and cAMP during stress and by anxiogenic- or anxiolytic-like neuropeptides in the prefrontal cortex of awake rats

The purpose of this study was to examine the effects of stress and the role of locally infused anxiogenic-like neuropeptides galanin, CCK-8, vasopressin, substance P and neurokinin A, and anxiolytic-like peptides NPY, nociceptin/orphanin FQ, somatostatin and neurotensin, on modulation of noradrenaline (NA) and cAMP efflux monitored simultaneously by microdialysis in the medial prefronatal cortex of awake rats. Concentrations of cAMP were determined by a newly developed method based on derivatization of cAMP with 2-chloroacetaldehyde followed by HPLC with fluorescence detection. Local infusion of forskolin (10 and 30 μM) dose-dependently increased the cAMP levels to 417% and 1050% of the control group, respectively. Similarly, local infusion of NA (10 μM) increased the cAMP to the peak level of 168%. A 5-min tail pinch and a 10-min swim stress rapidly increased the NA and cAMP levels to 167% and 203% (NA) and 141% and 161% (cAMP), respectively. Infusion of galanin and CCK-8 (0.5 nmol, and 1.5 nmol/0.5 μl) dose-dependently increased NA to the peak levels of 191% and 179% and cAMP levels to 174% and 166%, respectively. The peak levels following infusions of vasopressin, substance P and neurokinin A were 91%, 135% and 86% for NA and 131%, 83% and 76% for cAMP, respectively. Infusions of anxiolytic-like peptides at highest concentrations significantly increased (NPY, 136%) or decreased (nociceptin, 71%; somatostatin, 86%) the NA levels, whereas neurotensin had no effect. The cAMP levels decreased to 86% (NPY, neurotensin), 78% (nociceptin), somatostatin infusion was without effect. The present findings confirmed a close correlation between the stress-induced increases in prefrontal cortical NA and cAMP levels, as well as, concurrent changes in NA and cAMP levels following infusions of galanin and CCK-8 (increased levels) and nociceptin/orphanin FQ (decreased levels). Infusions of other neuropeptides showed a more complex pattern of NA and cAMP responses.

Neurokinin-1 receptor: functional significance in the immune system in reference to selected infections and inflammation

The G protein-coupled receptor (GPCR), neurokinin-1 receptor (NK1R), and its preferred ligand, substance P (SP), are reviewed in relationship to the immune system and selected infections. NK1R and SP are ubiquitous throughout the animal kingdom. This important pathway has unique functions in numerous cells and tissues. The interaction of SP with its preferred receptor, NK1R, leads to the activation of nuclear factor-kappa B (NF-κB) and proinflammatory cytokines. NK1R has two isoforms, both a full-length and a truncated form. These isoforms have different functional significances and differ in cell signaling capability. The proinflammatory signals modulated by SP are important in bacterial, viral, fungal, and parasitic diseases, as well as in immune system function. The SP-NK1R system is a major class 1, rhodopsin-like GPCR ligand-receptor interaction.

Repeated social defeat-induced depression-like behavioral and biological alterations in rats: involvement of cholecystokinin

Cholecystokinin (CCK) involvement in depression-like disorders is poorly documented. Here, we investigated whether CCKergic neurotransmission is relevant to depressive-like symptoms and antidepressant therapy using a novel preclinical model based on repeated social defeat over 4 weeks in rats. Repeated social defeat triggers changes that could be considered as behavioral and biological correlates of depressive symptoms in humans, such as a hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis (increase of serum corticosterone levels and of adrenal gland weight), increased immobility time in the forced swimming test (FST), decrease of body weight and of sweet water consumption and reduction of hippocampal volume associated with a decreased cell proliferation in the dentate gyrus. In addition, in vivo microdialysis showed that cortical CCK release was tonically increased in defeated rats. Chronic imipramine treatment (16 mg kg(-1) per day for 25 days) prevented both the repeated social defeat-induced alterations of biological and behavioral parameters and the associated increase of cortical CCK release. Chronic blockade of CCK2 receptors by the specific antagonist CI-988 (1 mg kg(-1) per day for 25 days) also normalized immobility time in the FST and prevented HPA axis hyperactivity, reduction of hippocampal volume and cell proliferation and decreased sweet water intake normally evoked by repeated social defeat. These data showed that the repeated social-defeat paradigm can be considered as a suitable model of 'depression' in rats. The causal link between social defeat-evoked (1) increase in cortical CCKergic neurotransmission and (2) depression-like symptoms that we highlighted here strongly suggests that CCKergic systems may be a relevant target for novel antidepressant therapy.

The role of substance P in stress and anxiety responses

Substance P (SP) is one of the most abundant peptides in the central nervous system and has been implicated in a variety of physiological and pathophysiological processes including stress regulation, as well as affective and anxiety-related behaviour. Consistent with these functions, SP and its preferred neurokinin 1 (NK1) receptor has been found within brain areas known to be involved in the regulation of stress and anxiety responses. Aversive and stressful stimuli have been shown repeatedly to change SP brain tissue content, as well as NK1 receptor binding. More recently it has been demonstrated that emotional stressors increase SP efflux in specific limbic structures such as amygdala and septum and that the magnitude of this effect depends on the severity of the stressor. Depending on the brain area, an increase in intracerebral SP concentration (mimicked by SP microinjection) produces mainly anxiogenic-like responses in various behavioural tasks. Based on findings that SP transmission is stimulated under stressful or anxiety-provoking situations it was hypothesised that blockade of NK1 receptors may attenuate stress responses and exert anxiolytic-like effects. Preclinical and clinical studies have found evidence in favour of such an assumption. The status of this research is reviewed here.

The selective neurokinin (NK)(1) antagonist, GR205,171, stereospecifically enhances mesocortical dopaminergic transmission in the rat: a combined dialysis and electrophysiological study

Upon acute, systemic administration, the selective, non-peptidergic NK(1) receptor antagonist, GR205,171, dose-dependently enhanced the firing rate of ventrotegmental dopaminergic neurones. Dialysate levels of dopamine were increased in the frontal cortex, but not in the striatum and nucleus accumbens, of conscious rats. These actions were stereospecific in that its less-active isomer, GR226,206, was ineffective. Further, they were selective for dopaminergic pathways inasmuch as the firing rate of dorsal raphe serotonergic neurones and dialysate levels of serotonin were unaffected by GR205,171. Activation of mesocortical dopaminergic pathways may be involved in the influence of NK(1) antagonists upon mood.

Electroconvulsive shock increases tachykinin NK(1) receptors, but not the encoding mRNA, in rat cortex

Recent studies have suggested that the substance P (tachykinin NK(1)) receptor may be a pharmacological target for the treatment of mood disorders. Here, the effects of electroconvulsive shock on tachykinin NK(1) receptor gene expression in the rat brain was investigated. Rats received either a single electroconvulsive shock or five shocks on alternate days. Quantitative autoradiography with [(125)I]Bolton Hunter-substance P, and in situ hybridisation histochemistry, were used to measure tachykinin NK(1) receptor-binding site densities and mRNA abundance, respectively. Densities of tachykinin NK(1) receptor-binding sites were significantly increased in the cerebral cortex following repeated electroconvulsive shock compared to sham treated animals. Densities remained unchanged in the hippocampus, striatum and amygdala. Neither single nor repeated electroconvulsive shock altered tachykinin NK(1) receptor mRNA in the brain regions examined. Hence, repeated electroconvulsive shock increases tachykinin NK(1) receptors in the rat brain in a regionally specific way. Upregulation of receptor-binding sites without a change in mRNA indicates that translational or post-translational mechanisms underlie this process.

Enhanced cortical extracellular levels of cholecystokinin-like material in a model of anticipation of social defeat in the rat

The involvement of cholecystokinin (CCK) in the mechanisms of stress and/or anxiety was assessed by in vivo microdialysis in rats subjected to a social stress paradigm. During the initial 30 min period of each conditioning session, a male Sprague Dawley rat (intruder) was placed in a protective cage inside the cage of a male Tryon Maze Dull rat (resident), allowing unrestricted visual, olfactory, and auditory contacts but precluding close physical contact between them. During the following 15 min period, both the protective cage and the resident were removed (nondefeated intruders) or only the protective cage was removed allowing the resident to attack the intruder (defeated rats). This procedure was repeated once daily for 4 d. On the fifth day, a guide cannula was implanted into the prefrontal cortex of intruders. During a single 30 min test session, performed 4 d later, intruders were subjected to only the 30 min protected confrontation to the resident. Anxiety-like behavior (immobility, ultrasonic vocalizations, and defensive postures), associated with an increase (approximately +100% above baseline) in cortical outflow of CCK-like material (CCKLM), were observed in defeated intruders. Pretreatment with diazepam (5 mg/kg, i.p.), but not buspirone (0.5-2 mg/kg, i.p.), prevented both the anxiety-related behavior and CCKLM overflow. The selective CCK-B receptor antagonist CI-988 (2 mg/kg, i.p.) reduced the anxiety-like behavior without affecting the increase in CCKLM outflow. These data indicate that anticipation of social defeat induces a marked activation of cortical CCKergic neurons associated with anxiety-related behaviors in rats.

Central changes in nociceptin dynorphin B and Met-enkephalin-Arg-Phe in different models of nociception

The newly identified neuropeptide nociceptin/orphanin FQ (NOC) was measured in different rat brain areas related to the descending anti-nociceptive pathways and compared to two opioid peptides, dynorphin B (DYN B) and Met-enkephalinArgPhe (MEAP). Two experimental models of chronic nociception, one neurogenic and one inflammatory, used in this study, reveal how different pathological conditions may influence these endogenous systems. Nerve injury is induced by ligation of the sciatic nerve and inflammation by a carrageenan injection in the gluteal muscle, 2 weeks prior to decapitation. Selected brain areas were dissected out and frozen. NOC-, DYN B- and MEAP-like immunoreactivity (LI) is determined by radioimmunoassay. Nerve injury increased the NOC-LI levels in the cortex cinguli, DYN B-LI levels in the dorsal and the ventral part of the spinal cord, whereas a decrease in the MEAP-LI levels is seen in the dorsal part of the periaqueductal grey (PAG). After inflammation, the NOC-LI levels increased in cortex cinguli, hypothalamus and in the dorsal spinal cord, whereas DYN B-LI levels increased in the dorsal part of the PAG. A general increase in MEAP-LI levels is found after inflammation in all analyzed brain areas except in hippocampus. In conclusion, increased levels of NOC-LI were found in cortex cinguli in both treatment groups and in hypothalamus and spinal cord following carrageenan treatment. The changes in the NOC-LI concentrations were not parallelled by changes in DYN B-LI and MEAP-LI, suggesting that NOC and opioid peptides elicit different reactions in the systems of nociception/antinociception.

Substance P antagonists: the next breakthrough in treating depression?

Several lines of evidence implicate the neuropeptide substance P in depression, either in the pathogenesis or as a novel target for amelioration of symptoms. NK1 (substance P) receptor antagonists have been reported to have antidepressant-like actions in animal models. The first clinical trial of an NK1 antagonist showed promising results. A second trial, using a more potent compound, is underway. If the clinical trials show that NK1 (substance P) antagonism represents a well-tolerated, distinct mechanism for antidepressant activity, novel antidepressant agents will emerge as mono- or adjunct-therapy.

Cholecystokinin and psychiatric disorders : role in aetiology and potential of receptor antagonists in therapy

Cholecystokinin (CCK) is one of the most abundant neuropeptides in the brain. It is found in the highest levels in cortical and limbic structures and also in the basal ganglia. Two subtypes of CCK receptors have been described in the brain and gastrointestinal tissues. CCK(A) (alimentary subtype) receptors are mainly located in the gastrointestinal tract, regulating secretion of enzymes from the pancreas and emptying of the gallbladder. However, CCK(A) receptors are also found in several brain regions, with the highest densities in structures poorly protected by the haematoencephalic barrier (the area postrema, nucleus tractus solitarius and hypothalamus). The distribution of CCK(B) (brain subtype) receptors overlaps with the localisation of CCK and its mRNA in different brain areas, with the highest densities in the cerebral cortex, basal ganglia, nucleus accumbens and forebrain limbic structures.Both subtype of CCK receptor belong to the guanine nucleotide-binding protein-(G protein)-linked receptor superfamily containing 7 transmembrane domains. Signal transduction at CCK receptors is mediated via G(q) protein-related activation of phospholipase C and the formation of inositol 1,4,5-triphosphate (IP(3)) and 1,2-diacylglycerol (DAG). Recent cloning of CCK(A) and CCK(B) receptors has shown that mRNA for both receptors is distributed in the same tissues as established in radioligand binding and receptor autoradiography studies, with few exceptions.The existence of multiple CCK receptors has fuelled the development of selective CCK(A) and CCK(B) receptor antagonists. These antagonists belong to distinct chemical groups, including dibutyryl derivatives of cyclic nucleotides, amino acid derivatives, partial sequences and derivatives of the -COOH terminal sequence heptapeptides of CCK, benzodiazepine derivatives, 'peptoids' based on fragments of the CCK molecule, and pyrazolidinones. At the present time, the compounds of choice for blockade of the CCK(A) receptor are lorglumide, devazepide and lintitript (SR27897). L-365,260, CI-988, L-740,093 and LY288513 are the drugs most widely used to block CCK(B) receptors.Studies with CCK antagonists (and agonists) in animals and humans suggest a role for CCK in the regulation of anxiety and panic. The administration of CCK agonists [ceruletide (caerulein), CCK-4, pentagastrin] has an anxiogenic action in various animal models and in different animal species. However, the anxiogenic action of CCK agonists is restricted to nonconditioned (ethological) models of anxiety, with very limited activity in the 'classical' conditioned models. Pharmacological studies have revealed that CCK(B) receptors are the key targets in the anxiogenic action of CCK agonists. Nevertheless, CCK(B) antagonists displayed very little activity, if any at all, in these models, but strongly antagonised the effects of CCK(B) agonists. The anxiogenic/panicogenic action of CCK(B) agonists (CCK-4, pentagastrin) is even more pronounced in human studies, but the effectiveness of CCK(B) antagonists as anxiolytics remains unclear. Clinical trials performed to date have provided inconclusive data about the anxiolytic potential of CCK(B) receptor antagonists, probably because of limiting pharmacokinetic factors.The results of some animal experiments suggest a role for CCK in depression. The administration of CCK(B) antagonists causes antidepressant-like action in mouse models of depression. However, human studies replicating this result have yet to be carried out.A prominent biochemical alteration in schizophrenia is a reduction of CCK levels in the cerebral cortex. This change may be related to the loss of cortical neurons, due to the schizophrenic process itself. In animal studies (mainly in mice), administration of CCK agonists and antagonists has been shown to be effective in several models, reflecting a possible antipsychotic activity of these drugs. However, the data obtained in human studies suggest that CCK agonists and antagonists do not improve the symptoms of schizophrenia. Taking into account the reduced levels of CCK and its receptors found in schizophrenia, treatments increasing, but not blocking, brain CCK activity may be more appropriate.

Rapid but transient increases in cholecystokinin mRNA levels in cerebral cortex following amygdaloid-kindled seizures in the rat

Cholecystokinin-octapeptide (CCK-8S) is widely distributed in neurones of the central nervous system, where it is thought to act as a transmitter or modulator. CCK-8S has been shown to exert anti-convulsant activity in animal seizure models and changes in cortical and hippocampal CCK-immunoreactivity and preproCCK messenger RNA (mRNA) have been reported following electrically- and chemically-induced seizures. In the present study, the spatiotemporal effect of amygdaloid-kindled seizures on levels of preproCCK messenger RNA in rat brain were determined using quantitative in situ hybridization histochemistry. Stimulation-evoked seizures produced bilateral increases (45-70%) in preproCCK mRNA throughout layers II-III of the cerebral cortex. These increases were rapidly induced, occurring 30-60 min after the last stage 5 seizure, but transient, as no significant changes were detected after 2 h, or subsequently at 24 or 72 h, or 2-8 weeks, post-stimulation. Rapid changes in the relative levels of preproCCK mRNA, post-seizure, suggest a possible stabilization of preproCCK transcripts and increased production of CCK-8S peptide, which may be involved in anticonvulsant mechanisms in response to the acute seizures.

Limbic effects of repeated electroconvulsive stimulation on neuropeptide Y and somatostatin mRNA expression in the rat brain

The aim of this study was to determine the effect of repeated electroconvulsive stimulation (ECS) on the expression of neuropeptide Y (NPY) and somatostatin (SS) mRNA in the rat brain. For that purpose, quantitative in situ hybridization histochemistry and RNA blot analysis were used. In the hippocampal formation the prevalence of NPY mRNA positive neurons increased in the hilus of the dentate gyrus and the CA3 while a decrease was seen in layers II-III of the entorhinal cortex. In contrast, SS mRNA was increased in the granule cells of the dentate gyrus and in most neurons of the outer parts of the layer III in the entorhinal cortex with cell bodies of perforant pathway projections to the hippocampal CA1 region. Both NPY and SS mRNA expressing neurons were increased in numerical density in the prefrontal cortex with similar amounts of mRNA in individual NPY positive neurons after the stimulations while SS mRNA levels decreased in hybridization positive neurons. In the striatum the only observed significant effect was an increased prevalence of NPY mRNA positive neurons in the caudal nucleus accumbens. Our results provide an outline of a complex functional anatomy of ECS in the rat brain. This type of investigations contributes to map the neuronal systems involved in the action of ECT used in the treatment of affective and schizophrenic disorders.

Spatiotemporal selective effects on brain-derived neurotrophic factor and trkB messenger RNA in rat hippocampus by electroconvulsive shock

Electroconvulsive therapy is used in the treatment of affective disorders and schizophrenia and experimental electroconvulsive shock may serve as an animal model for this treatment. The aim of this study was to investigate a possible role for neurotrophins in the mechanism of action of experimental electroconvulsive shock and thus in clinical electroconvulsive therapy. The effect of electroconvulsive shock on levels of messenger RNAs encoding the neurotrophin brain-derived neurotrophic factor and the receptor trkB in rat hippocampus was determined by in situ hybridization with RNA probes 1, 3, 9 and 27 h following the shock. Brain-derived neurotrophic factor messenger RNA levels were increased at 1, 3 and 9 h following the shock and normalized after 27 h. Granule cells of the dentate gyrus showed a more rapid response as compared to hilar cells and pyramidal cells of CA1. Total trkB messenger RNA levels, including the transcripts for both the truncated and full length trkB receptor protein (gp95trkB and gp145trkB, respectively), showed a pattern of increase very similar to that of the brain-derived neurotrophic factor messenger RNA. However, using a probe selective for the full length (gp145trkB) trkB messenger RNA, we determined a delayed pattern of activation with significant increase only at 3 and 9 h after the shock. In hippocampus total trkB messenger RNA was found to consist of approximately one-quarter of mRNA encoding gp145trkB and three-quarters encoding gp95trkB as revealed by RNAase protection. While brain-derived neurotrophic factor and the truncated trkB messenger RNAs appear to increase with a similar pattern, suggesting a similar mechanism of activation by electroconvulsive shock, full length receptor trkB messenger RNA appears to increase with a delayed pattern suggesting a separate mechanism of activation. Electroconvulsive shock-induced seizures seem to include activation of a brain neurotrophin known to be important for neuronal plasticity.

Clomipramine and clonazepam increase cholecystokinin levels in rat ventral tegmental area and limbic regions

Recent reports suggest that a cholecystokinin (CCK)-related dysfunction may be a target by which drugs can modulate anxiety and panic disorders. In the present study, effects of subchronic (14 days) treatment with the monoamine uptake inhibitors nortriptyline (30 mumol/kg per day), amitriptyline (29 mumol/kg per day), clomipramine (32 mumol/kg per day) and alaproclate (39 mumol/kg per day), as well as with the benzodiazepine clonazepam (0.25 mumol/kg per day), on rat brain levels of CCK- and substance P-like immunoreactivity, were compared. The drugs were administered by continuous s.c. infusion using implanted osmotic pumps. The plasma concentrations of the monoamine uptake inhibitors were similar after 1 and 2 weeks of treatment, indicating that steady-state plasma levels had been reached during the first week. Treatment with clomipramine or clonazepam increased the CCK-like immunoreactivity level in the ventral tegmental area (by 64.4 +/- 28.8% and 105.1 +/- 28.8%, respectively) and in the cingulate cortex (by 30.3 +/- 10.1% and 36.0 +/- 11.8%, respectively) (P < 0.05 or P < 0.01). Clomipramine also significantly increased the CCK-like immunoreactivity level in the periaqueductal grey by 85.1 +/- 29.7%. Neither nortriptyline nor amitriptyline or alaproclate produced any significant alterations in the CCK- or substance P-like immunoreactivity levels in the areas examined. The present results may suggest that an altered utilization of CCK in limbic circuits could be of importance for the well documented clinical effect of clomipramine and clonazepam in panic disorders.

Pentagastrin infusions in patients with panic disorder. II. Neuroendocrinology

Cholecystokinin (CCK) has well-documented anxiogenic effects in animals and normal people, and panicogenic effects in patients with panic disorder, but little is known about its neuroendocrine profile. We examined neuroendocrine responses to intravenous infusions of pentagastrin, a selective CCK-B receptor agonist, in 10 patients with panic disorder and 10 normal control subjects. Pentagastrin potently activated the hypothalamic-pituitary-adrenal (HPA) axis, but did not release growth hormone or any of several vasoactive peptides (neurokinin A, substance P, vasoactive intestinal peptide). The HPA axis response was unrelated to increases in symptoms. Panic patients did not differ from controls in neuroendocrine responses to the CCK agonist. Differential sensitivity to novelty stress accounted for the only patient-control differences in neuroendocrine profiles. The data suggest that CCK may help modulate normal HPA axis activity, but its anxiogenic effects are unrelated to its stimulatory effects on the HPA axis. Pentagastrin provides a safe and readily available probe for further study of CCK receptor systems in humans.

CCK antagonists: pharmacology and therapeutic interest

CCK was first identified and characterized in the digestive tract where it is known to be a factor involved in the control of gut motility. Later, CCK and CCK receptors were identified in regions of the central nervous system that are associated with the control of emotion, motivation and sensory processing. The recent discovery and development of CCK-receptor antagonists having selective affinity for either CCKA or CCKB receptors has led to a better understanding of the functional role of CCK and its binding sites in the brain and periphery. Some of these compounds are being examined in man for their therapeutic usefulness in mental as well as in digestive disorders. This review will highlight the results from both basic and clinical investigations that have examined the effects of selective CCK receptor ligands. The focus will be on the central nervous system pharmacology of CCK antagonists and the involvement of CCK in gastrointestinal and colonic motility.

Substance P and neuropsychiatric disorders: an overview

Substance P (SP) is a naturally-occurring tachykinin peptide isolated from brain tissues and gastrointestinal tract. In the brain, substantia nigra and basal ganglia contain relatively high amounts of substance P. There is evidence suggesting that substance P functions as a neurotransmitter. It has been implicated in the pathophysiology of several neuropsychiatric disorders. Substance P may also serve as a useful tool in studying the effects of antidepressant drugs and electroconvulsive therapy. However, the contribution of substance P to the understanding of neuropsychiatric disorders is far from clear. Future studies should focus on the interactions and coexistence of substance P with other neurotransmitters and neuropeptides.

Brain neuropeptides: changes by treatment with the convulsants pentylenetetrazole and bicuculline

1. The effects of chemically induced convulsions, clinically similar to those elicited by electroconvulsive treatment (ECT), on brain regional distribution of neuropeptide Y-, neurokinin A-, substance P- and neurotensin-like immunoreactivities were studied in the rat. 2. Pentylenetetrazole (PTZ) and bicuculline (BIC) were used to induce grand mal seizures. Rats were divided into three groups receiving one of the following treatments: Saline, PTZ (45 mg/kg) or BIC (1.5 mg/kg). 3. After sacrifice by focused microwave irradiation, brains were dissected, peptides extracted and measured by specific radioimmunoassays. 4. Repeated grand mal convulsions induced by PTZ, in similarity to ECT, markedly increased NPY-LI concentrations in frontal cortex and hippocampus. In contrast to ECT, no changes in NKA- or SP-LI levels were seen. NT-LI was lowered in striatum. 5. Bicuculline effects were more circumscribed: some animals developed grand mal and died while convulsing (peptides not measured), others did not develop generalized seizures and were sacrificed after the fourth treatment. 6. The results demonstrate a similar effect of PTZ and ECT on regional NPY-LI concentrations and raise the possibility that grand mal, regardless of etiology, is necessary for effects on peptides.

Repeated electroconvulsive shock increases tachykinin and cholecystokinin mRNA expression in ventral periaqueductal gray

The effect of repeated electroconvulsive shock (five shocks during 10 days) on preprocholecystokinin and preprotachykinin-A messenger RNA expression was studied in the mesencephalic periaqueductal gray and adjacent areas of rat using in situ hybridization histochemistry with specific oligonucleotide probes. An increased number of preprocholecystokinin and preprotachykinin-A messenger RNA hybridization positive neurons (+30% and +47%, respectively) in the Edinger-Westphal nucleus was observed following repeated electroconvulsive shock. In addition, both preprocholecystokinin and preprotachykinin-A messenger RNA expression, measured as grain density over single neurons, was significantly increased (+37% and +45%, respectively). The results indicate that cholecystokinin- and substance P-containing neurons in the Edinger-Westphal nucleus are activated by repeated electroconvulsive shock, which may be related to the antidepressant and analgesic effects of electroconvulsive shock treatment.