Discrete Areas Of Rat Brain Research Articles

Concurrent tissue oxymetry and blood flowmetry to assess the effect of drugs on cerebral oxygen metabolism

An Oxylite/LDF system (Oxford Optronix, UK) driven by a sensor made of optical fibres for the tissue oxygen tension (pO2) and for the Laser Doppler Blood Flow (BF) was implemented. This has allowed pO2 and BF real time measurements in discrete brain areas of anaesthetised rats that were then challenged with exogenous oxygen (O2) and carbon dioxide (CO2). The results gathered were compared with data obtained following treatment with drugs that have excitatory influence upon the brain activity such as amphetamine or with a central nervous system (CNS) depressant such as CI-966. Altogether these experiments support the methodology for in vivo investigation of pharmacological effects on cerebral oxygen metabolism and could provide new understandings on the effects of psychostimulants and anticonvulsants on selected brain regions.

Neuroprotective Effects of Galantamine on Nerve Agent-Induced Neuroglial and Biochemical Changes.

Neuroprotection from nerve agent such as soman-induced neural damage is a major challenge for existing drugs. Nerve agent exposure can cause many neural effects in survivors arising mainly due to acetylcholinesterase (AChE) inhibition or death within minutes. Unraveling the mechanisms underlying the nerve agent-induced multiple neurological effects is useful to develop better and safe drugs. The present study aimed to understand the molecular response during soman exposure and to evaluate the neuroprotective efficacy of galantamine on nerve agent-induced neurotoxic changes. mRNA expression studies using quantitative real-time PCR revealed significant changes in S-100β, Gfap, c-fos, and Bdnf in the hippocampus and piriform cortex after soman (90μg/kg, s.c) exposure. Immunoblot analysis showed acute soman exposure significantly increased the protein levels of neuroglial markers (S100-β and GFAP); c-Fos and protein oxidation in discrete rat brain areas indicate their role in nerve agent-induced neurotoxicity. Induction of BDNF levels during soman exposure may indicate the recovery mechanisms activation. AChE was inhibited in the blood and brain up to 82% after soman exposure. Antidotal treatment with galantamine alone (3mg/kg) and galantamine plus atropine (10mg/kg) has protected animals from nerve agent-induced intoxication, death, and soman-inhibited AChE up to 45% in the blood and brain. Animal received galantamine displayed increased levels of neuroprotective genes (nAChRα-7, Bcl-2, and Bdnf) in the brain suggest the neuroprotective value of galantamine. Neuroglial changes, c-Fos, and protein oxidation levels significantly reduced after galantamine and galantamine plus atropine treatment indicate their potential antidotal value in nerve agent treatment.

Hypo- and hyperthyroidism affect NEI concentration in discrete brain areas of adult male rats

To date, there has been only one in vitro study of the relationship between neuropeptide EI (NEI) and the hypothalamic–pituitary–thyroid (HPT) axis. To investigate the possible relationship between NEI and the HPT axis, we developed a rat model of hypothyroidism and hyperthyroidism that allows us to determine whether NEI content is altered in selected brain areas after treatment, as well as whether such alterations are related to the time of day. Hypothyroidism and hyperthyroidism, induced in male rats, with 6-propyl-1-thiouracil and l-thyroxine, respectively, were confirmed by determination of triiodothyronine, total thyroxine, and thyrotropin levels. All groups were studied at the morning and the afternoon. In rats with hypothyroidism, NEI concentration, evaluated on postinduction days 7 and 24, was unchanged or slightly elevated on day 7 but was decreased on day 24. In rats with hyperthyroidism, NEI content, which was evaluated after 4 days of l-thyroxine administration, was slightly elevated, principally in the preoptic area in the morning and in the median eminence-arcuate nucleus and pineal gland in the afternoon, the morning and afternoon NEI contents being similar in the controls. These results provide the bases to pursue the study of the interaction between NEI and the HPT axis.

Effects of root extract of withania somnifera in 3- nitropropionic acid-induced cognitive dysfunction and oxidative damage in rats

Purpose: To investigate the possible modulatory role of root extract of Withania somnifera (WS) in 3-Nitroproiponic acid (3-NP)-induced cognitive impairment and altered level of oxidative defense in discrete areas of rat brain. Methods: 3-NP was administered in a dose of 10 mg/kg for 14 days where as WS root extract (100 and 200 mg/kg) was administered orally along with 3-NP. Cognitive dysfunctions were assessed in Morris water maze and plus-maze performance task paradigms. On 15th day the animals were scarified and reduced glutathione, total glutathione, oxidized glutathione (GSSG), glutathione-S-transferase (GST) and acetylcholinesterase enzyme levels were estimated in the striatum, cortex and hippocampus of the rat brian. Results: Chronic WS root extract (100, 200 mg/kg) treatment for a period of 14 days significantly improved 3-NP-induced cognitive impairment in Morris water and plus maze tests (p

Possible role of sertraline against 3-nitropropionic acid induced behavioral, oxidative stress and mitochondrial dysfunctions in rat brain

Oxidative stress and disrupted energy metabolism are major events leading to nerve cell death. Oxidative stress and related reactive oxygen species is one of the common cooperative sharing pathways involved in neurodegenerative disorders including Huntington's disease. The present study evaluated the possible role of sertraline on the 3-nitropropionic acid induced behavioral, biochemical, and mitochondrial alterations in discrete areas of rat brain. 3-Nitropropionic acid (10 mg/kg) administration for 14 days significantly induced Huntington's disease like symptoms in rats as indicated by change in locomotor activity, body weight, rotarod activity performance, oxidative damage (elevated levels of lipid peroxidation, nitrite concentration, depletion of antioxidant enzyme levels) and mitochondrial dysfunction (Complexes-I, II, II and IV) in striatum, cortex and hippocampal region of brain. Treatment with sertraline (5 and 10 mg/kg) significantly reversed behavioral, biochemical and mitochondrial enzyme dysfunctions in 3-nitropropionic acid treated group. Further, combination of yohimbine (2 mg/kg) (non selective serotonin with the higher dose of sertraline (10 mg/kg) did not influence the protective action of sertraline. The present study suggests the possible antioxidant role of sertraline against 3-nitropropionic acid induced alterations in animals.

In vivo receptor occupancy method that simultaneously quantifies four tracers: raclopride, pirenzepine, MDL‐100907, and SB‐221284

The atypical antipsychotics share the common attributes of working on serotonin and dopamine receptors. However, a comprehensive mechanism of action of these agents is unknown. In order to better elucidate the mechanism by which these drugs produce their therapeutic and the undesired effects, a robust method for measuring in vivo receptor binding is needed. The authors developed a liquid chromatography/triple quad mass spectral detectors (LC/MS/MS) method to measure the brain distribution of receptor occupancy using tracers targeting dopamine D2, serotonin 5‐HT2A, 5‐HT2C and muscarinic M1 receptors. The tracers are raclopride, MDL‐100907, SB‐221284 and pirenzepine, respectively. All four non‐radiolabeled tracers were detectable in discrete rat brain areas after intravenous administration. These tracers demonstrated a differential brain distribution corresponding to the regional differences in their respective receptor densities. Oral pretreatment of various antipsychotic agents that occupy these receptors decreased this differential distribution in a dose‐dependent manner. Our results demonstrate the utility of LC/MS/MS to quantify the in vivo receptor occupancy of antipsychotic and other agents acting in the CNS.

The effect of CB1 receptor antagonism in the right basolateral amygdala on conditioned fear and associated analgesia in rats

The endocannabinoid system mediates analgesia expressed following exposure to conditioned or unconditioned aversive stimuli, and controls the extinction of conditioned aversive behaviour. The present study investigated the effects of administration of the cannabinoid(1) (CB(1)) receptor antagonist SR141716A into the right basolateral amygdala (BLA) on expression of conditioned fear, formalin-evoked nociceptive behaviour, fear-conditioned analgesia and associated alterations in monoamine levels in discrete rat brain areas. Re-exposure to a context previously paired with footshock significantly reduced formalin-evoked nociceptive behaviour. Intra-BLA administration of SR141716A did not attenuate fear-conditioned analgesia, but reduced formalin-evoked nociceptive behaviour and attenuated the formalin-induced decrease in freezing and 22-kHz ultrasonic vocalizations in the early part of the trial. Furthermore, intra-BLA SR141716A significantly prolonged the duration of these fear-related behaviours in fear-conditioned rats not receiving formalin. Fear-conditioned analgesia was accompanied by increased homovanillic acid (HVA) : dopamine (DA) ratio and reduced serotonin (5-HT) in the cerebellum, an effect not altered by SR141716A. SR141716A-induced analgesia was accompanied by reduced DA, increased HVA : DA ratio and reduced 5-HT levels in the cerebellum, increased hippocampal HVA levels and increased 5-hydroxyindole-3-acetic acid (5-HIAA) in the amygdaloid cortex. The SR141716A-induced prolongation of contextually induced aversive behaviour was accompanied by reduced DA and 3,4-dihydroxyphenylacetic acid (DOPAC), levels in the hippocampus, and increased DA and 5-HIAA in the periaqueductal grey. These data suggest an important role for CB(1) receptors in the right BLA in mediating short-term extinction of conditioned aversive behaviour but not fear-conditioned analgesia. The results also enhance our understanding of endocannabinoid-monoamine interactions of relevance to conditioned fear and associated analgesia.

Use of LC/MS to assess brain tracer distribution in preclinical, in vivo receptor occupancy studies: Dopamine D2, serotonin 2A and NK-1 receptors as examples

High performance liquid chromatography combined with either single quad or triple quad mass spectral detectors (LC/MS) was used to measure the brain distribution of receptor occupancy tracers targeting dopamine D2, serotonin 5-HT2A and neurokinin NK-1 receptors using the ligands raclopride, MDL-100907 and GR205171, respectively. All three non-radiolabeled tracer molecules were easily detectable in discrete rat brain areas after intravenous doses of 3, 3 and 30 μg/kg, respectively. These levels showed a differential brain distribution caused by differences in receptor density, as demonstrated by the observation that pretreatment with compounds that occupy these receptors reduced this differential distribution in a dose-dependent manner. Intravenous, subcutaneous and oral dose–occupancy curves were generated for haloperidol at the dopamine D2 receptor as were oral curves for the antipsychotic drugs olanzapine and clozapine. In vivo dose–occupancy curves were also generated for orally administered clozapine, olanzapine and haloperidol at the cortical 5-HT2A binding site. In vivo occupancy at the striatal neurokinin NK-1 binding site by various doses of orally administered MK-869 was also measured. Our results demonstrate the utility of LC/MS to quantify tracer distribution in preclinical brain receptor occupancy studies.

A short-term diabetes induced changes of catecholamines and p38-MAPK in discrete areas of rat brain

Chronic diabetes is associated with the alteration of second messengers and CNS disorders. We have recently identified that protein kinases (CaMKII and PKC-α) and brain neurotransmitters are altered during diabetes as well as in hyperglycemic and acidotic conditions. In this study, we investigated the effects of acute diabetes on the levels of dopamine (DA), norepinephrine (NE), epinephrine (E) and p38-Mitogen-Activated Protein Kinase (p38-MAPK) in striatum (ST), hippocampus (HC), hypothalamus (HT), midbrain (MB), pons medulla (PM), cerebellum (CB) and cerebral cortex (CCX). Alloxan (45mg/kg) diabetic untreated rats that showed hyperglycemia (> 260mg%), revealed significant increases of DA level in ST (1.5 fold), HC (2.2 fold) and PM (2.0 fold) and the E level also found to be increased significantly in HT (2.4 fold), whereas the NE level was decreased in CB (0.5 fold), after 7 days of diabetes. Immunoblotting study of p38-MAPK expression under identical conditions showed significant alterations in ST, HC, HT and PM (p < 0.05) correlated with the changes of catecholamines (DA and E). On the other hand, the above changes were reversed in insulin-treated diabetic rats maintained under normal glucose level (80 –110mg %). These results suggest that p38-MAPK may regulate the rate of either the synthesis or release of DA and E in corresponding brain areas, but not NE, under these conditions.

An acute hyperglycemia or acidosis-induced changes of indolamines level correlates with PKC-α expression in rat brain

Hyperglycemia and ketoacidosis are the two most serious factors in acute metabolic complications of both type 1 and type 2 diabetes. Dysfunction of the central nervous system is a well-documented complication of diabetes. We and others have previously reported that acute or chronic diabetes in animal's results in altered brain neurotransmitter levels. In this study, we investigated the effects of acute (7 days) glucose-induced hyperglycemia and sodium acetoacetate (NaAcAc) or ammonium chloride (NH 4Cl) induced acidosis on the level of indolamines (5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA)) as well as PKC-α expression/activity in discrete areas of rat brain. Glucose-induced (500 mg/kg, bw) hyperglycemic (∼249 mg%) rats showed significant ( p < 0.05) increase in 5-HT levels in mid brain (MB), pons medulla (PM) and cerebellum (CB), respectively. 5-HIAA level increased in hippocampus (HC) ( p < 0.05) as compared to control. The rats treated with sodium acetoacetate (NaAcAc) for 7 days (60 mg/kg, bw) showed significant decrease ( p < 0.05) of 5-HT level in hypothalamus (HT). Whereas, the 5-HIAA level increased in MB ( p < 0.05). Similarly, the PKC-α expression as well as the enzyme activity showed significant increase in HC, MB, PM and CB under glucose-induced hyperglycemia and that changes correlated the changes of indolamines, suggesting that the hyperglycemia may be the major metabolic disorder in diabetic complications.

Attenuation of paraquat-induced motor behavior and neurochemical disturbances by l-valine in vivo

Alterations of motor behavioral patterns and monoamine contents in the discrete rat brain areas after acute paraquat exposure (3, 5, 10, 20 mg/kg, s.c.) have been studied. The results showed that paraquat at the doses of 5, 10, and 20 mg/kg significantly reduced locomotive, stereotypic, and rotational behaviors. Significant decreases of norepinephrine (NE) contents in cortex and hypothalamus, as well as striatal contents of dopamine (DA) and its acidic metabolites, were detected. In addition, l-valine (200 mg/kg, i.p.) significantly attenuated paraquat-induced toxicity at moderate dose (5 mg/kg) but not at high dose (20 mg/kg). The results provide evidence that paraquat can enter the brain as illustrated by the alterations in the motor behavioral pattern and neurochemical contents. Furthermore, the attenuation effect of l-valine against systemic administration of paraquat-induced motor behaviors was detected, with a slightly protective effect on paraquat-induced neurochemical alterations.

An HPLC tracing of the enhancer regulation in selected discrete brain areas of food-deprived rats

The recent discovery of the enhancer regulation in the mammalian brain brought a different perspective to the brain-organized realization of goal-oriented behavior, which is the quintessence of plastic behavioral descriptions such as drive or motivation. According to this new approach, ‘drive’ means that special endogenous enhancer substances enhance the impulse-propagation-mediated release of transmitters in a proper population of enhancer-sensitive neurons, and keep these neurons in the state of enhanced excitability until the goal is reached. However, to reach any goal needs the participation of the catecholaminergic machinery, the engine of the brain. We developed a method to detect the specific enhancer effect of synthetic enhancer substances [(-)-deprenyl, (-)-PPAP, (-)-BPAP] by measuring the release of transmitters from freshly isolated selected discrete brain areas (striatum, substantia nigra, tuberculum olfactorium, locus coeruleus, raphe) by the aid of HPLC with electrochemical detection. To test the validity of the working hypothesis that in any form of goal-seeking behavior the catecholaminergic and serotonergic neurons work on a higher activity level, we compared the amount of norepinephrine, dopamine, and serotonin released from selected discrete brain areas isolated from the brain of sated and food-deprived rats. Rats were deprived of food for 48 and 72 hours, respectively, and the state of excitability of their catecholaminergic and serotonergic neurons in comparison to that of sated rats was measured. We tested the orienting–searching reflex activity of the rats in a special open field, isolated thereafter selected discrete brain areas and measured the release of norepinephrine, dopamine, and serotonin from the proper tissue samples into the organ bath. The orienting–searching reflex activity of the rats increased proportionally to the time elapsed from the last feed and the amount of dopamine released from the striatum, substantia nigra and tuberculum olfactorium, that of norepinephrine released from the locus coeruleus and that of serotonin released from the raphe increased significantly in the hungry rats proportionally to the time of fasting. For example: the amount of dopamine released from the substantia nigra of sated rats (4.62 ± 0.20 nmoles/g wet weight) increased to 5.95 ± 0.37 (P < 0.05) and 10.67 ± 0.44 (P < 0.01) in rats deprived of food for 48 and 72 hours, respectively.

Argemone oil augmented oxidative stress in discrete areas of rat brain.

Argemone oil augmented oxidative stress in discrete areas of rat brain.

Alterations in signal transduction cascade in young and adult rat brain and lymphocytes

Signal transduction cascade, phosphoinositide metabolism, and protein kinases were studied from discrete areas of rat brain like cerebral hemispheres, cerebellum, brainstem, and diencephalon as well as lymphocytes isolated from three different age groups of rats; young (1 month), young adult (3–4 months), and adult (12 months) rats. The activities of protein kinase A, protein kinase C, phospholipase A 2 and phospholipase C and inositol 1, 4, 5-triphosphate, diacylglycerol, cyclic adenosine monophosphate contents were assayed from different brain areas and lymphocytes from these three age group rats. An upregulatory effect on the signal transduction system was observed from 1 month to 3–4-month age group, whereas, the brain tissue and lymphocytes of adult rats showed lower contents and activities of signal transduction components as compared to young adults. In view of the established ‘cross talk’ between signal transduction system, the present results suggests that molecular/cellular changes in brain and immune cells signal transduction pathway along with neuronal cell loss may contribute to age-related decline in nervous as well as immune system functions.

Glutathione deficiency potentiates manganese-induced increases in compounds associated with high-energy phosphate degradation in discrete brain areas of young and aged rats.

Aging is a factor known to increase neuronal vulnerability to oxidative stress, which is widely accepted as a mechanism of manganese-induced neuronal damage. We previously showed that subchronic exposure to manganese induced greater energy impairment (as revealed by increases in hypoxanthine, xanthine and uric acid levels) in the striatum and brainstem of aged rats vs young rats. This study shows that inhibition of glutathione (GSH) synthesis, by means of buthionine (SR) sulfoximine, decreased GSH levels and increased the ascorbic acid oxidation status in the striatum and limbic forebrain of both young and aged rats. In addition, inhibition of GSH synthesis greatly potentiated the manganese-induced increase in inosine, hypoxanthine, xanthine and uric acid levels in both regions of aged rats; moreover, inhibition of GSH synthesis significantly increased inosine, hypoxanthine, xanthine and uric acid levels in both regions of young rats, compared with the manganese-treated group. These results suggest that an impairment in the neuronal antioxidant system renders young rats susceptible to manganese-induced energetic impairment, and further support the hypothesis that an impairment in this system plays a permissive role in the increase of neuronal vulnerability that occurs with aging.

Intracerebroventricular injection of the N-terminal substance P fragment SP 1–7 regulates the expression of the N-methyl- d-aspartate receptor NR1, NR2A and NR2B subunit mRNAs in the rat brain

Studies have implicated substance P (SP) in the regulation of affective behaviour, memory function, pain influx, stress and opioid reward. All these dimensions are known to involve glutamate transmission mediated through the N-methyl- D-aspartate (NMDA) receptor. The SP N-terminal fragment SP 1–7 is shown to share some but oppose other effects of the parent compound. We have examined the effect of intracerebroventricular injections of SP 1–7 on the expression of the NMDA receptor subunits NR1, NR2A and NR2B mRNAs in the spinal cord and in discrete areas of the male rat brain. The results indicated that the heptapeptide induced a dose-dependent upregulation of the NR2A transcript in hippocampus, periaqueductal grey and ventral tegmental area, already within a few hours. The level of the NR2B mRNA was increased in hippocampus and nucleus accumbens. The expression of the transcript of the NR1 was enhanced in hippocampus and nucleus accumbens but attenuated in spinal cord. The observed effects of the SP 1–7 fragment are in agreement with what could be expected from the known effects of the heptapeptide on various behaviours involving glutamate transmission.

Differential effects of haloperidol on phencyclidine-induced reduction in substance P contents in rat brain regions

We investigated the effects of a schizophrenomimetic drug, phencyclidine (PCP), on substance P (SP) contents in the discrete rat brain areas using an enzyme-immunoassay for SP. The acute intraperitoneal (i.p.) administration of PCP (10 mg/kg), which is a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) type glutamate receptor and a dopamine uptake inhibitor, reduced the concentration of the peptide in the prefrontal cortex, limbic forebrain, striatum, and substantia nigra, but not in the ventral tegmental area, at 60 or 120 min postinjection. A selective noncompetitive NMDA antagonist, dizocilpine hydrogen maleate ((+)-MK-801) (1 mg/kg, i.p.), also caused a decrease in the SP content in the prefrontal cortex and limbic forebrain but failed to alter the content in the other areas studied 30 min thereafter. Dopamine agonists, methamphetamine (4.8 mg/kg, i.p.) and apomorphine (4.4 mg/kg, i.p.), diminished the SP contents in the striatum and substantia nigra 60 min after their injection without effects in the prefrontal cortex, limbic forebrain, and ventral tegmental area. Furthermore, pretreatment with haloperidol (1 mg/kg, i.p.), a D2 preferable dopamine receptor antagonist and a typical antipsychotic, blocked the ability of PCP to decrease the SP concentrations in the substantia nigra but not in the prefrontal cortex. PCP, therefore, might diminish the SP levels by NMDA receptor-mediated and dopamine-independent mechanisms in the prefrontal cortex and limbic forebrain, but by NMDA receptor-independent and dopamine-dependent mechanisms in the striatum and substantia nigra. The haloperidol-insensitive reduction of the frontal SP could be involved in certain neuroleptic-resistant symptoms of PCP-treated animals, PCP psychosis, or schizophrenia. Synapse 35:292–299, 2000. © 2000 Wiley-Liss, Inc.

Differential effects of haloperidol on phencyclidine-induced reduction in substance P contents in rat brain regions.

We investigated the effects of a schizophrenomimetic drug, phencyclidine (PCP), on substance P (SP) contents in the discrete rat brain areas using an enzyme-immunoassay for SP. The acute intraperitoneal (i.p.) administration of PCP (10 mg/kg), which is a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) type glutamate receptor and a dopamine uptake inhibitor, reduced the concentration of the peptide in the prefrontal cortex, limbic forebrain, striatum, and substantia nigra, but not in the ventral tegmental area, at 60 or 120 min postinjection. A selective noncompetitive NMDA antagonist, dizocilpine hydrogen maleate ((+)-MK-801) (1 mg/kg, i.p.), also caused a decrease in the SP content in the prefrontal cortex and limbic forebrain but failed to alter the content in the other areas studied 30 min thereafter. Dopamine agonists, methamphetamine (4.8 mg/kg, i.p.) and apomorphine (4.4 mg/kg, i.p.), diminished the SP contents in the striatum and substantia nigra 60 min after their injection without effects in the prefrontal cortex, limbic forebrain, and ventral tegmental area. Furthermore, pretreatment with haloperidol (1 mg/kg, i.p.), a D2 preferable dopamine receptor antagonist and a typical antipsychotic, blocked the ability of PCP to decrease the SP concentrations in the substantia nigra but not in the prefrontal cortex. PCP, therefore, might diminish the SP levels by NMDA receptor-mediated and dopamine-independent mechanisms in the prefrontal cortex and limbic forebrain, but by NMDA receptor-independent and dopamine-dependent mechanisms in the striatum and substantia nigra. The haloperidol-insensitive reduction of the frontal SP could be involved in certain neuroleptic-resistant symptoms of PCP-treated animals, PCP psychosis, or schizophrenia.

Purification of serine racemase: biosynthesis of the neuromodulator D-serine.

High levels of D-serine occur in mammalian brain, where it appears to be an endogenous ligand of the glycine site of N-methyl-D-aspartate receptors. In glial cultures of rat cerebral cortex, D-serine is enriched in type II astrocytes and is released upon stimulation with agonists of non-N-methyl-D-aspartate glutamate receptors. The high levels of D-serine in discrete areas of rat brain imply the existence of a biosynthetic pathway. We have purified from rat brain a soluble enzyme that catalyzes the direct racemization of L-serine to D-serine. Purified serine racemase has a molecular mass of 37 kDa and requires pyridoxal 5'-phosphate for its activity. The enzyme is highly selective toward L-serine, failing to racemize any other amino acid tested. Properties such as pH optimum, Km values, and the requirement for pyridoxal phosphate resemble those of bacterial racemases, suggesting that the biosynthetic pathway for D-amino acids is conserved from bacteria to mammalian brain.

Effects of Lithium on cAMP-Dependent Protein Kinase in Rat Brain

We have investigated the effects of lithium treatment on cAMP-dependent protein kinase in discrete brain areas of rat by using photoaffinity labeling as well as western blotting. Lithium administered for 5 weeks resulted in a significant increase of the cAMP binding to the 52 kDa cAMP-receptor in the soluble, but not in the particulate, fractions of both hippocampus and frontal cortex. Moreover, immunoblotting experiments revealed that chronic lithium treatment significantly increased the immunoreactivity against the regulatory and the catalytic subunits of the cAMP-dependent protein kinase in the soluble fraction of both brain areas. In contrast, no appreciable effect was observed in the particulate fractions. Short-term lithium treatment induced a significant increase in the immunolabeling of the catalytic subunits in the soluble fraction of both areas; whereas, the regulatory subunits and the actin were unchanged. In the particulate fractions, short-term lithium treatment did not elicit any substantial modification. Taken together, the results of the present study add to the growing evidence indicating that components of the cAMP signalling could play a crucial role in the biochemical action of lithium.