Evidence for the contribution of CCKB receptor mechanisms to individual differences in amphetamine-induced locomotion

Recent evidence shows that rats exhibit individual differences in their locomotor response to amphetamine (AMP). Moreover, evidence has accumulated showing that high-AMP responders exhibit more mesolimbic dopaminergic (DAergic) activation in response to AMP treatment than low-AMP responders. Cholecystokinin (CCK) is a peptide that is colocalised with mesolimbic DA and exerts complex modulatory actions on DA function. Two CCK receptor subtypes have been identified and selective antagonists have been developed. To examine the possible contribution of endogenous CCK mechanisms to individual differences in responsivity to AMP treatment, male Wistar rats were divided into low- and high-AMP responders based on a median split of their locomotor response to AMP and the effects of the selective CCK antagonists L365-260 (CCKB; 0.01, 0.1, 0.5 mg/kg; n = 16) and devazepide (CCKA; 0.001, 0.01, 0.1 mg/kg; n = 23) were determined. Results showed that L365-260 (0.1 mg/kg) potentiated AMP-induced hyperactivity in low-AMP responders but did not affect AMP-induced hyperactivity in high-AMP responders. Devazepide was without effect in both groups of animals. This pattern of results suggests that CCKB, but not CCKA, receptor mechanisms contribute to interindividual variation in responsivity to AMP.

Low doses of the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH DPAT) increase ethanol intake

Previous work has reported that the 5-hydroxytryptamine (5-HT)1A agonist, 8-hydroxy 2-(di-n-propylamino)tetralin (8-OH DPAT), reduces ethanol intake by rats. However, as 8-OH DPAT reduces 5-HT neurotransmission, these findings are inconsistent with the proposed inhibitory role of central 5-HT neurons on ethanol intake. We examined the effect of 8-OH DPAT on ethanol, water and food intake in rats maintained on a limited access schedule using a lower dose range (6-250 micrograms/kg) and by assessing concomitant changes in behaviour. Low doses of 8-OH DPAT enhanced ethanol intake even when food and water were offered as alternatives. Suppression in ethanol intake was observed at higher doses where elements of the 5-HT syndrome were apparent. Similar observations were made in both fluid and non-fluid deprived water drinking rats, suggesting the latter effect is non-selective. Therefore 8-OH DPAT may both increase or decrease ethanol consumption in the rat depending on the dose used.

Influence of 5-HT3 receptor antagonists and the indirect 5-HT agonist, dexfenfluramine, on heroin self-administration in rats

The purpose of the present study was to examine the effects of the 5-HT3 antagonists ondansetron and MDL72222, and the 5-HT releaser and reuptake inhibitor dexfenfluramine, on intravenous heroin self-administration by Wistar rats. Using separate squads of animals, two separate schedules of heroin reinforcement were used; a relatively low dose (0.03 mg/kg per infusion) made available under a FR5 schedule for 1 h each day, and a moderate heroin dose (0.1 mg/kg per infusion) available under a FR1 schedule for 2 h each day. Following the acquisition of stable levels of responding across days, both naloxone pretreatment (0.25 mg/kg SC) and halving the heroin infusion dose produced increases in operant responding for heroin at each concentration. Neither ondansetron (0.01-1 mg/kg SC) nor MDL72222 (0.1-3 mg/kg SC) pretreatment influenced heroin self-administration. Chronic treatment (5 day) of ondansetron (0.01-0.1 mg/kg) was similarly ineffective. However, dexfenfluramine (0.5-2.5 mg/kg IP) consistently reduced heroin self-administration at doses producing only modest decreases in food responding. These findings are in contrast to place conditioning studies, which show that 5-HT3 antagonists but not indirect 5-HT agonists block a morphine-induced place preference. Reasons for such discrepancies remain to be determined.

Antagonist-precipitated opioid withdrawal in rats: evidence for dissociations between physical and motivational signs

In rats made opioid dependent by the implantation of a single morphine 75 mg base pellet, an attempt was made to determine whether any correlational existed between physical and motivational withdrawal signs by adjusting the dose of naloxone used to precipitate withdrawal. The models used to study motivational signs were taste (one- and two-bottle) conditioning and operant responding for food under an FR15 schedule of reinforcement. Naloxone at doses of 0.01 mg/kg and above produced both a conditioned taste aversion (two-bottle test only) and reduced food responding in morphine pellet, but not placebo pellet, implanted animals. No physical withdrawal signs, e.g., wet dog shakes, diarrhoea, were noted until naloxone doses of 0.05 mg/kg and above were used. It is concluded that the difference in naloxone doses required to elicit physical and motivational withdrawal components provides further support for their dissociation.

The CCKA receptor antagonist devazepide does not modify opioid self-administration or drug discrimination: comparison with the dopamine antagonist haloperidol

We previously reported that the selective cholecystokininA (CCKA) receptor antagonist, devazepide, blocked the acquisition of a morphine conditioned place preference (ref 28). An interpretation of this finding is that devazepide may either affect an opioid discriminative stimulus and/or modify the rewarding properties of opioids. The present study was designed to investigate these issues by determining the effect of equivalent doses of devazepide in a morphine drug discrimination paradigm and a model of heroin self-administration. In each case, devazepide (0.001-1 mg/kg) was ineffective, i.e there was no antagonism of a morphine discriminative cue, and in a separate group of rats trained to self-administer heroin (0.03 mg/kg/infusion, FR5 schedule, 1h per day), devazepide did not alter the pattern of heroin responding. Because of evidence implicating an interaction between accumbens CCK and dopamine (DA) systems and evidence suggesting an apparent differential involvement of DA in opioid place conditioning, self-administration and drug discrimination behaviour, the effect of the DA antagonist haloperidol was examined in the latter two paradigms. In each test, haloperidol produced an effect inconsistent with a direct DAergic involvement. In a final study the CCKB antagonist L365-260 was also found not to affect an opioid discriminative cue. The present results therefore cast doubt on the potential utility of selective CCKA antagonists as treatments for opioid abuse, and further suggest that CCKB antagonists may not potentiate the subjective effects of opioids, an important finding considering that such drugs have been proposed as adjuncts to opioid therapy for the treatment of pain relief.

Effect of dexfenfluramine on saccharin drinking: behavioural and pharmacological studies

We have previously reported that the 5-hydroxytryptamine (5-HT) releaser/reuptake blocker dexfenfluramine suppresses voluntary ethanol intake. To further analyse the generality of these findings, in the present study we examined the effect of equivalent doses of dexfenfluramine (0.5-2.5 mg/kg) on the intake of another preferred fluid, saccharin. Saccharin was made available for 2 h daily across a wide concentration range chosen to promote varying degrees of intake. Following stable levels of intake, the behaviour of vehicle-pretreated rats was assessed immediately prior to (anticipatory/preparatory phase) and during (consumatory phase) saccharin access. These behaviours were compared and contrasted with those produced following dexfenfluramine pretreatment at the optimally preferred saccharin concentration (0.2%). In a preliminary study the effects of various 5-HT antagonists were also examined against the dexfenfluramine response. The present results suggest that dexfenfluramine produced a dose-related suppression of saccharin intake at doses similar to those which reduced ethanol intake. However, the magnitude of this suppression was similar across each saccharin concentration. Behavioural analysis indicated that the profile of the dexfenfluramine (0.5- and 1-mg/kg doses only) suppression of the 0.2% solution was similar to that observed in vehicle-pretreated rats presented with saccharin solutions of lesser palatability to this concentration. Pharmacological studies indicated a 5-HT1 (non-5-HT1C) receptor involvement in the dexfenfluramine response. These studies imply that at certain doses dexfenfluramine may produce a subtle alteration in the motivation to consume a preferred fluid.

Differences between three rat strains in sensitivity to prepulse inhibition of an acoustic startle response: influence of apomorphine and phencyclidine pretreatment

In the present study we have examined the effect of varying three prepulse parameters (prepulse intensity, prepulse duration, prepulse-pulse interval) on the level of prepulse inhibition (PPI) in Lister hooded, Wistar and Sprague-Dawley rats. The results indicate that each strain showed subtle differences in sensitivity to the prepulse. For instance, Sprague-Dawley and Lister hooded rats showed PPI to prepulses of lower saliency compared to Wistar rats. Optimal prepulse parameters were selected for each strain to examine the effects of apomorphine and phencyclidine on PPI. Further inter-strain differences were noted; apomorphine (0.1-1 mg/kg) increased startle amplitude in Lister hooded and Sprague-Dawley, but not Wistar rats. PPI was attenuated in each strain by apomorphine pretreatment. In a final series of experiments, phencyclidine disrupted PPI in each strain, although with greater potency in the Lister hooded rats. A marked behavioural syndrome was seen at phencyclidine doses that disrupted PPI. It is concluded that rat strain and prepulse parameters are important variables in studying drug effects on PPI.

Stimulation of central 5-HT1D receptors causes hypothermia in the guinea-pig

The 5-HT(1) receptor agonist GR46611 (3-30 mg/kg s.c.) caused a dose-related decrease in rectal temperature in the adult guinea-pig. A lower dose (20 μg) administered directly into the lateral cerebral ventricle also caused a hypothermic response, suggesting that this effect is centrally mediated. GR46611-induced (10 mg/kg s.c.) hypothermia was not attenuated by WAY100135 (3-10 mg/kg s.c.), ritanserin (0.3-1 mg/kg s.c.), spiperone (0.1-0.3 mg/kg s.c.) and ondansetron (0.1-1 mg/kg s.c.), suggesting that 5-HT(1A), 5-HT(2A), 5-HT( 2C) and 5-HT(3) receptors are unlikely to be involved in this response. In contrast, the poorly selective 5-HT receptor antagonist, metergoline (1-10 mg/kg s.c.), and the potent 5-HT(1D) receptor antagonist, GR127935 (0.1-1 mg/kg p.o.), antagonized the effects of GR46611. The present data suggest that antagonism of GR46611-induced hypothermia may be useful for assessing the potency and duration of action of centrally-acting 5-HT( 1D) receptor antagonists in the guinea-pig.

Preliminary findings with the indirect 5-HT agonist dexfenfluramine on heroin discrimination and self-administration in rats

In the present study, the effect of the 5-HT releaser/reuptake inhibitor dexfenfluramine in heroin self-administration and morphine (3 mg/kg) drug discrimination paradigms was examined. Dexfenfluramine (1 mg/kg) reduced heroin self-administration (heroin dose 0.03 mg/kg/infusion; FR5 schedule; 1-h session/day). This effect was antagonised by the 5-HT1/2 receptor antagonist metergoline (1 mg/kg). In the drug discrimination model, dexfenfluramine (0.5-2.5 mg/kg) produced no significant generalisation to a morphine cue, and also failed to modify the generalization curve to heroin. Dexfenfluramine (1 mg/kg) produced a slight decrement in response rate in the drug discrimination model and this effect was potentiated by heroin. The mechanism(s) by which dexfenfluramine reduces heroin self-administration remain to be determined, however substitution for heroin would seem unlikely. Furthermore, this effect of dexfenfluramine is probably mediated by either 5-HT1 or 5-HT2 receptors.

Behavioral effects of the 5-hydroxytryptamine3 receptor agonists 1-phenylbiguanide and m-chlorophenylbiguanide in rats

We have investigated the behavioral effect of the 5-hydroxytryptamine3 (5-HT3) receptor agonists 1-phenylbiguanide (PBG) and m-chlorophenylbiguanide (mCPBG) in rats after i.p. and i.c.v. injection. It was hoped that this approach may provide an alternative means of studying the role of 5-HT3 receptors on animal behavior, for the majority of related studies have used antagonists at this subtype. Both PBG (3-60 mg/kg, i.p.) and mCPBG (1-30 mg/kg i.p.) produced abdominal constrictions, writhing and salivation in some, but not all, rats. The most marked behaviors were seen after mCPBG (30 mg/kg, i.p.), where paw shakes and chin rubbing was also recorded. Almost certainly as a consequence of these behaviors, PBG (3-30 mg/kg, i.p.) and mCPBG (0.3-10 mg/kg, i.p.) produced a conditioned place aversion. Pretreatment with the 5-HT3 antagonists ondansetron (0.01-0.1 mg/kg, s.c.), ICS205-930 and quaternized ICS205-930 (both 0.1 mg/kg, i.p.) blocked the PBG (30 mg/kg, i.p.)-induced place aversion. PBG (30 mg/kg, i.p.) and mCPBG (10 mg/kg, i.p.) also produced a conditioned taste aversion. The central administration of PBG (1-30 micrograms, i.c.v.) and mCPBG (0.1-10 micrograms, i.c.v.) enhanced locomotor- and gnawing-related behavior, although the effects with PBG seemed more consistent. These PBG (10 micrograms, i.c.v.)-induced behaviors were completely blocked by haloperidol (0.01-0.1 mg/kg, s.c.). In contrast, ondansetron (0.0001-1 mg/kg, s.c.) and ICS205-930 (0.1 mg/kg, i.p.) produced only a mild and inconsistent attenuation of these responses. PBG (1-30 micrograms, i.c.v.) failed to produce any place conditioning (i.e., neither a preference nor aversion was found). It is concluded that activation of peripheral 5-HT3 receptors leads to aversive-type behaviors, which may be related to gastrointestinal discomfort or malaise. In contrast, central injection of PBG and mCPBG produced a range of dopamine-related behaviors; however, a 5-HT3 receptor involvement is unclear. Because both PBG and mCPBG have dopamine releasing properties, the use of 5-HT3 agonists lacking such effects and/or the use of more discrete microinjection studies are needed to more clearly elucidate the roles of 5-HT3 receptors in the central nervous system.

Effect of 5-HT3 receptor antagonists on the discriminative stimulus properties of morphine in rats

5-HT3 receptor antagonists, e.g. MDL72222, ondansetron and ICS205-930, have been previously reported to block a morphine (1.5 mg/kg)-induced conditioned place preference in rats. This finding suggests that these drugs may modify the morphine discriminative stimulus which underlies place conditioning. To study this further we have examined the effects of MDL72222, ondansetron and ICS205-930 against a morphine discriminative stimulus using a two-choice, food reinforced, operant paradigm. In an attempt to provide consistency with previous place conditioning studies, a morphine training dose of 1.5 mg/kg was used in addition to a higher 3 mg/kg dose which was studied in separate animals. Stimulus control of behaviour was attained at both morphine training doses, the characteristics of each being consistent with an effect at the mu opioid receptor. Ondansetron (0.001-1 mg/kg), MDL72222 (0.1-3 mg/kg), and ICS205-930 (0.001-1 mg/kg) all failed to consistently antagonise the morphine cue at both training doses, although a mild attenuation was seen in the 1.5 mg/kg group following pretreatment with an intermediate dose of ondansetron and ICS205-930 (both 0.01 mg/kg). The present results therefore suggest hat 5-HT3 antagonists do not block a morphine discriminative state, at least in rats.

Conditioned place preference induced by microinjection of 8-OH-DPAT into the dorsal or median raphe nucleus

Experiments were conducted to examine the ability of the selective 5-hydroxytryptamine (5-HT)1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) to induce a conditioned place preference following peripheral injection, and direct microinjection into the dorsal or median raphe nuclei. An unbiased place preference paradigm was used in which control animals showed no preference for either of two compartments differing in terms of colour (white versus black), floor texture (rough versus smooth) and olfactory cues (no odour versus acetic acid odour). Drug treatments were paired with access to either of the two compartments, and saline injections were paired with access to the other compartment. Rats experiencing a low dose of 8-OH-DPAT (125 micrograms/kg) with a specific compartment demonstrated a significant preference for that compartment over one paired with saline injections. The magnitude of this effect was similar to that observed in rats treated with 1.5 mg/kg d-amphetamine. A significant place preference was found in animals receiving injections of 8-OH-DPAT in the dorsal raphe at 0.1 microgram but not 1 microgram. Animals also displayed a preference for the compartment paired with 1 microgram 8-OH-DPAT injected into the median raphe; lower doses were not effective. These results indicate that the mechanism by which 8-OH-DPAT induces a conditioned place preference involves activation of raphe somatodendritic 5-HT1A autoreceptors, leading to a reduction in 5-HT neurotransmission. This demonstration of the rewarding properties of 8-OH-DPAT, together with previous results showing increased feeding and sexual behaviour following 8-OH-DPAT treatment, strongly suggests an important role for brain 5-HT systems in reward and reinforcement processes.

Regulated splicing of the amyloid precursor protein gene during postnatal development of the rat basal forebrain

The expression of the amyloid precursor protein (APP) gene has been examined in the basal forebrain of rats from birth to adulthood. Levels of total APP mRNA are highest at birth and at postnatal day 15 (P15). The most abundant transcript in rat brain is APP-695, whose expression has previously been found to be largely restricted to the central nervous system. Comparison of the developmental profiles of APP-695 mRNA with that of Kunitz-protease inhibitor (KPI)-containing APP mRNA shows that the greatest difference in expression occurs at P15, when APP-695 message levels are over 6-fold higher than KPI-containing APP mRNA (APP-751, APP-770). This is the largest difference in the APP-695/KPI-APP ratio observed during postnatal development and coincides with the period of maximal neurotrophic responsiveness in the basal forebrain. These results suggest that the APP gene is alternatively spliced during postnatal development and that regulated expression of APP-695 may be influenced by neurotrophic factors in vivo.

Distribution and expression of SNAP-25 immunoreactivity in rat brain, rat PC-12 cells and human SMS-KCNR neuroblastoma cells

Immunocytochemical, immunoblotting and in situ hybridization studies were used to map the distribution of SNAP-25 protein and mRNA in the rodent nervous system. These experiments demonstrated that subsets of neurons expressed SNAP-25, and that several patterns of expression emerged: SNAP-25 expression in caudate nucleus was initially concentrated in axons, which subsequently was localized in presynaptic regions of these axons. Other regions, typified by neocortex, showed developmental increases and persistent adult neuronal immunoreactivity for SNAP-25. Finally, olfactory bulb contained neurons which initially expressed SNAP-25, but lost expression during maturation. Additional studies in cultured human and rat cell lines derived from neural crest suggested that SNAP-25 is expressed in such lines, but not in glial or fibroblast lines. Differentiation of rat PC-12 cells with nerve growth factor failed to alter steady-state levels of SNAP-25 protein; similar responses were seen in human SMS-KCNR neuroblastoma cells differentiated using retinoic acid. The presence of SNAP-25 in presynaptic regions of numerous neuronal subsets and in neural crest cell lines suggests that this protein subserves an important function in neuronal tissues.

Morphine place conditioning is differentially affected by CCKA and CCKB receptor antagonists

In the present study we have examined the interaction between the selective cholecystokinin (CCK)A and CCKB receptor antagonists, devazepide and L365-260 on morphine conditioned place preference (CPP). Using an unbiased procedure, morphine (1.5 mg/kg) produced a reliable CPP which was observed irrespective of the conditioning compartment type. Pretreatment with devazepide (0.001-0.01 mg/kg s.c.) produced a dose related attenuation of this response. At higher doses (0.1-1 mg/kg) this antagonism became variable and dependent on the training compartment with blockade only observed when conditioning was to the white/rough textured environment. This profile has also been reported for the serotonin (5-HT)3 receptor antagonist ondansetron. The CCKB antagonist L365-260 (0.000001-0.01 mg/kg) failed to antagonize the morphine CPP, if anything a mild potentiation was observed. To study this further we examined the interaction between L365-260 (0.01 mg/kg) and a subthreshold dose of morphine (0.3 mg/kg). At these doses neither drug elicited CPP, however when co-administered a significant CPP was recorded. Finally, L365-260 at 1 mg/kg induced a mild but significant CPP when administered alone. These results suggest a differential role of CCK receptor subtypes on reward-related behaviour and complement previous studies suggesting bimodal effects of CCK systems on mesolimbic dopamine function.

5-HT and alcohol abuse

Recent experimental data, both in animals and the clinic, suggest that drugs selectively interacting with the 5-HT system may reduce alcohol intake. Although the precise mechanisms underlying these drug effects are unknown, it seems that there are at least two pharmacological strategies available, described in this review by Edward Sellers and colleagues. The first is enhancement of 5-HT neuronal activity using compounds that will release 5-HT, block 5-HT reuptake, or act as selective 5-HT receptor agonists. A second approach involves selective 5-HT3 receptor antagonists. If the initial research findings with these drugs are confirmed and extended, they may present useful therapies for the treatment of alcohol abuse, especially if used in conjunction with psychosocial therapy.

Effect of the 5-HT3 receptor antagonists, MDL72222 and ondansetron on morphine place conditioning

The purpose of the present study was to reassess the original findings of Carboni et al. (1988) who suggested that 5-HT3 receptor antagonists may block morphine-induced place conditioning in rats. These workers used a biased protocol with treatments allocated to compartments based on initial preference. In the present study we have adopted an unbiased approach with treatments randomly assigned to conditioning compartment in a counter-balanced fashion. Thus treatments were equally paired between distinct environmental cues. Using this protocol, morphine produced a dose-related place preference (0.3-3 mg/kg SC). Thirty-minute pretreatment with the selective 5-HT3 antagonists, MDL72222 (1 mg/kg SC) and ondansetron (0.01 mg/kg SC) before morphine (1.5 mg/kg SC), significantly antagonized the place conditioning to this treatment. However, with higher doses of ondansetron (0.1-1 mg/kg SC), the antagonism of morphine-induced place preference became variable and dependent on the conditioning compartment. This was probably a reflection of the fact that ondansetron when administered alone also appeared to produce an environmentally dependent place conditioning at these doses. Therefore it is concluded that at certain doses, 5-HT3 receptor antagonists may antagonize morphine place conditioning in a manner consistent with a blockade of the appetitive effects of this drug. However, at higher doses, at least with ondansetron, this antagonism became non-specific and dependent on the training environment. It is suggested that other animal models of opioid reinforcement (e.g., self-administration) are now needed to validate the hypothesis that 5-HT3 receptor antagonists may modify opioid reward.

The NMDA antagonist dizocilpine (MK801) attenuates motivational as well as somatic aspects of naloxone precipitated opioid withdrawal

The non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine has recently been reported to antagonize certain overt withdrawal signs in morphine dependent rats. The purpose of the present study was to reassess this response and examine the effect of this drug in a model presumably reflective of the motivational impact of withdrawal using the place conditioning technique. Rats were made opiate dependent by the subcutaneous implantation of a 75 mg morphine pellet. Three-4 days later withdrawal was precipitated by naloxone 0.5 mg/kg. Dizocilpine (0.1-0.5 mg/kg) attenuated many of the subsequent behaviours elicited by naloxone, notably diarrhoea, mouth movements, paw shakes and ptosis. In a separate group of morphine dependent rats, naloxone (0.05 mg/kg) precipitated withdrawal produced a clear place aversion. This place aversion was blocked by dizocilpine (0.02-0.1 mg/kg) pre-treatment prior to conditioning. Therefore dizocilpine may modify both motivational and somatic aspects of opioid withdrawal.

Effect of drugs influencing 5-HT function on ethanol drinking and feeding behaviour in rats: studies using a drinkometer system

In the present study, we have investigated how various 5-HT agonists (m-chlorophenylpiperazine (mCPP) (0.1-1 mg/kg), 8-hydroxy 2-(di-N-propylamino) tetralin (8-OH DPAT) (0.125-2 mg/kg) and 5-HT (0.5-2 mg/kg)), the 5-HT uptake blocker sertraline (1-10 mg/kg), and the 5-HT uptake blocker and releaser dexfenfluramine (0.5-2.5 mg/kg), affect ethanol intake in a continual access paradigm using Wistar rats. By means of a drinkometer system the effect of each drug on microdrinking parameters (e.g., drink latency, number, and duration of drinking bouts) was assessed. The effect of various 5-HT antagonists (metergoline, ritanserin, ondansetron, and xylamidine) against the dexfenfluramine-induced suppression was studied. Furthermore, threshold doses for the anorectic and the suppressant effects of mCPP, sertraline and dexfenfluramine on ethanol intake were identified. From these studies, it seemed that similar mechanisms may be responsible for the suppressant effects of the various 5-HT agonists studied (direct and indirect) on ethanol and food intake. The 5-HT3 receptor antagonist, ondansetron, also reduced ethanol (but not food) intake. However, the profile of this effect may suggest an alternative means by which 5-HT3 receptors regulate ethanol intake in the rat by comparison to the various 5-HT agonists studied.

In situ hybridization of calcium/calmodulin dependent protein kinase II and tau mRNAs; species differences and relative preservation in Alzheimer's disease

Abnormal phosphorylation of the microtubule associated protein tau component of neurofibrillary tangles (NFTs) in Alzheimer's disease (AD) may result from alterations in protein kinase expression. Calcium/calmodulin dependent protein kinase II (CaM kinase II) has been shown to phosphorylate tau in vitro in such a way to decrease its electrophoretic mobility. A68, apparently a modified form of tau in AD brain, also shows abnormal phosphorylation and slower mobility than tau. To further examine the role of CaM kinase II in AD, in situ hybridization studies were performed on tissues from rat, monkey and human to examine and compare the patterns of CaM kinase II mRNA expression in different brain regions. The most notable differences among the three species were observed in dendrites in layer I of isocortex, in the molecular layer of the dentate gyrus and stratum radiatum and stratum lacunosum-moleculare in hippocampus, where hybridization was detected in rat, but not in monkey or human brain. In addition, comparisons between tau and CaM kinase II mRNA expression were made in tissue from normal aged adults and AD patients, especially in areas prone to NFT formation. CaM kinase II and tau mRNAs were co-expressed in many neuronal populations, both those which are prone to NFT formation as well as those which are rarely affected by AD changes. No major differences in the relative abundance of either CaM kinase II or tau mRNA within particular neuronal populations was noted between normal aged and AD brain. Diminished hybridization was associated with serve neuronal pathology and cell loss.

Effect of 5-HT1A receptor agonists in two models of anxiety after dorsal raphe injection

The purpose of the present study was two-fold. Firstly, to present a more comprehensive analysis of the disinhibitory effects of 5-HT1A receptor agonists after discrete dorsal raphe (DRN) injections (Higgins et al. 1988). Secondly, the effects of the 5-HT1B receptor agonist CGS12066B and the 5-HT1B/1C agonist mCPP were examined following injection into this nucleus. The increases in social interaction (SI) induced by intra-raphe injections of 8-OH DPAT (0.02-1 micrograms), buspirone (0.04-0.2 microgram), ipsapirone (0.2 microgram) and gepirone (0.2-1 micrograms) under a high light unfamiliar paradigm (HLU) were typically due to increased bout frequency, duration and a higher incidence of sniff, follow, allogroom behaviour. These increases were qualitatively similar to those seen in control animals tested under low light/familiar (LLF) conditions, thus supporting the belief that the drug-induced increases in SI reflected decreases in anxiety. Furthermore, at doses effective under the HLU condition, 8-OH DPAT, buspirone and gepirone failed to modify SI under conditions of minimal suppression (LLF paradigm). At doses which significantly increased punished responding in a water-lick conflict test 8-OH DPAT, ipsapirone and gepirone tended to also increase unpunished rates of drinking. However, in drug untreated rats, prior habituation to the test apparatus also increased unpunished drinking, suggesting some neophobia-induced suppression. At a comparatively high dose, the 5-HT1B agonist CGS12066B (2.5 micrograms), but not the putative 5-HT1B/1C agonist mCPP (0.5-12.5 micrograms), increased SI under the HLU condition.(ABSTRACT TRUNCATED AT 250 WORDS)