Anabolic steroids alter the physiological activity of aggression circuits in the lateral anterior hypothalamus.

Syrian hamsters exposed to anabolic/androgenic steroids (AAS) during adolescence consistently show increased aggressive behavior across studies. Although the behavioral and anatomical profiles of AAS-induced alterations have been well characterized, there is a lack of data describing physiological changes that accompany these alterations. For instance, behavioral pharmacology and neuroanatomical studies show that AAS-induced changes in the vasopressin (AVP) neural system within the latero-anterior hypothalamus (LAH) interact with the serotonin (5HT) and dopamine (DA) systems to modulate aggression. To characterize the electrophysiological profile of the AAS aggression circuit, we recorded LAH neurons in adolescent male hamsters in vivo and microiontophoretically applied agonists and antagonists of aggressive behavior. The interspike interval (ISI) of neurons from AAS-treated animals correlated positively with aggressive behaviors, and adolescent AAS exposure altered parameters of activity in regular firing neurons while also changing the proportion of neuron types (i.e., bursting, regular, irregular). AAS-treated animals had more responsive neurons that were excited by AVP application, while cells from control animals showed the opposite effect and were predominantly inhibited by AVP. Both DA D2 antagonists and 5HT increased the firing frequency of AVP-responsive cells from AAS animals and dual application of AVP and D2 antagonists doubled the excitatory effect of AVP or D2 antagonist administration alone. These data suggest that multiple DA circuits in the LAH modulate AAS-induced aggressive responding. More broadly, these data show that multiple neurochemical interactions at the neurophysiological level are altered by adolescent AAS exposure.

Glutamate-vasopressin interactions and the neurobiology of anabolic steroid-induced offensive aggression.

In the latero-anterior hypothalamus (LAH) increased glutamate and vasopressin (AVP) activity facilitate anabolic androgenic steroid (AAS)-induced offensive aggression. In addition, adolescent AAS treatment increases the strength of glutamate-mediated connections between the LAH and the brain nucleus of stria terminalis (BNST). The current set of studies used male Syrian hamsters exposed to AAS during adolescence to examine whether increased glutamate-mediated stimulation of the BNST is dependent on LAH-AVP signaling and whether this neural pathway modulates adolescent AAS-induced offensive aggression. In the first set of AAS-treated animals offensive aggression was measured following blockade of glutamate activity within the BNST using NBQX. Then, in a second group of AAS-treated animals aggression levels were examined following simultaneous blockade of LAH-AVP activity using Manning compound and stimulation of BNST glutamate using AMPA. Lastly, the number of AVP fibers in apposition to glutamate cells was examined in AAS and control animals, using double-label immunofluorescence. The results showed that administration of NBQX into the BNST dose-dependently reduced aggressive behavior in AAS-treated animals. Further, the current results replicated previous findings showing that blockade of LAH-AVP significantly reduces aggressive behavior in AAS-treated animals. In these animals stimulation of BNST-AMPA receptors had a linear effect on aggression, where the smallest dose exacerbated the inhibitory effect of the V1a antagonist, the medium dose had no effect and the highest dose recuperated aggression to control levels. Finally when compared with control animals, AAS treatment produced a significant increase in the number of AVP fibers in apposition to LAH-glutamate cells. Overall, these results identify the BNST as a key brain region involved in aggression control and provide strong evidence suggesting that AVPergic-mediated stimulation of BNST-glutamate is a possible mechanism that facilitates aggression expression in adolescent AAS-treated animals.

Anterior hypothalamic vasopressin modulates the aggression-stimulating effects of adolescent cocaine exposure in Syrian hamsters.

Repeated low-dose cocaine treatment (0.5 mg/kg/day) during adolescence induces offensive aggression in male Syrian hamsters (Mesocricetus auratus). This study examines the hypothesis that adolescent cocaine exposure predisposes hamsters to heightened levels of aggressive behavior by increasing the activity of the anterior hypothalamic-vasopressinergic neural system. In a first experiment, adolescent male hamsters were treated with low-dose cocaine and then scored for offensive aggression in the absence or presence of vasopressin receptor antagonists applied directly to the anterior hypothalamus. Adolescent cocaine-treated hamsters displayed highly escalated offensive aggression that could be reversed by blocking the activity of vasopressin receptors within the anterior hypothalamus. In a second set of experiments, adolescent hamsters were administered low-dose cocaine or vehicle, tested for offensive aggression, and then examined for differences in vasopressin innervation patterns and expression levels in the anterior hypothalamus, as well as the basal- and stimulated-release of vasopressin in this same brain region. Aggressive, adolescent cocaine-treated hamsters showed no differences in vasopressin afferent innervation and/or peptide levels in the anterior hypothalamus compared with non-aggressive, saline-treated littermates. Conversely, significant increases in stimulated, but not basal, vasopressin release were detected from the anterior hypothalamus of aggressive, cocaine-treated animals compared with non-aggressive, saline-treated controls. Together, these data suggest that adolescent cocaine exposure increases aggression by increasing stimulated release of vasopressin in the anterior hypothalamus, providing direct evidence for a causal role of anterior hypothalamic-vasopressin activity in adolescent cocaine-induced offensive aggression. A model for how alterations in anterior hypothalamic-vasopressin neural functioning may facilitate the development of the aggressive phenotype in adolescent-cocaine exposed animals is presented.

Behavioural and neuroendocrine adaptations to repeated stress during puberty in male golden hamsters.

In adult animals, the consequences of stress are often severe and long lasting. Repeated subjugation in adult male golden hamsters inhibits aggression and increases submissive and avoidant behaviours. By contrast, subjugation during puberty enhances offensive aggression. The goals of this study were to characterize behavioural and neuroendocrine responses of naïve and repeatedly subjugated juveniles to social defeat and to assess potential recovery from social stress. From the onset of puberty on postnatal day 28 (P28) to mid puberty (P42), animals were either socially subjugated or placed in a clean and empty cage for 20 min daily. The subjugated and control groups were further divided into subgroups and sacrificed under basal conditions or after social defeat on P28, P35 (early puberty), P45 (mid puberty) and P70 (early adulthood). On P35 and P45, repeatedly subjugated juveniles showed a complete inhibition of olfactory investigation (i.e. risk assessment) towards aggressive adults. Repeatedly subjugated also animals had lower postdefeat cortisol levels than controls on P45. Interestingly, basal cortisol levels increased gradually during puberty but did not differ between treatment groups at any point. Repeated subjugation was also associated with increased tyrosine hydroxylase immunoreactivity (ir-TH) within the extended medial amygdala. After a 4-week recovery period, none of these variables differed between subjugated and control groups. In an additional experiment, subjugated adults also had increased ir-TH in the medial extended amygdala, suggesting that these neurones are particularly responsive to social stress. In conclusion, puberty may be a developmental period characterized by behavioural and neuroendocrine plasticity in stress responsiveness. Furthermore, peri-pubertal changes in stress hormones may explain why juvenile hamsters are more resilient to social stress than adults.

Neither ibotenic acid nor volkensin lesions of the nucleus accumbens shell affect the expression of cocaine sensitization.

Studies have shown that the nucleus accumbens shell plays an integral role in the expression of psychostimulant-induced behavioural sensitization. Dopaminergic regulation of excitatory amino acid inputs in this region of the brain could be a key factor in the neural influence of this phenomenon. Alterations in the dopaminergic innervation patterns in the shell have been demonstrated in rats that received repeated cocaine injections. Furthermore, lesions of brain regions that send projections to the shell alter psychostimulant-induced locomotion, both acutely and in sensitization paradigms. A previous study from our laboratory demonstrated that lesions of the shell before repeated cocaine treatment decrease the locomotor response to cocaine during the induction phase of behavioural sensitization. To better understand the role of this brain region during the expression phase of behavioural sensitization, the present study examined the effects of two forms of cytotoxic lesions of the shell. Rats received a sensitization-inducing regimen of cocaine (bi-daily injections of 15 mg/kg i.p. for 5 consecutive days). Two days after the last injection, rats demonstrating behavioural sensitization received one of three bilateral microinjections into the shell: (i) 0.5 micro L 0.9% saline; (ii) 2.5 micro g/0.5 micro L ibotenic acid (which lesions the cell bodies at the injection site); or (iii), 0.5 ng/0.2 micro L of volkensin (a retrograde suicide transport lectin). Upon challenge with cocaine (15 mg/kg) 12 days after surgery, neither ibotenic acid- nor volkensin-lesioned rats showed any difference in their locomotor response compared with sham controls. These data indicate that bilateral shell lesions do not affect the long-term expression of behavioural sensitization in cocaine-sensitized rats.

The dorsomedial shell of the nucleus accumbens facilitates cocaine-induced locomotor activity during the induction of behavioral sensitization.

The mesolimbic dopamine system has been intensely studied as the neural circuit mediating the locomotor response to psychostimulants and behavioral sensitization. In particular, the dopaminergic innervation of the nucleus accumbens has been implicated as a site responsible for the manifestations of behavioral sensitization. Previous studies have demonstrated an augmented release of dopamine in the nucleus accumbens upon a systemic injection of a psychostimulant. In addition, alterations in the dopaminergic innervation patterns in this brain region have been demonstrated in animals that received repeated injections of cocaine. Furthermore, lesions of projection sites that have terminations in the nucleus accumbens have demonstrated alterations in psychostimulant induced locomotion, both acutely, as well as in sensitization paradigms. Since dopamine in the nucleus accumbens is believed to regulate several excitatory amino acid inputs, the present study examined the effects of a localized electrolytic lesion in the dorsomedial shell of the nucleus accumbens in order to better understand the functional role this brain region has in behavioral sensitization. All animals received bi-daily injections of 15 mg/kg i.p. cocaine. Only those demonstrating behavioral sensitization after a subsequent challenge dose were included in the analysis. Following acute exposure to cocaine, lesioned animals did not show any difference in their locomotor response when compared with sham controls. However, after repeated exposure to cocaine, sensitized animals demonstrated a significant attenuation in locomotor behavior when compared with sensitized sham controls. This decrease in horizontal locomotion persisted 2 days into withdrawal, yet dissipated in the sensitized animals that were challenged 2 weeks following their last injection. The data presented here demonstrate that the dorsomedial shell of the nucleus accumbens plays an important role in the initial stages of behavioral sensitization to cocaine.

Repeated cocaine treatment activates flank marking in adolescent female hamsters.

Cocaine abuse during adolescence represents a significant health risk due to the potential for both acute and long-term negative physical and psychological sequelae, including increased aggressive behavior. This study examined the effect of adolescent cocaine treatment on flank marking (i.e., a stereotypic motor behavior that is part of the response pattern of offensive aggression) in female and male Syrian hamsters (Mesocricetus auratus). Adolescent cocaine treatment activated flank marking in female hamsters when animals were measured upon return to their home cage immediately following drug treatment. Sex differences were observed in cocaine-induced flank marking, as males failed to flank mark when returned to the home cage. In females, the behavioral response was most marked on Day 11 of cocaine treatment in all doses tested. Yet, animals treated with low-dose cocaine (0.5 mg/kg/day) showed the most significant increase in flank marking on and from Day 11 forward as compared to medium- and high-dose cocaine-treated animals and controls. In addition, the response of cocaine-treated animals was vigorous and nearly immediate, as >75% of the flank marks scored were performed within the first 2 min of the behavioral test in >85% of animals examined. Measures of locomotion showed that cocaine had stimulatory effects on motor activity in adolescent female hamsters at all doses tested. Cocaine-treated animals did not differ in body weight gain from controls, suggesting no dramatic physiological effects of adolescent cocaine exposure on body growth at the doses tested.

Chronic low-dose cocaine treatment during adolescence facilitates aggression in hamsters.

Cocaine abuse during adolescence represents a significant health risk because of the potential for both acute and long-term negative physical and psychological sequelae, including increased aggressive behavior. This study examined the effects of chronic adolescent cocaine exposure on aggression in an animal model. It was hypothesized that chronic cocaine exposure during adolescence predisposes animals to heightened levels of aggressive behavior. To test this hypothesis, adolescent male golden hamsters (Mesocricetus auratus) were administered cocaine hydrochloride during their entire adolescent development (Postnatal Days 27-54) and then tested for offensive aggression using the resident-intruder model. Animals treated with low-dose cocaine during adolescence showed significantly elevated measures of offensive aggression (i.e., increased number of bites, attacks, and decreased latencies to bite), whereas measures of social communication, sexual motivation and motor activity remained constant. Cocaine-treated animals did not differ in body weight gain from controls, suggesting no dramatic physiological effects of adolescent cocaine exposure on body growth at the doses tested.

Chronic anabolic-androgenic steroid treatment during adolescence increases anterior hypothalamic vasopressin and aggression in intact hamsters.

The present study examines the hypothesis that exposure to anabolic-androgenic steroids (AAS) during adolescent development predisposes hamsters to heightened levels of aggressive behavior by influencing the anterior hypothalamic-arginine vasopressin (AH-AVP) neural system. To test this, adolescent male hamsters (Mesocricetus auratus) were treated with high doses of AAS, tested for offensive aggression in the absence or presence of AH-AVP receptor antagonists, and then examined for changes in AH-AVP expression and neural organization. AAS exposure during adolescence significantly increased aggression intensity (number of attacks and bites) and initiation (latency to the first bite). Yet, only increases in aggression intensity were inhibited by AH-AVP receptor antagonism. Adolescent AAS-treated hamsters showed significant increases in AH-AVP fiber density and peptide content. However, no alterations in AH-AVP neuronal organization or mRNA expression were found. Together, these data suggest that adolescent AAS exposure increase aggression intensity by altering AH-AVP expression and activity, providing direct evidence for a causal role of AH-AVP expression and function in early onset AAS-stimulated aggression.

Prevalence and patterns of psychotropic and anticonvulsant medication use in children and adolescents referred to residential treatment.

The prevalence and patterns of use of psychiatric and anticonvulsant medications were studied in 83 seriously emotionally disturbed children and adolescents at the time of their admission to a residential treatment facility. Youths (aged 5-19, mean = 13.6 years), consecutively admitted over 17 months, were assessed for the prevalence and patterns of use of psychotropic and anticonvulsant treatments. At admission, 76% of the youths were receiving psychiatric pharmacotherapy, 40% with more than one psychiatric agent, and 15% with a combination of psychotropic and anticonvulsant medications. Frequently prescribed medications were neuroleptics (35 % of the medicated youths), sedative-hypnotics (26 %), and anticonvulsants (15%). Psychostimulants (16%) and antidepressants (22%) were under-prescribed relative to their diagnostic indications. Over 50 different medication combinations were used. The neuroleptic + lithium combination was most common (25 % of the polypharmacological treatments). Neuroleptics were the most commonly prescribed medication and mostly used for nonpsychotic, nontic, and nonbipolar indications (55% of neuroleptic trials). Neuroleptics were used primarily for aggression regardless of diagnosis. Neuroleptics were used more in symptomatic treatments than in treatments for indicated diagnoses. The high prevalence of psychiatric and antiepileptic medication use in children and adolescents admitted to a residential treatment facility, and especially the pattern of their use, raises questions about prescribing practices for youths entering residential treatment and about pediatric psychopharmacotherapy in general.

Behavioral and neurobiological consequences of social subjugation during puberty in golden hamsters.

In golden hamsters, offensive aggression is facilitated by vasopressin and inhibited by serotonin. We tested whether these neurotransmitter systems respond to modifications resulting from the stress of threat and attack (i.e., social subjugation) during puberty. Male golden hamsters were weaned at postnatal day 25 (P25), exposed daily to aggressive adults from P28 to P42, and tested for offensive aggression as young adults (P45). The results showed a context-dependent alteration in aggressive behavior. Subjugated animals were more likely to attack younger and weaker intruders than nonsubjugated controls. Conversely, subjugated animals were less likely to attack animals of similar size and age. After testing, the animals were killed, and their brains were collected to determine whether these behavioral changes are underlined by changes in the vasopressin and serotonin systems. Social subjugation resulted in a 50% decrease in vasopressin levels within the anterior hypothalamus, a site involved in the regulation of aggression. Furthermore, whereas the density of vasopressin-immunoreactive fibers within the area was not significantly altered in subjugated animals, the number of serotonin-immunoreactive varicosities within the anterior hypothalamus and lateral septum was 20% higher in subjugated animals than in their controls. These results establish puberty as a developmental period sensitive to environmental stressors. Furthermore, the results show that changes in the vasopressin and serotonin systems can correlate with behavioral alterations, supporting the role of these two neurotransmitters in the regulation of aggression.

Overt categorical aggression in referred children and adolescents.

OBJECTIVE: To investigate descriptive and predictive correlates of aggression in children and adolescents who exhibit a high frequency of daily physical assault after admission to a structured residential treatment program and to examine correlations between subcategories of overt categorical aggression (OCA) in the same population. METHOD: Fifty-one admissions to a residential treatment program were assessed for frequency of physical assault after admission; analyses were corrected for length of stay. Patients with a high frequency of daily assault were compared with patients with a low frequency of daily assault on variables assessing demographics, history, family, concurrent behavior, treatment, and outcome. RESULTS: A high prevalence of OCA was found in this sample. Variables assessing history and concurrent behavior were significantly associated and predictive of subjects exhibiting a high frequency of daily physical assault after admission. Physical assault was significantly correlated with verbal aggression, property destruction, and self-injurious behavior. CONCLUSIONS: These findings support the distinctiveness of OCA as a separate subtype of aggression encompassing four subcategories. Further research on treatment, outcome, and associated comorbidity of OCA is warranted.

Vasopressin/serotonin interactions in the anterior hypothalamus control aggressive behavior in golden hamsters.

Studies in several species of rodents show that arginine vasopressin (AVP) acting through a V1A receptor facilitates offensive aggression, i.e., the initiation of attacks and bites, whereas serotonin (5-HT) acting through a 5-HT1B receptor inhibits aggressive responding. One area of the CNS that seems critical for the organization of aggressive behavior is the basolateral hypothalamus, particularly the anterior hypothalamic region. The present studies examine the neuroanatomical and neurochemical interaction between AVP and 5-HT at the level of the anterior hypothalamus (AH) in the control of offensive aggression in Syrian golden hamsters. First, specific V1A and 5-HT1B binding sites in the AH are shown by in vitro receptor autoradiography. The binding for each neurotransmitter colocalizes with a dense field of immunoreactive AVP and 5-HT fibers and putative terminals. Putative 5-HT synapses on AVP neurons in the area of the AH are identified by double-staining immunocytochemistry and laser scanning confocal microscopy. These morphological data predispose a functional interaction between AVP and 5-HT at the level of the AH. When tested for offensive aggression in a resident/intruder paradigm, resident hamsters treated with fluoxetine, a selective 5-HT reuptake inhibitor, have significantly longer latencies to bite and bite fewer times than vehicle-treated controls. Conversely, AVP microinjections into the AH significantly shorten the latency to bite and increase biting attacks. The action of microinjected AVP to increase offensive aggression is blocked by the pretreatment of hamsters with fluoxetine. These data suggest that 5-HT inhibits fighting, in part, by antagonizing the aggression-promoting action of the AVP system.

Dde-I restriction endonuclease fragmentation: a novel method of generating cDNA probes for in situ hybridization in brain.

We present a novel procedure for detection of low- and high-abundance messenger RNAs in the brain by in situ hybridization histochemistry, by using fragmented double-stranded cDNA as molecular probes. The procedure involves digesting the cDNA of interest with the restriction endonuclease from Desulfocibrio desulfuricans (Dde I digestion), followed by random primed labeling, which generates a family of high specific activity cDNA fragments. This procedure is a rapid, straightforward, and reproducible method of obtaining sensitive probes for in situ hybridization and is generally applicable to the analysis of the expression of a large number of genes. Here we report the use of this procedure to prepare probes for the detection of synapsin I, p150Glued, neurotensin, c-fos, and c-jun mRNAs in brain, using both isotopic and non-isotopic labeling methods. Because this procedure does not require complex recombinant DNA manipulations or oligonucleotide design, it should prove useful to the non-molecular biologist examining the expression of genes in the central nervous system.

Anabolic-androgenic steroid exposure during adolescence and aggressive behavior in golden hamsters.

Anabolic androgenic steroid (AAS) abuse by adolescents represents a significant health care risk due to the potential for long-term negative physical and psychological sequelae, including increased aggressive behavior. The current experiments examined the effects of AAS use in young male adolescent hamsters (Mesocricetus auratus) and their consequences on aggressive behavior. It was hypothesized that AAS administration during adolescence predisposes hamsters to heightened levels of aggressive behavior (i.e., offensive aggression). To test this hypothesis adolescent male hamsters were administered high doses of synthetic AAS to mimic a 'heavy use' self-administration regimen used by athletes. Immediately following the exposure to AAS hamsters were tested for aggressive behavior using a resident-intruder model. Animals treated with high doses of AAS during their adolescent development showed heightened measures of offensive aggression i.e., decreased latency to bite and increased total number of attacks and bites) during the test period, while measures of total activity (total contact time) between the animals remained unchanged. AAS-treated males did not differ in body weight from controls, suggesting that the increased aggression was not due to increased body mass. The results of this study show that exposure to AAS during adolescence facilitates aggressive response patterns, but does not alter body weight.

Combined pharmacotherapy in children and adolescents in a residential treatment center.

OBJECTIVE: To investigate characteristics of children and adolescents with a history of combined pharmacotherapy (CPT) and compare them with a group with no history of CPT. METHOD: Eighty-three consecutive admissions to a residential treatment center were divided into a CPT and a no-CPT group based on treatment history and compared by chart review. Prevalence of lifetime psychiatric medication use and CPT exposure were assessed. Demographic, diagnostic, treatment, behavioral, and medication variables were compared across the two groups. RESULTS: Medication use was present in the treatment history for 89.2% and a history of CPT was found for 60.3% of subjects. Admission to current placement from inpatient psychiatry, lifetime number of psychiatric placements, lifetime number of psychiatric diagnoses, and nonseizure neuropsychiatric comorbidity were significantly associated with CPT. Aggression and neuroleptic use were also significantly associated with CPT. Admission psychiatric diagnostic comorbidity was not associated with CPT. CONCLUSIONS: A high prevalence of psychiatric medication use and CPT was found in this population. Variables assessing illness severity, aggressive behavior, and nonseizure neuropsychiatric comorbidity may identify youths in psychiatric treatment settings with a high prevalence of past or current CPT exposure. Further research on the CPT of aggression is warranted.

Adolescent anabolic steroid use and aggressive behavior in golden hamsters.

In the present study, the ability of high-dose androgens, namely AAS, administered during adolescence to facilitate aggressive behavior in experimental animals was examined. Data from these studies show clearly that exposure to high doses of multiple AAS during adolescent development can predispose animals to intense bouts of aggressive behavior during young adulthood. Specifically, young adult hamsters treated with high doses of AAS throughout adolescence were more likely to attack and bite intruders placed in their home cage than sesame oil (vehicle)-treated control animals. Further, AAS-treated animals displayed a higher intensity of attack during the test period, exhibiting greater than four times the number of attacks/bites of control animals. Given the recent reports of increased incidence of AAS abuse in the adolescent population and the documented stimulatory effects of AAS on aggressive behavior, the study of the behavioral and neurobiological effects of prolonged exposure to AAS during critical phases of development such as adolescence warrants further investigation.

Vasopressin and developmental onset of flank marking behavior in golden hamsters.

Golden hamsters start displaying flank marking behavior (a form of scent marking) around postnatal day 20 (P-20). Because the behavior is dependent upon the central activity of arginine vasopressin (AVP), the present study was conducted to correlate this activation with changes in the vasopressinergic system. A first set of experiments was performed to compare flank marking activity between P-18 and P-22. A second set of experiments was performed to compare the density of AVP receptors between the age periods and assess responsiveness to AVP microinjection. Finally, a third set of experiments incorporated immunocytochemistry, radioimmunoassay, in situ hybridization, and Northern blot analysis to determine the location and numbers of AVP immunoreactive neurons and the level of mRNA correlating with the developmental onset of flank marking behavior. Our results show that flank marking develops between P-18 and P-22. Male and female hamsters do not display odor-induced flank marking anytime before P-19. However, all animals show odor-induced flank marking by P-22. The onset of flank marking does not appear to be associated with any change in AVP receptor binding in the anterior hypothalamus. Indeed, flank marking can be triggered in hamsters on P-18 by the microinjection of AVP in the anterior hypothalamus. This would suggest that the postsynaptic mechanisms contributing to the transduction of the AVP signal and the motor control of flank marking are intact prior to the onset of odor-induced flank marking. In contrast, AVP levels in the hypothalamus and pituitary increase by two to threefold between P-18 and P-22, suggesting that changes in AVP synthesis and release from presynaptic sites may contribute to the onset of flank marking. Interestingly, there is no change in AVP mRNA between P-18 and P-22, which raises questions about posttranslational processing during this developmental period. These results suggest that heightened synthesis and release of AVP between P-18 and P-22 may contribute to the developmental onset of flank marking.

Mutant and native human beta-amyloid precursor proteins in transgenic mouse brain.

Human beta-amyloid precursor protein (beta APP) has been targeted to transgenic neurons using synapsin I promoter-based chimeric transgenes. Native human beta APP was introduced as well as beta APP containing mutations genetically linked to familial Alzheimer's disease (AD) and to hereditary cerebral hemorrhage with amyloidosis-Dutch type. In mouse brain, human beta APP RNA was up to 60% as abundant as total endogenous beta APP RNA. Human beta APP gene expression was most abundant in the CA subfields of the hippocampus and in the piriform cortex. Correct processing of human beta APP at the beta-secretase cleavage site was demonstrated in transgenic mouse brains. Despite a 40% increase in total beta APP immunoreactivity in lines expressing mutant human beta APP, no evidence of amyloid deposition was found in brains of mice up to 14 months in age. Higher levels of mutant human beta APP, increased age, or other factors may be necessary to elicit beta-amyloid-related neuropathologies in the rodent brain.

Expression of the p150Glued component of the dynactin complex in developing and adult rat brain.

p150Glued is a component of the dynactin (Glued) complex that has been shown in vitro to be a required activator of cytoplasmic dynein-mediated transport of vesicles along microtubules and, thus, may be an essential component of retrograde axonal transport. In vivo, a dominant mutation in the Drosophila homologue of p150Glued induces aberrant neuronal development when heterozygous and is lethal when homozygous. In order to characterize the role of the dynactin complex in the development and function of vertebrate neurons, the distribution of the p150Glued message was examined via in situ hybridization to serial sections of adult rat brain and to a developmental series of sections. In the adult rat brain, the most intense hybridization observed with the p150Glued probe was in the pyramidal cells of the hippocampus proper, the dentate granule neurons, the cingulate and piriform cortices, the ventromedial hypothalamus, and the granular cell layer of the cerebellum. White-matter fiber tracts and the neuropil were generally devoid of signal. The data indicate that the mRNA encoding p150Glued is highly enriched in the cell bodies of neurons within the central nervous system. In developing rat, p150Glued is expressed at very high levels in neural tissue from the earliest time points assayed. Particularly intense hybridization was observed in the multiple layers of the retina, which is consistent with the phenotype of the Drosophila mutation. Therefore, the distributions observed via in situ hybridization are consistent with an essential role for p150Glued in retrograde axonal transport.