Abdominal ultrasonography of the normal St. Kitts vervet monkey (Chlorocebus sabaeus).

BACKGROUND: Normal ultrasonography of non-reproductive abdominal and male reproductive anatomy in the vervet monkey were prospectively assessed. This has not been previously reported. METHODS: Ten non-sexually active male and 10 non-gravid female clinically healthy vervet monkeys between 5 and 12 years of age and weighing between 3.13 and 6.85 kg were evaluated with ultrasound. Individuals were randomly divided by gender groups into one of two immobilization protocols and scanned at 18.0 MHz. RESULTS: High-quality images of the liver, gallbladder, kidneys, urinary bladder, spleen, adrenal glands, gastrointestinal tract, and testes were acquired. The prostate was never visualized. Abdominal lymph nodes other than an ileocolic, the pancreas, and the female reproductive tract were not evaluated. Gastric and duodenal motility were significantly different between immobilization protocols (P<0.05). CONCLUSIONS: Abdominal sonographic anatomy was successfully characterized and normal size parameters for non-reproductive abdominal viscera and the testes were established.

Differential effects of nicotine treatment and ethanol self-administration on CYP2A6, CYP2B6 and nicotine pharmacokinetics in African green monkeys.

In primates, nicotine is metabolically inactivated in the liver by CYP2A6 and possibly CYP2B6. Changes in the levels of these two enzymes may affect nicotine pharmacokinetics and influence smoking behaviors. This study investigated the independent and combined effects of ethanol self-administration and nicotine treatment (0.5 mg/kg b.i.d. s.c.) on hepatic CYP2A6 and CYP2B6 levels (mRNA, protein, and enzymatic activity), in vitro nicotine metabolism, and in vivo nicotine pharmacokinetics in monkeys. CYP2A6 mRNA and protein levels and in vitro coumarin (selective CYP2A6 substrate) and nicotine metabolism were decreased by nicotine treatment but unaffected by ethanol. CYP2B6 protein levels and in vitro bupropion (selective CYP2B6 substrate) metabolism were increased by ethanol but unaffected by nicotine treatment; CYP2B6 mRNA levels were unaltered by either treatment. Combined ethanol and nicotine exposure decreased CYP2A6 mRNA and protein levels, as well as in vitro coumarin and nicotine metabolism, and increased CYP2B6 protein levels and in vitro bupropion metabolism, with no change in CYP2B6 mRNA levels. Chronic nicotine resulted in higher nicotine plasma levels achieved after nicotine administration, consistent with decreased CYP2A6. Ethanol alone, or combined with nicotine, resulted in lower nicotine plasma levels by a mechanism independent of the change in these enzymes. Thus, nicotine can decrease hepatic CYP2A6, reducing the metabolism of its substrates, including nicotine, whereas ethanol can increase hepatic CYP2B6, increasing the metabolism of CYP2B6 substrates. In vivo nicotine pharmacokinetics are differentially affected by ethanol and nicotine, but when both drugs are used in combination the effect more closely resembles ethanol alone.

Reduced soma size of the M-neurons in the lateral geniculate nucleus following foetal alcohol exposure in non-human primates.

Visual impairment is commonly reported as a consequence of heavy prenatal ethanol exposure in humans. Children generally display characteristic cranio-facial dysmorphology and represent typical severe cases of foetal alcohol syndrome. Binge-like rodent model systems have concluded that third trimester equivalent ethanol exposure results in widespread apoptosis in the visual system from the retina to the visual cortex. Neither clinical nor animal studies address the consequences of more moderate prenatal ethanol exposure on the visual system. The current study uses a naturalistic and voluntary consumption approach in non-human primates (Chlorocebus sabeus) in order to more closely model prenatal ethanol consumption patterns in humans. Pregnant vervet monkeys voluntarily drank on average 2.418 +/- 0.296 g etoh/kg/day four times a week during the third trimester. Using unbiased stereology, we estimated the neuronal and glial population of the parvocellular (P) and magnocellular (M) layers of the lateral geniculate nucleus (LGN) following foetal alcohol exposure (FAE) in infant subjects. Layer volume and total number of neurons and glia in the LGN of the FAE subjects were not significantly different from age-matched control subjects. The M neuronal soma size of FAE subjects, however, was significantly reduced to resemble the size of the P-neurons. These results suggest that alterations at the level of morphology and anatomy of the M-neurons may lead to behavioural deficits associated with the integrity of the dorsal visual pathway.

Mood-lowering effect of tryptophan depletion. Enhanced susceptibility in young men at genetic risk for major affective disorders.

METHODS: A double-blind placebo-controlled cross-over study in which plasma tryptophan was manipulated by administration of a tryptophan-deficient amino acid mixture. In the placebo condition, all subjects received a nutritionally balanced amino acid mixture that contained tryptophan. To further standardize baseline amino acids, each subject was provided with a low-protein diet the day before amino acid challenges. Subjects were euthymic, healthy men aged 18 to 30 years with either a multigenerational family history of affective illness or no family history of psychiatric illness in the present or in the two previous generations. Each subject was screened with a structured clinical interview to rule out a personal history of psychiatric illness. RESULTS: Plasma tryptophan was reduced by 89% 5 hours after the administration of the tryptophan-deficient amino acid mixture. Six of 20 subjects with a family history of affective illness and none of 19 subjects without a family history of psychiatric illness showed a lowering of mood of 10 or more points on the Profile of Mood States depression scale (P = .012, Fisher's Exact Test) 5 hours after tryptophan depletion. No significant mood changes were observed following the control treatment (balanced amino acid mixture) in either group. CONCLUSIONS: Our data support the hypothesis that subjects with no prior depressive episodes but with a multigenerational family history of major affective disorder show a greater reduction in mood after tryptophan depletion. They are also consistent with theories that implicate deficient serotonergic function as one possible etiological factor in major depressive disorders.

In vitro stabilization of the unoccupied glucocorticoid receptor by adenosine 5'-diphosphate.

The addition of ATP to rat liver cytosol slows the rate of heat inactivation of the unoccupied glucocorticoid receptor (25 C) and stimulates the rate of activation of the preformed glucocorticoid-receptor complex (15 C). Dose-response curves and kinetic studies show that ADP is as effective as ATP in stabilizing the unoccupied glucocorticoid receptor against heat inactivation. ATP can also be replaced by analogs with a hydrolysis-resistant alpha, beta-pyrophosphate linkage (5'-adenylyl methylenephosphonophosphate or 5'-adenylyl methylenephosphonate); however, the hydrolysis-resistant beta, gamma analog (5'-adenylyl methylenediphosophonate) is ineffective. The addition of creatine phosphate plus creatine kinase, a condition favoring ATP formation, stimulates the rate of inactivation of the unoccupied glucocorticoid receptor, and the effect is only partially overcome by ADP. A condition that favors ADP formation, the addition of creatine plus creatine kinase, has no effect on the rate of inactivation of the unoccupied receptor and does not decrease the protective effect afforded by ATP alone. Collectively, these results suggest that ATP stabilization of the steroid-binding site in vitro is due to ADP generated from the triphosphate by endogenous enzymes and is not due to phosphorylation or adenylation of the receptor by ATP. Unlike ATP stabilization of the steroid-binding site, the ATP-stimulated increase in the rate of activation of the preformed glucocorticoid-receptor complex (15 C) does not require hydrolysis of the beta, gamma-pyrophosphate bond. Dose-response curves show that both ATP and 5'-adenylyl methylenediphosophonate stimulate the rate of activation of the glucocorticoid-receptor complex. Quantitation of nucleotide levels in unfractionated rat liver cytosol by high performance liquid chromatography shows that the effective concentration of added ATP that produces an optimal response is within the physiological range reported for intact cells.

Behavioral disinhibition induced by tryptophan depletion in nonalcoholic young men with multigenerational family histories of paternal alcoholism.

OBJECTIVE: A deficit in serotonergic neurotransmission has been linked to impulsive behavior, as well as to disorders characterized by disinhibition. The present study tested the hypothesis that young men at high risk for alcoholism demonstrate greater behavioral disinhibition after acute dietary depletion of tryptophan, the amino acid precursor of serotonin. METHOD: A double-blind, placebo-comparison, between-subjects study design was used. Nonalcoholic young men with a multigenerational paternal family history of alcoholism (N = 13) or with no family history of alcoholism (N = 15) in two previous generations were administered mixtures of tryptophan-deficient amino acid to achieve plasma tryptophan depletion. Comparison subjects with a multigenerational paternal family history of alcoholism (N = 1) and comparison subjects with no family history of alcoholism (N = 18) were given a balanced mixture. Five hours after this, all were tested on a modified Taylor task and a go/ no-go task measuring aggressive response and disinhibition, respectively. RESULTS: Plasma tryptophan levels were reduced by 89% in both groups. Tryptophan depletion had no effect on aggressive response. In contrast, tryptophan-depleted individuals with a family history of alcoholism made more commission errors (responses to stimuli associated with punishment or loss of reward) than did tryptophan-depleted individuals with no family history of alcoholism and those receiving the balanced (comparison) mixture of amino acid in either group. CONCLUSIONS: Low serotonin levels may be implicated in the high disinhibition or impulsivity observed in some individuals with a genetic vulnerability to alcohol abuse or dependence.

Mood response to acute tryptophan depletion in healthy volunteers: sex differences and temporal stability.

We investigated (1) the mood response of normal women, without a family history of major affective disorder, to acute tryptophan depletion, and (2) the temporal stability of the mood change, within subjects, when rechallenged at least 1 month later. To deplete tryptophan, a tryptophan deficient amino acid mixture was ingested. The control treatment was a nutritionally balanced amino acid mixture containing tryptophan. A marked lowering of plasma tryptophan (80% to 90%) was achieved by both depletions. Compared to the balanced condition, the women exhibited a significant lowering of mood after the first tryptophan depletion on the elation-depression (p < .05), energetic-tired (p < .005), confident-unsure (p < .01), and clearheaded-confused (p < .01) scales of the bipolar profile of mood states. Whereas a lowering of mood was not found in a comparable sample of males studied earlier, these results were similar to those obtained in healthy males at genetic risk for major affective disorder (MAD). Inasmuch as a family history of MAD and female sex are predisposing factors to depression, these results suggest that a mood-lowering response to acute tryptophan depletion may occur preferentially in subjects with a susceptibility to lowered mood. However, the mood response to tryptophan depletion exhibited poor temporal stability in individual subjects.

Tryptophan depletion, executive functions, and disinhibition in aggressive, adolescent males.

Low serotonin has been associated with aggressive behavior and impulsivity. Executive functions (cognitive abilities involved in the initiation/maintenance of goal attainment) have also been related to aggression. We tested whether dietary depletion of tryptophan, the amino acid precursor of serotonin, would increase disinhibition (impulsivity) in aggressive male adolescents. Cognitive-neuropsychological variables predictive of disinhibition were explored. Stable aggressive and nonaggressive adolescent men received balanced and tryptophan-depleted, amino acid mixtures separately (counterbalanced, double-blind). Commission errors on a go/no-go learning task (i.e., failures to inhibit responding to stimuli associated with punishment/nonreward) measured disinhibition. Aggressive adolescent males made more commission errors as compared to nonaggressives. Lower executive functioning was significantly related to commission errors over and above conventional memory abilities. Tryptophan depletion had no effect on commission errors in the aggressive adolescents, possibly because of a ceiling effect.

The effect of tryptophan depletion on mood in medication-free, former patients with major affective disorder.

Acute tryptophan depletion (ATD) induces transient clinical relapse in medicated patients with major affective disorder. Our objective was to determine whether this effect persists once patients are euthymic and off antidepressants. Thus, we examined the effects of ATD in fully remitted, medication-free, former patients with major depression (n = 14). ATD had no significant effect on mood. These results suggest that the previous report that ATD substantially lowers mood in pharmacologically treated patients reflects a reversal of mechanisms involved in the therapeutic effects of antidepressants. Alternatively, ATD might induce clinical relapse only in subgroups that have yet to be identified.

Characterization of a primate model of hypertension. The response of hypertensive and normotensive male vervets (Cercopithecus aethiops) to cold pressor stress, captopril administration, and acute bolus of atrial natriuretic factor.

In feral populations of African green monkeys or vervets (Cercopithecus aethiops), between 5 and 15% of adults have spontaneously elevated blood pressure (BP). We report here the initial biological and pharmacological characterization of this potential animal model of hypertension. Captive male monkeys with elevated systolic pressures show a modest pressure increase in response to stressors such as capture, phlebotomy and cold challenge. Acute captopril administration lowers BP in monkeys with high blood pressure (HBP), but has no effect on BP in control animals. Furosemide does not acutely reduce BP. Animals with elevated BPs have lower levels of angiotensin II than do age- and weight-matched controls. An acute infusion of atrial natriuretic factor (ANF) diminishes BP and stimulates urinary output in control and HBP vervets. However, both effects are more pronounced in animals with HBP. Heart rate is not affected by any of the experimental manipulations. Taken together, these data suggest that African green monkeys with spontaneously elevated BP may be a useful experimental model for particular types of human hypertension. Additional studies are required to complete the endocrine and pharmacological characterization of individual animals with HBP.

An amino acid mixture deficient in phenylalanine and tyrosine reduces cerebrospinal fluid catecholamine metabolites and alcohol consumption in vervet monkeys.

An amino acid mixture devoid of tryptophan, given orally, was previously shown to reduce cerebrospinal fluid levels of tryptophan and 5-hydroxyindoleacetic acid in vervet monkeys, as compared to a control mixture containing all essential amino acids. In the present study, we tested the possibility that a similar amino acid mixture containing tryptophan, but devoid of phenylalanine and tyrosine (the amino acid precursors of catecholamine neurotransmitters), would influence dopamine and noradrenaline metabolism. Five hours after the administration of this mixture to vervet monkeys, cerebrospinal fluid levels of homovanillic acid and 3-methoxy-4-hydroxyphenylethylene glycol were reduced by 27.4% and 26.9%, respectively. Both effects were statistically significant. Plasma tyrosine (-30%) and the ratio of tyrosine to the sum of other large neutral amino acids (sigmaLNAA) were also significantly reduced. The behavioral efficacy of phenylalanine/tyrosine depletion was compared with that of tryptophan depletion in a primate model of voluntary alcohol consumption. All three drinks lowered alcohol consumption, but the effects of the tryptophan-deficient amino acid mixture were not different from those of the balanced amino acid control. The phenylalanine/tyrosine-deficient drink differentially lowered alcohol consumption, consistent with other data in this species and elsewhere implicating dopamine in the rewarding effects of alcohol.

Altered dopamine transporter densities in alcohol-preferring vervet monkeys.

Altered dopamine (DA) transporter densities have been implicated in mechanisms of vulnerability and relapse in human alcoholics. The regional distribution and density of the DA transporter was studied in alcohol-preferring vervet monkeys to investigate baseline status and regulation of the DA transporter at different stages of chronic alcohol drinking. Combined ligand binding and in vitro autoradiography of the cocaine congener [125I]RTI-55 (beta-CIT) demonstrated a significant increase in DA transporter densities in abstinent alcohol-preferring monkeys over those in alcohol-avoiding monkeys. Chronic alcohol consumption down-regulated DA transporter densities, and this effect was reversed by acute withdrawal. These results demonstrate that the DA transporter is regulated by alcohol exposure and suggest that increased DA transporter densities may be a phenotypic marker of alcohol preference in vulnerable monkeys.

Development of a sensitive and specific assay system for cholecystokinin tetrapeptide.

Cholecystokinin is a gastrointestinal and neuropeptide which has been implicated in a wide range of physiological and behavioral processes. We have developed a sensitive and specific assay system to measure the various forms of cholecystokinin (CCK) in human plasma. This 3-step system involves i) extraction of CCK fragments from plasma using reverse phase chromatography; ii) separation of peptides by high performance liquid chromatography; and iii) detection and quantification of peptides with a double-antibody radioimmunoassay, using an antibody raised against cholecystokinin tetrapeptide (CCK-4) coupled to thyroglobulin and 125I Bolton-Hunter CCK-4 as tracer. The antibody detects CCK-4, sulfated CCK-8 (CCK-8S) and nonsulfated CCK-8 (CCK-8ns) with equal affinity. The lower limit of detection is 2.7 fmol, with an ED50 of 10.6 +/- 2.2 fmol. Mean CCK-like immunoreactivity (CCK-LI) in the plasma of 12 healthy subjects was determined to be 12.9 +/- 2.1 pM CCK-4 equivalents. Concentrations of each individual peptide in plasma were determined to be 1.0 +/- 0.2 pM, 3.4 +/- 0.8 pM and 1.9 +/- 0.4 pM for CCK-4, CCK-8s and CCK-8ns respectively.

Pharmacological and immunological characterization of the Leu5 analogue of human beta-endorphin.

The potencies of beta h-endorphin, Met (O)5-beta h-endorphin, and synthetic Leu5-beta h-endorphin have been compared in three bioassays of opioid activity, and in two radioimmunoassays. In all assays, a peptide isolated from hemodialysates from a psychotic patient behaved like Leu5-beta h-endorphin; it has been distinguished unambiguously from beta h-endorphin and Met(O)5-beta h-endorphin. Leu5-beta h-endorphin was one-fifth as potent as beta h-endorphin in guinea pig ileum myenteric plexus, but was only slightly less active in mouse vas deferens and in guinea pig brain opiate receptor binding assay. The low cross-reactivity of Leu5-beta h-endorphin relative to beta h-endorphin with an antiserum raised to beta-endorphin suggests that the preferred solution conformations of these peptides are different. In all bioassays beta h-endorphin was 2- to 3-fold less potent than beta c-endorphin.

The beta-endorphin response to stress during postnatal development in the rat.

The plasma beta-endorphin and adrenocortical responses to ether and handling stress were examined in animals of various ages. At each age studied there was a significant, stress-induced elevation of plasma beta-endorphin-like immunoreactivity levels. Moreover, basal beta-endorphin-like immunoreactivity levels were higher in animals 3, 7, and 14 days of age than in adults. In contrast, plasma corticosterone levels in the Day 7 pups were not elevated by stress; a finding consistent with several previous reports on the absence of increased release of adrenocorticotropin and corticosterone during stress in the neonate. These data suggest that the release of adrenocorticotropin and beta-endorphin in response to stress differ in the developing animal.

Caffeine and propranolol block the increase in rat pineal melatonin production produced by stimulation of adenosine receptors.

The adenosine agonist 5'-N-ethylcarboxamidoadenosine (NECA) injected i.p. during the light period increased rat pineal melatonin levels and this increase was blocked by simultaneous administration of the non-selective adenosine receptor antagonist caffeine. A single dose of the adenosine A1 agonist cyclopentyladenosine had no effect on nocturnal melatonin production. The NECA-stimulated increase was also blocked by the beta-adrenergic receptor antagonist propranolol. Given alone, neither caffeine nor propranolol had any effect on melatonin levels. The results point to an intermediate role for beta-adrenergic receptors in the adenosine-stimulated increase of melatonin production.

Genetic models for the study of aggressive behavior.

The analysis of genetic contributions to aggressive behavior is both conceptually and methodologically difficult, so that substantive findings remain sparse. Like other major psychiatric disease states, inappropriately aggressive behavior must be considered a multifactorial disorder, with both genetic and environmental contributions required for clinical expression. The documented heterogeneity of these determinants suggests the futility of searching for unitary causes. This contribution reviews studies of major gene effects in inbred strains of mice with high aggressivity, and considers the relevance of some rare single-gene disorders in man which include uncontrollably aggressive behavior as part of the phenotype.

Morphine-6-glucuronide: analgesic effects and receptor binding profile in rats.

The antinociceptive effects of morphine-6-glucuronide (M6G) were examined in two animal models of pain, the tail immersion test (reflex withdrawal to noxious heat) and the formalin test (behavioral response to minor tissue injury). In the tail immersion test, M6G produced an increase in withdrawal latency that rose rapidly between 0.01 and 0.025 ug ICV or 1 and 2 mg/kg SC. A further increase occurred at doses greater than 0.2 ug ICV or 4 mg/kg SC and was associated with marked catalepsy and cyanosis. Naloxone, 0.1 mg/kg SC, shifted the lower component of the dose-effect relation by a factor of 24. In the formalin test, 0.01 ug M6G ICV produced hyperalgesia, while between 0.05 and 0.2 ug ICV, antinociception increased rapidly without toxicity. The dose effect relations for hyperalgesia and antinociception were shifted to the right by factors of 20- and 3-fold, respectively. By comparison, ICV morphine was 60 (formalin test) to 145-200 (tail immersion test) times less potent than M6G. At sub-nanomolar concentrations, M6G enhanced the binding of [3H]-etorphine, [3H]-dihydromorphine and [3H]-naloxone to rat brain membrane receptors by 20-40%. At higher concentrations, M6G displaced each ligand from binding sites, with Ki values of about 30 nM, as compared to morphine Ki values of about 3 nM. The data indicate that the in vivo and in vitro effects of M6G are complex and that M6G may play an important role in analgesia in experimental animals, and by implication, in man.

Adenosine analogs inhibit fighting in isolated male mice.

The potent adenosine analogs N-ethylcarboxamide adenosine (NECA) and phenylisopropyladenosine (PIA) inhibit fighting and associated agonistic behaviors in isolated male mice. These effects are reversed by methylxanthines; moderate doses of NECA which inhibit fighting have minimal effects on spontaneous locomotor activity. At very low doses, both NECA and PIA increase fighting in parallel with previously reported increases of motor activity. Brain levels of [3H]-NECA and [3H]-PIA achieved at behaviorally effective doses suggest an involvement of adenosine receptors. The biochemical mechanism of adenosine receptor action with respect to fighting is unknown, but may include neuromodulatory effects on the release of other, more classical neurotransmitters.

Depressive relapse following acute tryptophan depletion in patients with major depressive disorder.

Acute tryptophan depletion (ATD) lowers serotonin synthesis and elicits depressive symptoms in some, though not all, remitted patients with major depressive disorder (MDD). In the present study, eight medication-free remitted patients with MDD, seasonal pattern, were tested twice, once following the ingestion of a tryptophan-containing mixture, once following ATD. ATD significantly increased Hamilton depression scores (p < 0.001). Four of the patients had a family history of psychiatric disorders: substance abuse (n = 4), mood disorders (n = 3) or Cluster B personality disorders (n = 3). The mood-lowering response to ATD was significantly greater in those patients with, than without, affected relatives (p < 0.001). These preliminary findings (1) support the hypothesis that depressed states are related to disturbed serotonin neurotransmission and (2) suggest that depressive symptoms following ATD might identify a subgroup of patients at high genetic risk for disorders associated with affective lability and dysregulated impulse-control, conditions thought to be related to low serotonin neurotransmission.