Plasma concentrations of amino acids in chronic schizophrenics treated with clozapine

Peripheral amino acid changes have been reported in schizophrenia, but results are not consistent. We measured serum levels of different amino acids in 11 neuroleptic-resistant schizophrenic patients before and after clozapine treatment and in 11 age- and sex-matched healthy subjects. The schizophrenic patients exhibited significantly higher levels of serum aspartate, glutamate, isoleucine, histidine and tyrosine and significantly lower concentrations of serum asparagine, tryptophan and serine. In patients, the ratio between tryptophan and large neutral amino acids (LNAA) was significantly lower than in matched controls, whereas the tyrosine/LNAA ratio did not differ significantly. Moreover, 12 weeks of clozapine administration significantly reduced serum levels of glutamate but did not restore the values observed in normal controls, nor did it affect other amino acid concentrations. These data show changes in serum amino acids that may influence central serotonergic, dopaminergic and glutamatergic transmission in neuroleptic-resistant schizophrenics.

Inhibition of prostaglandin synthesis reduces hyperthermic reactions induced by hypocretin-1/orexin A

This experiment tested (i) the effect of orexin A injected into a lateral cerebral ventricle on sympathetic and thermogenic activity and (ii) the involvement of prostaglandins in these phenomena. The firing rates of the sympathetic nerves to interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures and heart rate were monitored in urethane-anesthetized male Sprague-Dawley rats before and 6 h after an injection of orexin A (1.5 nmol) into the lateral cerebral ventricle. The same variables were monitored in rats with an intraperitoneal administration of lysine acetylsalicylate (100 mg/kg bw), an inhibitor of prostaglandins synthesis. The results show that orexin A increases the sympathetic firing rate, IBAT and colonic temperatures and heart rate. This increase is reduced by lysine acetylsalicylate. These findings suggest that orexin A affects sympathetic activity, which controls body temperature. Prostaglandins are involved in this control.

Botulinum toxin injected in the gastric wall reduces body weight and food intake in rats

BACKGROUND

Botulinum toxin is a powerful, long-acting inhibitor of muscular contractions in both voluntary and smooth muscle. It acts by blocking the release of the neurotransmitter acetylcholine. In the stomach, propulsive contractions of the antrum are necessary for the gastric contents to pass into the duodenum.

AIMS

To investigate whether intramuscular injections of botulinum toxin type A into the gastric antrum of rats would cause a reduction in food intake and hence body weight, by inhibition of gastric emptying.

MATERIALS AND METHODS

This was a prospective, randomized, 3-way parallel group study in rats. The first group was anaesthetized, laparotomized and given 20 U of botulinum toxin type A by intramuscular injection into the gastric antrum (botulinum toxin type A group, n=14). The second group was anaesthetized, laparotomized and injected with saline (sham group, n=14) and the third group did not have any intervention (control group, n=5). Food intake was measured daily for 7 weeks and body weight was measured daily for 10 weeks.

RESULTS

There was a significant difference in loss of body weight between the two treated groups (14.0 +/- 8.2% botulinum toxin type A group, 4.4 +/- 2.7% sham group; P < 0.001). Further, the time to reach the weight nadir was significantly longer in the botulinum toxin type A group (8.7 +/- 3.9 days) compared with the sham group (5.3 +/- 3.8 days; P < 0.04). There were no significant differences between the sham and control groups for any of the body weight parameters. The minimum dietary intake was significantly lower in the botulinum toxin type A group than in the sham group (37.8 +/- 21.8% of the basal value in the botulinum toxin type A group, vs. 65.5 +/- 32.0 in the sham group, P < 0.05). In addition, the time to reach the nadir was significantly prolonged (8.2 +/- 3.5 days, botulinum toxin type A group vs. 4.9 +/- 1.7 days, sham group, P < 0.001).

CONCLUSIONS

The parallel reduction of body weight and food intake in botulinum toxin type A treated animals is consistent with a long lasting inhibition of the antral pump. This is probably due to slowed gastric emptying leading to early satiety. Patients with morbid obesity might benefit from endoscopic injections of botulinum toxin type A into the stomach wall.

Agomelatine (S20098) modulates the expression of cytoskeletal microtubular proteins, synaptic markers and BDNF in the rat hippocampus, amygdala and PFC

RATIONALE

Agomelatine is described as a novel and clinical effective antidepressant drug with melatonergic (MT(1)/MT(2)) agonist and 5-HT(2C) receptor antagonist properties. Previous studies suggest that modulation of neuronal plasticity and microtubule dynamics may be involved in the treatment of depression.

OBJECTIVE

The present study investigated the effects of agomelatine on microtubular, synaptic and brain-derived neurotrophic factor (BDNF) proteins in selected rat brain regions.

METHODS

Adult male rats received agomelatine (40 mg/kg i.p.) once a day for 22 days. The pro-cognitive effect of agomelatine was tested in the novel object recognition task and antidepressant activity in the forced swimming test. Microtubule dynamics markers, microtubule-associated protein type 2 (MAP-2), phosphorylated MAP-2, synaptic markers [synaptophysin, postsynaptic density-95 (PSD-95) and spinophilin] and BDNF were measured by Western blot in the hippocampus, amygdala and prefrontal cortex (PFC).

RESULTS

Agomelatine exerted pro-cognitive and antidepressant activity and induced molecular changes in the brain areas examined. Agomelatine enhanced microtubule dynamics in the hippocampus and to a higher magnitude in the amygdala. By contrast, in the PFC, a decrease in microtubule dynamics was observed. Spinophilin (dendritic spines marker) was decreased, and BDNF increased in the hippocampus. Synaptophysin (presynaptic) and spinophilin were increased in the PFC and amygdala, while PSD-95 (postsynaptic marker) was increased in the amygdala, consistent with the phenomena of synaptic remodelling.

CONCLUSIONS

Agomelatine modulates cytoskeletal microtubule dynamics and synaptic markers. This may play a role in its pharmacological behavioural effects and may result from the melatonergic agonist and 5-HT(2C) antagonist properties of the compound.

Paradoxical [correction of parodoxical] effect of orexin A: hypophagia induced by hyperthermia

This experiment tested the effect of the sympathetic and thermogenic activation induced by orexin A on eating behavior. The food intake, firing rate (FR) of the sympathetic nerves to interscapular brown adipose tissue (IBAT), IBAT and abdominal temperatures (T(IBAT) and T(ab)), and heart rate (HR) were monitored in 24 h-fasting male Sprague-Dawley rats for 15 h after food presentation. Orexin A (1.5 nmol) was injected into the lateral cerebral ventricle 6 h before food presentation while FR, T(IBAT) and T(ab), and HR were also monitored. The same variables were controlled in rats receiving orexin A contemporaneously to food presentation. Two other groups of control animals were tested with the same procedure, however orexin A was substituted by saline. The results showed that food intake was significantly lower in the group receiving orexin A 6 h before food presentation in comparison to all the other groups. FR, T(IBAT) and T(ab), and HR were significantly higher in the rats receiving orexin A with respect to rats receiving saline. These findings demonstrate that orexin A, so-called for its orexigen action, can also induce hypophagia. On the other hand, orexin A always induces an activation of the thermogenesis. These results suggest a revision of the role played by orexin A in the control of food intake, assigning to this peptide a primary role in the thermoregulation. The possibility that orexin A can induce hypophagia is well demonstrated by this experiment, so that the scientific community should use a different name for this peptide. An appropriate name could be 'hyperthermine' A.

Review article: the use of botulinum toxin in the alimentary tract

New and future indications for the treatment of disorders of the alimentary tract using local injections of botulinum toxin are reviewed. Clinical experience shows that overactive smooth muscle sphincters may be weakened to treat disorders such as achalasia or chronic anal fissure. By contrast, injections placed into the sphincter of Oddi have proven less effective for postcholecystectomy pain syndrome. Experimental evidence suggests that food intake may be reduced by weakening the distal stomach with botulinum toxin. This approach may possibly lead to the treatment of obesity. There are some new possible indications for the use of botulinum toxin on the alimentary tract, and infantile hypertrophic pyloric stenosis seems to be the most promising new development.

Aspartic and glutamic acids increase in the frontal cortex during prostaglandin E1 hyperthermia

The aim of the present experiment was to evaluate the role played by aspartic acid and glutamic acid of frontal cerebral cortex during the hyperthermia induced by prostaglandin E1. Two groups of six Sprague Dawley male rats were anaesthetized with ethyl-urethane. The frontal cortical concentrations of aspartic and glutamic acids, the firing rate of the sympathetic nerves to the interscapular brown adipose tissue, the colonic and interscapular brown adipose tissue temperatures were monitored both before and after an intracerebroventricular injection of prostaglandin E1 (500 ng) or saline. Aspartic and glutamic acids were collected using a microdialysis probe placed in the frontal cortex. Concentrations of aspartic and glutamic acids were measured by high-pressure liquid chromatography with fluorescence detector. Prostaglandin E1 induced an increase in the concentrations of aspartic and glutamic acids, in the firing rate of sympathetic nerves and in the colonic and interscapular brown adipose tissue temperatures. The findings of the present experiment indicate that an intracerebroventricular injection of prostaglandin E1 causes release of aspartic and glutamic acids in the frontal cortex.

Activity of autonomic nervous system is related to body weight in pre-menopausal, but not in post-menopausal women

This study analyzed vegetative modulation, expressed as heart rate variability (HRV) power spectral analysis, in lean and obese women at pre-menopausal or post-menopausal age to reveal possible differences in menopause-related autonomic activity in lean and obese subjects. Sedentary women (n = 40) were divided in four groups: pre-menopausal lean and obese women, post-menopausal lean and obese subjects. The HRV-power spectrum was evaluated on a 5-min long ECG recording. The absolute values of the spectrum were summed in the following frequencies: a low-frequency (0.04-0.15 Hz; LF) and high-frequency (0.15-0.40; HF) range. LF and HF were values used to estimate the sympathetic and parasympathetic activity. LF and HF values of pre-menopausal obese women are lower than values of lean women. The menopause induced a same decrease in LF and HF values in lean and obese subjects, so that no difference was found in post-menopausal groups. This experiment indicates that modifications of autonomic modulation can be included among factors related to obesity in pre-menopausal, but not post-menopausal women.

Mastication overload causes an increase in O2- production into the subnucleus oralis of the spinal trigeminal nucleus

The aim of the present study was to evaluate the production of superoxide anion (O(2)(-)) in the trigeminal complex nuclei after a functional mechanical overload of the teeth due to the preference for masticating on one side in rats. The preference for masticating on one side was induced by the discomfort due to a small abrasion of one molar; such lateralisation in mastication was confirmed by electromyography. The production of O(2)(-) was evaluated in the trigeminal nuclei by fluorescence microscopy after an injection of dihydroethidium. The results showed that there was an increased production of O(2)(-) in the subnucleus oralis of the spinal trigeminal nucleus in the same side where the mastication was preferred. This result demonstrates that an increased activity of non-painful sensory neurons can enhance the production of reactive oxygen species within the central second order sensory nuclei.

Haloperidol reduces the sympathetic and thermogenic activation induced by orexin A

This experiment tested the effect of haloperidol on the sympathetic and thermogenic effects induced by orexin A. The firing rates of the sympathetic nerves to interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures and heart rate were monitored in urethane-anesthetized male Sprague-Dawley rats before and 5 h after an injection of orexin A (1.5 nmol) into the lateral cerebral ventricle. The same variables were monitored in rats with an intraperitoneal administration of haloperidol (1 mg/kg bw), a D(2) receptor antagonist. The results show that orexin A increases the sympathetic firing rate, IBAT and colonic temperatures and heart rate. This increase is reduced by the haloperidol. These findings suggest that dopaminergic system is activated during the orexin A-induced hyperthermia.

Inhibition of long-term potentiation by CuZn superoxide dismutase injection in rat dentate gyrus: involvement of muscarinic M1 receptor

Long-term potentiation (LTP) and long-term depression represent important processes that modulate synaptic transmission that carries out a key role in neural mechanisms of memory. Many studies give strong evidences on a role of the reactive oxygen species in the induction of LTP in CA1 region of hippocampal slices that was inhibited by adding the scavenger enzyme superoxide dismutase (SOD1). Previous data showed that SOD1 is secreted by many cellular lines, including neuroblastoma SK-N-BE cells through microvesicles by an ATP-dependent mechanism; moreover, it has been shown that SOD1 interacts with human neuroblastoma cell membranes increasing intracellular calcium levels via a phospholipase C-protein kinase C pathway activation. The aim of this study was to investigate the effect of intracerebral injection of SOD1 or the inactive form of enzyme (ApoSOD) on the modulation of synaptic transmission in dentate gyrus of the hippocampus in urethane anesthetized rats. The results of the present research showed that intracerebral injection of SOD1 and ApoSOD in the dentate gyrus of the rat hippocampal formation inhibits LTP induced by high-frequency stimulation of the perforant path. This result cannot be only explained by the dismutation of oxygen radical induced by SOD1 since also ApoSOD, that lacks the enzymatic activity, carries out the same inhibitory effect on LTP induction.

Acute lesions of the ventromedial hypothalamus reduce sympathetic activation and thermogenic changes induced by PGE1

The aim of this experiment was to evaluate the effects of an intracerebroventricular (icv) injection of prostaglandin E1 (PGE1) on the sympathetic activation and the thermogenic changes in rats with acute lesions of the ventromedial hypothalamus (VMH). Four groups of six Sprague-Dawley male rats were anesthetized with ethyl-urethane. The firing rate of the sympathetic nerves innervating the interscapular brown adipose tissue (IBAT) and the colonic and IBAT temperatures were monitored both before and after one of the following treatments: 1) VMH lesion plus icv injection of PGE1 (500 ng); 2) VMH lesion plus icv injection of saline: 3) sham lesion plus icv injection of PGE1; and 4) sham lesion plus icv injection of saline. PGE1 induced an increase in the firing rate of IBAT nerves and the colonic and IBAT temperatures. These effects were reduced by VMH lesion. The findings indicate that acute lesions of the VMH reduce the effects of PGE1 and seem to suggest a possible role played by the VMH in the control of the sympathetic activation and the thermogenic changes during PGE1 hyperthermia.

Anxiety as a neurodevelopmental disorder in a neuronal subpopulation: Evidence from gene expression data

The relationship between genes and anxious behavior, is nor linear nor monotonic. To address this problem, we analyzed with a meta-analytic method the literature data of the behavior of knockout mice, retrieving 33 genes whose deletion was accompanied by increased anxious behavior, 34 genes related to decreased anxious behavior and 48 genes not involved in anxiety. We correlated the anxious behavior resulting from the deletion of these genes to their brain expression, using the Allen Brain Atlas and Gene Expression Omnibus (GEO) database. The main finding is that the genes accompanied, after deletion, by a modification of the anxious behavior, have lower expression in the cerebral cortex, the amygdala and the ventral striatum. The lower expression level was putatively due to their selective presence in a neuronal subpopulation. This difference was replicated also using a database of human gene expression, further showing that the differential expression pertained, in humans, a temporal window of young postnatal age (4 months up to 4 years) but was not evident at fetal or adult human stages. Finally, using gene enrichment analysis we also show that presynaptic genes are involved in the emergence of anxiety and postsynaptic genes in the reduction of anxiety after gene deletion.

Procaine injection into the paraventricular nucleus reduces sympathetic and thermogenic activation induced by frontal cortex stimulation in the rat

These experiments were designed to test the effect of procaine injection into the paraventricular nucleus on the sympathetic and thermogenic changes induced by frontal cortex stimulation. Oxygen consumption, firing rate of the sympathetic nerves to interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures (T(IBAT) and T(C)) were monitored in fasted male Sprague-Dawley rats before and 25 min after an electrical stimulation of the frontal cortex. The same variables were monitored in rats with administration of procaine into the paraventricular nucleus. The results show that cortical stimulation raises oxygen consumption, sympathetic neuron firing rates, T(IBAT), and T(C). This increase is reduced by procaine injection. These findings suggest that the paraventricular nucleus plays a key role in the sympathetic and thermogenic changes induced by cortical stimulation.

Mastication induces long-term increases in blood perfusion of the trigeminal principal nucleus

Understanding mechanisms for vessel tone regulation within the trigeminal nuclei is of great interest because some headache syndromes are due to dysregulation of such mechanisms. Previous experiments on animal models suggest that mastication may alter neuron metabolism and blood supply in these nuclei. To investigate this hypothesis in humans, arterial spin-labeling magnetic resonance imaging (MRI) was used to measure blood perfusion within the principal trigeminal nucleus (Vp) and in the dorsolateral-midbrain (DM, including the mesencephalic trigeminal nucleus) in healthy volunteers, before and immediately after a mastication exercise consisting of chewing a gum on one side of the mouth for 1 h at 1 bite/s. The side preference for masticating was evaluated with a chewing test and the volume of the masseter muscle was measured on T1-weighted MRI scans. The results demonstrated that the mastication exercise caused a perfusion increase within the Vp, but not in the DM. This change was correlated to the preference score for the side where the exercise took place. Moreover, the basal Vp perfusion was correlated to the masseter volume. These results indicate that the local vascular tone of the trigeminal nuclei can be constitutively altered by the chewing practice and by strong or sustained chewing.

Intracerebroventricular injection of prostaglandin E(1) changes concentrations of biogenic amines in the posterior hypothalamus of the rat

Since the posterior hypothalamus (PH) plays a key role in the control of body temperature, the aim of this study was to evaluate the changes in adrenaline, noradrenaline and dopamine levels in the PH during the hyperthermia induced by prostaglandin E(1) (PGE(1)). The concentration of adrenaline, noradrenaline and dopamine in the PH, the firing rate of the sympathetic nerves innervating interscapular brown adipose tissue (IBAT), IBAT and colonic temperatures (T(IBAT) and T(C)) were monitored in 12 urethane-anaesthetized male Sprague-Dawley rats before and after an intracerebroventricular injection of 500 ng PGE(1) dissolved in 2 microl of 0.9% NaCl saline solution or only saline. The catecholamines were collected using a microdialysis probe and quantified by HPLC. The results showed that PGE(1) caused a significant increment in the concentration of adrenaline from 15. 83+/-2.69 to 34.95+/-3.9 ng ml(-1) and of dopamine from 35.15+/-4.48 to 55.68+/-6.21 ng ml(-1). A significant decrease in the level of noradrenaline from 18.75+/-2.05 to 8.56+/-2.26 ng ml(-1) was registered. The firing rate of sympathetic nerves to IBAT was increased from 100+/-0% to 204.83+/-15.22% by PGE(1). T(IBAT) and T(C) rose respectively from 36.91+/-0.15 degrees C to 38.88+/-0.29 degrees C, and from 36.7+/-0.15 degrees C to 38.13+/-0.36 degrees C after the injection of PGE(1). The changes in adrenaline and noradrenaline occurred during the first 20 min as did the changes in temperature and firing rate, while the change in dopamine was delayed until 21-60 min after the PGE(1) injection. No significant change of analyzed variables was found in the control rats. These findings suggest that these biogenic amines of the PH are involved in the control of the sympathetic and thermogenic changes induced by PGE(1).

Procaine into the VMH inhibits IBAT activation caused by frontal cortex stimulation in urethane-anesthetized rats

This experiment tested the effect of procaine injection into the ventromedial hypothalamus on the sympathetic and thermogenic activation induced by frontal cortex stimulation. Oxygen consumption, firing rate of the sympathetic nerves to interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures were monitored in fasted male Sprague-Dawley rats before and during 25 min after an electrical stimulation of the frontal cortex. The same variables were monitored in rats with administration of procaine into the ventromedial hypothalamus. The results show that cortical stimulation increases oxygen consumption, sympathetic firing rate, IBAT and colonic temperatures. The increase in sympathetic firing rate was reduced by procaine injection, and the increase in IBAT and colonic temperatures as well as oxygen consumption was fully inhibited by procaine. These findings suggest that the ventromedial nucleus plays an important role in the sympathetic and thermogenic changes induced by cortical stimulation.

L-threonine injection into PPC modifies food intake, lateral hypothalamic activity, and sympathetic discharge

Food intake and the firing rate of lateral hypothalamic neurons and nerves innervating interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures, were monitored in male Sprague-Dawley rats fed a threonine-free diet. These variables were measured before and after a bilateral injection of L-threonine (2 nmol into each side) into the prepiriform cortex (PPC). The same variables were also monitored in 1) rats fed a threonine-free diet and injected with saline, 2) animals fed a standard diet and injected with L-threonine, and 3) rats fed a standard diet and injected with saline. The results showed that injection of L-threonine into PPC increases food intake and firing rate of lateral hypothalamic neurons, whereas it decreases the sympathetic discharge and body temperature in animals fed a threonine-free diet. No changes were found in the animals fed a standard diet. These findings suggest a correlation between 1) threonine level in the PPC and 2) lateral hypothalamic activity and sympathetic discharge to IBAT.

Functional decortication lowers ventromedial hypothalamic activation induced by hippocampal neostigmine injection

This experiment tested the effects of cortical spreading depression (CSD) on the ventromedial hypothalamic activity and on the related thermogenesis, both stimulated by an injection of neostigmine in the hippocampus. The firing rate of the neurons of the ventromedial hypothalamus, and the temperature of the interscapular brown adipose tissue and of the colon (T:(IBAT) and T:(C)) were monitored in 24 urethane-anesthetized male Sprague-Dawley rats divided into four groups. These variables were measured before and after hippocampal injection of neostigmine (5 x 10(-7) mol) in the first and second groups or of saline in the third and fourth groups. The hippocampal injection was preceded by CSD in the first and third groups, while CSD was not induced in the second and fourth groups. The same procedure was carried out in the other four groups of six rats each and oxygen consumption was monitored. The results show an increase in the firing rate, T:(IBAT), T:(C) and oxygen consumption after the neostigmine injection. CSD significantly reduces these enhancements. The findings demonstrate that: (i) the activation of ventromedial hypothalamic neurons are involved in the thermogenic changes due to the effects of a neostigmine injection into the hippocampus; and (ii) integrity of cerebral cortex is required for this activation of thermogenesis.

Tanshinone VI Inhibits the Expression of Intercellular Adhesion Molecule-1 and Vascular Cell Adhesion Molecule-1

This study investigated the possible antitumor mechanisms of action of Tanshinone VI, one of the components of Salvia miltiorrhiza Bunge, which is used in traditional Chinese herbal medicine. To this end, the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), were evaluated in-vitro in tumor necrosis factor-α (TNF-α)-stimulated endothelial cells, with, or without the addition of Tanshinone VI (10, 20, 30, or 40 mM) in the culture medium; the effects of Tanshinone VI on angiogenesis was also evaluated with an epithelial cell tube formation assay and its toxicity was evaluated with a colorimetric (MTT) cell viability assay. The results showed that the up-regulation of ICAM-1 and VCAM-1 induced by TNF-α was dose-dependently inhibited by Tanshinone VI, with restoration of control levels at the dose of 40 mM; Tanshinone VI also had a remarkable anti-angiogenesis effect, already at the dose of 10 mM, while none of the doses tested had significant effects on cell viability. These results indicate that the antitumor properties of Tanshinone VI can be ascribed to the inhibition of cell adhesion, due to blockage of the up-regulation of cell adhesion molecules, with the consequent inhibition of metastases formation and/or angiogenesis. The lack of toxic effects at the dosage used makes Tanshinone VI a good candidate for its therapeutic use in humans.

Cortical spreading depression reduces paraventricular activation induced by hippocampal neostigmine injection

The firing rate of the neurons of the hypothalamic paraventricular nucleus, the temperatures of the interscapular brown adipose tissue and of the colon (TIBAT and Tc) were monitored in 24 urethane-anesthetized male Sprague-Dawley rats divided into four groups. These variables were measured before and after hippocampal injection of neostigmine (5x10(-7) mol) in the 1st and 2nd groups or of saline in the 3rd and 4th groups. The hippocampal injection was preceded by cortical spreading depression in the 1st and 3rd groups, while the cortical depression was not induced in the 2nd and 4th groups. The results show an increase of firing rate, TIBAT and Tc after neostigmine injection in the rats without cortical depression. Cortical spreading depression significantly reduces these enhancements. These findings demonstrate that: (1) the paraventricular nucleus plays a significant role in the hyperthermia induced by neostigmine injection into the hippocampus; and (2) the cerebral cortex is involved in the control of the paraventricular activity.

Nitric oxide reduces hypophagia induced by threonine free diet in the rat

Food intake and concentrations of glutamic (GLU) and aspartic (ASP) acids in the nucleus accumbens were monitored in male Sprague-Dawley rats fed a threonine free diet. These variables were measured before and after an intracerebroventricular injection of 20 nmole nitroprusside (NP), a non-enzymatic nitric oxide donor. The same variables were also monitored in: (a) rats fed a threonine free diet and injected with saline; (b) animals fed a standard diet and injected with nitroprusside; (c) rats fed a standard diet and injected with saline. The results showed that the threonine-free diet reduced food intake and GLU and ASP concentrations in the accumbens. NP reduced the hypophagia, but it did not change GLU and ASP levels in rats fed the threonine-free diet. In animals fed the standard diet, NP increased GLU and ASP concentration, and food intake. No change was found in the animals with saline injection. These findings suggest that nitric oxide reduces the hypophagia in the rats fed a threonine-free diet. The lack of increase in GLU and ASP concentration in the nucleus accumbens of the hypophagic rats indicates that NP acts on hypophagia independently by GLU and ASP.

Sucrose rich diet modifies thermogenic response to injection of muscimol into the posterior hypothalamus in the rat

The firing rate of the nerves innervating interscapular brown adipose tissue, temperatures of colon and interscapular brown adipose tissue, heart rate and oxygen consumption were monitored in urethane-anaesthetized male Sprague-Dawley rats fed with a sucrose rich diet. These variables were measured for 40 min before (baseline values) and 40 min after a 56 ng muscimol injection into the posterior hypothalamus. The same variables were monitored in other rats fed with a laboratory standard diet. Saline was injected into the posterior hypothalamus of control rats fed with sucrose or standard diet. Muscimol injection induced a decrease in firing rate, interscapular brown adipose tissue and colonic temperatures and oxygen consumption. This reduction was more evident in the rat fed with a sucrose rich diet than animals fed with standard diet. The kind of diet did not modify the decrease in heart rate induced by muscimol. These findings suggest that a sucrose rich diet modifies GABA-ergic responses to muscimol injection into the posterior hypothalamus.