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M Mas

Publications and source records attributed to M Mas.

At least 55 records · Page 3Linked to original sources
PubMed1995

Voltammetric and microdialysis monitoring of brain monoamine neurotransmitter release during sociosexual interactions.

The monoamine neurotransmitters have long been ascribed important modulatory actions on male sexual behavior by a wealth of pharmacological studies. Methodological developments have now made possible the assessment of the extracellular levels of amine transmitters and their metabolites in discrete brain areas of sexually behaving animals using in vivo voltammetry and microdialysis. Studies in our and other laboratories consistently show increased dopamine release in forebrain structures known to be involved in mating activity, including the nucleus accumbens and the medial preoptic area, during both the appetitive (i.e., non-contact exposure to sexual stimuli) and consummatory phases of this behavior. Serotonin utilization seems to be mainly related to consummatory events. These findings are consistent with the pharmacological evidence as well as previous ex vivo work. The state of sexual inactivity that follows unrestricted mating associates with increased dopamine turnover in the preoptic area. According to the available information, it could reflect some blockade of dopaminergic receptors, possibly involving prolactin. No disturbance of ongoing sexual behavior was observed during the neurochemical monitoring sessions with either methodology. These studies show voltammetry and microdialysis as powerful complementary tools for the assessment of sociosexual interactions.

Animals↗
PubMed1994

Changes in monoamine turnover in forebrain areas associated with masculine sexual behavior: a microdialysis study.

This report compares the changes in the main dopamine (DA) and serotonin (5-HT) metabolites, respectively dihydroxyphenylacetic acid (DOPAC) and 5-hydroxy indoleacetic acid (5-HIAA) in three relatively close brain regions, namely the nucleus accumbens (ACB), the medial preoptic area, and the medial basal hypothalamus (MBH), as well as DA in the ACB, of copulating male rats. All these neurochemicals remained fairly stable when the animals were exposed to non sexual social stimuli (castrated females), and they increased during mating with receptive females. There were regional differences in these copulation-related changes, however, with those in the MBH being shorter-lived. There were also differences in the time-course of the changes in DOPAC and 5-HIAA the latter being slower. It is suggested that they reflect the involvement of the DA and 5-HT innervation of diencephalic structures in, respectively the appetitive and consummatory/satiation mechanisms of sexual behavior. The physiological relevance of these neurochemical changes is supported by the lack of differences between the standard measures for sexual behavior recorded before surgery and during the dialysis session.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Fixed versus removable microdialysis probes for in vivo neurochemical analysis: implications for behavioral studies.

The levels of several neurochemicals, i.e., uric acid (UA), dopamine (DA), dihydroxyphenylacetic acid, and 5-hydroxyindoleacetic acid, collected daily from the rat striatum with either fixed or removable microdialysis probes for 7 days after surgery were compared. The implantation of the fixed cannula was followed by a 10-fold increase in the UA content in the dialysates collected from the first day after surgery onward and by a steady decrease in dihydroxyphenylacetic acid levels, whereas those of DA remained fairly stable. With the removable cannula system, only a smaller, transient increase in UA during the first 3 days after surgery was observed, with no change in DA or monoamine metabolites. The glial reaction around the cannula tracks was assessed by both quantitative histological techniques and measuring the glutamine levels in the dialysates collected at the time of surgery and 7 days later. Both the glial cell number and nuclear size, as well as the glutamine outflow, were considerably larger in the animals implanted with the fixed probes. It is, therefore, likely that the UA levels in the dialysate reflect the glial reaction to the probe. The suitability of the removable probe system for behavioral experiments involving repeated microdialysis sampling was illustrated in an experiment showing that the DA release in the nucleus accumbens of male rats assessed daily at postsurgery days 5-10 was virtually identical in three alternating sessions of sexual behavior as was the smaller release of this neurotransmitter detected during intervening nonsexual social interactions.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Voltammetric monitoring of brain extracellular levels of serotonin, 5-hydroxyindoleacetic acid and uric acid as assessed by simultaneous microdialysis.

We have previously developed a microcomputer-assisted curve-fitting method for measuring the components of the mixed electrochemical signals recorded by differential normal pulse voltammetry in the living brain. It was initially used for resolution of the dopamine and dihydroxyphenylacetic acid components of the catechol signal (peak 2). This report shows how it can be applied to analysis of the indoleamine/uric acid (UA) components of the more complex peak 3. The voltammogram is modeled as a mixture of 3 normal curves of known parameters corresponding to the oxidation of UA, 5-hydroxyindoleacetic acid and serotonin, which is solved by non-linear iterative procedures. Performance was assessed by treatments with drugs having well-known effects on the substances monitored, pargyline and allopurinol, and by the chromatographic analysis of microdialysates collected simultaneously from the contralateral side.

Allopurinol↗
PubMed1992

Peripheral gangrene associated with Kawasaki disease.

Three American infants with Kawasaki disease (KD) complicated by peripheral extremity gangrene are reported. Eight such patients (only 1 from Japan) have been reported previously. These 11 patients, infants less than 7 months old at onset of KD, are predominantly non-Asian. At least nine had associated giant coronary aneurysms, and eight had associated peripheral arterial aneurysms. In eight infants the diagnosis of KD was not established and therapy was not instituted until greater than or equal to 14 days after onset. Peripheral ischemia initially was noted 15-31 days after onset. Although the pathogenesis of this complication is not well understood, it likely includes some combination of local peripheral arteritis, arteriospasm, thrombosis peripherally and/or more proximally (e.g., in an axillary artery aneurysm), and cardiogenic shock. Treatment may include use of antiinflammatory agents such as salicylates and intravenous gamma globulin, vasodilative agents and/or methods, and thrombolytic and/or anticoagulant agents in an attempt to prevent the potentially devastating consequences of progressive gangrene.

Aneurysm↗
PubMed1991

Sex-related olfactory stimuli induce a selective increase in dopamine release in the nucleus accumbens of male rats. A voltammetric study.

Changes in the dopaminergic (DA) transmission in the nucleus accumbens were investigated in male rats exposed to sociosexual olfactory stimuli from different conspecifics: receptive female, non-receptive female and intact male. DAergic transmission was assessed by measurement of extracellular levels of DA and dihydroxyphenylacetic acid (DOPAC). Both compounds were recorded by using differential normal pulse voltammetry (DNPV) with electrochemically pretreated carbon fiber electrodes and numerical analysis of the catechol peak. Exposition to receptive female odors induced a marked and selective increase in DA release compared to control values. Exposition to non-receptive female odors and male odors induced an increase in DA release not significantly different from that following the change of environment. In conclusion, mesencephalic DAergic neurons reaching the nucleus accumbens appear to be involved in the perception of behaviorally significant olfactory cues.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Mathematical resolution of mixed in vivo voltammetry signals. Models, equipment, assessment by simultaneous microdialysis sampling.

A microcomputer-assisted curve-fitting procedure was developed for the quantitative estimation of the components of the mixed "catechol peak" recorded with differential normal pulse voltammetry (DNPV) at electrochemically pretreated carbon fiber microelectrodes in the living brain. The contribution of each of the relevant electroactive species is fitted by a normal probability function, the parameters of which are previously determined in vitro for each electrode and substance. The voltammogram is thus modeled as a mixture of normal curves corresponding to the individual oxidizable substances plus a low order polynomial approximating the baseline. In a former approach the function was solved by linear least squares techniques. As a further improvement, we now propose a non-linear model of the voltammogram and a Gauss-Newton iterative algorithm with stepwise regression for parameter estimation. This report shows the application of the method for the resolution of the dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) components of the DNPV signal recorded from the striatum of freely moving animals in response to amphetamine and pargyline. The method was validated by the chemical assay of contralateral microdialysates collected simultaneously. The changes detected by both methodologies were closely parallel, with highly significant correlation coefficients (0.87 and 0.99 for DA and DOPAC, respectively, P less than 0.001). This study further illustrates that the in vivo voltammetry methodology can be improved substantially by incorporating a suitable mathematical treatment of the electrochemical signals.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1991

Anomalously high concentrations of brain extracellular uric acid detected with chronically implanted probes: implications for in vivo sampling techniques.

The height of peak 2, h2, recorded using linear sweep voltammetry with 350-micron-diameter carbon paste electrodes in rat striatum was measured from the day of implantation (day 0) to 4 months after surgery. The value of h2 was at a minimum on day 0 (0.6 +/- 0.2 nA; n = 20), rose sharply to a maximum on day 2 (6.3 +/- 0.9 nA; n = 12), and decreased to a stable level by day 7 (3.3 +/- 0.7 nA; n = 16), which lasted for 4 months (3.2 +/- 0.6 nA; n = 9). These changes were shown by microinfusion of uricase to be due to variations in the concentrations of extracellular uric acid, although h2 appears to have a small baseline contribution of approximately 0.3 nA from 5-hydroxyindoleacetic acid. The stable value of h2 recorded under chronic conditions was estimated to correspond to a minimal uric acid concentration of 50 mumol/L, which represents a 10-fold increase in the extracellular level of this purine metabolite compared with the initial (acute) value. Very similar results were obtained using a microdialysis technique that detected uric acid directly. These estimates of striatal uric acid concentration are in marked contrast to those obtained using 40-micron diameter carbon fiber electrodes, which showed a decrease from the acute preparation to less than 1 mumol/L under chronic conditions. Large values of h2 were also recorded with chronically implanted paste electrodes in the hippocampus and frontal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Increased dopamine release in the nucleus accumbens of copulating male rats as evidenced by in vivo voltammetry.

This report describes the changes in extracellular levels of dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) detected in the nucleus accumbens of male rats engaged in copulatory activity. They were monitored by using differential normal pulse voltammetry (DNPV) with electrochemically pretreated carbon fiber microelectrodes and numerical analysis of the catechol signal. The copulatory pattern displayed during the voltammetric recordings was similar to those recorded prior to surgery. Copulating animals showed a conspicuous increase in the DA and DOPAC electrochemical signals up to, respectively, 170% and 150% of baseline levels. This response was much attenuated when the experimental animals were exposed to either non-receptive castrated females or intact males. These data are consistent with the permissive role currently ascribed to the dopaminergic innervation of the n. accumbens in the selection and the initiation of behavioral adaptive sequences.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Effects of intrathecal administration of 8-OH-DPAT on genital reflexes and mating behavior in male rats.

Systemic administration of the 5HT1A receptor agonist, 8-OH-DPAT, consistently decreases the threshold of ejaculatory behavior and enhances some aspects of arousal. Previous findings by others demonstrated the in copula ejaculatory behavior effect using intrathecal (IT) injection at the level of the lumbosacral spinal cord, but the dose used was in the range that produced results systemically. This study aimed at a) a more comprehensive study of the sexual effects of 8-OH-DPAT and b) use of IT doses of 8-OH-DPAT below those effective when administered systemically. The ex copula genital reflex test showed severe inhibition. At doses of 5 micrograms or more, significant inhibition of the percentage of rats displaying ejaculation occurred, and the two highest doses also significantly reduced the percentage of rats displaying erection. In the in copula mating test, 20 and 80 micrograms IT 8-OH-DPAT, significantly reduced ejaculation latency, intromission frequency and intercopulatory interval. Copulatory plugs, collected at the highest dose only, showed a trend towards weight reduction. We conclude that the facilitation of ejaculatory behavior and some measure of arousal by 8-OH-DPAT can be mediated directly via the lumbosacral spinal cord. An hypothesis for explaining the inhibitory effect on ejaculation ex copula is presented, but the inhibitory effect on erectile reflexes is without interpretation.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1990

In vivo voltammetry study of the modulatory action of prolactin on the mesolimbic dopaminergic system.

The effects of an acute subcutaneous injection of ovine prolactin (PRL) or its vehicle on total motor activity and the extracellular levels of dopamine (DA), DOPAC and ascorbic acid (AA) in the nucleus accumbens were monitored simultaneously in freely behaving male rats. The neurochemical data were obtained by Differential Normal Pulse Voltammetry using electrochemically pretreated carbon fiber microelectrodes and numerical waveform analysis of the catechol peak. PRL treatment increased the extracellular levels of DA and DOPAC in the nucleus accumbens, which is consistent with previous reports using other methodologies. Furthermore, there was a concomitant decrease in the AA signals and motor activity. These findings suggest an antagonistic action of PRL on dopaminergic transmission in the mesolimbic system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Penile and finger sensory thresholds in young, aging, and diabetic males.

To investigate the possible role of sensory function in conditions affecting sexual function, sensory thresholds were compared between young healthy men (n = 14, means age = 29.8), aging men (n = 15, means age = 67.3), and men suffering from diabetic impotence (n = 15, means age = 45.0). Using the psychophysical method of forced choice, vibrotactile and electrical stimulation thresholds were deterlmined in two separate sessions at two body sites: the fingertip and the ventral surface of the penis, just proximal to the glans. Vibrotactile penile thresholds (VTP) were lowest for young (Y) subjects and much higher for both aging (A) and diabetic (D) subjects. Electrical stimulation of the penis (ESP) showed the same trends, although the differences only approached significance (p = 0.06). The vibrotactile finger threshold (VTF) was significantly higher for A subjects as compared with Y and D subjects, but there was no difference between the Y and D groups. Diabetic patients had significantly higher thresholds for electrical stimulation of the finger (ESF), in contrast to the VTF finding. Finger thresholds were significantly lower than penile thresholds for all groups, and the change in threshold from finger to penis was greater in both aging and diabetic than in young subjects. Age was positively correlated with thresholds for ESF, ESP, VTF, and marginally for VTP when all three groups were analyzed together. However, in general the results of threshold determinations could not be attributed merely to age. Based on a detailed questionnaire of sexuality, VTP was negatively correlated with sexual activity and both ESP and VTP were negatively correlated with erectile capacity. The data are consistent with a genital sensory role for age-related and diabetic changes in sexual function.

Adult↗
PubMed1989

Changes in forebrain Na,K-ATPase activity and serum hormone levels during sexual behavior in male rats.

We have previously shown that Na,K-ATPase activity (the enzymatic machinery for the sodium pump) in brain areas such as the medial basal hypothalamus (MBH) and the preoptic-suprachiasmatic region (POSC) can be changed by experimental manipulations of gonadal function. We now report enzyme levels in brain regions as related to hormonal changes occurring during sexual behavior. Male rats were exposed to receptive females and decapitated immediately after displaying one of the following behavioral events: the start of copulatory activity, first ejaculation, and the beginning of a second copulatory series. A group of noncopulating animals were used as control. The variables measured included serum levels of LH, PRL and testosterone and Na,K-ATPase activity in MBH, POSC and parietal cerebral cortex (CC). A steady increase in enzyme activity in the POSC, but not the MBH or CC, was found in copulating animals. Serum LH levels changed in a similar fashion. A sharp increase in serum PRL levels, seemingly related to ejaculation, was also observed. These data are consistent with our previous findings on monoaminergic neurotransmission in brain regions related to male sexual behavior.

Animals↗
PubMed1989

A component analysis of the effects of DPAT on male rat sexual behavior.

Male rat sexual behavior was examined in a variety of tests following a single acute IP injection of the serotonin1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (DPAT). The objective was to determine the effects of 5-HT1A receptor stimulation on the components of sexual behavior (arousal/motivation, erection and ejaculation) using this prototypical 5-HT1A ligand. In the ex copula genital reflex test, DPAT dramatically inhibited ejaculation and the display of penile erections. When examined in the mating behavior test, DPAT caused a significant reduction in intromission frequency (IF), ejaculation latency (EL), intercopulatory intervals (ICI) and postejaculatory interval (PEI). The decrease in IF and EL indicated a lowering of the behavioral-ejaculatory threshold, while the reduction in ICI and PEI indicated a stimulation of two aspects of sexual arousal. Further tests, however, revealed complexities. Using the mounting test (with genital anesthesia) as an assessment of sexual arousal, no effect of DPAT was found. Collection and examination of the coagulated ejaculates resulting from mating (copulatory plugs) provided evidence of an impairment in ejaculation, as a result of DPAT treatment. The data suggests that 5-HT1A receptor stimulation lowers the behavioral-ejaculatory threshold despite inhibition of ejaculation in and ex copula; as well as stimulating specific aspects of sexual arousal. It remains to be determined whether the effects on arousal were either due to nonselectivity as currently believed or because 5-HT1A receptor stimulation affects alpha 2-adrenoceptor activity by some as yet undefined mechanism; and as a result modulates sexual arousal.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1988

Concurrent on-line analysis of striatal ascorbate, dopamine and dihydroxyphenylacetic acid concentrations by in vivo voltammetry.

A new method for on-line analysis of in vivo differential normal pulse voltammograms is reported. They are fitted by least squares to an expression describing the contribution of different electroactive species and the baseline. Its validity for resolving ascorbate (AA), dopamine (DA) and DOPAC signals is evidenced by both in vitro testing and the changes recorded in the striatum of anesthetized rats following drug treatments having well-known effects on DA release and metabolism. Thus, pargyline and amphetamine treatments respectively increased and decreased DA and DOPAC, whereas they both were increased by haloperidol. AA levels followed those of DA except when haloperidol was given.

3,4-Dihydroxyphenylacetic Acid↗