DISTRIBUTION OF DIFFERENT FIBER TYPES OF M-EXTENSOR CARPI RADIALIS LONGUS OF THE RAT

As revealed by the NADH-diaphorase and myosine ATPase, the M. extensor carpi radialis longus of the rat possesses at least 3 main kinds of fibres, with different distribution on the superficial and deep portions of the muscle. The superficial portion revealed that 67.68 % are FG (fast-twitch-glycolytic) fibres, 14.72 % are FOG (fast-twitch-oxidative) fibres and 17.60 % are SO (slow-twitch-glycolytic) fibres. Already the deep portion revealed that 71.29 % are SO (slow-twitch-glycolytic) fibres, 17.46 % are FOG (fast-twitch-oxidative-glycolytic) fibres and 11.25 % are FG (fast-twitch-glycolytic) fibres. The miosine ATPase reaction was used to demonstrate contracting characteristics. These findings suggest that the movements of fast contraction of the M. extensor carpi radialis longus are predominant.

Potentiation of panic-like behaviors of the rat by subconvulsive doses of strychnine

The present study was carried out to determine possible panicogenic effects of strychnine administered in subconvulsive doses to rats. Two experiments were conducted to assess two major features of panic in animal models: panic-related flight (through the observation of wild running [WR]) and defensive fights. In the first one, 20 adult male Wistar rats were injected with six different doses of strychnine ranging from 0.5 to 4.0 mg/kg. After 15 min of free observation, the animals were submitted to high-intensity acoustic stimulation and the incidence of WR was recorded. Higher doses of strychnine (above 2.5 mg/kg) easily evoked seizures, but lower doses raised the incidence of WR in a dose-dependent manner. The most effective dose for WR (1.5 mg/kg) was used in the second experiment, in which we investigated the effects of strychnine on sleep-deprivation-induced fights (SDIFs) that have defensive characteristics. For this purpose, 40 subjects were submitted to 5 days of REM-sleep deprivation by the single-platform method and were then assigned into two groups, i.e., strychnine vs. control. After the injections, the animals were observed in social groupings for SDIF recordings over a period of 60 min. The strychnine-treated groups had more SDIF than the control groups (P<.05, Mann-Whitney U test). We conclude that the high level of neural excitability promoted by partial blockade of the glycinergic system can contribute to the manifestation of panic reactions. (C) 2003 Elsevier B.V. All rights reserved.

Elastic system of the rat ventral prostate and its modifications following orchiectomy

BACKGROUND. The extracellular matrix (ECM) has important roles in prostatic development, and marked stromal changes take place in the rat ventral prostate (VP) after androgen deprivation. However, little knowledge exists about individual ECM components.METHODS. The distribution of elastic fibers (EF) and elastic-related fibers (ERF) in the VP of castrated and control rats was investigated, using histochemistry and transmission electron microscopy (TEM).RESULTS. EF are barely detected in the prostatic stroma, but ERF are relatively abundant. Castration results in a relative increase in the number and thickness of ERF. TEM showed an open network of ECM microfibrils throughout the stroma and thin and short EF, which increase in number and thickness after orchiectomy.CONCLUSIONS. The presence of elastic system components in the rat VP warrants the deformability required for the secretion exclusion under the action of smooth muscle cells, and the castration-induced modification may be related to the contraction of the tissue and maintenance of peculiar arrangements of other ECM components. (C) 1997 Wiley-Liss, Inc.

Acute swimming stress induces changes in noradrenergic mechanisms in order to maintain the response pattern of the rat vas deferens to norepinephrine

This study investigated mechanisms involved in the maintenance of the functional response pattern of the postjunctional alpha(1)-adrenoceptor in vas deferens isolated from rats submitted to acute swimming stress. The plasma corticosterone levels increased approximately three times after the swimming stress in the nontreated rats as well as after swimming stress in the rats pretreated with desipramine (DMI), yohimbine (YO), or DMI with YO. No alteration was detected in the sensitivity to norepinephrine (NE) in the vasa deferentia from the stressed rats or stressed rats treated with DMI or DMI with YO, in relation to their respective control. However, when the vasa deferentia were previously incubated with DMI, a reduction in sensitivity to NE in organs from stressed rats was observed. Vasa deferentia excised from rats pretreated with YO before the swimming stress showed an increase in postjunctional alpha(1)-response that was abolished by prazosin (PZ). Thus, the neuronal uptake, the prejunctional alpha(2)-adrenoceptors (mediating prejunctional inhibition), the occupancy and functional response of the postjunctional alpha(1)-adrenoceptors, and the emotional stress component were very important for the determination of the noradrenergic response pattern in vas deferens from rats submitted to acute swimming stress. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Alcohol-induced alterations in the palate epithelium of the rat fetus.

Maternal alcoholism (ethanol and sugar cane brandy) during gestation induces delayed cellular growth and differentiation in fetal rat palate epithelium, with increased nuclear, cytoplasmic and cellular volumes, increased epithelial and keratin thickness and decreased cellular numerical density.

The possible involvement of hyperpolarizing mechanisms in histamine-induced relaxation of the rat portal vein

The present study evaluated the effects of histamine 10 -2 M on longitudinal preparations of rat portal vein. It was observed that histamine 10 -2 M induced relaxation of rat portal vein preparations pre-contracted with phenylephrine 10 -4 M. On the other hand, no pharmacological effects were observed in preparations not pre-contracted. The observed histamine-induced relaxing effect was absent in preparations pre-contracted with KCl (120 mM) or in the presence of depolarizing nutritive solution. However, the histamine-induced relaxation was still present in the endothelium-removed preparations. The histamine-induced relaxation also was not prevented by astemizole (10 -6 M, 10 -5 M and 10 -4 M), cimetidine (10 -5 M, 10 -4 M and 10 -3 M) or thioperamide (10 -6 M, 10 -5 M and 10 -4 M), selective antagonists H 1, H 2 and H 3, respectively. The presence of L-NAME 10 -4 M or L-NAME 10 -4 M plus indomethacin 10 -5 M also did not prevent the histamine-induced relaxation observed in rat portal vein. Thus, the histamine-induced relaxation observed in rat portal vein appears to involve a non-endothelial hyperpolarizing mechanism independent of H 1, H 2 and H 3 receptors.

Paraventricular nucleus of the hypothalamus glutamate neurotransmission modulates autonomic, neuroendocrine and behavioral responses to acute restraint stress in rats

In the present study, the involvement of paraventricular nucleus of the hypothalamus (PVN) glutamate receptors in the modulation of autonomic (arterial blood pressure, heart rate and tail skin temperature) and neuroendocrine (plasma corticosterone) responses and behavioral consequences evoked by the acute restraint stress in rats was investigated. The bilateral microinjection of the selective non-NMDA glutamate receptor antagonist NBQX (2 nmol/ 100 nL) into the PVN reduced the arterial pressure increase as well as the fall in the tail cutaneous temperature induced by the restraint stress, without affecting the stress-induced tachycardiac response. On the other hand, the pretreatment of the PVN with the selective NMDA glutamate receptor antagonist LY235959 (2 nmol/100 nL) was able to increase the stress-evoked pressor and tachycardiac response, without affecting the fall in the cutaneous tail temperature. The treatment of the PVN with LY235959 also reduced the increase in plasma corticosterone levels during stress and inhibited the anxiogenic-like effect observed in the elevated plus-maze 24 h after the restraint session. The present results show that NMDA and non-NMDA receptors in the PVN differently modulate responses associated to stress. The PVN glutamate neurotransmission, via non-NMDA receptors, has a facilitatory influence on stress-evoked autonomic responses. On the other hand, the present data point to an inhibitory role of PVN NMDA receptors on the cardiovascular responses to stress. Moreover, our findings also indicate an involvement of PVN NMDA glutamate receptors in the mediation of the plasma corticosterone response as well as in the delayed emotional consequences induced by the restraint stress. © 2012 Elsevier B.V. and ECNP.

Ethopharmacological evaluation of the rat exposure test: A prey-predator interaction test

The rat exposure test (RET) is a prey (mouse)-predator (rat) situation that activates brain defensive areas and elicits hormonal and defensive behavior in the mouse. Here, we investigated possible correlations between the spatiotemporal [time spent in protected (home chamber and tunnel) and unprotected (surface) compartments and frequency of entries into the three compartments] and ethological [e.g., duration of protected and unprotected stretched-attend postures (SAP), duration of contact with the rat's compartment] measures (Experiment 1). Secondly, we investigated the effects of systemic treatment with pro- or anti-aversive drugs on the behavior that emerged from the factor analysis (Experiment 2). The effects of chronic (21 days) imipramine and fluoxetine on defensive behavior were also investigated (Experiment 3). Exp. 1 revealed that the time in the protected compartment, protected SAP and rat contacts loaded on factor 1 (defensive behavior), while the total entries and unprotected SAP loaded on factor 2 (locomotor activity). Exp. 2 showed that alprazolam (but not diazepam) selectively changed the defensive factor. Caffeine produced a mild proaversive-like effect, whereas yohimbine only decreased locomotor activity (total entries). Fluoxetine (but not imipramine) produced a weak proaversive-like effect. 5-HT1A/5-HT2 receptor ligands did not change any behavioral measure. In Exp. 3, chronic fluoxetine (but not imipramine) attenuated the defensive behavior factor without changing locomotion. Given that the defensive factor was sensitive to drugs known to attenuate (alprazolam and chronic fluoxetine) and induce (caffeine) panic attack, we suggest the RET as a useful test to assess the effects of panicolytic and panicogenic drugs. © 2012 Elsevier B.V.