Ventromedial hypothalamus lesions increase the dipsogenic responses and reduce the pressor responses to median preoptic area activation

In this study, we investigated the participation of adrenergic receptors of the median preoptic area (MnPO) and the participation of ventromedial hypothalamus (VMH) in angiotensin II- (ANG II)-induced water intake and presser responses. Male rats with sham or electrolytic VMH lesions and a stainless steel cannula implanted into the MnPO were used. Noradrenaline, clonidine (an alpha(2)-adrenergic receptor agonist), or phenylephrine (an alpha(1)-adrenergic receptor agonist) injected into the MnPO of sham-lesioned rats reduced water ingestion induced by ANG II injected into the same area. In VMH-lesioned rats ANG II-induced water intake increased with a previous injection of noradrenaline, phenylephrine, or isoproterenol. The presser response induced by ANG II injected into the MnPO was reduced in VMH-lesioned rats, whereas the presser response induced by clonidine was abolished. Previous treatment with noradrenaline and phenylephrine into the MnPO of sham-lesioned rats produced a presser response, and a hypotensive response was obtained with the previous administration of noradrenaline, phenylephrine or isoproterenol into the MnPO of VMH-lesioned rats. These results show that VMH is essential for the dipsogenic and presser responses induced by adrenergic and angiotensinergic activation of the MnPO in rats. (C) 1997 Elsevier B.V.

Complete staining of nerve fiber and myoneural junctions with acetylthiocholine and silver

We describe a combined stain for simultaneous demonstration of the preterminal axons and cholinesterase activity at myoneural junctions of mammalian muscles. This technique employs acetylthiocholine iodide as the substrate for cholinesterase activity and silver nitrate impregnation of preterminal axons. The procedure is rapid, simple and uses fresh muscles. Intramuscular nerves, preterminal axons and myoneural junctions are stained simultaneously brown or black with minimal background staining of connective tissue and muscle fibers.

EFFECT OF TESTOSTERONE ON THE PRESSOR-RESPONSE TO COMMON CAROTID OCCLUSION IN GONADECTOMIZED CONSCIOUS MALE-RATS WITH LESION OF THE MEDIAN-EMINENCE

The influence of testosterone on the development of the pressor response to common carotid occlusion was investigated in control and median eminence-lesioned male rats. In control rats (N = 9), gonadectomy performed 21 days before the experiments reduced by 22% (from 51 +/- 2 to 40 +/- 2 mmHg) and treatment with testosterone (300-mu-g for 4 days before the measurements) increased the initial peak pressor response (from 51 +/- 2 to 57 +/- 2 mmHg) which depends on carotid innervation. The maintained response which is of central origin (probably ischemic) was less affected. In nongonadectomized rats (N = 6), lesions of the median eminence (6 days) decreased the initial peak by 19% (from 52 +/- 2 to 42 +/- 3 mmHg) and the maintained response by 56% (from 32 +/- 2 to 14 +/- 1 mmHg). Sham-operated rats served as controls. In gonadectomized animals (N = 6) the lesion reduced only the maintained response (from 23 +/- 2 to 11 +/- 1 mmHg). Testosterone supplementation restored the maintained response but did not alter the initial peak. These results indicate that the pressor response to common carotid occlusion in male rats is modulated by testosterone and that the depression in the maintained response caused by median eminence lesion can be reversed by steroid supplementation.

A column generation approach to capacitated p-median problems

The Capacitated p-median problem (CPMP) seeks to solve the optimal location of p facilities, considering distances and capacities for the service to be given by each median. In this paper we present a column generation approach to CPMP. The identified restricted master problem optimizes the covering of 1-median clusters satisfying the capacity constraints, and new columns are generated considering knapsack subproblems. The Lagrangean/surrogate relaxation has been used recently to accelerate subgradient like methods. In this work the Lagrangean/surrogate relaxation is directly identified from the master problem dual and provides new bounds and new productive columns through a modified knapsack subproblem. The overall column generation process is accelerated, even when multiple pricing is observed. Computational tests are presented using instances taken from real data from Sao Jose dos Campos' city.

Effect of electrolytic and neurotoxic lesions of the median raphe nucleus on anxiety and stress

To study the role played by 5-HT mechanisms of the MRN, behavioural and physiological parameters were presently measured in rats having either electrolytic or 5,7-dihydroxytryptamine (5,7-DHT) lesion of the MRN made 7 days before testing. Half the animals were submitted to 2-h restraint 24 h before the test. In the elevated plus-maze, the electrolytic lesion increased the percentage of open-arm entries and of time spent on open arms - an anxiolytic effect - in both restrained and nonrestrained rats. The neurotoxic lesion had a similar effect, but only on restrained rats. Restraint had anxiogenic effect. The electrolytic lesion increased transitions between the light and dark compartments and the time spent in the bright compartment of the light-dark box in both restrained and nonrestrained rats. The neurotoxic lesion only increased bright time in restrained rats. The incidence, number and size of gastric ulcers were increased by either the electrolytic or the neurotoxic lesion in both restrained and nonrestrained animals. Both types of lesion depleted 5-HT in the hippocampus in restrained and nonrestrained rats. Restraint increased 5-HT levels. These results implicate 5-HT mechanisms of the median raphe nucleus in the regulation of anxiety and in the genesis of gastric stress ulcers. (C) 2001 Elsevier B.V. All rights reserved.

Regulation of contextual conditioning by the median raphe nucleus

The median raphe nucleus (MRN) has been suggested as the origin of a behavioral inhibition system that projects to the septum and hippocampus. Electrical stimulation of this mesencephalic area causes behavioral and autonomic manifestations characteristic of fear such as, freezing, defecation and micturition. In this study we extend these observations by analyzing the behavioral and autonomic responses of rats with lesions in the MRN submitted to a contextual conditioning paradigm. The animals underwent electrolytic or sham lesions of the median raphe nucleus. One day (acute) or 7 days (chronic) later they were tested in an experimental chamber where they received 10 foot-shocks (0.7 mA, 1 s with 20-s interval). The next day, sham and MRN-lesioned animals were tested again either in the same or in a different experimental chamber. During this, the duration of freezing, rearings, bouts of micturition and number of fecal boli were recorded. Sham-operated rats placed in the same chamber showed more freezing than rats exposed to a different context. This freezing behavior was clearly suppressed in rats with acute or chronic lesions in the MRN. MRN lesions also reduced the bouts of micturition and number of fecal boli. These rats showed a reduced number of rearings than sham-lesioned rats. This effect is probably the result of the displacement effect provoked by freezing since no significant differences in the number of rearings could be observed between these animals and the NMR-lesioned rats tested in an open field. This lesion produced higher horizontal locomotor activity in this test than the controls (sham-lesioned rats). These results point to the importance of the median raphe nucleus in the processing of fear conditioning with freezing being the most salient feature of it. Behavioral inhibition is also under control of MRN but its neural substrate seems to be dissociated from that of contextual fear. (C) 1998 Elsevier B.V. B.V.