Mild hypothermia reduces polymorphonuclear leukocytes infiltration in induced brain inflammation

Over the last 50 years deep hypothermia (23 degrees C) has demonstrated to be an excellent neuroprotective agent in cerebral ischemic injury. Mild hypothermia (31-33 degrees C) has proven to have the same neuroprotective properties without the detrimental effects of deep hypothermia. Mechanisms of injury that are exaggerated by moderate hyperthermia and ameliorated by hypothermia include, reduction of oxygen radical production, with peroxidase damage to lipids, proteins and DNA, microglial activation and ischemic depolarization, decrease in cerebral metabolic demand for oxygen and reduction of glycerin and excitatory amino acid (EAA) release. Studies have demonstrated that inflammation potentiates cerebral ischemic injury and that hypothermia can reduce neutrophil infiltration in ischemic regions. To further elucidate the mechanisms by which mild hypothermia produces neuroprotection in ischemia by attenuating the inflammatory response, we provoked inflammatory reaction, in brains of rats, dropping a substance that provokes a heavy inflammatory reaction. Two groups of ten animals underwent the same surgical procedure: the skull bone was partially removed, the duramater was opened and an inflammatory substance (5% carrageenin) was topically dropped. The scalp was sutured and, for the group that underwent neuroprotection, an ice bag was placed covering the entire skull surface, in order to maintain the brain temperature between 29.5-31 degrees C during 120 minutes. After three days the animals were sacrificed and their brains were examined. The group protected by hypothermia demonstrated a remarkable reduction of polymorphonuclear leukocytes (PMNL) infiltration, indicating that mild hypothermia can have neuroprotective effects by reducing the inflammatory reaction.

Nos últimos 50 anos, a hipotermia tem demonstrado ser um excelente agente neuroprotetor nas lesões isquêmicas encefálicas. A hipotermia moderada (310 C - 330 C) provou também apresentar as mesmas propriedades protetoras, sem os efeitos deletérios da hipotermia profunda. Dentre alguns mecanismos de lesão que são melhorados pela hipotermia e piorados pela hipertermia moderada, podemos citar a diminuição da demanda de oxigênio pelo encéfalo e a redução da glicina e aminoácidos excitatórios, evitando a produção de radicais de oxigênio, com aumento da peroxidase e conseqüente lesão aos lípides, proteínas e DNA, assim como pela ativação microglial e despolarização isquêmica. Alguns estudos demonstraram que a inflamação potencializa a lesão isquêmica e que a hipotermia pode reduzir a infiltração leucocitária nas áreas isquêmicas. Para melhor elucidar os mecanismos pelos quais a hipotermia apresenta efeito neuroprotetor através da redução da inflamação, no processo isquêmico, escolhemos o método utilizando a indução de uma reação inflamatória com a utilização de uma substância com capacidade promover intensa reação inflamatória em encéfalos de ratos. Dois grupos de dez animais foram submetidos a um mesmo procedimento cirúrgico: a calota craniana foi parcialmente removida, a duramáter aberta e uma substância com potente efeito inflamatório (carragenina a 5%) foi gotejada. A pele foi suturada e, para o grupo com neuroproteção, uma bolsa de gelo foi colocada, cobrindo toda a superfície craniana, de modo a manter a temperatura encefálica entre 29,50 C e 310 C durante 120 minutos. Três dias após, os animais foram sacrificados e os encéfalos examinados. O grupo protegido pela hipotermia apresentou considerável redução na infiltração leucocitária, demonstrando que a hipotermia pode apresentar função neuroprotetora por meio de uma redução no processo inflamatório.

Neuromuscular activity of Bothrops neuwiedi pauloensis snake venom in mouse nerve-muscle preparations

The pharmacological effects of Bothrops neuwiedi pauloensis venom on mouse phrenic nerve-diaphragm (PND) preparations were studied. Venom (20 mug/ml) irreversibly inhibited indirectly evoked twitches in PND preparations (60 ± 10 percent inhibition, mean ± SEM; p<0.05; n=6). At 50 mug/ml, the venom blocked indirectly and directly (curarized preparations) evoked twitches in mouse hemidiaphragms. In the absence of Ca2+, venom (50 mug/ml), produced partial blockade only after an 80 min incubation, which reached 40.3 ± 7.8 percent (p<0.05; n=3) after 120 min. Venom (20 mug/ml) increased (25 ± 2 percent, p< 0.05) the frequency of giant miniature end-plate potentials in 9 of 10 end-plates after 30 min and the number of miniature end-plate potentials which was maximum (562 ± 3 percent, p<0.05) after 120 min. During the same period, the resting membrane potential decreased from - 81 ± 1.4 mV to - 41.3 ± 3.6 mV 24 fibers; p<0.01; n=4) in the end-plate region and from - 77.4 ± 1.4 to -44.6 ± 3.9 mV (24 fibers; p<0.01; n=4) in regions distant from the end-plate. These results indicate that B. n. pauloensis venom acts primarily at presynaptic sites. They also suggest that enzymatic activity may be involved in this pharmacological action.(AU)

The water extract of Coleus barbatus Benth decreases gastric secretion in rats

Coleus barbatus (Labiatae) Benth is popularly used in Brazil "for the healing of liver and stomach diseases". The water extract (WE 1 to 10 g/Kg, p.o.) of stem and leaves given to rats and mice did not induce signs of intoxication. Preveious treatment of mice with WE (1 g/kg, p.o.) shortened the sleeping time induced by pentobarbital (50 mg/Kg, i.p.) by 37 por cento, althoyugh the extract alone did not increase the spontaneous activity nor did it induce hyperexcitability. In mice WE (2 g/Kg, p.o.) increased the intestinal transit of charcoal by 30 por cento, while reduced gastric secretions ion rats treated with WE (2g/Kg intraduodenal) 3,9 ± 1.0 to 0.5 ± 0.2 ml/4h, respectively). The treatment also reduced the total acid secretion from 34.4 ± 11.0 to 2.7 ± 0.5 mEq/l and raisedgastric pH from 2.2 ± 0.3 to 6.5 ± 0.8. Treatment with WE (2g/Kg, p.o.) protected against gastric ulcers induced by stress (5.3 ± 1.6 and 1.5 ± 0.5 ulcers/cm²), but did nor protect against indonethacin induced ulcers. The results show that the water extract of C barbatus Benth produces mild stimulation of thecentral nervous system and increases intestinal movements. The extract also reduces gastric secretion indicating an antidyspeptic activity, and protects against gastric ulcers induced by stress.

Efflux of acetylcholine in dimorphic skeletal muscle from castrated male rats

The effect of testosterone on motor neurons of dimorphic muscles is demostrable by increased frequency of miniature end-plate potentials (mepp) and decreased end-plate acetylcholinesterase activity observed in castrated rats. No change occurs in induced acetylcholine (ACh release. Although these muscles atrophy after castration there is no loss of muscle fibers. In the present study we reinvestigate the neuromuscular transmission in levator ani (LA) muscles from normal (N) adult (120 days) male rats and from rats castrated (C) 30 days before. The measurement of radioactive [3H]-choline was used to evaluate ACh release since it permits simultaneous estimation of quantal and non-quantal and non-quantal ACh release. The LA muscle was incubated with [3H]-choline (1µCi/ml) for 30 min and ACh efflux was measured after washout. The basal release of [3H]-choline (dpm total tissue radioactivity-1 number of fibers-1) was 296 ñ 33 and 156 ñ 24 in N and C, respectively. Induced ACh release (25 Hz, 5 min) was the same in N and C (653.19 ñ 66.46) and 496.62 ñ 68.67, respectively). These results indicate that castration increased nepp frequency buth reduced the total spontaneous release of ACh

Globular and asymmetric forms of acetylcholinesterase in the rat levator ani muscle

The endplate (+EP) and non-endplate (-EP) distribution of molecular formas of acetylcholinesterase (AChE) was compared in the dimorphic levator ani and disphragm muscles from adult male rats. Enzyme activity was measured by the thicholine method and AchE forms were separated on the basis of solubility in sodium phosphate buffer of different ionic strenght. For the dimorphic levator ani muscle, total AchE activity was 342.6 ñ 18.9 nmol ASCh hydrolyzed min-1 muscle-1, 90% of which was globular and predominated in the-EP region (78%). The asymmetric forms were almost exclusively detected in the +EP region (9%). In diaphragm muscler, total AChE activity was 176.7 ñ 11.0 units; 66% was mainly globular and located in the-EP region (56%); the asymmetric forms (34%) were either in -EP (11%) or + EP (23%) regions. Thus, a greater proportion of globular form was presented in the dimorphic levator ani muscle than in diaphragm muscle. In view of the control exerted by testosterone on dimorphic muscles, its is suggested that the grater synthesis of the globular form in the levator ani occurs under the trophic influence of testosterone

Androgen regulation of the nicotinic acetylcholine receptor-ionic channel in a hormone-dependent skeletal muscle

The trophic influence of testosterone on the nicotinic acetylcholine receptor-ionic channel (AChR) was studied in the levator ani (LA) muscle of adult malr rats (120 days) intact (C) or gonadectomized when 90 days old (G). In the indirectly elicited muscle twitch, the LA from G rats was less sensitive to d-tubocurarine (0.1-1µM) than control muscles (IC25:C = 0.30µM,G=0.46µM). In G rats, the amplitude of neurally evoked endplate currents (EPC) was reduced by 70%, but the EPC time constant was not changed. Maximal junctional binding of [125I] alfa-bungarotoxin in the LA(C: 72.5 ñ 13.2 amol/endplate) was reduced by 18.8-fold in LA from G rats, with no change of the association rate constant (C: 5.64 ñ 1.29 10**6 M-1 min**-1). The results indicate that testosterone deprivation reduces the junctional AChR density in the rat LA without modifying the binding properties of the receptor

Phentonium induces a transient increase of acetylcholine efflux from motor nerve terminals

Phenthonium (10-50 µM), a quaternary derivative of 1-hyoscyamine, increases the frequency of miniature end-plate potentials (205 fold) and blocks the nicotinic receptor-ionic channel in skeletal muscles. When tested on rat diaphragms previously incubated with [3H] choline, phenthonium (50µM) increased the spontaneous release of radiolabelled acetylcholine (ACh) from 11.6 ñ 6.4 to 110.5 ñ 40.2 x 10**3 dpm/g within 15 min. The effect was transient, declining to 24.6 ñ 14.7 after 50 min. Subsequent electrical stimulation still in the prsence of phenthonium increased the efflux to 164.7 ñ 45.3. The fractional release relative to the level before stimulation did not differ from controls. Phenthonium (20 µM) did not increase the spontaneous ACh release but doubled the efflux induced by nerve stimulation. The present results, compared to previous electrophysiological findeings, indicate that quantal and nonquantal release are increased by phenthonium. They also show that the transient effect is not due to ACh depletion in nerve terminals

Efeitos da administracao endovenosa do delta 9-tetrahidrocanabinol na pressao intraocular de coelhos. / Effects of intravenous administration of delta 9-tetrahydrocannabinol on intraocular pressure of rabbits

Os efeitos da administracao aguda do delta-9 tetrahidrocanabinol (THC; 5 mg/kg) na pressao arterial (PA) e na pressao intraocular (PIO) foram comparados em coelhos integros e coelhos com sistema nervoso central (SNC) destruido. Apos destruicao do SNC os animais eram mantidos sob respiracao artificial e a pressao sistemica elevada com a infusao e.v.de metaraminol (+/- 0,1 mg/kg/min.). As PA e a PIO registradas nao diferiram nos grupos de coelhos integros e com SNC destruido (PA = 71,6 +/- 5,2 e 85,2 +/- 9,5 mmHg; PIO = 19,7 +/- 3,9 e 18,9 +/- 2,1 mmHg respectivamente).Foi verificado que a hipotensao arterial produzida pelo THC nos animais integros (delta = 28,1 +/- 2,6 mmHg) foi acompanhada paralelamente por diminuicao (25%) da pressao intraocular. Apos destruicao do SNC as respostas ao THC foram bloqueadas sem que os efeitos da noradrenalina e acetilcolina sofressem modificacoes significativas. Conclui-se que a diminuicao do PIO de coelhos apos administracao aguda do THC e causada pela hipotensao arterial sitemica devida a inibicao bulbar produzida pelo canabinoide