O extrato etanólico da planta tóxica brasileira, Psedocalymma elegans apresenta efeitos estimulantes sobre o sistema nervoso central / The central nervous system stimulant effects of the ethanolic extract from the toxic Brazilian plant Pseudocalymma elegans

Os efeitos do extrato etanólico da planta tóxica Pseudocalymma elegans (Vell.) Kuhlm. sobre o comportamento de camundongos foi estudado. Camundongos que receberam injeçöes intraperitoneais (i.p.), nas doses de 1.6 a 3g/kg de peso corporal, apresentaram convulsöes e morreram com uma latência média de 8 min. A LD50 foi estimada em 1.8g/kg. Os camundongos que receberam 1g/kg (i.p.) do extrato apresentaram um maior número de "rearings" e um maior tempo de "freezing" do que o grupo controle, quando observados em um campo aberto 30 min após a injeçäo. Durante o tempo em que esses animais foram observados no campo aberto näo ocorreram alteraçöes significativas no número de cruzamentos, tempo de "grooming" e número de bolos fecais. Quando esses animais foram colocados em um labirinto em cruz elevado exploraram menos os braços abertos do labirinto que os animais controle: apresentaram uma menor porcentagem de entradas e uma menor porcentagem de tempo de permanência nos braços abertos do labirinto. Esses animais apresentaram também uma menor atividade locomotora medida de forma automatizada e nenhuma alteraçäo no tônus muscular, avaliado pelo tempo de permanência em um arame esticado. Os três primeiros testes sugerem que a administraçäo de doses moderadas do extrato desencadeia um efeito "ansiogênico" contrário ao observado com a administraçäo de ansiolíticos depressores do sistema nervoso central (SNC). Doses maiores do extrato provocam uma super-estimulaçäo do SNC com convulsöes que, eventualmente, podem contribuir para a letalidade do extrato

Effect of brain lesions on rat shuttle behavior in four different tests.

Rats were trained to perform shuttle responses to a buzzer in four different situations: pseudoconditioning or D test (buzzers and footshocks presented at random), classical conditioning or DP test (buzzers and footshocks paired on every trial), avoidance without stimulus pairing or DC test (buzzer-shock intervals varied at random, shocks contingent upon non-emission of a shuttle response to the preceding buzzer), and standard two-way avoidance or DPC test (buzzers paired to shocks, but the latter omitted every time there was shuttling to the buzzer). The letters in each test disignate the factors involved in the emission of responses in each one, which were shown in previous papers to be: a non-associative factor or "drive" (D), the Pavlovian or stimulus-stimulus relation ("pairing", P), and the shuttle-no shock or main avoidance contingency (C). The effects of various brain lesions on these behaviors were studied. Ventral caudate and amygdala lesions depress both the Pavlovian (P) and the avoidance (C) component. Dorsal caudate lesions have an opposite influence on these two factors. Septal (n.medialis + lateralis, and n.accumbens) and tuberculum olfactorium lesions enhance the non-associative component (D); accumbens lesions, in addition, impair operation of the C factor. The effect of the diverse lesions on jumping responses to the buzzer or on performance of intertrial crossings does not correlate with the effect on shuttle responses.

Brain dopamine and noradrenaline levels in rats submitted to four different aversive behavioral tests.

Rats were trained to perform shuttle responses to a buzzer in four different situations: Pseudoconditioning (buzzers and footshocks presented at random), classical conditioning (buzzers and footshocks paired on every trial), avoidance without stimulus pairing (buzzer--shock intervals varied at random, shocks contingent upon the nonemission of a shuttle response to the preceding buzzer), and standard two-way avoidance (buzzers paired to shocks, but the latter omitted every time there was a shuttle to the buzzer). Animals were killed immediately after the last trials and the noradrenaline and dopamine content of their hypothalamus, amygdala, caudate nucleus, and nucleus accumbens was determined. There were falls of dopamine content in the caudate and accumbens and falls of noradrenaline levels in all structures except the caudate after the pseudoconditioning test. Noradrenaline levels were normal, and dopamine levels were partially recovered, in the animals submitted to the other training situations. Thus learning factors (stimulus pairing and/or the avoidance contingency) offset the depleting influence of footshocks per se on both catecholamines in at least the structures studied.