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B Dib

Publications and source records attributed to B Dib.

25 records · Page 2Linked to original sources
PubMed1983

Dissociation between peripheral and central heat loss mechanisms induced by neonatal capsaicin.

Fifty-eight 4-day-old male rats were studied. Peripheral desensitization was induced in 36 rats by sc administration of capsaicin in increasing doses (350, 700, 1,400, 2,100, and 2,800 micrograms) on 5 consecutive days. When adult, 9 treated and 5 control rats were chronically implanted with a lateral intracerebroventricular (icv) guide cannula. This tube was used for icv capsaicin injection. Eleven treated rats and 6 controls were implanted with a hypothalamic thermode. Hypothalamic heating was activated with the aid of this water-perfused thermode. Twenty-eight rats, 12 control and 16 treated, were injected ip and sc with capsaicin. Results showed that in control rats, icv, ip, and sc capsaicin injections produced a fall in body (core) temperature and an increase in cutaneous temperature. These changes are attributed to cutaneous vasodilation. In capsaicin-treated rats, sc and ip injections had no effect on body temperature. However, neonatal treatment did not inhibit the effect of capsaicin on body temperature. Furthermore, in these rats thermoregulatory behavior for fresh air was identical to that of controls at all ambient temperatures before and during hypothalamic heating. These results suggest that the central heat receptors responsible for autonomic and behavioral thermoregulation in the treated rats function normally when icv capsaicin is injected or when the hypothalamus is heated. In contrast, neonatal injection of capsaicin produced an inhibition of the heat loss mechanisms induced by ip or sc capsaicin, i.e., by stimulation of the peripheral nervous system.

Animals↗
PubMed1983

[Acute effects of intrathecal capsaicin and substance P on nociceptive thresholds in rats].

We have compared the effects of a single intrathecal injection of capsaicin or substance P (SP) on the motor responses to radiant heat and electrical nociceptive stimulations in the Rat. With nociceptive electrical stimulation, an immediate hyperalgesia followed capsaicin injection in all Rats. On the other hand, some Rats displayed hyperalgesia after SP while others showed hypoalgesia. Both capsaicin and SP, induced hypoalgesia to radiant heat in 17 rats. In 5 rats no response was obtained.

Animals↗
PubMed1982

Behavioral self warming and cooling of spinal canal by rats.

Rats with a chronic thermode implanted in their spinal canal could bar-press to warm or cool their spinal cord. With a "cold" lever, they cooled their spinal canal less in a cold environment than in a warm environment. With a "warm" lever they behaved in the same way, i.e., warmed their spinal canal more in a warm than in a cold environment. In a two-lever situation they pressed the cold and the warm levers alternatively in warm environment, but did not press either in cold environment. These results suggest that cold and warm spinal cord provided the rats with rewards of a different nature.

Animals↗
PubMed1982

Effects of intracerebroventricular capsaicin on thermoregulatory behavior in the rat.

To clarify the action of capsaicin on the thermoregulatory system of rat, behavioral and autonomic responses were studied following intracerebroventricular (ICV) injection. Rats were chronically implanted with a lateral cerebral ventricular guide cannula. After the recovery period they were placed in a climatic chamber at ambient temperature (Ta) of 20, 30 or 35 degrees C. In the first series of experiments, they had access to a lever which activated a fan that drew cool outside air into the chamber. After ICV capsaicin (23 micrograms), the rats increased bar-pressing behavior for fresh air at Ta ranging from 20 degrees C to 35 degrees C. In the second series of experiment, the rats had no access to fanning. ICV capsaicin produced a fall in rectal and hypothalamic temperature (Thy) and an increased in cutaneous temperature. These changes depended on Ta. At a Ta of 30 degrees C Thy fell slightly (mean of 0.2 +/- 0.16 degrees C). At a Ta of 20 degrees C Thy fell to a mean of 1 degree C +/- 0.17 degrees C. The conclusion drawn is ICV capsaicin activated behavioral as well as autonomic thermoregulatory heat-loss responses. The effect of capsaicin resembles the effect of local heating of the hypothalamus. However, since hypothalamic temperature decreased the drug may have lowered the thermal set point, or excited directly hypothalamic warm-sensitive neurons.

Animals↗
PubMed1982

Intracerebroventricular self-injection of morphine in response to pain in the rat.

Rats were chronically implanted with a lateral cerebral ventricular guide cannula. After recovery they were trained to self-inject morphine sulfate. A week after this training period, self-injection behavior was studied during nociceptive stimulation. In response to a nociceptive stimulation rats increased their intracerebroventricular self-administration of morphine. This effect is specific for morphine since under identical conditions rats did not increase NaCl administration. Naloxone pretreatment inhibits self-administration of morphine in 5 rats. However, two rats increased morphine self-intake. These results show that rats can directly perceive a decrease of pain sensation induced by the morphine self-administration. This experimental situation is therefore similar to the therapeutic situation in humans, in which the criterion of efficacy of an analgesic is a reduction of the conscious pain sensation. Experimental self-administration during painful stimulation might therefore be used for preclinical evaluation of the efficacy of an analgesic drug.

Animals↗