Journal of anesthesia
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Journal of anesthesia · Sep 1996
Cervical sympathectomy inhibits axonal transport of gonadotropin-releasing hormone during continuous exposure to light in male rats.
To examine the effects of cervical sympathectomy on the transport of gonadotropin-releasing hormone (GnRH) between the hypothalamic neurons and the median eminence, 16 male rats were assigned into four groups: control (C), light (L), light-sympathectomy (LS), and light-colchicine (LC). The C group was kept under a normal circadian rhythm for 2 weeks, and the L group was kept under continuous exposure to light for the same period. The LS group underwent bilateral cervical sympathectomy before being kept under continuous light conditions for 2 weeks. ⋯ The L group showed a decreased number of GnRH neurons, increased concentrations of GnRH fibers and granules, and an increased LH level; however, in the LS and LC groups, these changes were not seen. The response in the LS group resembled that in the LC group. Considering the action of colchicine, which inhibits axonal transport, it is suggested that cervical sympathectomy also inhibits axonal transports of GnRH between the GnRH neurons and the median eminence during continuous exposure to light.
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Journal of anesthesia · Sep 1996
Flumazenil does not antagonize the cardiac effects of midazolam in the isolated rat heart-lung preparation.
We examined the effects of midazolam and flumazenil on cardiac function and metabolism in the isolated rat heart-lung preparation. Wistar rats were divided into five groups (each group:n=8) as follows: (1) control (saline); (2) flumazenil (1.3×10(-5)M); (3) flumazenil (10(-4)M); (4) midazolam (60μg·ml(-1)); and (5) midazolam (60μg·ml(-1)) and flumazenil (1.3×10(-5)M). Systolic blood pressure and calculated left ventricular dP/dt maximum in the midazolam or midazolam conbined with flumazenil groups increased significantly in comparison with those in the control group. ⋯ There were no significant differences in the myocardial tissue concentration of ATP, lactate, and glycogen in all groups. In this study, midazolam decreased heart rate; however, flumazenil had no effect on the heart, nor did it antagonize the cardiac effects of midazolam. These results suggest that flumazenil has no effect on the peripheraltype benzodiazepine receptor of the myocardium.
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Journal of anesthesia · Sep 1996
Effects of spinal naloxone and naltrindole on the antinociceptive action of intrathecally administered dexmedetomidine.
Intrathecally administered alpha-2 adrenoceptor and opioid agonists are well known to exert antinociceptive effects in humans and various animals. To examine the interaction of these two groups of agents in the spinal cord, we tested the effect of the opioid antagonists naloxone or naltrindole on the antinociceptive action of an intrathecally administered alpha-2 agonist, dexmedetomidine, using a formalin test in rats. 19 groups of Sprague-Dawley rats (250-300 g) were prepared with chronic intrathecal catheters and examined for the effects of agents on the formalin test. Each group contained 6 animals. 50 μl of 5% formalin was injected subcutaneously in the plantar surface of one hind paw. ⋯ Intrathecal dexmedetomidine (1 μg) maximally depressed the behavioral changes in both phase 1 and phase 2 of the formalin test, which was antagonized by the alpha-2 adrenoceptor selective antagonist atipamezole (0.3 μg). Naloxone (0.1-10 μg) or naltrindole (1-10 μg), when coadministered with dexmedetomidine, showed a dose-dependent antagonism to the effect of dexmedetomidine, whereas naloxone, naltrindole, or atipamezole alone showed no effect on the nocieptive behavior due to formalin injection. These results indicate that the antinociceptive effect of intrathecally administered alpha-2 adrenoceptor agonists may involve opioid receptors in the spinal cord.