Effects of xylazine, lignocaine and their combination for lumber epidural analgesia in water buffalo calves (Bubalus bubalis).
The study was conducted to evaluate the effects of xylazine alone (0.05 mg/kg), lignocaine alone (2.0 mg/kg) and a combination of xylazine and lignocaine (0.05 mg/kg and 2.0 mg/kg, respectively) after lumbar epidural administration in water buffalo calves. Fifteen nondescript, male water buffalo calves of 6-8 months of age and weighing between 55 and 75 kg were randomly placed in 3 groups (A, B and C). The agents were administered at the 1st lumbar epidural space. Clinico-physiological parameters such as analgesia, ataxia, sedation, salivation, heart rate, respiratory rate and rectal temperature were studied. Other haematological and biochemical parameters monitored were haemoglobin, packed cell volume, total leukocyte count, plasma glucose, cortisol, protein albumin, globulin, blood urea nitrogen, creatinine, ALT, sodium, potassium and chloride. The onset of analgesia was faster in group C (3.0 +/- 0.44 min) compared with that of group B (4.4 +/- 0.40 min) and group A (34.0 +/- 1.86 min). Analgesia of the thorax, flank, inguinal region, hind limbs, perineum and tail was complete in group C, but mild to moderate in groups A and B. Ataxia was severe in groups B and C and mild in group A. Mild to deep sedation were produced by groups A and C animals. Longer duration and greater depth of analgesia was produced in animals in group C. Heart rate, respiratory rate and rectal temperature decreased in groups A and C. The haematological parameters decreased in all the groups. The biochemical parameters like glucose, cortisol, blood urea nitrogen, creatinine, ALT increased in all the animals. However, total proteins and albumin decreased in the 3 groups. The plasma electrolytes sodium, potassium and chloride did not show any significant change. The results of this study indicated a possible additive analgesic interaction between epidurally administered xylazine and lignocaine, without causing any marked systemic effects in water buffalo calves.
Xylazine induced central antinociception mediated by endogenous opioids and μ-opioid receptor, but not δ-or κ-opioid receptors
Endogenous opioids have been implicated in compound-induced antinociception, and our group previously suggested that xylazine induces peripheral antinociception by releasing endogenous opioids that act on their respective receptors. In this study, we investigated the involvement of endogenous opioids in α2-adrenoceptor agonist xylazine-induced central antinociception. The nociceptive threshold for thermal stimulation was measured in Swiss mice using the tail-flick test. The drugs were administered via the intracerebroventricular route. Probabilities less than 5% (p<0.05) were considered to be statistically significant (ANOVA/Bonferroni's test). Our results demonstrated that opioid receptor antagonist naloxone and μ-opioid receptor antagonist clocinnamox, but not δ-opioid receptor antagonist naltrindole and κ-opioid receptor antagonist nor-binaltorphimine, antagonized xylazine-induced central antinociception. These data provide evidence for the involvement of endogenous opioids and μ-opioid receptors in xylazine-induced central antinociception. In contrast, δ- and κ-opioid receptors do not appear to be involved in this effect. The results contribute to a greater understanding of the central antinociceptive mechanisms of a drug widely used in veterinary therapy.
Histopathology after repeated intrathecal injections of preservative-free ketamine in the rabbit: a light and electron microscopic examination.
Epidural and spinal administration of ketamine has been used in humans. Single-dose studies have shown that preservative-free ketamine lacks neurotoxic effects, but there are no studies after repeated administrations. The aim of this study was to examine the effects of daily administration of preservative-free ketamine. Fourteen New Zealand albino rabbits were assigned to two groups receiving either intrathecal preservative-free ketamine 5 mg, 0.5 mL 1% solution (eight rabbits) or saline 0.5 mL (six rabbits) once a day for 14 consecutive days. The rabbits had a total subcutaneous implanted intrathecal catheter, which was introduced during general anesthesia. On Day 15 the rabbits were anesthetized and in vivo fixated by transcardial perfusion with Tyrode's solution followed by a mixture of 2% glutaraldehyde and 1% formaldehyde in a 0.1 mol/L phosphate buffer. A segment 5 cm on each side of the catheter tip was removed and kept in a cold solution of the fixative. Light microscopic, electron microscopic, and morphometric examinations showed no differences between the spinal cords from the rabbits injected with ketamine versus saline. Intrathecal ketamine produced motor impairment for a period of 15 min. We conclude that repeated intrathecal administration of preservative-free ketamine confirms the lack of neurotoxicity from single-dose studies.