Comparison of the pharmacokinetics and thermal antinociceptive pharmacodynamics of 20 µg kg−1 buprenorphine administered sublingually or intravenously in cats

Little is known about the analgesic action of buprenorphine (BUP) in cats. Relative to man, the cat has a more alkaline oral pH, which may make this an effective route for administering BUP in this species. This study aimed to assess and compare the pharmacokinetics and pharmacodynamics of sublingual (S‐L) and IV administration of BUP. Thermal threshold (TT) was measured and blood samples were collected following IV or S‐L administration (20 µg kg^?1) of the injectable formulation. Six cats (five spayed females, one castrated male, 4.1–6.6 kg) were used. Each cat received both treatments in a randomized cross‐over study design with 1 month between experiments. Twenty‐four hours prior to each study, the lateral thorax of each of the cats was shaved, cephalic and jugular catheters placed, and oral pH measured. On the day of the study, TT was measured using a ‘thorax‐mounted’ thermal threshold‐testing device specifically developed for cats. The cats were free to move around. Skin temperature was recorded before each test, then the heater activated. When the cat responded by flinching, turning, or jumping, the stimulus was terminated and the threshold temperature was recorded. The thermal threshold cut‐off point was 55.5 °C. Three baseline thresholds were recorded before treatment with S‐L or IV (via cephalic catheter) BUP (20 µg kg^?1). Blood was withdrawn (jugular) at 1, 2, 4, 6, 10, 15, 30, 45, 60 minutes and at 2, 4, 6, 8, 12, and 24 hours post‐administration. TT was measured every 30 minutes?6 hours, 1–12 hours, and at 24 hours post‐administration. Plasma was immediately separated, stored at ?20.5 °C, and assayed within 4 months using a commercially available ¹²⁵I radioimmunoassay. Threshold data were analyzed using anova with a repeat factor of time. No adverse effects were noted. Pupils were dilated for up to 9 hours post‐BUP. Behavioral changes were calm euphoria. Measured oral pH was 9 in each cat. Pre‐treatment mean threshold (±SD) was 41.2 ± 0.9 °C in the S‐L group and 40.8 ± 0.85 °C in the IV group. There were no significant differences between the groups with respect to thresholds over time (p = 0.72). Thresholds were significantly increased from 30 to 360 minutes in both the groups (>44.615 °C). Peak plasma BUP (C_max) was lower (11 ± 6.7 ng mL^?1vs. 92.9 ± 107.9 ng mL^?1) and occurred later (T_max) (30 minutes vs. 1 minute) after S‐L compared to IV administration, respectively. BUP (20 µg kg^?1)‐administered S‐L or IV provided antinociception between 30 and 360 minutes after administration. Plasma levels did not correspond to TT.     

Seroprevalence of Toxoplasma gondii in mainland and sub-Antarctic New Zealand sea lion (Phocarctos hookeri) populations

AIMS: To investigate the seroprevalence of antibodies to Toxoplasma gondii in New Zealand sea lions (Phocarctos hookeri), as a potential contributor to reproductive failure.

METHODS: Archived sera were sourced from New Zealand sea lions from two recolonising mainland populations in the Otago Peninsula (n=15) and Stewart Island (n=12), as well as a declining population at Enderby Island (n=28) in the New Zealand sub-Antarctic. Sera were tested for antibodies to T. gondii using a commercially available ELISA (with samples considered positive if the sample to positive ratio was?>30%), and latex agglutination test (LAT; with titres ≥1:32 considered positive). Western blot analysis was used to validate the results of a subset of 14 samples.

RESULTS: Five samples from sea lions in mainland locations were confirmed positive for antibodies to T. gondii. Two adult females exhibited high LAT antibody titres (min 1:2048, max 1:4096) on both occasions when sampled 1 and 2 years apart, respectively. No animals from Enderby Island were seropositive.

CONCLUSIONS: Toxoplasma gondii infection is unlikely to be a major contributor to poor reproductive success in New Zealand sea lions. However, continued surveillance is pertinent to assess subclinical and clinical impacts of the parasite on these threatened populations. The commercial tests evaluated here, with further species-specific threshold refinement could provide a fast, inexpensive and reliable indicator of T. gondii exposure in New Zealand sea lions.     

Effect of strain and age on the relationship of oviposition time to shell strength

1. The relationships between oviposition time and specific gravity, shell thickeness, deformation and breaking strength of eggs from six commercial layer strains were examined after 6 and 12 months of production.

2. Shell strength, assessed by any of the methods, was relatively low in eggs collected at 10.00 h and was generally successively greater in those collected at 12.00, 14.00 or 16.00 h. Over the same period egg weight decreased.

3. These time‐related changes in shell strength were similar for the two production ages despite the difference in shell quality due to age.

4. No consistent significant differences were observed between strains in time of oviposition.