Perioperative Gewichtsentwicklung nach verschiedenen intrakraniellen neurochirurgischen Eingriffen unterschiedlicher Komplexität und subkutaner Transmitterimplantation im neurowissenschaftlichen Rattenmodell

Body weight is one of the most frequently reported measure monitored during experimental settings, as it correlates, at least to some extent, with the degree of pain, distress or suffering. Rat models used in neuroscience cover a wide range of intracranial neurosurgical interventions of potentially different severity levels. We analyzed the relative weight development after different surgical procedures and subcutaneous transmitter implantation in neuroscience models.

All rats (male Sprague Dawley, BDIX or Wistar, female Spraque Dawley) were anaesthetized with chloral hydrate (360mg/kg, 10 ml/kg i.p.). Lidocaine hydrochloride (Xylocain® 2%) was used as a local anesthetic on the periost. Rats were further treated with the analgesic carprofen (Rimadyl®, 5mg/kg, s.c.) intraoperative and on the two following days (2.5mg/kg s.c.). Body weight was measured before and up to 7 days after intracranial surgery, i.e. vehicle / 6-OHDA / tumor cell / blood / pilocarpine injection, tumor resection, electrode implantation, induction of a status epilepticus, cerebellar fastigial lesion, as well as cochlear manipulation (intracochlear neomycin injection). Peripheral subcutaneous transmitter implantation was included (without/with bupivacaine for local anesthesia).

Perioperative weight loss was found after i.e. 6-OHDA injection (97%, p<0.05), hearing loss (juvenile rats 92%, p<0.001), tumor resection (98%, p<0.05) and subarachnoid hemorrhage (95%, p<0.05). Cerebellar fastigial lesions and induction of hearing loss in adult rats did not lead to significant weight loss, although 40% (fastigial lesion) and 15% (adult rats with hearing loss) lost weight of more than 5%. Electrode implantation, as well as vehicle or cell injection did not affect weight (p>0.05). After subcutaneous transmitter implantation in a first group weight was reduced (98%, p<0.05), whereas the following groups, that treated with the long-acting local anesthetic bupivacaine before implantation, did not lose weight.

To date, weight as a core parameter seems suitable for the grading of severity of intracranial neurosurgical interventions of different complexity in rat models used in neuroscience research, as well as to verify refinement of perioperative analgesia.

Acknowledgement: This project was supported by grants of the Deutsche Forschungsgemeinschaft (FOR 2591, GZ:SCHW1176/7-2 and GZ: BA5768/2-1).