Minimally invasive technique for intrathecal administration of morphine in rats: practicality and antinociceptive properties

Abstract

The intrathecal (IT) route of administration represents a means to reduce the dose of morphine administered for analgesia, potentially minimizing interactions between opioid effects and experimental outcomes. Perceived technical difficulty, and previously described invasive methods, may limit its use. This report describes a minimally invasive technique for IT administration of morphine by direct transcutaneous lumbosacral puncture in rats; and assesses antinociceptive properties of morphine in anaesthetized rats. Rats ( n = 28) anaesthetized with sevoflurane (inspired fraction of sevoflurane: FSevo = 2.4%) were randomly allocated to receive: IT morphine (0.2 mg/kg); subcutaneous (SC) morphine (3 mg/kg); SC buprenorphine (0.05 mg/kg); or SC or IT sodium chloride (NaCl). After a wash-in period (40 min), thermal nociceptive stimuli were applied at nine locations corresponding to different rostrocaudal dermatomes of the rat. Nociceptive stimulation cycles were repeated at all locations after successive decrement of FSevo by 15%. Presence or absence of gross purposeful movement (GPM) was recorded for each individual stimulation. IT injection of morphine by direct puncture with a 25 G hypodermic needle is easily performed (successful first attempt: 82%) without complications. IT morphine reduced the frequency of GPM following nociceptive thermal stimulation in a way comparable with SC buprenorphine or morphine. It was not possible to delimit any rostral spinal spread of morphine. This report describes a refined and effective technique of administering morphine IT in rats using readily available materials. IT doses being markedly smaller than the systemic equivalent, analgesia could be provided whilst minimizing the potential interactions of non-analgesic opioid effects with research protocols.

Ultrasound as a reliable guide for lumbar intrathecal injection in rats: A pilot study

“…Landmark in intrathecal injection is crucial to identify the correct level of injection. Previously described by Thomas AA, et al [5] identifications of the lumbosacral region can be achieved by positioning the rats in a sternal recumbent position, maximally bending the vertebrae. In our case, we identified the proposed level of L1-L2 by palpating the back region of the rat, corresponding to the linear region of L4-L5.…”

Refinement in the European Union: A Systematic Review

“…A total of 384 references were identified by electronic search; 338 full-text studies were evaluated in accordance with the eligibility criteria and 290 were excluded. Finally, 48 studies [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ] complied with all the established eligibility criteria and were included in the study ( Figure 1 ).…”

Epidural and Intrathecal Drug Delivery in Rats and Mice for Experimental Research: Fundamental Concepts, Techniques, Precaution, and Application

“…Appropriate intrathecal positioning can typically be confirmed via the tail-flick test, but this response does not occur every time. Dura mater puncture can also be confirmed by other characteristics, such as the formation of an "S" shape by the tail, by hind paw retraction, and occasionally by backflow of the CSF [14,15,20]. After injecting a drug, temporary motor paralysis also occurs, which is a sign of successful drug administration.…”

“…Substantial experimental research and a review of the literature in human medicine have been reported [1,[8][9][10]. Numerous research studies have used the epidural [4,11,12] and intrathecal routes [13][14][15] in mice and rats; however, to the best of our knowledge, no review of the literature has discussed the delivery process, challenges, and application of these routes in rats and mice.…”

“…For an effective IT injection via acute puncture, only one try is required; however, if the first effort fails, the needle should be removed, and a second attempt may be made. If the second effort fails, a different intervertebral space should be chosen [15]. In addition, shaving and aseptic preparation of the skin, needles, and administering agents are also important for success.…”