Name: neurodevelopmental reflex testing in neonatal rat pups
Uploaded: 2017-04-24T14:00:00
Description: Watch this Scientific Journal Video about Neurodevelopmental Reflex Testing in Neonatal Rat Pups at JoVE.com

The authors wish to thank our funding agencies, which include NeuroDevNet (a National Centres of Excellence), the ALVA Foundation, the Women's and Children's Health Research Institute, and the University of Alberta.

The Animal Care and Use Committee, Health Sciences at the University of Alberta approved all animal studies.
Note: While this protocol may be adapted to other species and strains, this protocol is written for Long-Evans rats. These rats have been shown to have superior motor performances and visual acuity compared to other rodent strains. 25,26 The protocol for timed pregnancies, dietary supplementation, maternal inflammatio...

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Neurodevelopmental reflex testing is a predictive measure of abnormal cortical development and maturation, which may be of significance under circumstances where overt neuropathology is not evident. During neurodevelopmental testing, it is critical to ensure that pups are examined at the same time daily. Rats are nocturnal and therefore, their circadian rhythm may alter performance if testing is performed at different times during the day.34 Testing should be completed in a quiet room as loud nois...

Neurodevelopmental reflexes, or developmental milestones, are one of the earliest assessments used on human newborns and infants. Neurological reflexes are involuntary and repetitive movements that demonstrate brain stem and spinal cord reflexes. Maturation of higher cortical networks characterized by evolving migration, myelination, and synaptogenesis promote voluntary control and cortical inhibition. Alterations in the normal progression of the central nervous system evolution can disrupt brain development, resulting in abnormal cortical wiring, functioning, and myelination, causing neurodevelopmental reflex delays or absences. Human infants at high risk for neurodevelopmental disability often display abnormal early reflexes. Abnormal reflexes can present as a delay in acquisition, absence, prolonged presence, or reappearance later in life, and are predictive of developmental disabilities.1,2 Therefore, it is important to mimic reflex delays in experimental models of neurodevelopmental disabilities.
Rodents are commonly employed as experimental models. Rat pups are altricial when born, and therefore too immature to undertake specific or complex motor, sensory and/or cognitive behavioral tasks. In this regard, their developmental immaturity relates to both their physical and organ development. Rats are born hairless with an inability to thermoregulate, are blind, and unable to walk. With reference to brain development, substantial cortical maturation occurs postnatally. Newborn rat pups (day of birth referred to as postnatal day 1; PD1) have been suggested to reach a brain maturation level that is similar to a preterm human brain of 23 - 28 weeks gestation, whereas PD7-10 pups are equivalent to near-term human brain. 3,4,5,6 This correlation is based on gross anatomical analyses, however, other measures of brain maturation such as myelination and amplitude integrated electroencephalograms have also been described. 5,7 For example, pre-oligodendrocytes are the predominant cells in the developing human fetal brain from 23 - 32 weeks in utero, and this maturational stage corresponds to a PD1-3 rodent. 5,8,9,10 Moreover, myelination begins in utero in humans whereas in rat pups it appears in the forebrain around PD7-10; the newborn rodent brain remains largely un-myelinated. 11,12 Tucker et al. found that the amplitude integrated electroencephalogram pattern of a P1 rat to be similar to a 23-week gestation human fetus, whereas a PD7 and PD10 pup is akin to a 30 - 32 week and term infant, respectively.7 For these reasons, newborn reflex testing in neonatal rat pups provides an opportunity for capturing the ontogeny and/or disruption of brain development.
The battery of reflexes described below are adapted from studies by W.M. Fox and A. Lubics13,14 W.M. Fox was one of the earliest investigators with respect to the ontogeny of reflexes in the mouse. 13 These reflexes include, but are not limited to, limb grasping and placing, cliff avoidance, righting, accelerated righting, gait, auditory startle, posture, and eye opening. Both forelimb and hindlimb grasp (referred to as palmar and plantar grasp in humans, respectively) are facilitated by spinal reflexes and corticospinal inhibition from non-primary motor areas. 15,16 Hindlimb placing (plantar reflex) reflects maturation of the corticospinal tract. 16,17,18 Cliff avoidance (protective responses), righting (labyrinth), and accelerated righting involve integration and communication between sensory input and motor output (such as those involved with the vibrissae and vestibular systems). 19,20,21 Gait reflects locomotion.14 Auditory startle assesses acoustic stimulation and synaptic connections of giant neurons in the nucleus reticularis pontis caudalis.21 Posture involves appropriate cortical-spinal/spinal-cortical projections, muscle strength, and neuromuscular innervation. 22,23 Maturation of the gamma-aminobutyric acid receptors may correlate with eye opening.24 It is important to keep in mind that the reflexes reflect a much more complicated network and provided here is a general correlation. Moreover, these reflexes provide a quick and easy method of assessing neurological development at very young ages where more complex behavioral testing is not feasible.
The objective of this paper is to provide a general guideline for neurodevelopmental reflex testing that can be easily incorporated into experimental neonatal rat studies. The methodology described was carried out in Long-Evans neonatal rat pups and quantification of the results was based on first day of appearance. The day that reflex testing is initiated and the equipment utilized may be modified to better suit a different experimental model (such as for different strains and species). By establishing the normal physiological progression of reflex maturation in a specific animal model, investigators can evaluate the effects of external stressors, endogenous manipulations, and/or therapeutic interventions on neurodevelopment in neonatal rat models. Overall, the use of reflexes as a determination of brain maturity is advantageous in predicting perinatal brain injury, and is reflective of later neurodevelopmental outcomes.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Breeding</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Transfer pipettes</td>
			<td>Fisherbrand</td>
			<td>12-711-9AM</td>
			<td>Used for vaginal flushes.</td>
		</tr>
		<tr>
			<td>Sterile Saline</td>
			<td>Hospira</td>
			<td>7983254</td>
			<td>The solution used to collect cells during vaginal flushes.</td>
		</tr>
		<tr>
			<td>400 &#181;l Microcentrifuge tubes</td>
			<td>Fisherbrand</td>
			<td>05-408-120</td>
			<td>Used to hold the saline solution.</td>
		</tr>
		<tr>
			<td>Light microscope</td>
			<td>Leica</td>
			<td>Leica ATC 2000</td>
			<td>For observation of the saline solution. Can be any light microscope used in the lab.</td>
		</tr>
		<tr>
			<td>Slides</td>
			<td>Fisherbrand</td>
			<td>12-552-5</td>
			<td>The saline solution is placed on the slide. Can be any slides used in the lab.</td>
		</tr>
		<tr>
			<td>Coverslips</td>
			<td>Fisherbrand</td>
			<td>12-545-F</td>
			<td>To coverslip the slides. Can use any coverslips used in the lab.</td>
		</tr>
		<tr>
			<td>Dietary&#160; Supplementation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Broccoli Sprouts seeds</td>
			<td>Mumm&#39;s Sprouting Seeds</td>
			<td></td>
			<td>Broccoli sprouts seeds are ordered and grown in the lab.</td>
		</tr>
		<tr>
			<td>Countertop Seed Sprouter Box</td>
			<td>Mumm&#39;s Sprouting Seeds</td>
			<td></td>
			<td>A box is used to germinate and grow the seeds prior to harvest.</td>
		</tr>
		<tr>
			<td>250 mL beaker</td>
			<td></td>
			<td></td>
			<td>The beaker is used to soak the seed. Any size beaker that would fit can be used.</td>
		</tr>
		<tr>
			<td>Maternal Inflammation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lipoplysaccharide (LPS)</td>
			<td>Sigma</td>
			<td>L3129</td>
			<td>The endotoxin used to mimic maternal inflammation.</td>
		</tr>
		<tr>
			<td>1 mL Syringe</td>
			<td>BD Syringe</td>
			<td>309659</td>
			<td>Used to inject the pregnant rat.</td>
		</tr>
		<tr>
			<td>Gauge (30G X 1/2)</td>
			<td>BD PrecisionGlide Needle</td>
			<td>305106</td>
			<td>Use the smallest needle to avoid pain and discomfort.</td>
		</tr>
		<tr>
			<td>Sterile Saline (0.9% Sodium Chloride, USP)</td>
			<td>Hospira</td>
			<td></td>
			<td>Saline is used to dissolve LPS.</td>
		</tr>
		<tr>
			<td>Weights</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Scale</td>
			<td>Denver Instrument</td>
			<td></td>
			<td>For recording the weights. Can be any scale with 2 decimal places used in the lab.</td>
		</tr>
		<tr>
			<td>Neurodevelopmental Reflexes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Thin blunt rod</td>
			<td></td>
			<td></td>
			<td>Can be a paperclip or toothpick. This is for forelimb and hindlimb grasping.</td>
		</tr>
		<tr>
			<td>Round filter paper</td>
			<td>Whatman</td>
			<td>1001 150</td>
			<td>15 cm diameter paper used for gait analysis.</td>
		</tr>
		<tr>
			<td>Timer</td>
			<td>Fisher Scientific</td>
			<td>06-662-51</td>
			<td>For timing the time allocated to righting and gait.</td>
		</tr>
		<tr>
			<td>Blunt surface</td>
			<td></td>
			<td></td>
			<td>Can be an edge of a table. This is for hindlimb placing and cliff avoidance.</td>
		</tr>
		<tr>
			<td>Foam landing</td>
			<td></td>
			<td></td>
			<td>For when the pups perform accelerated righting.</td>
		</tr>
		<tr>
			<td>Video recorder</td>
			<td>Sony</td>
			<td>VCT-D580RM</td>
			<td>To record all reflexes tested. Must be able to record at 1/1000 fps</td>
		</tr>
		<tr>
			<td>Bell</td>
			<td></td>
			<td></td>
			<td>For auditory startle.&#160;</td>
		</tr>
		<tr>
			<td>Heat lamp or pad</td>
			<td></td>
			<td></td>
			<td>To maintain the body temperature of the pups underoing examination.</td>
		</tr>
	</tbody>
</table>

neurodevelopmental reflex testing in neonatal rat pups

Neurodevelopmental reflex testing is commonly used in clinical practice to assess the maturation of the nervous system. Neurodevelopmental reflexes are also referred to as primitive reflexes. They are sensitive and consistent with later outcomes. Abnormal reflexes are described as an absence, persistence, reappearance, or latency of reflexes, which are predictive indices of infants that are at high risk for neurodevelopmental disorders. Animal models of neurodevelopmental disabilities, such as cerebral palsy, often display aberrant developmental reflexes, as would be observed in human infants. The techniques described assess a variety of neurodevelopmental reflexes in neonatal rats. Neurodevelopmental reflex testing offers the investigator a testing method that is not otherwise available in such young animals. The methodology presented here aims to assist investigators in examining developmental milestones in neonatal rats as a method of detecting early-onset brain injury and/or determining the effectiveness of therapeutic interventions. The methodology presented here aims to provide a general guideline for investigators.

The timeline of this experimental design is presented in Figure 2. 30 The methods and results have previously been published. 30 The objective of the study was to assess whether dietary supplementation with broccoli sprouts during gestation and the preweaning period protected the offspring from neurodevelopmental delay induced by in utero exposure to LPS. Timed pregnant rats were given intraper...

Watch this Scientific Journal Video about Neurodevelopmental Reflex Testing in Neonatal Rat Pups at JoVE.com

Neurodevelopmental Reflex Testing in Neonatal Rat Pups

Behavioral testing is the gold standard for determining outcomes following brain injury, and can identify the presence of developmental disabilities in infants and children. Neurodevelopmental reflexes are an early indicator of these abnormalities. A host of easily accomplished developmental reflex tests in the neonatal rodent were developed and described here.

Neurodevelopmental reflex testing is commonly used in clinical practice to assess the maturation of the nervous system. Neurodevelopmental reflexes are ...

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