A novel rotometer based on a RISC microcontroller

F. J. HEREDIA-LPEZ 0 1 J. L. BATA-GARCA 0 1 F. J. LVAREZ-CERVERA 0 1 J. L. GNGORA-ALFARO Universidad Autnoma de Yucatn 0 1 Mrida 0 1 Mexico 0 1 0 HEREDIA-LPEZ, BATA-GARCA, LVAREZ-CERVERA, AND GNGORA-ALFARO 1 (Manuscript received February 1, 2002; accepted for publication May 27 , 2002.) A new, low-cost rotometer, based on a reduced instruction set computer (RISC) microcontroller, is presented. Like earlier devices, it counts the number and direction of full turns for predetermined time periods during the evaluation of turning behavior induced by drug administration in rats. The present stand-alone system includes a nonvolatile memory for long-term data storage and a serial port for data transmission. It also contains a display for monitoring the experiments and has battery backup to avoid interruptions owing to power failures. A high correlation was found (r . .988, p , 2 3 10214) between the counts of the rotometer and those of two trained observers. The system reflects quantitative differences in turning behavior owing to pharmacological manipulations. It provides the most common counting parameters and is inexpensive, flexible, highly reliable, and completely portable (weight including batteries, 159 g). - One of the most frequently used models in the study of the physiology of the basal ganglia is based on the turning (or circling) behavior induced by drug administration in animals with unilateral lesion of the nigrostriatal dopaminergic pathway (Glick, Jerussi, & Fleisher, 1976; Pycock, 1980; Ungerstedt, 1971; Ungerstedt & Arbuthnott, 1970). This experimental model, which has been compared with human hemiparkinsonism (Duvoisin, 1976), has been very useful in understanding the physiopathologyof Parkinsons disease (Duvoisin, 1976; Perese, Ulman, Viola, Ewing, & Bankiewicz, 1989), as well as for the evaluation of the therapeutic potential of drugs (Kebabian et al., 1992). The turning behavior model has been used to test the functionality of brain tissue implants as a means for correcting the neurological deficits caused by the degeneration of dopaminergic neurons (Bjrklund, Dunnett, Stenevi, Lewis, & Iversen, 1980; Brundin et al., 1988; Dunnett, Bjrklund, Schmidt, Stenevi, & Iversen, 1983; Horellou, Marlier, Privat, & Mallet, 1990) and has provided the basis on which to start clinical trials in humans (Backlund, Olson, Seiger, & Lindvall, 1987; Brundin et al., 1987). In the last few years, some studies of the physiology of the basal ganglia in the rat brain have been based on this model in combination with the unilateral injection of drugs into the substantia nigra (Bata-Garca, Heredia-Lpez, lvarez-Cervera, Arankowsky-Sandoval, & GngoraAlfaro, 2002). Circling behavior is commonly evaluated by placing the animal inside a flat or concave-bottomed enclosure. Carlson and Glick (1996) have found that the type of bottom This study was supported by CONACYT-Mexico Grants 1831M9211 and 31377-N to J.L.G.-A. Correspondence concerning this article should be addressed to F. J. lvarez-Cervera, Laboratorio de Neurofisiologa, Centro de Investigaciones Regionales Dr. Hideyo Noguchi, Universidad Autnoma de Yucatn, Av. Itzaes N 490 3 59, Mrida, Yucatn, C.P. 97000, Mexico (e-mail: ). is irrelevant to the characteristics of the turning behavior. The rotational movement of the subject is detected directly or indirectly by means of some type of sensor (optoelectronic, magnetic, resistive, mechanical, or video camera) or by direct observation. The direction of turning is designated as either contraversive (opposite side to the lesion) or ipsiversive (same side as the lesion). Net turns or net rotations result from subtracting the number of turns in the less preferred direction from those in the dominant direction. The easiest way to evaluate turning behavior is to have a trained observer count the number of full turns performed by the animal in specified time intervals, until the turning behavior disappears. The main disadvantage of this direct approach is that observation times are lengthy (typically, 2 h or more). In addition, counting mistakes owing to distraction or fatigue are possible, as well as subsequent data transcription errors. Likewise, the presence of the experimenter in the test room can be a distracting influence on the behavior of the animals under study. Various approaches for automatically measuring turning behavior in rodents have been used. These devices, also referred to as rotometers, can be broadly grouped into the following two categories: mechanical harnesses or strings, which transmit the rotational movement to some type of detector and counter, and video tracking systems. The first class comprises systems that provide results in printed form or on a dial (Barber, Blackburn, & Greenwood, 1973; Greenstein & Glick, 1975; Heredia-Lpez et al., 1992; Jerussi, 1982; Schwarz, Stein, & Bernard, 1978; Ungerstedt & Arbuthnott, 1970), as well as instruments that are able to save data electronically (DAnna et al.,1989; Hudson, Levin, & Hoffer, 1993; Kulmala, Boja, & Hutton, 1987; Pons, Lpez, Ramis, Planas, & Rial, 1990; Richards, Sabol, & Freed, 1990; Schmidt & Dubach, 1988). Earlier systems presented some disadvantages, such as not being able to distinguish between contraversive and ipsiversive turns (Ungerstedt & Arbuthnott, 1970) or offering only a printed report of the recorded turns (Barber et al., 1973; Heredia-Lpez et al., 1992; Schwarz et al., 1978). Some of the first versions also had problems when incomplete oscillatory turns were dealt with, but this inconvenience was overcome in a more recent prototype (Greenstein & Glick, 1975), and another one could record partial turns of any angle (Schwarz et al., 1978). Another prototype was able to indicate the duration of each turn, as well as to record 180 direction reversals, but the output was a printed trace from an external event recorder and required interpretation. This rotometer also included a mechanical revolution counter for displaying net rotations (Jerussi, 1982). Some systems are prepared to handle several chambers simultaneously (DAnna et al., 1989; Hudson et al., 1993; Kulmala et al., 1987). Others are designed to work with larger animals, such as primates (Schmidt & Dubach, 1988). In addition to recording turning behavior, another scheme can keep track of motor activity and some stereotyped movements (Pons et al., 1990). Besides, there is a report of a custom-made rotometer for conditioned rotation studies (Richards et al., 1990). Video tracking systems include an associated computer, and some have the capability to classify turns of several diameters and to record locomotion simultaneously (Bonatz, Steiner, & Huston, 1987). These systems consist of a computer, a video interface, and a camera, in addition to the animal chamber, thus entailing a high cost. For some of them, the background color of the chamber has to contrast with the color of the rat in order to generate a detectable signal. In ad (...truncated)