Absence of coherence between cervical and lumbar spinal cord dorsal surface potentials in the anaesthetized cat E. Manjarrez * , H. Pe ´ rez, J.G. Rojas-Piloni, D. Ve ´lez, L. Martı´nez, A. Flores Institutode Fisiologı´a, Beneme ´ rita Universidad Auto ´noma de Puebla, 14 Sur 6301, Col. San Manuel, Apartado Postal 406, Puebla, Pue. CP 72570, Me ´ xico Received 6 March 2002; received in revised form 24 April 2002; accepted 24 April 2002 Abstract Recordings of spontaneous cord dorsum potentials (CDPs) along the longitudinal axis of the spinal cord were made. These recordings were obtained from the surface of the dorsal horn at different points along the spinal cord caudally and cranially in relation to the point giving spontaneous potentials of maximal amplitude. We found two curves (lumbar and cervical) for the longitudinal distribution of the area of the power spectra of these recordings. Each of these curves had a symmetrical decrement on both sides of the position of the point for the maximal area of power. Such points were discovered on the L5–L7 and C3–C4 spinal segments. Spectral analysis of the spontaneous CDPs simultaneously recorded in both regions indicates no evidence of coherence, thus suggesting that the spontaneous CDPs recorded in the lumbar and cervical regions of the pentobarbitone-anaesthetized cat are generated by two independent populations of neurones not functionally interconnected between them. q 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Dorsal horn; Cervical; Background activity; Spontaneous activity; Spontaneous cord dorsum potentials; Coherence; Power spectra A previous study [9] has shown that in the anaesthetized cat the neuronal ensemble involved in the generation of the lumbar spontaneous negative cord dorsum potentials (CDPs) is located in laminae III–VI (see also Refs. [5–8]). It was not clear, however, the extent to which this neuronal ensemble is distributed along the longitudinal axis of the lumbar [9,13] and cervical spinal cord. The purpose of the present report was to present evidence that the neurones producing the spontaneous CDPs are independently distrib- uted in the lumbar and cervical spinal segments. Disclosure of these distributions along the longitudinal axis of the spinal cord could be important since the spontaneous activ- ity of the neurones producing the lumbar spontaneous nega- tive CDPs sets a background level of transmission regulation in the Ia-motoneuron pathway [9], and in the cortical responses elicited by tactile stimuli [11,12]. Guidelines contained in the NIH publication (Guide for the Care and Use of Laboratory Animals, U.S. Department of Health and Human Services, National Institutes of Health, Publication No. 85-23, Revised in 1985) were followed throughout. Briefly, experiments were carried out in adult cats (2.5–3.5 kg) initially anaesthetized with pentobarbitone (35 mg kg 21 of weight, intraperitoneally), supplemented during the dissection and recording periods with additional doses of 10 mg kg 21 , intravenously as neces- sary to maintain deep anaesthesia. Blood pressure was recorded from a cannula inserted into the right femoral artery. Adequacy of anaesthesia was assessed by verifying that the pupils were constricted, and that blood pressure was stable (between 100 and 120 mmHg) and was not affected by noxious stimulation to the skin. After the surgical proce- dures, the animal was fixed in a metal frame using spinal and pelvic clamps. The head was fixed in a stereotaxic apparatus. The animals were paralyzed with pancuronium bromide (Pavulon, Organon) and artificially ventilated. The lumbo-sacral, low thoracic, and cervical spinal segments were exposed. Pools were formed with the skin around the exposed tissues, filled with mineral oil and maintained at a constant temperature (37 8C) by means of radiant heat. Spontaneous CDPs were recorded from the surface of the dorsal horn with two silver ball electrodes against indiffer- ent electrodes placed on the near paravertebral muscles. Simultaneous recordings were made along the longitudinal axis of the cervical and lumbar segments. Spontaneous Neuroscience Letters 328 (2002) 37–40 0304-3940/02/$ - see front matter q 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S0304-3940(02)00446-9 www.elsevier.com/locate/neulet * Corresponding author. Tel.: 152-22-22-44-1657; fax: 152-22- 22-33-4511. E-mail address: emanjar@siu.buap.mx (E. Manjarrez).