Responses of feline trigeminal spinal tract nucleus neurons to stimulation of the middle meningeal artery and sagittal sinus

Abstract

1. Extracellular single-unit activity was recorded from 250 trigeminal (V) spinal tract nucleus neurons that were excited by electrical stimulation of the middle meningeal artery (MMA) and/or sagittal sinus (SS) in anesthetized cats. One hundred and thirty of these neurons were located in the V subnucleus caudalis (Vc), and the remaining 120 neurons were located in the V subnucleus oralis (Vo) or rostral part of the V subnucleus interpolaris (Vi). In many cases these neurons were also examined for the existence of orofacial receptive fields (RFs) by applying mechanical stimuli to the orofacial region. 2. The mean minimum latencies to suprathreshold electrical stimulation of the MMA and the SS were similar for Vc and Vo/Vi neurons. Excitation of Vc neurons occurred at latencies of 14.3 +/- 1.0 (n = 102) and 17.4 +/- 1.6 ms (n = 36) to MMA and SS stimulation, respectively. Excitation of Vo/Vi neurons occurred at latencies of 12.4 +/- 0.9 (n = 86) and 16.4 +/- 1.1 ms (n = 58) to MMA and SS stimulation, respectively. These latencies correspond to mean conduction velocities of approximately 5.2 and 4.0 m/s to MMA and SS stimulation, respectively. 3. Mechanical stimulation of the vessels evoked neuronal responses in five of eight MMA-activated neurons tested and three of five SS-activated neurons tested. 4. Almost all of the neurons tested (127 of 131) had peripheral RFs, and all were in the orofacial region. Nearly all (95%) Vc neurons had RFs within or including the ophthalmic facial region. The RFs of most (67%) Vo/Vi neurons also had RFs within or including ophthalmic regions, but in some cases were only within maxillary and/or mandibular regions. 5. Most of the Vc neurons (87%) were classified on the basis of their cutaneous inputs as nociceptive. The incidence of nociceptive neurons in Vo/Vi was also high (61%), although less than in Vc. In both the Vc and Vo/Vi neuronal populations, MMA-activated neurons were more likely to have nociceptive peripheral inputs than SS-activated neurons. 6. Histological reconstruction of recording sites indicated that the MMA- and/or SS-activated Vc neurons were concentrated in the lateral half of laminae III-V. The responsive neurons at the level of Vo/rostral Vi were not confined to any particular portion of these subnuclei. 7. These findings indicate that sensory afferents that innervate the dural arteries and venous sinuses are capable of activating neurons throughout the V spinal tract nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)