Functional organization of trigeminal subnucleus interpolaris: nociceptive and innocuous afferent inputs, projections to thalamus, cerebellum, and spinal cord, and descending modulation from periaqueductal gray

Abstract

In view of continuing uncertainties concerning the organization, afferent inputs, and projection sites of neurons in the subnucleus interpolaris of the trigeminal (V) spinal tract nucleus, the characteristics of 222 single neurons in and adjacent to the subnucleus were examined electrophysiologically in adult cats anesthetized with chloralose. Neurons were tested for orthodromic responsiveness to a variety of stimuli that included nonnoxious tactile stimuli, noxious mechanical and radiant-heat stimuli, and graded electrical stimulation of the skin, mucosa, tooth pulp, and masseter nerve. Antidromic activation techniques were also used to determine if the functionally identified neurons projected directly to the contralateral posterior thalamus, ipsilateral cerebellum, or cervical spinal cord. In addition, the periaqueductal gray matter (PAG) was stimulated to test for conditioning influences from the PAG on orthodromic responses to noxious and nonnoxious oral-facial stimuli. Interpolaris neurons were somatotopically arranged in subnucleus interpolaris in a pattern conforming in general to the medially facing, inverted-head representation characteristic of other parts of the V brain stem sensory nuclear complex. On the basis of their responsiveness to cutaneous stimuli, the neurons could be functionally classified as either cutaneous nociceptive or low-threshold mechanoreceptive (LTM) neurons. The LTM neurons constituted the major neuron type, accounting for over 75% of our neuron sample. Most of them had a localized mechanoreceptive field of less than 100 mm2 in area that was restricted to one V division, and they had skin-evoked response latencies indicative of afferent input predominantly from A-beta cutaneous afferents. A population of nociceptive neurons was also encountered in the lateral, marginal region of interpolaris and at its medial or ventral border with the reticular formation. These neurons were of two types: nociceptive-specific (NS) neurons, which did not respond to nonnoxious stimuli but which required noxious stimuli for their activation; and wide dynamic range ( WDR ) neurons, which responded to both noxious and nonnoxious stimuli applied to the facial skin. Most had an ipsilateral receptive field that was greater than 100 mm2 in area and that often involved two or three V divisions. Their properties generally conformed to those previously described for nociceptive neurons in the medullary dorsal horn (V subnucleus caudalis) and spinal cord dorsal horn. Interpolaris neurons of all classes (LTM, WDR , and NS) were found to have direct axonal projections to the thalamus, cerebellum, and spinal cord.(ABSTRACT TRUNCATED AT 400 WORDS)

Spontaneous Discharge and Peripherally Evoked Orofacial Responses of Trigemino–Thalamic Tract Neurons during Wakefulness and Sleep

“…Our calculated conduction velocities ranged from 4.5 to 24.4 m/sec (mean 12.9 Ϯ 0.5 m/sec; Fig. 2 B) and are commensurate with conduction velocities reported for TGT neurons in anesthetized cats Hyashi et al, 1984) and the awake monkey (Bushnell et al, 1986).…”

“…2 A) is similar to antidromic latencies reported in acute studies (Dubner and Sessle, 1971;Sessle and Greenwood, 1976;Dostrovsky and Hellon, 1978;Hu et al, 1981;Sessle and Hu, 1981;Hyashi et al, 1984;Amano et al, 1986;Sunada et al, 1990;Ro and Capra, 1994).…”

“…This was accomplished by combining extracellular recording methodologies with classical antidromic techniques to identify TGT neurons in unanesthetized cats. The basic physiological characteristics of these neurons, i.e., antidromic latency and conduction velocity, and their anatomical location substantiate results obtained for TGT neurons in acute anesthetized cats (Mizuno, 1970;Dubner and Sessle, 1971;Sessle and Greenwood, 1976;Dostrovsky and Hellon, 1978;Burton and Craig, 1979;Hu et al, 1981;Sessle and Hu, 1981;Matsushita et al, 1982;Hyashi et al, 1984;Matthews et al, 1987;Sunada et al, 1990;Ro and Capra, 1994).…”

Subcortical barrelette-like and barreloid-like structures in the prosimian galago ( Otolemur garnetti )

“…The lima-bean shape probably comes from devoting a similarsized volume of tissue to the representation of both the upper and the lower jaws, instead of the nucleus being dominated by the representation of the upper jaw. The inverted representation is consistent with that found in other animals, including rodents (25,26), cats (27), moles (28), and pigeons (29).…”

Efeito do acetaminofeno e do celecoxib na distalização de incisivos e na ativação de regiões cerebrais relacionadas à nocicepção durante a movimentação ortodôntica em ratos

“…O subnúcleo caudalis é um importante centro de retransmissão de informações nociceptivas de estruturas orofaciais, incluindo os dentes (Sessle, 1987b;Sessle, 1987a;Coimbra e Coimbra, 1994;Oakden e Boissonade, 1998;Sessle, 2000), e apresenta anatomia semelhante à do corno dorsal da medula, tanto que também é chamado de corno dorsal do bulbo (Bradley, 1995;Lent, 2004;Takemura, Sugiyo et al, 2006). A região localizada acima do obex, que inclui os subnúcleos interpolaris e oralis, é caracterizada por receber informações dos ramos trigeminais que inervam a cavidade oral, recebendo aferências da polpa dental além de cutâneas e mucosas (Hayashi, Sumino et al, 1984;Marfurt e Turner, 1984;Shigenaga, Chen et al, 1986;Fujiyoshi, Yamashiro et al, 2000;Woda, 2003;Balam, Yamashiro et al, 2005;Shimizu, Asano et al, 2006;Takemura, Sugiyo et al, 2006). Desses núcleos, as informações são passadas para regiões mais superiores do cérebro, como o tálamo posterior, para que sejam processadas (Bradley, 1995;Lent, 2004;Takemura, Sugiyo et al, 2006).…”