THE PARABRACHIAL AREA - ELECTROPHYSIOLOGICAL EVIDENCE FOR AN INVOLVEMENT IN VISCERAL NOCICEPTIVE PROCESSES
THE PARABRACHIAL AREA - ELECTROPHYSIOLOGICAL EVIDENCE FOR AN INVOLVEMENT IN VISCERAL NOCICEPTIVE PROCESSES
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DOI：
10.1152/jn.1994.71.5.1646
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发表时间：
1994-05-01
影响因子：
2.5
通讯作者：
BESSON, JM
中科院分区：
文献类型：
--
作者：
BERNARD, JF;HUANG, GF;BESSON, JM
1. Neurons(n = 142) were recorded with extracellular micropipettes in the parabrachial (PB) area, in the anesthetized rat, some of them being antidromically driven from the centralis nucleus of the amygdala (Ce). The spontaneous activity of these neurons was low, (10th percentile < median frequency < 90th percentile; 0.01 < 0.3 < 11 Hz), and the activity of a very high proportion of the PB neurons (89%, 127/142) were affected by mechanical or thermal cutaneous stimuli almost exclusively in the noxious range; most of them were activated and received inputs from A partial derivative and/or C fibers.2. A majority of the PB neurons (66%, 93/142) were affected by visceral stimuli (bradykinin intraperitoneal and/or colorectal distension), almost exclusively in the noxious range; all of them (except one) were also affected by cutaneous noxious stimuli. The remaining neurons not affected by these visceral stimuli were only activated by cutaneous noxious stimuli (n = 35) or completely unresponsive(n = 14; i.e., only 10% of the whole population).3. Thirty-five percent (49/142) of the whole population of PB neurons responded to bradykinin intraperitoneal and/or to strong colorectal distension with an intense and sustained increase of discharge. The response to bradykinin and to colorectal distension was often dissociated, i.e., the activation was often produced by only one of the stimuli the other being ineffective or inhibitory. The intensity of responses to visceral noxious stimuli was between 5-45 Hz with a mean value of 20 +/- 2 (SE) Hz (n = 49). The visceral activated neurons exhibited a clear capacity to encode the colorectal distension in noxious range: 1)the stimulus-response function was almost always positive and monotonic; 2) as for the individual curves, the slope of the mean curve progressively increased up to the highest interval of pressure tested (100-125 mmHg); and 3) the threshold for neuronal response to colorectal distension was between 25-100 mmHg with a mean pressure threshold of 56 +/- 24 (SD) mmHg (n = 19). Viscerosomatic convergence was observed for 84% of these neurons: they were also activated by thermal and/or mechanical cutaneous noxious stimuli while only 16% of them were activated only by visceral noxious stimulation.4. Thirty-one percent (44/142) of the whole population of PB neurons were inhibited by both strong colorectal distension and intraperitoneal bradykinin (82%) or only by one of the stimuli being unresponsive to the other(18%). These neurons were not affected, or only very little, by weak colorectal distension less than or equal to 25 mmHg. Most of these neurons (80%, 35/44) were activated by thermal and/or mechanical cutaneous noxious stimuli.5. For the whole neuronal population, 52 units were antidromically driven by electrical stimuli applied in the Ce (PB-Ce units) with the remaining 90 units, which were not backfired from the Ce, being termed PB-NCe units. The responses of PB-Ce and PB-NCe units to cutaneous and visceral stimuli were qualitatively similar. However, the mean visceral responsiveness of activated PB-Ce neurons (13.5 +/- 2.2 Hz) was significantly(P < 0.01)lower than PB-NCe neurons (22 +/- 2.1 Hz). In addition, the proportion of neurons completely unresponsive to both visceral and cutaneous stimuli was very significantly (P < 0.001) higher in the PB-Ce group (21%) than in the PB-NCe group (3%).
