Modulation of activity of gustatory neurons in the hamster parabrachial nuclei by electrical stimulation of the ventroposteromedial nucleus of the thalamus

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 294; no. 5; pp. R1461 - R1473
• Main Authors: Mao, Limin, Cho, Young K, Li, Cheng-Shu
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.05.2008
• Subjects: Animals; Brachial Plexus - physiology; Brain; Cricetinae; Data Interpretation, Statistical; Electric Stimulation; Electrodes, Implanted; Electrophysiology; Entropy; Male; Mesocricetus; Nervous system; Neural Pathways - physiology; Neurology; Neurons; Neurons, Afferent - physiology; Rodents; Synaptic Transmission - physiology; Taste; Taste - physiology; Ventral Thalamic Nuclei - cytology; Ventral Thalamic Nuclei - physiology
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00802.2007

1 Department of Oral and Maxillofacial Surgery, Harbin Medical University School of Dentistry, Harbin, Heilongjiang, Peoples Republic of China; 2 Department of Physiology and Neuroscience, Kangnung National University College of Dentistry, Kangnung, Kangwon, Korea; and 3 Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, Illinois Submitted 2 November 2007 ; accepted in final form 3 March 2008 The parvicellular part of the ventroposteromedial nucleus of the thalamus (VPMpc) is positioned at the key site between the gustatory parabrachial nuclei (PbN) and the gustatory cortex for relaying and processing gustatory information via the thalamocortical pathway. Although neuroanatomical and electrophysiological studies have provided information regarding the gustatory projection from PbN to VPMpc, the exact relationship between PbN and VPMpc, especially the efferent projection involving VPMpc to PbN, is obscure. Here we investigated the reciprocal connection between these two gustatory relays in urethane-anesthetized hamsters. We recorded from 114 taste-responsive neurons in the PbN and examined their responsiveness to electrical stimulation of the VPMpc bilaterally. Stimulation of either or both of the ipsilateral or contralateral VPMpc antidromically activated 109 gustatory PbN neurons. Seventy-two PbN neurons were antidromically activated after stimulation of both sides of the VPMpc, indicating that taste neurons in the PbN project heavily to the bilateral VPMpc. Stimulation of VPMpc also orthodromically activated 110 of PbN neurons, including 106 VPMpc projection neurons. Seventy-eight neurons were orthodromically activated bilaterally. Among orthodromic activations of the PbN cells, the inhibitory response was the dominant response; 106 cells were inhibited, including 10 neurons that were also excited contralaterally, indicating that taste neurons in the PbN are subject to strong inhibitory control from VPMpc. Moreover, stimulation of VPMpc altered taste responses of the neurons in the PbN, indicating that VPMpc modulates taste responses of PbN neurons. These results may provide functional insight of neural circuitry for taste processing and modulation involving these two nuclei. central gustatory pathway; pons; electrophysiology Address for reprint requests and other correspondence: C.-S. Li, Dept. of Anatomy, Southern Illinois Univ. School of Medicine, Life Science III, Rm. 2073, 1135 Lincoln Dr., Carbondale, IL 62901 (e-mail: cli{at}siumed.edu )