Effects of Stimulation of the Substantia Innominata and Caudate Nucleus on Postsynaptic Reactions of Neurons of the Cat Somatosensory Cortex Activated by Excitation of Nociceptors

• Published in: Neurophysiology (New York) 2014-02, Vol.46 (1), p.50-56
• Main Authors: Labakhua, T. Sh, Dzhanashia, T. K., Gedenavishvili, G. I.
• Format: Article
• Language: English
• Subjects: Acetylcholine; Analysis; Biomedical and Life Sciences; Biomedicine; Cats; Neurons; Neurosciences; Sensory perception
• ISSN: 0090-2977; 1573-9007
• DOI: 10.1007/s11062-014-9405-x

We studied effects of electrical stimulation of the substantia innominata (SIn) and nucleus caudatus (NC) on postsynaptic processes evoked in neurons of the cat somatosensory cortex by excitation of nociceptive and non-nociceptive afferent inputs (intense stimulation of the dental pulp and moderate stimulation of the thalamic ventroposteromedial nucleus, VPMN, respectively). We analyzed intracellularly recorded activity of seven cortical cells activated exclusively by stimulation of nociceptors and nine cells activated by both nociceptive and non-nociceptive influences (“nociceptive” and convergent neurons). In neurons of both groups, stimulation of both nociceptive afferents and thalamic VPMN resulted in the development of successions of EPSP – action potential (AP) or their series – IPSP (IPSP duration 200–300 msec). After isolated stimulations of the SIn and NC by short high-frequency series of stimuli, cortical neurons generated APs accompanied by long-lasting high-amplitude IPSPs. Conditioning stimulations of the NC and SIn preceding testing stimulations of the tooth pulp or thalamic VPMN with intervals from 100 to 900 msec induced intense suppression of impulse responses to test stimulations of the above-mentioned afferent inputs during an initial period of IPSP (100–150 msec) after conditioning stimulation. Partial recovery of the test responses was observed during the development of the second (GABAB-mediated) IPSP component. Complete recovery of the above responses developed within the borders of the latest segment of hyperpolarization evoked by conditioning stimulation and after termination of this potential. Stimulations of the NC and SIn result in the release of acetylcholine (ACh) in the cortex; ACh influences target neurons via muscarinic and nicotinic receptors and provides modulation of activity of the respective populations of nociceptive and non-nociceptice cortical neurons. Such modulation is probably based on changes realized in both pre- and post-synaptic cortical mechanisms.