Full evidence and obvious reasons made it possible to arrive at the conclusion that the nature of transmission upon cerebrospinal neurons is overwhelmingly mechanical, not only in the periphery- between various receptors and afferent nerve terminals, and between surrounding tissues and free nerve endings- but also in the cerebral cortex. When viewed from the standpoint of the everchanging patterns of natural mechanical stimuli, the neurons in the conscious cerebral cortex and the pain endings in an acute inflammatory locus have the same situation very much in common. It is quite likely that natural mechanical stimuli dominate over cerebrospinal nervous phenomena and physiologists have been watching the missing mechanism at work in every experiment upon afferent nerve terminals and cerebral cortex that they have done. The terms "psychic tension" and "central excitatory state" comparable to muscular tonus are of interest because they involve the use of mathematical techniques in psychology and neurophysiology. They are capable of becoming weak or strong, and they serve as an inner stimulus to give impetus to behavior. Unfortunately, however, it is an elusive inner stimulus, and it defies a lucid definition. But natural mechanical stimuli embody the psychic tension and the central excitatory state ultimately. It seems now that we just found a place where constant complaints against neurophysiology and physiological psychology are ventilated. We may conclude that natural mechanical stimuli are the leading direct stimuli to cerebrospinal neurons in the human body, and the plastic and developmental nervous phenomena and mental phenomena can be explained objectively by a familliar datum of mechanical energy and that we can reasonably expect the day of regarding material world and spiritual world in the monistic conception of matter-energy system.
Animals ; Anura ; Cerebral Cortex/*physiology ; Human ; In Vitro ; Motor Neurons/physiology ; Nerve Endings/physiology ; Receptors, Sensory/*physiology ; Spinal Cord/*physiology

AIMTo study the correlation between 5-HT-induced pain response and the contribution by individual 5-HTR subtypes including 5-HT1R, 5-HT2R and 5-HT3R at the level of peripheral primary afferent.

METHODSThe experiments were done on acutely isolated trigeminal ganglion (TG) neurons using whole-cell patch clamp technique and the nociceptive effect was observed on behavior experiments by intraplantar injection of test drugs.

RESULTSThe majority of cells examined responded to 5-HT in a manner of concentration dependence (10(-6) - 10(-3) mol/) (61.4%, 54/88) and with a fast activating and rapid desensitizing inward current (I(5-HT)), which was thought to be mediated by the activation of 5-HT3R, since it could be blocked by 5-HT3R antagonist ICS 205930 and mimicked by 5-HT3R agonist 2-methyl-5-HT. It was found that I(5-HT) was potentiated by 5-HT2R agonist alpha-methyl-5-HT markedly, while 5-HT1R agonist R-(+)-UH 301 did not. In behavioral experiment performed on conscious rats, intraplantar injection of 5-HT(10(-5), 10(-4) and 10(-3) mol/L) induced an increment of cumulative lifting time first 20 min in a manner of concentration dependence. By dissociating 5-HTR subtypes using their corresponding antagonists (ICS and CYP) the potency order of hindpaw lifting time was identified as follows: 5-HT > 5-HT + ICS > 5-HT + CYP.

CONCLUSIONThe results suggest that in 5-HT-induced nociceptive response at the primary sensory level 5-HT3R may play a role of initiation, but 5-HT2R mediates maintaining and modulatory effect in the processes of nociceptive information convey.

Animals ; Male ; Membrane Potentials ; Pain ; physiopathology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Receptors, Serotonin, 5-HT1 ; metabolism ; Receptors, Serotonin, 5-HT2 ; metabolism ; Receptors, Serotonin, 5-HT3 ; metabolism ; Sensory Receptor Cells ; metabolism ; physiology