Serotonin depletion does not prevent intrinsic sensitization in the leech.
Intrinsic sensitization is a form of behavioral facilitation that is distinct from the extrinsic sensitization normally studied. To examine whether intrinsic and extrinsic sensitization are mediated by different physiological processes, the effects of 5,7-dihydroxytryptamine-induced serotonin (5-HT) depletion on intrinsic sensitization of the leech whole-body shortening response were observed. Previous experiments have shown that 5-HT depletion disrupts dishabituation and extrinsic sensitization of this behavior in the leech. Intrinsic sensitization was observed in preparations from both control and 5-HT-depleted animals, indicating that this form of behavioral facilitation was not affected by 5-HT depletion. The differences in the effects of 5-HT depletion on intrinsic versus extrinsic sensitization suggest that there are distinct neurophysiological processes mediating these two forms of behavioral facilitation. In addition, 5-HT depletion appeared to disrupt a putative extrinsic form of habituation of the shortening reflex. These data support the hypothesis that both intrinsic and extrinsic processes of neuromodulation mediate habituation and sensitization.
Burrell
B D
BD
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
Sahley
C L
CL
D000704:Analysis of Variance; D000818:Animals; D006185:Habituation, Psychophysiologic / Q000502:physiology; D007865:Leeches; D012018:Reflex / Q000502:physiology; D012095:Repression-Sensitization; D012701:Serotonin / Q000378:metabolism*
D012701:Serotonin