Enhanced retention in the passive-avoidance task by 5-HT(1A) receptor blockade is not associated with increased activity of the central nucleus of the amygdala.
The effect of blockade of 5-HT1A receptors was investigated on (1). retention in a mildly aversive passive-avoidance task, and (2). spontaneous single-unit activity of central nucleus of the amygdala (CeA) neurons, a brain site implicated in modulation of retention. Systemic administration of the selective 5-HT1A antagonist NAN-190 immediately after training markedly-and dose-dependently-facilitated retention in the passive-avoidance task; enhanced retention was time-dependent and was not attributable to variations in wattages of shock received by animals. Systemic administration of NAN-190 had mixed effects on spontaneous single-unit activity of CeA neurons recorded extracellularly in vivo; microiontophoretic application of 5-HT, in contrast, consistently and potently suppressed CeA activity. The present findings-that 5-HT1A receptor blockade by NAN-190 (1). enhances retention in the passive-avoidance task, and (2). does not consistently increase spontaneous neuronal activity of the CeA-provide evidence that a serotonergic system tonically inhibits modulation of retention in the passive-avoidance task through activation of the 5-HT1A receptor subtype at brain sites located outside the CeA.
Schneider
Allen M
AM
Department of Psychology, Swarthmore College, Swarthmore, Pennsylvania 19081, USA. Aschnei1@Swarthmore.edu
Wilkins
Emily
E
Firestone
Aaron
A
Everbach
E Carr
EC
Naylor
Jennifer C
JC
Simson
Peter E
PE
D000200:Action Potentials; D000679:Amygdala / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D008297:Male; D010879:Piperazines / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D020318:Rats, Long-Evans; D044282:Receptor, Serotonin, 5-HT1A / Q000502:physiology*; D012153:Retention, Psychology / Q000187:drug effects* / Q000502:physiology*; D058829:Serotonin 5-HT1 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology*
D010879:Piperazines; D058829:Serotonin 5-HT1 Receptor Antagonists; D012702:Serotonin Antagonists; D044282:Receptor, Serotonin, 5-HT1A; C058895:1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine