alpha-melanocyte-stimulating hormone and habituation of prey-catching behavior in the Texas toad, Bufo speciosus.
We investigated dose-dependent effects of alpha-melanocyte-stimulating hormone (alpha-MSH) on habituation in the Texas toad, Bufo speciosus. Additionally, we determined changes in plasma and brain levels of alpha-MSH following peripheral administration of the peptide or following exposure to an ether stressor. The ability of alpha-MSH to facilitate acquisition of habituation was dose dependent. Plasma alpha-MSH concentrations were elevated within 5 min of dorsal lymph sac injection and remained elevated up to 600% over controls after 30 min. Administration of 50 microgram alpha-MSH had no effect on plasma corticosterone levels. Radiolabeled alpha-MSH was detected in cerebrospinal fluid microdialysates within minutes of peripheral injection. Concentrations of alpha-MSH in the telencephalon and preoptic area were significantly lowered after ether exposure, whereas levels in the optic tectum, thalamus/hypothalamus, brainstem, and plasma were unchanged. We conclude that alpha-MSH administered peripherally facilitates habituation in a dose-dependent fashion. Our results confirm that the effects of alpha-MSH are independent of corticosterone secretion. The peptide is cleared rapidly into the bloodstream and enters the cerebrospinal fluid after dorsal lymph sac injection. Neuronal alpha-MSH may help toads gather information about their environment when exposed to certain stressors.
Olsen
C M
CM
Department of Biological Sciences, Texas Tech University, Lubbock, Texas, 79409-3131, USA.
Lovering
A T
AT
Carr
J A
JA
D000818:Animals; D001143:Arousal / Q000502:physiology; D001921:Brain / Q000502:physiology; D001931:Brain Mapping; D002025:Bufonidae / Q000502:physiology*; D003345:Corticosterone / Q000502:physiology; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D008297:Male; D010902:Pituitary Gland / Q000502:physiology; D011235:Predatory Behavior / Q000502:physiology*; D011340:Problem Solving / Q000502:physiology; D000521:alpha-MSH / Q000502:physiology*
D000521:alpha-MSH; D003345:Corticosterone