Galanin-mediated anxiolytic effect in rat central amygdala is not a result of corelease from noradrenergic terminals.
Galanin is colocalized extensively with norepinephrine in brain. Although this suggests possible activity-dependent neurotransmitter interactions, the functional significance of such colocalization remains elusive. Previously, we showed that enhancing stress-activation of the noradrenergic system by yohimbine pretreatment released galanin in central amygdala, attenuating the anxiety-like behavioral response to stress on the elevated plus-maze. The present study was conducted to determine, in this context, whether galanin was indeed coreleased from noradrenergic terminals, or instead from another galanin afferent or local stress-responsive galanin neurons in the amygdala. In experiment 1, galanin-mediated anxiolytic effects on the plus-maze following yohimbine + stress were unaltered by lesioning the noradrenergic innervation of central amygdala. In experiment 2, combining immunohistochemistry and in situ hybridization, galanin neurons specifically activated by yohimbine + stress treatment were found only in the locus coeruleus and intraamygdalar bed nucleus of the stria terminalis, adjacent to central amygdala. In experiment 3, retrograde tracing combined with in situ hybridization revealed few if any galanin cells projecting to central amygdala in locus coeruleus or nucleus tractus solitarius, sources of noradrenergic innervation. Indeed, few retrogradely-labeled galanin neurons were observed anywhere in the brain, including a small number in the intraamygdalar bed nucleus. Together, these results suggest that stress following yohimbine may have induced galanin release from an afferent to central amygdala originating in the bed nucleus, or from local neurons in the intraamygdalar bed nucleus, but that anxiolytic effects exerted by galanin in this context of elevated noradrenergic activity were not the result of corelease from noradrenergic terminals innervating central amygdala.
Barrera
Gabe
G
Department of Pharmacology and Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, 78229, USA.
Hernandez
Angelica
A
Poulin
Jean-Francois
JF
Laforest
Sylvie
S
Drolet
Guy
G
Morilak
David A
DA
D018663:Adrenergic Agents / Q000633:toxicity; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000679:Amygdala / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D014151:Anti-Anxiety Agents / Q000008:administration & dosage* / Q000378:metabolism; D001345:Autoradiography / Q000379:methods; D001522:Behavior, Animal / Q000187:drug effects; D002452:Cell Count / Q000379:methods; D002772:Cholera Toxin / Q000378:metabolism; D004347:Drug Interactions; D005473:Fluoxetine / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D019004:Galanin / Q000008:administration & dosage* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D008125:Locus Coeruleus / Q000187:drug effects / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism*; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D016627:Oxidopamine / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D012149:Restraint, Physical / Q000379:methods; D012686:Septal Nuclei / Q000187:drug effects / Q000502:physiology; D013266:Stilbamidines / Q000378:metabolism; D013312:Stress, Physiological / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism; D014316:Tritium / Q000493:pharmacokinetics; D015016:Yohimbine / Q000494:pharmacology
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D018663:Adrenergic Agents; D000317:Adrenergic alpha-Antagonists; D014151:Anti-Anxiety Agents; D016761:Oncogene Proteins v-fos; D013266:Stilbamidines; D005473:Fluoxetine; D014316:Tritium; C011386:nisoxetine; D015016:Yohimbine; D019004:Galanin; D016627:Oxidopamine; D002772:Cholera Toxin; D009638:Norepinephrine