Demonstration of serotoninergic axons terminating on luteinizing hormone-releasing hormone neurons in the preoptic area of the rat using a combination of immunocytochemistry and high resolution autoradiography.
The synaptic relationship between serotoninergic terminals and luteinizing hormone-releasing hormone-containing neurons was investigated in the medial preoptic area using a combined technique. Axon terminals selectively taking up 5-[3H]hydroxytryptamine were labelled autoradiographically and luteinizing hormone-releasing hormone-containing neuronal elements were identified by means of immunocytochemistry. Synaptic contacts were observed between tritiated 5-hydroxytryptamine-labelled boutons and luteinizing hormone-releasing hormone-immunoreactive dendrites. About 5% of the boutons which formed synapses with luteinizing hormone-releasing hormone-immunoreactive dendrites were found to be labelled by the tritiated indolamine. Luteinizing hormone-releasing hormone-immunoreactive axon terminals occurred as presynaptic elements in contact with unidentified dendritic spines, shafts or perikarya. These observations provide morphological basis for the idea that 5-hydroxytryptamine-containing neurons can act directly on luteinizing hormone-releasing hormone release. Further, they support the assumption that luteinizing hormone-releasing hormone is not only a neurohormone but may also function as a neurotransmitter or neuromodulator.
D000818:Animals; D001345:Autoradiography; D001369:Axons / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D008297:Male; D008854:Microscopy, Electron; D011301:Preoptic Area / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism
D012701:Serotonin; D007987:Gonadotropin-Releasing Hormone