Response of medial preoptic/anterior hypothalamic neurones to ventrolateral medulla stimulation and its attenuation by adrenoceptor antagonists.
Extracellular single-unit recordings were made from medial preoptic/anterior hypothalamic (MPOAH) neurones in urethane-anaesthetized female rats, and the responses of these neurones to electrical stimulation of the ventrolateral medulla (VLM) were investigated. Of 189 neurones tested, 20% were excited and 21% were inhibited following VLM stimulation. The latency of inhibitory responses showed a normal distribution and the mean latency was 47 ms, whereas the latency of excitatory responses showed a bimodal distribution with peaks in the ranges of 0-10 ms and 40-50 ms, respectively. Excitatory responses with latencies greater than 15 ms and inhibitory responses were significantly attenuated by intravenous injections of the alpha-adrenoceptor antagonist phenoxybenzamine but not the beta-adrenoceptor antagonist propranolol. In the light of these observations and the known anatomical and electrophysiological findings, it is suggested that A1 noradrenergic and/or C1 adrenergic inputs from the VLM to MPOAH neurones are, at least in part, mediated by alpha-adrenoceptors.
Kaba
H
H
Department of Physiology, Kochi Medical School, Nankoku/Japan.
Saito
H
H
Sakamoto
M
M
Yamasaki
F
F
Otsuka
K
K
Seto
K
K
D000818:Animals; D004558:Electric Stimulation; D005260:Female; D007032:Hypothalamus, Anterior / Q000502:physiology*; D008526:Medulla Oblongata / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010643:Phenoxybenzamine / Q000494:pharmacology; D011301:Preoptic Area / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D013565:Sympatholytics / Q000494:pharmacology*
D011942:Receptors, Adrenergic, alpha; D013565:Sympatholytics; D010643:Phenoxybenzamine; D011433:Propranolol