Involvement of noradrenergic innervation from locus coeruleus to hippocampal formation in negative feedback regulation of penile erection in the rat.
We demonstrated previously that a novel negative feed back mechanism for the regulation of penile erection, which is triggered by ascending sensory inputs initiated by tumescence of the penis, exists in the hippocampal formation (HF). This study further elucidated the role of the locus coeruleus (LC), which is the largest aggregate of norepinephrine-containing neurons in the brain and provides the major noradrenergic innervation to the HF, in this process. Adult male Sprague-Dawley rats that were anesthetized and maintained with chloral hydrate were used. The intracavernous pressure (ICP) recorded from the corpus cavernosum of the penis was used as the experimental index for penile erection. Electrical activation of the LC elicited a significant reduction in baseline ICP. Similar observations were obtained on microinjection bilaterally into the hippocampal CA1 or CA3 subfield or dentate gyrus of equimolar doses (5 nmol) of norepinephrine (alpha1-, alpha2-agonist), phenylephrine (alpha1-agonist), or BHT 933 (alpha2-agonist). Bilateral electrolytic lesions of the LC discernibly enhanced the magnitude and/or duration of the elevation in ICP induced by intracavernous administration of papaverine (400 microgram). A potentiation of the papaverine-evoked ICP increase was also observed following pretreatment with bilateral hippocampal application of equimolar doses (250 pmol) of either prazosin (alpha1-, alpha2B-, alpha2C-antagonist), naftopidil (alpha1A/D-antagonist), yohimbine (alpha2-antagonst), or rauwolscine (alpha2B-, alpha2C-antagonist). None of these antagonists, however, affected baseline ICP. These results suggest that noradrenergic innervation of the HF that originates from the LC may play an active role in negative feedback regulation of penile erection, engaging at least alpha1A/D-, alpha2B-, and alpha2C-adrenoceptors in the HF.
Chang
A Y
AY
Center for Neuroscience, National Sun Yat-sen University, Kaohsiung, Taiwan, Republic of China. achang@mail.nsysu.edu.tw
Huang
C M
CM
Chan
J Y
JY
Chan
S H
SH
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D004525:Efferent Pathways / Q000502:physiology; D004558:Electric Stimulation; D005246:Feedback; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008125:Locus Coeruleus / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology*; D010208:Papaverine / Q000494:pharmacology; D010410:Penile Erection / Q000502:physiology*; D010413:Penis / Q000187:drug effects / Q000502:physiology; D011312:Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D014665:Vasodilator Agents; D010208:Papaverine; D009638:Norepinephrine