Abstract
1. Single unit extracellular recordings were made from medial preoptic/anterior hypothalamic neurones in response to electrical stimulation of the ipsilateral fimbria. The effects of castration on neuronal responses were investigated and the pathway of the fimbria input analysed using multiple stimulation and selective lesions. The percentage of responsive medial preoptic/anterior hypothalamic neurones which had connexions with the medial forebrain bundle was also investigated.
2. Orthodromic action potentials were recorded from 192 medial preoptic/anterior hypothalamic neurones in twenty animals (ten gonadally intact and ten castrated). These neurones responded to a single shock stimulus applied to the ipsilateral fimbria by producing one or one to three action potentials followed by an inhibitory period (similar to simple and complex spikes found in hippocampus and cerebellum). A further forty-eight neurones showed a post-stimulus inhibition. Castration significantly reduced the percentage of medial preoptic/anterior hypothalamic neurones that responded reliably to 0·6 Hz stimulation, lengthened the inhibitory periods, reduced the percentage of neurones producing one to three action potentials and lengthened their interspike intervals.
3. Further experiments using ten animals showed that medial preoptic/anterior hypothalamic neurones orthodromically stimulated from the fimbria were also driven by stimulation of the ipsilateral stria terminalis and the cortico-medial and basolateral amygdala. Lesioning the stria terminalis abolished the responses of medial preoptic/anterior hypothalamic neurones to stimulation of the fimbria.
4. In five animals the responses of fifty-seven medial preoptic/anterior hypothalamic neurones orthodromically stimulated from the fimbria were recorded after stimulation of the medial forebrain bundle. 44·5% of these neurones were stimulated antidromically and 25·6% orthodromically from the medial forebrain bundle. Neurones responding to fimbria stimulation by producing one to three action potentials were more likely to have connexions with the medial forebrain bundle.
5. The relevance of these findings to local neuronal circuitry and the control of sexual behaviour are discussed.
Full text
PDF
Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Barfield R. J., Wilson C., McDonald P. G. Sexual behavior: Extreme reduction of postejaculatory refractory period by midbrain lesions in male rats. Science. 1975 Jul 11;189(4197):147–149. doi: 10.1126/science.1138372. [DOI] [PubMed] [Google Scholar]
- Dyer R. G. An electrophysiological dissection of the hypothalamic regions which regulate the pre-ovulatory secretion of luteinizing hormone in the rat. J Physiol. 1973 Oct;234(2):421–442. doi: 10.1113/jphysiol.1973.sp010352. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fox S. E., Ranck J. B., Jr Electrophysiological characteristics of hippocampal complex-spike cells and theta cells. Exp Brain Res. 1981;41(3-4):399–410. doi: 10.1007/BF00238898. [DOI] [PubMed] [Google Scholar]
- Gardner C. R., Phillips S. W. Neuronal circuitry in the basal septum and preoptic area of the rat. Brain Res. 1977 Sep 9;133(1):95–106. doi: 10.1016/0006-8993(77)90051-8. [DOI] [PubMed] [Google Scholar]
- Hubbard J. I., DeFrance J. F., Marchand J. E. Responses in the rabbit medial preoptic region to stimulation of the fimbria. Brain Res. 1981 Feb 2;205(2):411–414. doi: 10.1016/0006-8993(81)90352-8. [DOI] [PubMed] [Google Scholar]
- Kendrick K. M. Inputs to testosterone-sensitive stria terminalis neurones in the rat brain and the effects of castration. J Physiol. 1982 Feb;323:437–447. doi: 10.1113/jphysiol.1982.sp014083. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Raisman G., Cowan W. M., Powell T. P. An experimental analysis of the efferent projection of the hippocampus. Brain. 1966 Mar;89(1):83–108. doi: 10.1093/brain/89.1.83. [DOI] [PubMed] [Google Scholar]
- Scouten C. W., Burrell L., Palmer T., Cegavske C. F. Lateral projections of the medial preoptic area are necessary for androgenic influence on urine marking and copulation in rats. Physiol Behav. 1980 Aug;25(2):237–243. doi: 10.1016/0031-9384(80)90211-5. [DOI] [PubMed] [Google Scholar]
- Szechtman H., Caggiula A. R., Wulkan D. Preoptic knife cuts and sexual behavior in male rats. Brain Res. 1978 Jul 21;150(3):569–595. doi: 10.1016/0006-8993(78)90821-1. [DOI] [PubMed] [Google Scholar]
- Udo M., Matsukawa K., Kamei H., Minoda K., Oda Y. Simple and complex spike activities of Purkinje cells during locomotion in the cerebellar vermal zones of decerebrate cats. Exp Brain Res. 1981;41(3-4):292–300. doi: 10.1007/BF00238886. [DOI] [PubMed] [Google Scholar]