Deficits in reproductive behaviour in septally lesioned female rats.

Estrous cycle and sexual behaviour were studied in septally lesioned female albino Wistar rats. In lesioned rats the vaginal smears showed continuous diestrus and the females failed to exhibit sexual receptivity during the postoperative period. Ovarian and uterine weights in lesioned rats were also significantly decreased. The results suggest that the septal nuclei exert a modulatory influence on female sexual behaviour.

Effects of medial septal stimulation & its blockade with atropine on hippocampal rhythmical slow activity in free-moving rabbits.

The influence of the medial septal nucleus (MSN) on hippocampal rhythmical slow activity (RSA) was investigated in hunger motivated free-moving rabbits. Single unit activity of 29 CA3 dorsal hippocampal neurones was studied under two paradigms viz., electrical stimulation (3v/1msec/5Hz) and chemical blockade of atropine-sensitive medial septal cells (dose of 5 micrograms in 5 microliters). The analysis of interspike interval sample histograms recorded with Apple II, along with single unit neuronal spikes recorded on polygraph showed bimodal pattern with two peaks; one at bin 10-20 (high frequency) and second at bin 100-300 (theta frequency). On stimulation of MSN, there was total suppression of bin 100-300 with peaks at bin 1-20 and at bin greater than 1000 (very low frequency). Blockade of cholinergic receptors at MSN showed reduction of bin 100-300 and peak at bin 700- greater than 1000; this was followed by gradual decrease of spike's amplitude and thereafter its total abolition. The results indicate that the septal region is not a pacemaker per se in the genesis of hippocampal RSA (theta rhythm), but serves more in the nature of a relay station for a number of inputs and that its influence on the hippocampal electrical activity depends on the integrity of cholinergic inputs, be it from hippocampus proper or from mid-brain reticular formation.

Effect of dehydration on the increase of arterial pressure and renal electrolyte excretion produced by central cholinergic stimulation in rats

Natriuresis, kaliuresis, diuresis, arterial pressure and heart rate were studied in rats following dehydration and cholinergic stimulation of the medial septal area (MSA). The increase in renal NA+ and K+ excretion produced by the injection of carbachol (2nmol) into the MSA in normal hydrated rats was abolished in 48-h water-deprived rats. Urinary volume was also reduced. Cholinergic stimulation of the MSA produced a smaller mincrease in arterial pressure in 48-h-deprived rats compared to normal hydrated animals. No change was observed in heart rate. These reults show that hydration state is essential for the central cholinergic control of electrolyte excretion and increase in arterial pressure

Role of the septal area in feeding behavior elicited by electrical stimulation of the lateral hipothalamus of the rat

The present study was undertaken to investigate the influence of the septal area on neural mechanisms involved in feeding behavior elicited by electrical stimulation of the lateral hypothalamic area of the rat. Electrolytic damage to medial and lateral septal nuclei induced a significant increase (18.29 + or - 1.69 to 25.05 + or - 2.31 g, P<0.05, N = 14) in food intake elicited by hypothalamic stimulation. The threshold current for stimulus-induced eating decreased by 20% after septal lesion. A significant decrease in food ingestion was observed after electrical stimulation of the septal nuclei, either preceding (27.47 + or - 1.57 to 19.30 + or - 2.06 g P <0.05, N = 13) or simultaneous (26.20 + or - 1.60 to 12.10 + or - 2.40 g, P<0.05, N = 11) with hypothalamic stimulation. The results indicate an inhibitory effect of the septum on the lateral hypothalamic area and also suggest that the functional state of the lateral hypothalamus, which is responsible for the feeding behavior, depends on the activity pattern of the septal area

Effect of cholinergic stimulation of the medial septal area on the secretory properties of atrial myocardial fibers

Adult male Wistar rats weighing 240-260 g were implanted with stainless steel guide cannulae into the medial septal area (MSA). Cholinergic stimulation of the MSA increased natriuresis (344.6 + or - 13.8 vs 22.2 + or - 2.1 micronEq for the controls), the number of atrial specific granules (61.0 + or - 6.7 vs 43,8 + or - 3.5 granules/100 micron m**2 sarcoplasma for the controls), and the number of electron-dense vesicles near the sarcolemma or appearing to undergo exocytotic extrusion (50.0 + or - 2.3 vs 21.4 + or - 5.7 vesicles/100 micronm sarcolemma for the controls) It is not yet clear how cholinergic stimulation of the MSA changes the secretory characteristics of atrial myocardial fibers. However, the present study provides evidence that release of an atrial natriuretic factor may be controlled by the central nervous system (CNS). This may occur through the sympathetic and parasympathetic innervation of the heart or through the release of some substance produced by the CNS or produced at another site whose release is controlled by the CNS