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Potential changes generated in the nucleus dorsomedialis after stimulation of the amygdala
EBBS ABSTRACTS
359
ejaculation using a gas-liquid chromatography method. Male littermates raised under an 8-h light/16-h dark illumination regimen were tested for 10 min on alternate days, beginning 20-21 days after birth, for the display of intromissions and ejaculation. Three conditions were established with 10 animals in each group: (a) peripheral shock to the flanks (3 mA pulse every 30 sec) in the presence o f an oestrous female; (b) peripheral shock 24 h before tests with an oestrous female; and (c) no peripheral shock. Animals shocked with females first showed the ejaculatory pattern at a younger age than animals in the non-shocked control group (mdn of 59 vs. 75 days, P < 0.002). Following the initial intromission in response to peripheral stimulation, males needed no further shocks to complete a normal copulatory sequence. Rats shocked 24 h before tests with females first ejaculated at the same age as non-shocked controls (mdn of 73 days). This finding suggests that precocious mating behaviour obtained with peripheral stimulation cannot be attributed to a shock-induced increase in blood testosterone concentrations. Testes and accessory organ weights of shock-induced copulators were significantly lighter following the first ejaculation than either the non-shocked control males or males shocked 24 h before each test. Testosterone concentrations of the behaviourally precocious males were about half the value of control males (mdn of 1.5 vs. 3.6 ng/ml) although this difference was not statistically significant. These findings show that if peripheral stimulation is applied, less testosterone over a shorter period of time is required for mating behaviour to occur. This suggests that a threshold amount of testosterone is necessary to permit the display of sexual responses, but that either additional testosterone or a strongly arousing external stimulus is sufficient to facilitate the initiation of sexual behaviour. 1 BARFIELD, R. J., AND SACHS, B. D., Effect of shock on copulatory behaviour in castrate male rats,
Hormones and Behav., 1 (1970) 247-253. 2 CAGGIULA, A. R., AND EIBERGEN, R., Copulation of virgin male rats evoked by painful peripheral
stimulation, J. comp. physiol. Psychol., 69 (1969) 414-419.
Potential changes generated in the nucleus dorsomedialis after stimulation of the amygdala A. FERNANDEZ DE MOLINA AND ARANZAZU ISPIZUA - - Instituto Cajal, C . S . L C . , M a d r i d (Spain)
Slow potential changes and unitary activity have been recorded in the nucleus dorsomedialis of chloralosed and unanaesthetized cats after stimulation of the amygdaloid nuclear complex. Four stimulating points were tested for each recording level. The slow potential consisted of 3 phases of activity with latencies to the peaks of 10-15, 40-50 and 100-130 msec. The largest amplitude was obtained when stimulating the anterior portion of the nucleus basalis and recording from the ventral third of the nucleus dorsomedialis. Activity was also recorded from single units which showed latencies distributed Brain Research, 37 (1972) 353-369
360
EBBS ABSTRACTS
in 3 ranges: 8-15, 25--40 and 300-600 msec. Short and middle range latency units discharged one spike when stimulating with threshold intensity. When stimulating with higher strengths the number of spikes increased up to five and the latency of the first spike was reduced. Long latency units discharged one or two bursts of 3-6 spikes and showed a great variation in latency under constant stimulus strength. Most of the short latency units were activated from the nucleus basalis. Usually only one unit fired after stimulation of one of the four points in the amygdala, showing no response to stimulation of the other 3 points. The results are consistent with the existence of direct connexions between the nucleus basalis of the amygdala and the nucleus dorsomedialis in the cat. Supported by a grant of the Fundacibn 'Eugenio Rodriguez Pascual'.
Contribution of midbrain structures to the control of the rat's mouse-killing behaviour J. P. CHAURAND, M. VERGNES, P. SCHMITTAND P. KARLI - - Laboratoire de Neurophysiologie, Centre de Neurochimie du CNRS, Strasbourg (France) Total destruction of the mesencephalic central grey entails a clear facilitation of the killer-rat's natural aggressive behaviour; furthermore, the lesion provokes a long-lasting aggressiveness toward mice in a small percentage of natural non-killers. The electrical stimulation of the central grey suppresses a killing response in progress. This midbrain structure seems to be a part of a periventricular suppressant system which also includes diencephalic midline structures. However, it should be noted that stimulation at a small number of central grey sites may facilitate the killing behaviour. Lesions placed in the ventromedial tegmentum between the ventral tip of the central grey and the interpeduncular nucleus induce a transient (up to 11 days) suppression of the killing response and, in some of the operated animals, a transient aphagia. When placed in the ventral tegmental area of Tsai, the lesions provoke a transient aphagia or anorexia, but do not modify the mouse-killing behaviour. On the other hand, electrical stimulation of a number of sites within the ventromedial mesencephalic tegmentum facilitates the killing response in the killer-rat or even elicits such a response in a natural non-killer. Ventromedial tegmental structures thus appear to be a part of a facilitating system which also includes the posterior twothirds of the lateral hypothalamic area as well as the centromedial amygdala. The electrical stimulation of the mesencephalic reticular formation does not facilitate the rat's mouse-killing behaviour. On the contrary, it invariably provokes an immediate arrest of the killing response. This suppressant effect may result from the predominant activation of inhibitory fibres irradiating from the central grey as well as from the medial tip of the cerebral peduncle into the lateral midbrain tegmentum.
Brain Research, 37 (1972) 353-369
359
ejaculation using a gas-liquid chromatography method. Male littermates raised under an 8-h light/16-h dark illumination regimen were tested for 10 min on alternate days, beginning 20-21 days after birth, for the display of intromissions and ejaculation. Three conditions were established with 10 animals in each group: (a) peripheral shock to the flanks (3 mA pulse every 30 sec) in the presence o f an oestrous female; (b) peripheral shock 24 h before tests with an oestrous female; and (c) no peripheral shock. Animals shocked with females first showed the ejaculatory pattern at a younger age than animals in the non-shocked control group (mdn of 59 vs. 75 days, P < 0.002). Following the initial intromission in response to peripheral stimulation, males needed no further shocks to complete a normal copulatory sequence. Rats shocked 24 h before tests with females first ejaculated at the same age as non-shocked controls (mdn of 73 days). This finding suggests that precocious mating behaviour obtained with peripheral stimulation cannot be attributed to a shock-induced increase in blood testosterone concentrations. Testes and accessory organ weights of shock-induced copulators were significantly lighter following the first ejaculation than either the non-shocked control males or males shocked 24 h before each test. Testosterone concentrations of the behaviourally precocious males were about half the value of control males (mdn of 1.5 vs. 3.6 ng/ml) although this difference was not statistically significant. These findings show that if peripheral stimulation is applied, less testosterone over a shorter period of time is required for mating behaviour to occur. This suggests that a threshold amount of testosterone is necessary to permit the display of sexual responses, but that either additional testosterone or a strongly arousing external stimulus is sufficient to facilitate the initiation of sexual behaviour. 1 BARFIELD, R. J., AND SACHS, B. D., Effect of shock on copulatory behaviour in castrate male rats,
Hormones and Behav., 1 (1970) 247-253. 2 CAGGIULA, A. R., AND EIBERGEN, R., Copulation of virgin male rats evoked by painful peripheral
stimulation, J. comp. physiol. Psychol., 69 (1969) 414-419.
Potential changes generated in the nucleus dorsomedialis after stimulation of the amygdala A. FERNANDEZ DE MOLINA AND ARANZAZU ISPIZUA - - Instituto Cajal, C . S . L C . , M a d r i d (Spain)
Slow potential changes and unitary activity have been recorded in the nucleus dorsomedialis of chloralosed and unanaesthetized cats after stimulation of the amygdaloid nuclear complex. Four stimulating points were tested for each recording level. The slow potential consisted of 3 phases of activity with latencies to the peaks of 10-15, 40-50 and 100-130 msec. The largest amplitude was obtained when stimulating the anterior portion of the nucleus basalis and recording from the ventral third of the nucleus dorsomedialis. Activity was also recorded from single units which showed latencies distributed Brain Research, 37 (1972) 353-369
360
EBBS ABSTRACTS
in 3 ranges: 8-15, 25--40 and 300-600 msec. Short and middle range latency units discharged one spike when stimulating with threshold intensity. When stimulating with higher strengths the number of spikes increased up to five and the latency of the first spike was reduced. Long latency units discharged one or two bursts of 3-6 spikes and showed a great variation in latency under constant stimulus strength. Most of the short latency units were activated from the nucleus basalis. Usually only one unit fired after stimulation of one of the four points in the amygdala, showing no response to stimulation of the other 3 points. The results are consistent with the existence of direct connexions between the nucleus basalis of the amygdala and the nucleus dorsomedialis in the cat. Supported by a grant of the Fundacibn 'Eugenio Rodriguez Pascual'.
Contribution of midbrain structures to the control of the rat's mouse-killing behaviour J. P. CHAURAND, M. VERGNES, P. SCHMITTAND P. KARLI - - Laboratoire de Neurophysiologie, Centre de Neurochimie du CNRS, Strasbourg (France) Total destruction of the mesencephalic central grey entails a clear facilitation of the killer-rat's natural aggressive behaviour; furthermore, the lesion provokes a long-lasting aggressiveness toward mice in a small percentage of natural non-killers. The electrical stimulation of the central grey suppresses a killing response in progress. This midbrain structure seems to be a part of a periventricular suppressant system which also includes diencephalic midline structures. However, it should be noted that stimulation at a small number of central grey sites may facilitate the killing behaviour. Lesions placed in the ventromedial tegmentum between the ventral tip of the central grey and the interpeduncular nucleus induce a transient (up to 11 days) suppression of the killing response and, in some of the operated animals, a transient aphagia. When placed in the ventral tegmental area of Tsai, the lesions provoke a transient aphagia or anorexia, but do not modify the mouse-killing behaviour. On the other hand, electrical stimulation of a number of sites within the ventromedial mesencephalic tegmentum facilitates the killing response in the killer-rat or even elicits such a response in a natural non-killer. Ventromedial tegmental structures thus appear to be a part of a facilitating system which also includes the posterior twothirds of the lateral hypothalamic area as well as the centromedial amygdala. The electrical stimulation of the mesencephalic reticular formation does not facilitate the rat's mouse-killing behaviour. On the contrary, it invariably provokes an immediate arrest of the killing response. This suppressant effect may result from the predominant activation of inhibitory fibres irradiating from the central grey as well as from the medial tip of the cerebral peduncle into the lateral midbrain tegmentum.
Brain Research, 37 (1972) 353-369