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K M Kendrick

Publications and source records attributed to K M Kendrick.

At least 91 records · Page 5Linked to original sources
PubMed1986

The activity of neurones in the lateral hypothalamus and zona incerta of the sheep responding to the sight or approach of food is modified by learning and satiety and reflects food preference.

Single unit recordings were made from neurones in the lateral hypothalamus and zona incerta of conscious sheep during the static visual presentation of food or visible approach of food towards the animal's mouth. The ability of this population of neurones to modulate their activity as a result of learning and satiety was investigated together with the extent to which their responsiveness reflected individual food preference. These neurones did not respond to either the sight or visible approach of a nonsense object or a food which they would not eat. Further, when the sight or approach of food which the animal desired to eat was not paired with ingestion the neurones rapidly extinguished their response. The magnitude of the neuronal response and the number of trials to extinction was dependent upon the animal's preference for a particular food: the most preferred food evoking the greatest response and being the most resistant to extinction. Following extinction the neuronal response to the sight or approach of food could be re-established after one or two trials with food reinforcement. If the sheep was repeatedly given the same food to eat the magnitude of the neuronal response and the number of trials to extinction gradually declined until no response occurred when the animal refused to eat. These cells could also be induced to respond differentially to the approach of non-food objects dependent upon whether they were associated with a food reward or not. Thus a response could be evoked to the sight or approach of a black bottle if it was associated with a food reward but not to a yellow bottle unassociated with feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Characterization of neuronal responses in the zona incerta of the subthalamic region of the sheep during ingestion of food and liquid.

Single-unit recordings were made from the zona incerta of the subthalamic region of conscious sheep during ingestion. Some cells responded to ingestion and not to associated chewing, arousal or odour stimuli. Most cells changed their activity shortly after food entered the mouth and throughout ingestion, but a few responded immediately food entered the mouth and not during the remaining period of ingestion. Most cells responded to ingestion of solids but not liquids, and preferred foods often evoked the greatest changes in firing rate. Other cells responded equally to ingestion of solids and liquids or to a single substance. A number of cells responded to chewing and had significantly higher firing rates and shorter action potentials than those responding to ingestion.

Animals↗
PubMed1986

Cerebrospinal fluid levels of acetylcholinesterase, monoamines and oxytocin during labour, parturition, vaginocervical stimulation, lamb separation and suckling in sheep.

Acetylcholinesterase (AChE) activity, and concentrations of monoamines, monoamine metabolites and oxytocin (OT) were measured in the cerebrospinal fluid (CSF) of sheep during late pregnancy, labour, parturition, vaginocervical stimulation, lamb separation and suckling. Concentrations of AChE, 4-hydroxy-3 methoxyphenylethan-1,2-diol (MHPG) and OT were significantly elevated during labour and parturition. OT levels were also significantly raised in cycling ewes given vaginocervical stimulation. Separation of the ewes from their lambs (0.5-2 h) caused significant increases in AChE and MHPG, but not in OT. During suckling, following reunion of the ewes and lambs, concentrations of AChE and OT were significantly raised. The dopamine metabolites 3,4-dihydroxyphenylacetic acid and homovanillic acid were significantly lower in CSF during late pregnancy than during parturition and post-partum. Intravenous injections of OT which produced high circulating levels of this hormone in plasma produced significant, but very small, increases in concentrations of OT in the CSF. Our results show that in the sheep, labour, parturition, suckling and vaginocervical stimulation provoke a release of OT in the brain similar to that in the peripheral circulation. Changes in CSF levels of AChE and MHPG during labour, parturition and lamb separation, but not during vaginocervical stimulation, may be related to stress or hypertension.

Acetylcholinesterase↗
PubMed1985

Effects of oestradiol 17B, progesterone and testosterone upon proceptivity and receptivity in ovariectomized common marmosets (Callithrix jacchus).

The sexual behaviour of eight pairs of marmosets was observed during blocks of 30 minute tests after the ovariectomized female partners were treated with physiological doses of testosterone, oestradiol and progesterone. The effects of an intra-vaginal progesterone treatment were also investigated. Pre-ovulatory levels of oestradiol significantly increased the females' proceptive and receptive tongue-flicking displays and reduced the percentage of mounts refused. Mid-luteal levels of progesterone, by comparison, virtually abolished proceptive and receptive tongue-flicking and significantly increased mount refusals. Testosterone treatment was without effect. Vaginal application of progesterone unlike subcutaneous implantation of the hormone did not significantly alter the females' sexual behaviour. These results indicate that central actions of oestradiol and progesterone upon proceptivity and receptivity may occur in this primate, although further research using intra-cranial implants of these steroids is required to test this hypothesis.

Animals↗
PubMed1985

Luteinizing hormone releasing hormone enhances proceptivity in a primate.

Luteinizing hormone releasing hormone (LHRH) administered to ovariectomized marmosets treated with a low dose of 17 beta-oestradiol significantly enhanced proceptivity within 2 h. Without oestradiol priming LHRH treatment did not produce this effect. The dose of LHRH given did not significantly alter plasma levels of cortisol or progesterone. The behavioural effect of this treatment is therefore likely to have been mediated via a direct central action rather than indirectly through stimulating adrenocortical steroid secretion. These results provide the first demonstration that LHRH can potentiate the proceptive behaviour of a female primate.

Animals↗
PubMed1984

Different electrophysiological effects of testosterone on medial preoptic/anterior hypothalamic neurons have similar time courses.

The time courses of different electrophysiological effects of testosterone on a specific subpopulation of medial preoptic/anterior hypothalamic neurons and sexual behavior were measured in castrated rats. Testosterone reduced the absolute refractory period of those neurons projecting into the medial forebrain bundle with the same time course as it restored maximal responsiveness to orthodromic stimulation of either the lateral septum or the fimbria and sexual responses (5 days). The similar time-courses for these different electrophysiological effects of testosterone argue for a common mechanism of action.

Animals↗
PubMed1984

Effects of tactile and electrical stimuli upon release of vasoactive intestinal polypeptide in the mammalian penis.

Plasma levels of vasoactive intestinal polypeptide (VIP) in the corpora cavernosa penis and dorsal penile veins greatly exceeded those measured in the limb or caudal veins during anaesthesia in various mammals (Bennett's wallaby, Barbary sheep, cheetah, puma, sooty mangabey, pigtail macaque and chimpanzee). Tactile stimulation of the penis immediately before or during collection of blood samples resulted in an increase. In the wallaby, VIP levels (mean +/- S.E.M.) in blood samples collected from the flaccid penis in the absence of tactile stimulation were very low (0.6 +/- 0.5 pmol/l). A 36-fold increase in VIP occurred after manual extension of the flaccid penis (24.8 +/- 3.2 pmol/l) or during manually stimulated erections (25.1 +/- 1.7 pmol/l). Electrical stimulation of erection produced no significant increase in VIP levels (2.3 +/- 0.9 pmol/l) unless accompanied by tactile stimulation (17.5 +/- 1.4 pmol/l). These studies provide the first demonstration that sensory feedback from the penis plays an important role in regulating vasoactive intestinal polypeptidergic activity. Since VIP is a potent vasodilator its release due to tactile stimuli during copulation may play a role in the maintenance of penile erection.

Acinonyx↗
PubMed1984

Ovariectomy does not abolish proceptive behaviour cyclicity in the common marmoset (Callithrix jacchus).

Unlike in other non-human primates, ovariectomy of the female marmoset did not alter heterosexual interactions. Proceptive behaviour bouts retained the same cyclicity, duration and frequency within tests as during the ovarian cycle. Significant rises in plasma levels of cortisol, progesterone, oestrone and testosterone were found during these proceptive behaviour bouts and in cortisol, progesterone and oestrone at their onset. Results suggest a role for adrenocortical steroids in both maintaining female sexuality and regulating its cyclicity during ovarian cycles in this primate.

Animals↗
PubMed1984

Hyperprolactinaemia abolishes sensitivity of stria terminalis neurones to testosterone.

Hyperprolactinaemia was induced in castrated, testosterone-treated male rats using ectopic pituitary grafts under the kidney capsules. After 6 weeks the absolute refractory period of stria terminalis neurones in these animals did not differ significantly from long-term castrated rats (mean = 1.72 vs 1.69 ms) in spite of the presence of normal testosterone concentrations. Gonadally intact animals, and sham-operated castrated animals treated with testosterone, showed by comparison the characteristic significantly shorter absolute refractory period normally associated with testosterone stimulation (mean = 1.15 and 1.08 ms respectively). These results provide the first demonstration that hyperprolactinaemia can abolish central sensitivity to testosterone.

Amygdala↗
PubMed1983

Effect of testosterone on medial preoptic/anterior hypothalamic neurone responses to stimulation of the lateral septum.

Electrophysiological recordings were made from medial preoptic/anterior hypothalamic (MPOAH) neurones which could be orthodromically excited from the lateral septum (LS) in gonadally intact and castrated male rats. Castration significantly reduced the mean percentage of MPOAH neurones which responded reliably to 0.6 Hz stimulation (from 81.1% to 54.1%) and this could be reversed by testosterone propionate (from 52.5% to 90.1%). Both in the gonadally intact (58.1%) and castrated (53.8%) groups these MPOAH neurones with LS inputs also had inputs from the contralateral fimbria (CFIMB). A further experiment investigated whether these MPOAH neurones responding to LS stimulation had connections with the arcuate/median eminence (ARC/ME) region or the medial forebrain bundle (MFB). Altogether, 23.2% projected directly into the MFB and 9.5% into the ARC/ME. A further 28.4% and 31.6% of these MPOAH neurones received inputs from these respective brain regions. A small population of MPOAH neurones were also found which could be driven antidromically both from the LS and the MFB. Results show that testosterone alters the responsiveness of MPOAH neurones to stimulation of the LS. Since subpopulations of these neurones project to the MFB and ARC/ME the effects of castration on them may reflect both changes in sexual behavior and, for example, gonadotropin release.

Animals↗
PubMed1983

The effect of the ovarian cycle on the sexual behaviour of the common marmoset (Callithrix jacchus).

The sexual behaviour of 7 pairs of marmosets was observed during 30 minute tests for 44-68 days and blood samples were collected from females for measurement of plasma progesterone, testosterone and oestrone. Copulations occurred throughout the ovarian cycle of 24-30 days. Females used a "tongue-flicking" display both as an invitational behaviour (proceptive tongue-flicks) and during copulation (receptive tongue-flicks) most frequently during the peri-ovulatory period. Frequencies of proceptivity were correlated positively with high mean levels of testosterone and oestrone during the cycle and with a short follicular phase. Males showed significant increases in tongue-flicks, mounts and ejaculations during the peri-ovulatory phase, together with a shortened post-ejaculatory interval and increased duration of penile erection after ejaculation. A retrospective analysis showed that these changes in the males' behaviour occurred only during tests where females were proceptive and not during other tests in the peri-ovulatory period. Females refused significantly more of the males' mounting attempts during the luteal phase and a corresponding reduction in mount frequency occurred at this time. Grooming, scent-marking, olfactory inspections and some other behaviours did not alter significantly in either sex during the ovarian cycle.

Animals↗
PubMed1983

Electrophysiological effects of testosterone on the medial preoptic-anterior hypothalamus of the rat.

Castration in the rat significantly lengthened the refractory period of medial preoptic-anterior hypothalamic neurones with outputs into the medial forebrain bundle but not of those with outputs to the lateral septum. Treatment with testosterone propionate reduced the neuronal refractory period to its lowest level at the same time as it restored mounts and intromissions (after 5 days). Equally, when treatment was ended at 15 days, mounts and intromissions were no longer shown when the refractory period lengthened again 14 days later. The sub-population of neurones which also received inputs from the contralateral fimbria (through the corticomedial amygdala) showed the same results as the overall population. Castration also significantly increased the baseline firing rates of medial preoptic-anterior hypothalamic neurones receiving inputs from the medial forebrain bundle. The same effect was observed for the sub-population of neurones which also had inputs from the contralateral fimbria, but castration significantly reduced the percentage of neurones responding to this additional input. The neurones having inputs with the fastest conduction velocity were responsible for these changes in firing rate and the input neurones were therefore probably non-dopaminergic.

Animals↗
PubMed1982

A quantitative analysis of the feeding behavior of suckling rabbits.

Three experiments are reported on the feeding behavior of suckling rabbits ("kittens"). In the 1st the latency with which the kittens attached to the nipple, and then left the nipple, was determined. Attachment was very rapid and wholly reliable: on the 80 tests the nipple was seized in every case in under 9 sec, and on 67 of these in less than 3 sec. The kittens also invariably left the nipple within the next minute. If the kittens were 5 or 10 days old speed of attachment was unaffected by the presence or absence of saliva on the nipple, but 15- and 20-day-old kittens seized the sucked nipples more rapidly than the unsucked nipples. In a 2nd experiment with 12-day-old kittens, washing the nipple with solvents did not affect speed of attachment; nor did saliva. The results show that suckling rabbits, in contrast to rat pups, are not heavily dependent on saliva cues. In the 3rd experiment both attachment latency and milk intake were shown to be affected by an internal stimulus, a gastric load of.9% saline, 5 g/25 g body weight: attachment latency was significantly increased and milk intake reduced by 75%.

Animals↗
PubMed1982

Inputs to testosterone-sensitive stria terminalis neurones in the rat brain and the effects of castration.

1. The inputs to cortico-medial amygdala neurones which project directly to the area of the medial preoptic/anterior hypothalamic junction were studied electrophysiologically in urethane anaesthetized male rats. 2. In experiments with fifteen male rats it was found that none of these neurones was responsive to electrical stimulation of the ipsilateral olfactory bulb or accessory olfactory bulb or odour stimulation. 3. Experiments with four rats showed that electrical stimulation of the lateral portion of the contralateral fimbria excited 81% of these cortico-medial amygdala neurones. Their typical response to stimulation of the contralateral fimbria was a single action potential followed by an inhibitory period (20-100 ms). 4. Analysis of the polarity of evoked waves in the amygdala suggested that the fimbria input terminated in the basolateral nucleus of the amygdala and that this nucleus subsequently projected to the cortico-medial amygdala. The fimbria input was found to be contralateral in origin, crossing the mid line in the anterior fornical commissure. 5. In a further experiment 118 identified cortico-medial amygdala neurones were recorded from twelve rats (six gonadally intact and six castrated). Castration significantly decreased the percentage of these neurones responding to stimulation of the ipsilateral fimbria (20 vs. 97%) and lengthened post-excitatory inhibitory periods. 6. Results are discussed with respect to the initial finding by Kendrick & Drewett (1979) of testosterone-sensitive absolute refractory periods in cortico-medial amygdala neurones.

Afferent Pathways↗
PubMed1982

Effect of castration on medial preoptic/anterior hypothalamic neurone responses to stimulation of the fimbria in the rat.

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.

Afferent Pathways↗
PubMed1981

Effect of testosterone and the oestrous cycle on neuronal refractory periods and firing rates of stria terminalis neurones in the female rat.

Absolute refractory periods of a subpopulation of corticomedial amygdala (CMA) neurones which project to the medial preoptic/anterior hypothalamic junction (MPH) via the stria terminalis were recorded in the female rat. Previous experiments have shown that this sub-population of CMA neurones is testosterone-sensitive in the male rat. In the ovariectomised female testosterone propionate (TP, 200 microgram/day for 18-22 days) significantly reduced the mean absolute refractory period of these CMA neurones compared to oil treated controls (from 1.34 ms to 0.87 ms). In a second experiment the absolute refractory periods of these CMA neurones were measured during the pro-oestrus and di-oestrus stages of the oestrous cycle as well as in ovariectomised controls. The mean absolute refractory period of these neurones was significantly shortened at pro-oestrus (0.99 ms) compared both to animals in di-oestrus 1 (1.45 ms) and ovariectomised controls (1.42 ms). The median firing rate of these CMA neurones was also significantly increased at pro-oestrus (1.24 Hz) compared to di-oestrus 1 (0.13 Hz) and ovariectomised controls (0.09 Hz). No firing rate increase was observed after TP treatment ov ovariectomised animals in the first experiment. Results show that the testosterone-sensitive CMA neurones sensitivity in the female rat. They also show that the refractory periods of these neurones are shortened at pro-oestrus. Further, these same neurones also show firing rate increases at this time, although such an increase has not been observed in gonadally intact male rats when compared to castrated ones. Results are interpreted in terms of a possible functional sexual dimorphism in the output of these CMA neurones.

Amygdala↗
PubMed1981

Effect of testosterone on neuronal refractory periods, sexual behaviour and luteinizing hormone: a comparison of time-courses.

Measurements of the refractory period of stria terminalis neurones that are sensitive to testosterone propionate, of sexual behaviour and of plasma levels of LH were taken in castrated rats at various times after initiation of treatment with testosterone propionate. Levels of LH dropped within 24 h, before there was any change in neuronal refractory periods. The period of latency to mounting, however, was reduced to its shortest only after 7-8 days and ejaculations first occurred at the same time; these sexual responses correlated in time with reduction of the neuronal refractory period to its lowest level.

Amygdala↗